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VAN  NOSTRAND'S 


ECLECTIC 


Engineering  Magazine. 


VOLUME  XIII. 


JULY-DECEMBER 


1875. 


NEW    YORK: 

D.     VAN     NOSTRAND,     PUBLISHER 

23  Murray  Street  and  27  Warren  Street  (up  states). 

18  7  5. 


A 


.V3 


CONTENTS. 


VOL.   XIII. 


American  Association 564 

Accidents,   railway 120 

American      Society     of     Civil 

Engineers 89,  472,  563 

Air  and  Ventilation 109 

Analysis     of     the     Peancellier 

Compound  Compass 81 

Arch,     application     of    graph- 
ical statics  to 341 

Arches,  stability  of 226 

Arches,  theories  of  Voussoir..  514 

Architectnre,  future  of 134 

Artificial    hardening    of    sand- 
stone   287 

Austro- Hungarian  navies 285 

Axle  Boxes « 142 


Balanced  valves  in  locomotives. .    436 
Beams,  strength  of..  164,  193,  289,  401 

Behavior  of  fluid 438 

Belgian  competition  in  the  iron 

trade 281 

Bessemer  steel,  manufacture  of.     143 

"Bessemer,"  the 78,  187 

Blast  furnace,  lime  in 509 

Boiler  incrustation 570 

Boilers  lined  with  copper 283 


Book  Notices : 

Allan,  Prof.  W.    Strength  of 

beams 568 

Axon,  W.  E.  A.    Mechanics' 

Friend 381 


Blasins,  W.  Storms :  Their 
nature,  classification  and 
laws 93 

Button,  T.  A.  Treatise  on 
the  origin,  proper  preven- 
tion and  cure  of  dry  rot  in 
timber 479 

Brown,  J.  C.  Horology  of 
SouthAfrica 381 

Brown,  J.  C.  Hydrology  of 
SouthAfrica 190 

Bryce,  J.  Elements  of  Eu- 
clid, adapted  to  modern 
methods  of  geometry 94 

Burgh,  N.  P.  Practical 
treatise  on  the  science  of 
steam 190 

Butler,  J.  G.  Systems  of 
projectiles  and  rifling, 
with  practical  suggestions 
for  their  improvement 285 


Catalogue  of  the  officers  and 
students  of  Columbia  Col- 
lege        93 

Chamber's  science  manuals.    568 


Page. 

Clark,  D.  K.  Elementary 
treatise  on  steam  and  the 
steam  engine 477 

Clarke,  G.  S.  Practical  ge- 
ometry and  engineering 
drawing 381 

Collins,  J.  H.  Principles  of 
metal  mining 95 

Croll.  J.  Climate  and  time 
in  their  geological  rela- 
tions     476 


Dawnay,  A.  D.  Treatise  ou 
railway  signals  and  acci- 
dents     190 

Day,  R.  E.  Examples  on 
heat 569 

DuBois,  Prof.  A.  J.  The 
new  method  of  graphical 
statics 569 

Elliot,  G.  H.  European 
lighthouse  system 190 

Field,  G.  A  grammar  of 
coloring 93 

Frankland,  E.  How  to  teach 
chemistry 381 

Gardner,  C.  C.  Homes,  and 
how  to  make  them— Illus- 
trated homes 477 

Grant,  J.  Strength  of  ce- 
ment      477 

Greenwood,  W.  H.  Manual 
of  Metallurgy '  476 

Heath,  D.  D.  Exposition  of 
the  doctrine  of  energy. ...      95 

Hill,  W.  jN.  Notes  on  cer- 
tain explosive  agents .   ...     381 

Hyde,  E.  W.  Skew  arches  : 
Advantages  and  disadvan- 
tages of  different  methods 
of  construction 286 

Iveson's  horse  power  dia- 
gram      476 

Journal  of  the  Iron  and  Steel 
Institute 477 

Laslett,  Thomas.  Timber 
and  timber  trees      568 

Millar,  W.  J.  Principles  of 
mechanics  and  their  appli- 
cations to  prime  movers . .      95 


Neales'  engineers,  architects 
and  contractors'  pocket- 
books,  for  the  year  1875. . . 


1S9 


Noble,  W.  H.    Useful  tables      93 
Normandy,  A.    Hand  -book 
of  chemical  analysis 95 

Parliamentary  report  on 
gunpowder 568 

Parliamentary  report  on 
scientific  education 568" 

Phin,  J.  Practical  hints  on 
the  selection  and  use  of 
the  microscope 1S9 

Plattner's  manual  of  analy- 
sis with  the  blowpipe 93 

Prestwich,  J.  Past  and  fu- 
ture of  geology 477 


Rice,  J.  M.  and  Johnson,  YV. 
W.  New  method  of  ob- 
taining the  differential 
functions 477" 

Roper,  S.  Hand-book  of 
land  and  marine  engines. .    1S9 

Rutledge,  Robt.  Discover- 
ies and  inventions  of  the 
nineteenth  century 568 


Sang,  E.    Applied  science . .     479 

Sevedelius,  G.  Hand-book 
for  charcoal  burners 476 

Sexton,  J.  Pocket-book 
for  boiler  makers  and 
steam  users 477 

Sharp,  S.  Rudiments  of  ge- 
ometry     381 

Shelton,  W.  V.  Mechanics" 
guide 3S2 

Smith,  C.  G.  Engineering 
papers 4?8 

Spon,  E.  Present  practice 
of  sinking  and  boring  wells    478 

Thurston,  R.  H.  The  me- 
chanical engineer:  His 
preparation  and  his  work.    478 


Valerius,  B.  Traite  theo- 
rique  et  practique  de  la  fa- 
brication du  fer  et  de 
Faciei- 

Verdet,  E.,  works  of 

Vincent,  C.  W.  "i  ear  book 
of  facts  in  science  and  arts 

Viollet-le-Duc,  E.  E.  Dis- 
courses on  architecture. . . 


Walker,  J.  Prime  cost  keep- 
ing, for  engineers,  iron 
founders,  boiler  and  bridge 
makers,  etc 

Warren,  S.  E.  Problems  in 
stone  cutting 


479 
477 


1S9 
568 


139 
4T6 


II 


CONTENTS. 


Page. 

M  atson,  W.  Course  in  de- 
scriptive geometry 93 

Watts,  H.  Dictionary  of 
Che  Lists? 381 

Welch,  E.  J.  C.  Designing 
valve  gearing 47S 

W  iL'hwick,  6.  Hints  to 
young    architects 189 

Young  seaman's  manual, 
compiled  for  the  use  of 
the  T.  S.  training  ships 
and  the  marine  schools 188 


Brake  experiments 565 

Brake  trials 92 

Breechloading  ordnance 137 

Bridge  accidents,  means  of  avert- 
ing   305 

Bridge  and  tunnel  centres 385,  481 

Bridge  in  Paris 313 

Bricks  and  brick  drying 383 

Brightening  iron 1S4 

Brilliant  experiment  in  railway 

warfare 474 

Building  materials 73 

Building,  new  materials  for 209 

Buildings,  protection  of 43 

Building  stones 499 


Calcutta,  drainage  of 180 

Carburation  of  iron 281 

Castalia,  the  steamer 567 

Casting  metals '. 191 

Cast  iron  chilled  wheels  for  car- 
riages    376 

Cleopatra's  needle 288 

Cleveland  and  the  World's  iron 

trade 2S 

Channel  tunnel 541 

Chemical  value    of   iron    water 

pipes 96 

Coignet  Beton  "  en  masse  " 203 

Compass,  Peaucellier  compound  81 

Consumption  of  iron  per  capita.  350 

Construction  of  ellipses 518 

Converted  Rodman  gun 298 

Copper    pyrites,    extraction    of 

precious  metal  from 177 

Coupled  locomotives 515 


Bank's  furnacejn  America 184 

Danube ,  Engineering  on 276 

Data  concerning  the  Mississippi 

River 275 

Dephosphorization  of  iron  ores.  376 

Deep  silver  mine 480 

Denver  and  Rio  Grande  road 185 

Deutschland 380 

Diamond  rock-boring 883 

Dimensions  of  the  earth 192 

"  Direct  Process  "  in  iron  manu- 
facture   313 

Disc  for  cutting  steel  rails  cold . .  96 

Domestic  motors 13 

Double  Float  and  river  gauging.  97 

Double  float,  use  of 563 

Drainage 147,  233,  353,  401 

Drainage  of  Calcutta ISO 

Drainage  of  Paris 547 

Drainage  of  the  Thames  valley . .  20S 

Drainage,  system  of  io\vn 426 

Durdhani  Down  tunnel 366 


Egyptian  Railway 312 

Egypt,  public  works  in 495 

Electrical  resistance  of  various 

metals , 384 

Elementary  discussion  of  strength 

of  beams 164,  193,  2S9,  401 

Ellioses,  construction  of 518 

Embankments  and  reservoirs .  .•.  491 

Emissive  power  of  the  sun 96 

Engineering  on  the  Danube 276 

Engineering  projects  in  Egypt . .  92 
Engineering  science,  origin  and 

growth  of 456 

Engine,  marine „ 257 


Page. 

English  lighthouses 140 

Enormous  engines 185 

Expansion  of  substances  on  so- 
lidification   521 

Experiment  with  wooden  rails..  474 

Explosions,  dynamite,  &c 384 

Explosions,  nitro-glycerine 25 

Extension  of  telegraphy  in  France  415 
Extiaction  of  the  precious  metals 

from  copper  pyrites 177 

Fast  railway .  travel 378 

Field   artillery   experiments   at 

Dartmoor 380 

Fuel  and  iron 564 

Fusion  of  styles 299 

Future  of  architecture 134 

Girders,  strains  in 65 

Glass,  toughened 416 

Graphical  statics,  application  to 

thearch 341 

Gunboat  Flotilla  on  the  Rhine...  1S8 

Gun,  converted  Rodman 298 

Gun,  the  eighty-one  ton 566 

Gunnery,  naval 15 

Hand  pumps 191 

Heat  absorbed  by  expansion ....  435 

Horse  power  of  the  world 192 

Hydraulic  double  float 330 

Hydraulic  engineering  in  India.  566 

Hyperbolic  wheels 536 

Improvements  in  tramways 378 

Improvement  of  the  Tiber 186 

Incrustation  of  boilers 480 

Incrustation  in  locomotives 185 

Indian  trigonometrical  survey  . .  367 
Inductive  magnetism  in  soft  iron  327 
Interesting  and  important  dis- 
covery   474 

Institution  of  civil  engineers. . . .  375 

Iron  and  steel  institute 56 

Iron  arched  bridges 186 

Iron  as  a  constructive  material..  371 

Iron,  consumption  of 350 

Iron  manufacture,  "  direct  pro- 
cess" in 313 

Iron  ores  of  Sweden 159 

Iron,  ores  of 83 

Iron,  relations  of  Titanium  to. . .  544 

Iron,  spongy 301 

Iron  trade,  Belgian 570 

Iron  trade  of  Cleveland  and  the 

world 28 

Iron  trade 564 

Kansas  City  bridge 284 

King's  College  Engineering  So- 
ciety   1S4 


Length  of  railways  in  Russia. . . .  185 

Lighthouses  and  wreck  signals . .  188 

Lighthouses,  English 140 

Light  hydraulic  motor 4S0 

Lime 20 

Lime  in  the  blast  furnace 509 

Locomotives ,  coupled 515 

Magnetic  ores  of  New  Jersey. . .  217 

Marine  engine  of  to-day 257 

Magnetism,  inductive 327 

Manufacture  of  Bessemer  steel. .  143 

Manufactories 424 

Materials  refractory 497 

Manufacture  of  glass 96 

Manufacture  of  steel  in  France..  474 
Maritime  attacks  by  torpedoes..  252 
Master  Mechanics  Association. .  281 
Means  of  averting  bridge  acci- 
dents   305 

Mechanic;  1  aids  to  puddling 473 

Mechanical  changes  in  Bessemer 

steel 346 


Page. 

Merchant  navies 286 

Mines  and  iron  works   of   the 

I  nited  States 35 

Mississippi  improvements 379 

ppi  Valley,  submersible 

lands  of IT 

Molecules 421 

Motors,  domestic "13 


Narrow  gauge  in  Switzerland. .  •  378 

Naval  great  guns  and  gunnery.. .  15 

New  Clyde  graving  dock .92 

New  materials  for  building 209 

New  metal  element 570 

New  method  of  developing  mag- 
netism   232 

New  Russian  gun 480 

New  signaling  apparatus 183 

New  York  Society  of  Practical 

Engineering 375 

Nitro-glycerine  explosions 25 

Notes  on  a  visit  to  mines  and 
iron  works  in  the  United 

States 35 

Notable  railway  bridge 187 


Origin  and  growth  of  engineer- 
ing science 466 

Ores,  iron,  of  Sweden 159 

Ores,  magnetic ._.  217 

Ores  of  iron  considered  in  their 

geological  relations 83 

Paris  drainage 547 

Paris,  sewage  of 32 

Pavement,  roadway 451 

Pine  timber 443 

Plummet  lamp 382 

Preservation  of  sodium 297 

Production  of  iron  and  steel. . . .  473 
Production  of  pig  iron  in   the 

United  States 184 

Protection   of    buildings    from 

lightning 43 

Public  works  in  Egypt 495 

Public  works  in  Jamaica 186 

Puddling,  Rotary 278 

Purifying  iron 3T6 

Railway  accidents. 120 

Railway  accidents  in  Great  Bri- 
tain   18« 

Railway  gauges 117 

Railroads  in  China 191 

Rapid  printing 192 

Railw  ay  safety  appliances 506 

Railway  to   unite    Greece   and 

Turkey 496 

Railroad  300  feet  above  a  city... .  378 
Reclamation  of  the  submersible 
lands    of   the   Mississippi 

Valley 17 

Refractory  clay 3 383 

Refractory  materials 497 

Relations  of  Titanium  to  iron. . .  544 
Remarkably  large  yield  of  pig 

iron 472 

Reservoirs  and  embankments. . .  491 
River  gauging  and  the  double 

float 97 

River  ganging 563 

Rivers  and  manufactories 424 

Roaaway  pavement 451 

Rotary  puddling 278 

Rotary  puddling  furnaces 192 

Sewage  of  Paris 32,  284 

Ships,  resistance  of 438 

Signalling  on  the  Ge;man  rail- 
ways    420 

Society  of  Engineers '. . .  88 

Sodium,  preservation  of 297 

Spongy  iron 301 

Stability  of  arches 226 

Steamers  for  Hayti 188 

Steam  magnet 28T 

Steam,  utilization  of 40 


CONTEXTS. 


Ill 


Page. 

Steel  axles 899 

Steel  for  Cannon 191 

Steel  Institute 56 

Steel,  manufacture  of  Bessemer,  143 
Steel,    mechanical    changes    in 

Bessemer 346 

Steel  rails 283 

Steel  rails  for  California 91 

Steel  rails  in  Italy 480 

Steel,  tests  of 229 

Steel,  use  of 550 

Steel  works  of  Frederick  Krapp,  3T6 

St.  Gothard  Tunnel 380 

Stones,  building 499 

Strains  in  continuous  girders. . .  65 
Strength  of  beams  under  trans- 
verse loads. . .  .164,  193,  289,  401 

Styles,  fusion  of 299 

Substances,  expansion  of 521 

Suez  Canal 379 

Survey,  Indian  367 

Survey,  United  States  Coast 1 

Testing  railway  steel  axles 399 


I  Page. 

!  Tests  of  steel 229 

I  Tests  of  the  strength  of  iron  and 

steel 90 

The  Alexandra 285 

Theories  of  Voussoir  arches 514 

Theory  of  Ventilation 332 

i  Timber,  pine 443 

Torpedo  boat  lor  the  Austrian 

Government 475 

Torpedo  experiments 92 

Torpedoes,  maritime  attack  by.  252 

Toughened  glass 416 

I  Traction  engines  on  roads 283 

Tramways  of  Paris 565 

Trial  trip  of  the  Solimoes 285 

Tunnel  centres 385,  481 

1  Tunnel  channel 541 

j  Tunnel  under  London  docks  . . .  566 

j  Tunis  expedition 379 

i  Twentieth    iron    steamship    of 

Roach  &  Son 285 

United  States  Treasury  Depart- 
ment   517 


U.   8.   Commission    of   Testing 

Metals 282 

U.  8.  Navy 188 

Use  of  rail   ends   in  blast  fur- 

naces 472 

Utilization  of  slag 377 

Use  of  steel 5.7j 

Utilization  of  waste  steam 40 

Utilizing  furnace  slag 281 

Valves,  balanced 436 

Vanguard,  the  steamship 567 

Ventilation  and  Air 109 

Ventilation,  by  vertical  shafts. . .  223 

Ventilation,  theory  of 332 


Water  contrivances  in  India 566 

Water  supply  and  drainage, 

147,  233,  353,  401 

Wheels,  hyperbolic 536 

!  White  brass  bearings 283 

i  Wonderful  engineering 475 


VAN     NO  STRAND'S 

ECLECTIC 

ENGINEERING    MAGAZINE. 


NO.  LXXIX -JULY,  1875 -VOL.  XIII. 


THE  UNITED   STATES  COAST  SURVEY. 

By  GEO.  L.  VOSE,  C.  E. 
"Written  for  Van  Nostrand's  Magazine. 


The  frequenter  of  any  of  our  larger 
libraries  may  have  seen  upon  the  lowest 
shelf  of  some  out-of-the-way  alcove  a 
group  of  substantial  quartos  clothed  in  sol- 
emn black  and  wedged  tightly  in  by  other 
heavy  volumes,  all  of  them  bearing  the 
most  unmistakable  evidence  of  enjoying 
a  dignified  repose  and  of  being  very  sel- 
dom called  for.  If  the  visitor  should  draw 
out  one  of  these  huge  quartos,  blow  the 
dust  from  the  upper  edges  of  the  leaves 
and  lay  the  volume  open,  he  would  find, 
perhaps,  half  its  thickness  taken  up  by 
various  maps,  any  one  of  which,  should 
he  be  rash  enough  to  unfold  it,  will  be  a 
good  exercise  of  his  skill  and  patience  to 
fold  up  again.  If  he  turns  to  the  text 
he  will  find  himself  involved  in  a  mass 
of  complex  formula  and  elaborate  dis- 
cussions of  various  highly  scientific  sub- 
jects, the  very  language  of  which,  for 
the  most  part,  he  will  fail  to  compre- 
hend. By  this  time  he  will  be  very  apt 
to  have  seen  enough,  and  will  gladly 
return  the  volume  to  its  resting-place, 
where  it  will  continue  its  long  slumber 
and  accumulate  a  new  coating  of  dust. 

This  group  of  neglected  volumes  can- 
not be  purchased  for  any  money.  Proba- 
bly no  man  except  the  proof  reader  has 
ever  read  one  of  them  through,  and  yet 
they  are  a  mine  of  wealth  to  the  student 
of  science,  a  noble  monument  of  consum- 
mate skill  and  of  patient  industry,  of 
Vol.  XIII. —No.  1—1 


long-continued  toil  and  untiring  devotion 
to  duty.  Learned  men  the  world  over 
have  been  glad  to  do  honor  to  the 
authors.  The  results  recorded  are  of 
immense  importance  alike  to  the  farmer, 
the  merchant,  and  the  manufacturer. 
We  have  moreover  in  these  volumes  a 
remarkable  example  of  the  practical  im- 
portance of  the  most  abstract  scientific 
research;  an  illustration  of  the  general 
law  that  the  conscientious  investigation 
of  truth  for  its  own  sake  shall  be  re- 
warded by  some  unforeseen  practical 
benefit.  The  works  to  which  we  refer 
are  the  "Reports  of  the  United  States 
Coast  Survey,"  and  from  these  docu- 
ments and  other  scientific  publications 
we  propose  to  extract  such  facts  as  will 
show  to  the  reader  something  of  the 
objects,  the  methods  and  the  results  of 
the  organization  which  has  employed 
the  best  scientific  talent  of  America  for 
upwards  of  twenty  years,  and  has  pro- 
duced results  which  are  no  less  remarka- 
ble for  their  high  scientific  character 
than  valuable  to  the  industry  of  the 
country. 

That  commerce  is  of  vast  importance 
to  any  nation,  and  especially  so  to  an 
isolated  country  like  America,  the  reader 
does  not  need  to  be  told,  nor  will  he 
fail  to  see  that  the  more  the  risks  attend- 
ing navigation  are  reduced,  the  better, 
not  only  for  those  directly  engaged  in 


VAN   NOSTRAND  S   ENGINEERING   MAGAZINE. 


commerce,  but  also  for  })roducers  in  every 
part  of  the  land.  Indeed,  so  closely 
interwoven  are  the  different  branches  of 
human  industry  that  what  affects  com- 
merce affects  all.  The  results  of  the  Coast 
Survey  are  thus  not  less  important  to 
the  interior  than  to  the  seaboard  states. 

Prominent,  if  not  chief,  among  the 
dangers  of  the  deep  are  the  reefs  and 
shoals,  the  tides  and  currents  that  fringe 
the  borders  of  the  land.  With  a  plenty 
of  room  and  deep  water  the  sailor  has 
comparatively  little  to  fear.  It  is,  there- 
fore, of  special  importance  that  the  outline 
of  the  coast  should  be  mapped  with  the 
utmost  exactness,  and  more  than  this, 
that  the  knowledge  of  the  nature  and 
shape  of  the  bottom  from  the  shore  out 
to  the  deep  sea  should  be  very  complete, 
the  more  so  as  all  beneath  the  water  is 
hidden  from  sight  and  can  only  be  shown 
to  the  navigator  by  correctly  prepared 
charts.  In  clear  weather,  even  though 
it  be  night,  we  may  find  no  difficulty  in 
working  into  a  harbor  provided  with 
suitable  beacons  and  lights  ;  but  in 
stormy  weather,  and  worse  yet,  when  all 
signals  are  swallowed  up  by  impenetra- 
ble mists,  the  case  is  very  different,  and 
just  here  is  where  the  admirable  charts 
of  the  Coast  Survey  come  in  to  take  the 
tired  mariner  by  the  hand  and  lead  him 
amongst  rocks  and  shoals  and  shifting 
<currents  to  an  anchorage  where  he  may 
lay  firm  hold  of  the  land,  safe  from  the 
dangers  of  the  deep. 

The  two  principal  objects  of  the  Coast 
Survey  are  thus  plainly  seen,  viz. — first, 
to  make  an  absolutely  exact  map  of  the 
■outline  of  the  coast,  and,  second,  to  pre- 
pare charts,  which  extending  from  the 
coast  line  out  to  deep  water  shall  give 
the  sailor  as  clear  a  knowledge  of  the 
nature  and  shape  of  the  bottom  as  if  the 
sea  was  drawn  off  and  its  bed  laid  bare. 

For  the  determination  of  points  upon 
a  coast  reaching  over  many  degrees  of 
latitude  the  ordinary  methods  of  survey- 
ing are  not  at  all  applicable.  Surveys  made 
upon  the  assumption  that  the  surface  of 
the  earth  is  a  plane  would  be  so  incorrect 
as  to  be  worse  than  useless;  and  not  only 
is  it  necessary  to  take  into  account  the 
spherical  form  of  the  globe,  but  still 
farther  the  flattening  of  the  sphere  at 
the  poles  must  be  regarded  or  we  do 
not  obtain  a  sufficiently  exact  result. 
All  of  this  precision  in  the  requirement 


demand  a  corresponding  amount  of  sci- 
entific knowledge  and  practical  skill  in 
the  execution  of  the  work.  In  fact,  the 
making  of  the  outline  map  of  the  coast 
has  drawn  upon  all  departments  of 
Astronomy  and  Physics,  and  not  only 
has  the  Coast  Survey  availed  itself  of 
all  that  was  known,  but  it  has  invented 
new  instruments  and  new  methods  of 
observation  and  of  computation  which 
have  been  adopted  by  astronomers  both 
in  this  country  and  in  Europe. 

It  will  be  evident  at  the  outset  that  it 
would  be  impracticable,  if  not  impossi- 
ble, to  determine  the  distance  from  point 
to  point  along  the  coast  by  direct  meas- 
urement with  a  chain  or  other  apparatus; 
for  not  only  would  such  a  line  pass 
through  swamps  and  woods  and  even 
into  the  water,  but  following  the  general 
trend  of  the  coast  it  would  be  very 
crooked,  and  unless  each  change  of 
direction  was  exactly  determined  we 
should  not  only  make  errors  in  the  posi- 
tion of  our  line,  but  such  errors  would 
be  carried  along,  and  accumulating, 
would  so  distort  the  survey  that  when 
we  undertook  to  lay  our  work  upon  the 
plans  we  should  find  a  wide  difference 
between  the  position  of  the  various 
points  as  given  by  our  measurements, 
and  the  position  of  the  same  points  as 
determined  by  fixing  their  latitude  and 
longitude  by  astronomical  observation. 
The  methods  employed  for  locating  the 
principal  points  along  the  coast  avoids 
all  such  errors,  and  also  saves  much  time 
and  expense.  The  principle  involved  is 
the  most  elementary  one  in  Trigonome- 
try, viz. — that  when  we  know  one  side 
of  a  triangle  and  two  angles  we  can 
compute  the  remaining  side.  An  exten- 
sion of  this  simple  principle,  carried  out, 
of  course,  with  all  the  refinements  of 
modern  science,  gives  what  is  termed 
the  Primary  Triangulation,  the  extent 
and  nature  of  which  will  be  understood 
from  the  following  sketches,  in  which 
Fig.  1  shows  the  commencement  of  the 
work  resting  on  the  Massachusetts  Base, 
and  Fig.  2  the  whole  system  from  East- 
port  to  Nantucket.  In  Fig.  1  AB  is  a 
line  on  the  Boston  and  Providence  Rail- 
road about  ten  miles  long,  measured 
with  the  utmost  accuracy  as  hereafter 
described.  From  C,  A,  and  B  the  several 
angles  of  the  triangle  ABC  are  measured, 
and  thus  the  remaining  sides  AO   and 


THE   UNITED   STATES   COAST  SURVEY. 


BC  become  known.  Next,  from  the 
stations  D,  A,  and  C  the  angles  of  the 
triangle   ACD   are  measured,  and   also 


two  angles  of  the  triangle  CDE,  E  being 
a  station  on  one  of  the  Blue  Hills  in 
Milton.     From    this  point,   as   well   as 


from  C,  angles  are  measured  to  F  and 
G,  and  by  computation  the  lengths  of 
all  the  lines  represented  in  the  sketch 
become  as  accurately  known  as  if  they 


had  been  measured  directly.  In  the 
same  way  the  triangulation  is  continued 
as  in  Fig.  2,  which  shows  the  triangles 
of  the  first  order  from  Passamaquoddy 


U.  S.  COAST  SURVEY. 

SKETCH  OF  THE 
TRIANGLES  of  the  1st  ORDER 
from 
EASTPORT  TO   NANTUCKET 


^Y   NANTUCKET 


VAN   NOSTRAND'S   ENGINEERING   MAGAZINE. 


Bay  to  Nantucket,  A  being  the  Grand 
Menan,  D  Mount  Desert,  F  Ragged 
Mountain,  at  Camden,  I  Mount  Blue,  at 
Farmington,  J  Pleasant  Mountain,  in 
Denmark,  K  Mount  Independence,  near 
Portland,  L  Mount  Washington,  M  Aga- 
menticus,  near  Portsmouth,  N  Gunstock, 
at  Lake  Winnepesaukee,  O  Unkonoonuc, 
near  Manchester,  P  Monadnoc,  in  Che- 
shire County,  N.  H.,  Q  Thompson's  Hill, 
Gloucester,  K  Wachusett,  in  Princeton, 
S  Blue  Hill,  in  Milton,  T  Beaconpole,  U 
Copecut  Hill,  V  Manomet,  W  Indian 
Hill,  on  Martha's  Vineyard,  X  a  station 
on  Cape  Cod,  and  Y  a  point  on  Nan- 
tucket. The  Massachusetts  Base  with 
its  triangles  is  shown  at  T,  but  on  a  very 
small  scale.  * 

By  this  method  of  proceeding  we  fix 
the  position  of  the  several  points  with 
great  exactness,  regarding  both  the 
globular  form  of  the  earth  and  also  the 
flattening  of  the  globe  at  the  poles;  and 
when  we  say  with  great  exactness  we 
mean  within  a  few  inches.  It  may  be 
asked  how  we  know  that  our  points  are 
within  so  short  a  distance  of  being  abso- 
lutely correct.  We  know  it  by  selecting 
a  suitable  place  on  the  ground  near  the 
end  of  our  series  of  triangles  and  meas- 
uring a  line  five  or  six  miles  long  with 
the  utmost  care.  This  line  is  then  con- 
nected with  our  primary  triangulation 
so  that  we  can  also  obtain  its  length, 
independently  of  actual  measurement, 
by  computation.  The  calculated  and 
measured,  lengths  should,  of  course,  be 
alike.  Such  a  line  is  called  a  Base  of 
Verification,  and  when  it  is  remembered 
that  a  single  false  step  in  the  whole  im- 
mense chain  of  triangles  would  prevent 
this  final  agreement,  we  can  appreciate 
the  splendid  practical  science  of  the  offi- 
cers of  our  Coast  Survey,  which  starting 
from  its  primary  base  and  working 
through  a  chain  of  triangles  over  three 
hundred  miles  long,  should  vary  no  more 
than  three  or  four  inches  in  a  base  of 
verification  five  and  one-half  miles  in 
length.  Such  results  as  this  are,  of 
course,  only  obtained  by  long-continued 
observations,  with  the  most  refined  in- 
struments, in  the  hands  of  the  most 
skillful  observers.  The  base  of  verifica- 
tion for  the  New  England  chain  of  tri- 
angles is  a  line  about  five  and  one-half 
miles  long  on  Epping  Plains,  in  Maine, 
and  is  shown  in  Fig.   2   by   the   short 


heavy  line  in  the  triangle  C  D  E.  The 
triangles  connecting  this  line  with  the 
points  C,  D,  and  E  are  not  shown  on  ac- 
count of  the  small  scale  to  which  our 
figure  is  drawn. 

It  will  be  observed  that  the  triangles- 
in  Fig.  2  are  very  large,  the  sides  of 
some  of  them  being  as  long  as  seventy 
miles.  This  is  desirable,  in  order  that  the 
number  of  measurements  may  be  few  as 
possible,  and  the  chance  of  error  reduced. 
The  large  theodolite  used  in  the  measure- 
ment of  angles  has  a  thirty-inch  circle 
divided  to  five  minutes,  and  reading  by 
the  microscopes  to  single  seconds.  The 
telescope  is  of  great  power  and  partly 
suppported  by  springs  within  the  up- 
right columns,  which  bear  the  axis  to 
relieve  the  bearings  from  friction.  The 
weight  of  the  upper  part  is  to  a  consider- 
able extent  borne  by  friction  rollers, 
which,  taking  the  weight  from  the  verti- 
cal axis,  allow  a  very  easy  horizontal 
motion.  This  fine  theodolite  was  de- 
signed by  Mi-.  Hassler  and  made  by 
Troughton  &  Simms,  of  London.  There 
are  many  causes  of  slight  error  even 
with  the  best  instruments  in  measuring 
an  angle.  Indeed,  it  is  not  possible  to 
measure  an  angle  with  absolute  correct- 
ness; but  by  multiplying  the  observa- 
tions the  error  is  reduced  to  a  very 
small  amount,  and  mathematicians  can 
tell  with  certainty  what  the  probable 
error  will  be  from  any  number  of  ob- 
servations. With  the  large  theodolite 
above  mentioned  the  probable  error  of  a 
single  measurement  of  an  angle  is  about 
one  and  one-fourth  seconds,  and  the 
mean  of  thirty  measurements,  the  usual 
number  made,  about  one-fourth  of  a 
second. 

In  order  to  measure  exactly  an  angle 
between  two  points  these  points  must  be 
very  closely  defined.  For  short  distances 
and  ordinary  work  the  signal  employed 
by  the  Coast  Survey  is  a  cone  of  tin 
fastened  on  top  of  a  pole;  but  for  the 
larger  triangles  and  for  long  distances 
an  instrument  called  a  heliotrope  is  used. 
This  consists  of  a  small  mirror  so  mount- 
ed with  a  telescope  that  the  reflection  of 
the  sun  may  be  thrown  in  any  desired 
direction.  This  reflection  will  often  be 
seen  eighty  or  ninety  miles  away  when 
the  outlines  of  mountains  are  entirely 
invisible  on  account  of  haze.  The  heli- 
otrope is  also  used  for  telegraphic  com- 


THE    UNITED   STATES   COAST   SURVEY. 


r> 


munication;  as  by  passing  the  hand  rap- 
idly in  front  of  it  the  reflection  is  for  a 
moment  cut  off,  and  a  code  of  signals 
made  by  a  combination  of  short  and 
long  flashes  has  been  found  sufficient  for 
transmitting  messages. 

By  what  has  preceded  it  will  be  seen 
that  every  thing  in  the  Primary  Triang- 
ulation  depends  upon  the  accuracy  with 
which  the  Base  Line  is  measured.  Now, 
while  we  can  easily  measure  an  angle 
over  a  hundred  times,  if  necessary  to  en- 
sure accuracy,  we  cannot  repeat  so  many 
times  the  measurement  of  a  line  without 
consuming  unwarrantable  time.  Again, 
as  the  base  which  may  be  ten  or  twelve 
miles  long  is  measured  with  a  bar  not 
more  then  twenty  feet  in  length;  if  the 
bar  is  not  exactly  correct  we  shall  multi- 
ply the  error,  say  three  thousand  times. 
Thus  it  is  that  the  correct  measurement 
of  the  base  line  is  an  object  of  so  much 
importance,  and  that  the  construction  of 
the  apparatus  calls  for  all  the  skill  both 
of  the  designer  and  the  maker.  A  sim- 
ple iron  bar  may  be  used  for  the  meas- 
urement of  distances,  but  such  a  bar  is 
affected  to  a  greater  or  less  extent  by 
heat,  and  although  we  may  keep  a  record 
of  the  temperature,  the  thermometer  be- 
comes heated  much  sooner  than  the  bar, 


and  thus  does  not  give  the  correct  allow- 
ance to  be  made  for  the  expansion  of  the 
metal.  To  overcome  this  difficulty  the 
compensation  obtained  by  combining  two 
different  metals  may  be  employed,  but 
we  shall  still  make  an  error,  as  different 
metals  do  not  undergo  equal  changes  of 
temperature  in  equal  times,  on  account 
of  the  different  absorbing  powers  of  their 
surfaces,  their  different  powers  of  con- 
ducting heat  from  the  surface  to  the  in- 
terior of  the  mass  and  the  difference  in 
the  total  quantity  of  heat  which  they 
can  take  up,  or  their  specific  heats.  The 
same  coating  of  varnish  upon  both  bars 
will  give  them  equal  absorbing  powers; 
and  by  so  arranging  the  sections  of  the 
two  bars  that  while  the  amount  of  sur- 
face is  the  same  the  masses  shall  be 
inversely  as  the  specific  heats,  a  small 
allowance  being  also  made  for  their 
different  conducting  rates,  a  system  is 
formed  which  not  only  retains  the  same 
length  at  all  temperatures,  but  what  is 
no  less  important,  during  all  changes  of 
temperature. 

We  give  in  Fig.  3  a  sketch,  half  full 
size,  showing  one  end  of  the  base  appa- 
ratus as  finally  arranged  for  use  on  the 
Coast  Survey.  A  bar  of  brass  and  a 
bar  of  iron,  each  about  twenty  feet  long, 


are  fastened  together  at  one  end,  but  at 
all  other  points  are  unconnected,  except 
that  the  upper  one  rests  on  the  lower  by 
means  of  little  rollers.  Thus  both  bars 
are  free  to  expand  at  their  own  special 
rates.  In  Fig.  3  the  free  ends  of  the 
bars    are  represented  by  A  and  B,  the 


upper  one  being  of  iron  and  the  lower  of 
brass.  The  end  of  a  short  lever,  C,  is 
attached  to  the  lower  bar, .  while  the 
upper  bar  presses  against  it  at  the  point 
D.  A  movement  of  the  upper  end  of 
the  lever  is  communicated  to  the  small 
rod  E,  the  square  point  of  which  is  the 


6 


van  nostrand's  engineering  magazine. 


end  of  the  apparatus.  If  now  we  sup- 
pose the  bar  A  to  remain  stationary 
while  B  expands,  it  is  plain  that  the 
point  of  the  rod  would  be  drawn  back 
to  the  position  shown  in  F.  If  A  ex- 
panded while  B  remained  still,  the  point 
would  be  pushed  ahead  to  the  position 
G.  If  both  bars  expanded  equally  the 
whole  apparatus  would  be  simply  moved 
ahead.  But  if  the  expansion  of  the  two 
bars  is  proportioned  to  the  two  arms  of 
the  lever,  the  expansion  of  the  upper 
bar  will  move  the  point  just  as  much 
ahead  as  the  expansion  of  the  lower  one 
will  draw  it  back.  The  point  will  thus 
remain  on  the  li?ie,  as  at  H,  under  all 
changes  of  temperature.  These  two  bars 
are  supported  from  a  stiff  rib  of  iron, 
and  very  carefully  guarded  from  chance 
of  damage  in  transportation,  the  whole 
being  enclosed  in  a  spar  shaped  covering 
which  serves  as  a  protection  from  the 
sun  and  weather,  making  hi  all  a  shape 
like  that  shown  in  Fig.  4,  where  one  set 


of  bars  with  its  covering  is  seen  support- 
ed upon  two  trestles.  To  measure  a  base 


we  require  two  sets  of  these  bars.  The 
back  end  of  the  first  is  brought  directly 
over  the  starting  point  and  carefully 
leveled  and  alligned.  The  back  end  of 
the  second  is  then  adjusted  exactly  tc 
the  front  end  of  the  first.  The  first  is 
then  carried  to  the  front  of  the  second, 
the  back  end  of  the  first  being  adjusted 
to  the  front  end  of  the  second,  and  thus 
the  operation  continues,  each  s.et  of  bars 
being  in  turn  moved  to  the  front.  The 
arrangements  by  which  the  two  sets  of 
bars  are  brought  not  only  into  exact 
contact,  but  always  into  contact  with 
exactly  the  same  force,  is  not  less  ingen- 
ious than  the  contrivance  for  compensa- 
tion already  described.  The  principal 
feature  of  this  device  is  shown  in  Fig.  5, 
though  in  order  to  convey  the  idea 
clearly  we  have  deviated  somewhat  from 
the  exact  form  and  have  omitted  several 
of  the  details.  A  short  metallic  bar, 
j\I  M,  is  attached  to  the  back  end  of  the 
base  apparatus,  carrying  a  small  sliding 
rod,  G,  terminating  with  an  agate  knife 
edge  at  the  left  hand  end,  while  the 
right  hand  end  bears  against  a  small 
curved  surface  attached  to  the  lever,  E, 
turning  on  a  pin  at  F.  The  upper  end 
of  this  lever  bears  against  the  short 
lever,  D,  turning  on  the  trunnion,  C, 
and  carrying  the  spirit-level,  A,  which  is 
loaded  at  one  end  with  the  weight,  B. 
H  is  the  forward  end  of  the  rod  shown 


in  Fig.  3.  If  now  we  move  the  bar  M 
by  a  delicate  screw  towards  H,  the  pres- 
sure of  G  against  the  lever  E  will  move 


the  lower  end  of  the  short  lever  D 
towards  the  right  and  will  raise  the 
weight  at  B.     If  we  carry  this  operation 


THE   UNITED   STATES    COAST   SURVEY. 


on  until  the  bubble  stands  in  the  middle 
of  the  level,  which  may  be  exactly  de- 
termined by  the  finely  divided  scale  on 
top  of  the  tube,  the  two  rods  will  be  in 
contact  with  a  certain  force.  We  have 
.thus  at  each  new  position  of  the  bars 
only  to  bring  them  together  with  force 
sufficient  to  move  the  bubble  to  the 
middle  of  the  level,  and  the  force  of  con- 
tact will  always  be  the  same.  This  ex- 
ceedingly simple  but  effective  contriv- 
ance may  be  seen  fully  illustrated  in  the 
Coast  Survey  report  for  1854.  So  perfect 
is  the  above  apparatus,  and  so  skillful 
have  the  operators  become,  that  after 
the  ground  has  been  prepared  and  every 
thing  made  ready,  no  less  than  a  mile 
has  frequently  been  measured  in  a  single 
day,  and  with  such  extreme  accuracy 
that  the  probable  error  is  estimated  to 
be  no  more  than  the  fiftieth  of  an  inch. 
At  Bodie's  Island,  in  North  Carolina,  a 
base  line  six  and  three  -  fourths  miles 
long  was  measured  in  ten  working  days 
with  a  total  probable  error  of  less  than 
one-tenth  of  an  inch;  and  the  correct- 
ness of  the  supposed  error  has  frequently 
been  proved  by  the  remeasurement  of  a 
line.  The  place  selected  for  a  base  is 
one  which  is  quite   or   nearly  level,  or 


one  which  can  without  much  expense  be 
made  so,  though  the  base  apparatus  is  so 
arranged  as  to  measure  equally  well 
upon  an  incline  of  as  much  as  three 
degrees. 

The  most  prominent  points  along  the 
the  coast  being  accurately  fixed  by  the 
Primary  Triangulation,  are  used  as  the 
starting  points  for  the  determination  of 
a  secondary  series  of  stations  nearer  to 
the  shore,  and  these  again  for  points 
nearer  to  the  water  line,  and  from  the 
last  of  these  points  the  shore  line  itself, 
and  the  topography  in  detail  are  drawn 
in  by  means  of  the  Plane  Table,  an  in- 
strument which  though  long  known  had 
never  been  so  perfected  in  this  country 
as  to  be  of  much  service  until  in  the 
hands  of  the  Coast  Survey  it  has  become 
an  appliance  well  suited  to  terminate 
the  long  series  of  operations  commenc- 
ing with  the  Primary  Triangulation. 
The  use  of  this  instrument  will  be  well 
understood  by  reference  to  Fig.  6.  Sup- 
pose that  we  have  the  river  BCDE,  of 
which  it  is  required  to  map  the  shore  line. 
At  any  convenient  point,  as  A,  we  place 
upon  the  ground  a  plain  rectangular 
board  supported  upon  a  tripod.  A  sheet 
of  paper  is  fastened  on  top  of  the  table, 


and  on  this  sheet  a  point  A  is  marked  so 
as  to  be  directly  over  the  point  A  on  the 
ground.  Next,  lay  on  the  table  a  ruler, 
one  end  being  placed  against  the  point 
A,  and  the  other  directed  to  any  point 
on  the  ground,  as  B,  which  it  is  desired 
to  put  upon  the  map.  Draw  a  line  along 
the  edge  of  the  ruler.     This  line  on  the 


paper  has  the  same  direction  as  the  real 
line  upon  the  ground.  In  the  same  way 
direct  the  ruler  to  each  point  in  succes- 
sion the  position  of  which  it  is  desired 
to  fix,  and  draw  the  correspondent  lines 
AC,  etc.  If  now  we  knew  the  distances 
from  A  to  each  of  the  points  B,  C.  I),  E 
on  the  ground,   and  laid  off  those   dis- 


VAN   NOSTRAND  S   ENGINEERING   MAGAZINE. 


tances  by  scale  on  the  paper,  and  through 
the  points  thus  obtained  drew  the  irregu- 
lar line,  we  should  evidently  have  a  fac- 
simile of  the  actual  shore  line.  These 
distances  might,  of  course,  be  obtained 
by  measurement,  but  there  is  a  mode  at 
once  more  correct  and  very  much  more 
rapid.  Instead  of  a  simple  ruler  we  em- 
ploy a  brass  bar  on  which  is  mounted  a 
telescope,  the  centre  Hue  of  which  is  ex- 
actly over,  and  parallel  with,  the  edge 
of  the  bar,  so  that  on  looking  through 
the  telescope  we  look  much  more  exact- 
ly in  the  direction  of  the  edge  of  the 
ruler  than  we  could  otherwise.  If  we 
should  look  through  the  telescope  we 
should  see  a  fine  vertical  hair  crossing 
the  field  of  the  glass,  and  also  a  series 
of  three  equi-distant  parallel  horizontal 
hairs.  If  now  we  should  hold  up  a  rod 
in  a  vertical  position  at  any  distance 
from  the  telescope  a  certain  part  of  that 
rod  would  be  included  between  the  upper 
and  the  lower  horizontal  hairs.  If  we 
moved  the  rod  twice  as  far  off,  twice  as 
much  of  its  length  would  be  included 
by  the  hairs.  This  rod  is  divided  into 
equal  parts  by  figures  painted  in  red  and 
black,  so  as  to  be  easily  read  through 
the  telescope  at  considerable  distances. 
Knowing  by  trial  the  number  of  divi- 
sions covered  by  the  hairs  for  different 
distances,  we  tell  at  once  by  looking 
through  the  telescope,  by  the  number  of 
divisions  covered,  the  distance  of  the 
rod  from  the  observer.  If  now  we  send 
an  assistant  with  the  rod  (telemeter)  to 
each  point  in  succession  A,  B,  C,  etc.,  we 
know  precisely  the  distances  which  laid 
off  by  scale  on  the  paper  enable  us  to 
trace  the  shore  line.  The  great  advant- 
age of  the  Plane  Table  method  is  speed 
and  accuracy  ;  for  while  the  rodman  is 
passing  from  A  to  B  the  assistant  at  the 
Table  is  laying  off  the  length  of  the 
first  line  on  the  paper.  By  this  method 
all  obstacles  to  chaining  are  avoided, 
irregularities  in  the  ground  being  no  im- 
pediment, and  indeed  with  two  men,  one 
on  each  side  of  a  river,  both  shores  may 
be  sketched  in  at  the  same  time  to  a 
degree  of  accuracy  and  with  an  amount 
of  detail  altogether  unknown  to  the 
common  methods  of  surveying,  to  say 
nothing  of  the  fact  that  all  chances  of 
error  in  note  taking  are  avoided,  and 
that  when  the  field  work  is  done  the 
plan  is  also  complete;    and  not  only  is 


the  outline  thus  traced,  but  all  of  the 
buildings,  land  boundaries,  and  the  mi- 
nutest details  of  topography  are  filled  in 
with  the  utmost  perfection,  as  may  be 
shown  by  reference  to  the  published 
charts.  Thus,  by  means  of  the  Primary 
Triangulation,  Secondary  Triangulation, 
and  Plane  Table,  we  obtain  a  minutely 
exact  outline  of  the  coast  both  in  its 
general  form  and  in  its  smallest  parts, 
every  most  insignificant  detail  being 
shown  exactly  on  the  paper. 

The  shore  line  being  correctly  mapped, 
we  are  in  condition  to  commence  the 
hydrographic  survey.  This  consists  in 
making  a  sufficient  number  of  soundings 
to  show  correctly  the  shape  of  the  bot- 
tom, to  fix  precisely  the  position  of  all 
sunken  ledges,  bars,  leefs,  and  shoals,  to 
determine  the  nature  of  the  material, 
whether  rock,  sand,  gravel,  mud,  or 
clay,  to  detect  all  currents,  the  set  of 
the  tides,  as  influenced  by  the  shape  of 
the  channels,  and  all  else  that  can  make 
the  route  to  be  followed  by  ships  as 
plainly  known  to  the  sailor  as  a  road 
upon  the  land  is  to  a  traveler.  The  ex- 
act position  of  a  boat  from  which  a 
sounding  is  made  is  easily  found  by 
reference  to  two  fixed  points  upon  the 
land.  The  sounding  lead  is  so  arranged 
as  to  bring  up  a  specimen  of  the  material 
when  it  is  in  any  way  soft,  which,  when 
desirable,  is  put  into  a  small  vial  and  so 
registered  as  to  agree  with  the  map. 
Vast  numbers  of  these  vials  may  be  seen 
in  the  offices  of  the  Coast  Survey,  care- 
fully arranged,  so  that  at  any  future 
time  changes  may  be  detected  in  the 
quality  of  the  submarine  deposit.  Such 
changes,  when  closely  studied,  will  point 
to  their  origin,  and  thus  to  the  means 
of  preserving  the  channel.  It  is  well 
known  that  the  peninsular  of  Sandy 
Hook  in  1855  was  steadily  growing  to 
the  northward  into  the  main  ship  chan- 
nel into  New  York  Harbor.  A  spot 
north  of  the  Hook,  where  formerly  there 
were  forty  feet  of  water,  in  less  than 
ten  years  was  nearly  bare  at  low  tide. 
Within  a  century  this  point  has  advanced 
nearly  a  mile.  A  careful  study  of  the 
locality  by  the  Coast  Survey  has  detected 
the  precise  movements  of  the  various 
currents,  and  shown  just  how  the- sedi- 
ments are  deposited,  and  whence  they 
were  derived,  and  thus  pointed  out  the 
steps   to   be   taken   for  maintaining  an 


THE   UNITED   STATES    COAST   SURVEY. 


g 


open  channel.  The  immense  amount  of 
labor  expended  in  the  hydrographic 
part  of  the  survey  may  be  understood 
by  a  glance  at  any  of  the  published 
charts.  The  number  of  soundings  thus 
far  made  has  reached  about  eight  mil- 
lions. One  hundred  and  forty  shoals 
and  reefs  and  fifty  important  channels 
not  before  known  have  been  discovered, 
and  accurately  located,  and  the  position 
of  many  hundred  isolated  rocks  and 
ledges  correctly  represented  upon  the 
charts. 

The  field  work  being  completed,  the 
work  of  computing,  digesting,  and  ar- 
ranging the  results,  as  well  as  the  draw- 
ing and  engraving,  is  done  in  the  offices 
at  Washington.  And  here,  too,  the 
Coast  Survey  has  made  a  most  important 
improvement,  viz. — in  the  application  of 
photography  to  the  reduction  of  maps, 
by  which  the  utmost  accuracy  and  fidel- 
ity to  the  original  are  secured  with 
speed  and  economy. 

The  designing  and  construction  of  the 
various  instruments  have  also  received  a 
great  deal  of  attention,  the  result  of 
which  may  be  seen  in  the  splendid  work 
of  Wurdemann,  which  is  unsurpassed  by 
that  of  any  maker  in  the  world.  Indeed, 
some  of  the  new  patterns  of  field  instru- 
ments have  been  sent  to  Europe  for  ge- 
odetic purposes,  being  found  better 
adapted  to  such  work  than  any  others  in 
use. 

With  regard  to  the  charts,  nothing 
but  an  examination  of  these  admirable 
sheets  can  convey  an  idea  of  the  amount 
of  labor  and  skill  involved  in  their  prepa- 
ration. Every  natural  feature  both  on 
land  and  beneath  the  water  is  shown, 
with  the  position  and  description  of 
lights,  beacons,  buoys,  and  signals  of 
every  kind,  the  course  of  the  channels 
and  character  of  the  bottom,  and  minute 
sailing  directions  for  entering  harbors, 
aided  by  marginal  landscape  sketches, 
showing  the  general  appearance  of  the 
shore  from  different  points  of  approach,all 
of  which  can  be  appreciated  only  by  those 
whose  needs  have  taught  them  the  value 
of  a  sure  guide  which  shall  never  fail 
in  summer  or  winter,  by  day  or  by 
night,  in  sunshine  or  in  storm. 

Besides  its  own  special  work,  the  Coast 
Survey  has  rendered  the  most  important 
services  to  almost  every  department  of 
science  and  art.     Its  discussions  of  the 


tides,  winds,  and  ocean  currents,  its  ex- 
ploration of  the  Gulf  Stream,  its  observa- 
tions upon  the  rise  and  fall  of  coast  lines, 
its  exhaustive  investigations  of  the  com- 
plex phenomena  of  terrestial  magnetism, 
have  all  served  to  augment  immensely 
our  knowledge  of  the  physics  of  the 
globe.  Its  magnificent  triaugulation  has 
furnished  accurate  base  lines  for  state 
surveys  and  for  geodetic  operations  in 
all  parts  of  the  country.  The  Depart- 
ment has  also  been  exceedingly  serviceable 
in  supplying  a  great  variety  of  valuable 
information  to  private  investigations,  to 
learned  institutions,  and  to  officers  of. 
public  works,  and  upon  proper  occasions 
both  men  and  instruments  are  freely 
lent  for  aiding  any  scientific  operations 
in  any  part  of  the  country. 

Probably  the  most  remarkable  result  ob- 
tained by  the  Primary  Triangulation,  cer- 
tainly one  which  shows  the  extreme  accu- 
racy of  the  work,  is  the  evidence  obtained 
as  to  the  figure  of  the  earth.  In  order  to 
represent  correctly  on  a  map  the  work 
done  upon  the  ground,  the  latitude  and 
longitude  of  the  several  points  are  re- 
quired. When  these  latitudes  are  found 
by  astronomical  observation,  their  posi- 
tion is  shown  to  be  not  exactly  the  same 
as  when  determined  by  the  geodetic 
work.  These  "  station  errors,"  as  they 
have  been  termed,  are  found  after  care- 
ful examination  to  arise  from  the  fact 
that  certain  irregularities  exist  both  in  the 
figure  and  in  the  density  of  the  earth; 
and  wonderful  to  relate,  there  appears 
to  be  a  close  connection  between  the 
amount  of  this  "  station  error  "  and  the 
amount  of  gelogical  disturbance  to  which 
the  rocks  in  the  different  sections  have 
been  subjected. 

Another  most  marked  advance  in  sci- 
ence due  to  the  Coast  Survey  is  the 
electro-magnetic  method  of  determining 
longitude.  The  latitude  of  a  place  is 
obtained  with  comparative  ease,  but 
correctly  to  determine  longitude  has 
always  been  a  difficult  operation.  By 
the  improvements  introduced  by  the 
Coast  Survey  longitude  is  now  as  accu- 
rately determined  as  latitude,  and  this 
new  mode,  known  as  "  The  American 
method,"  and  which  has  been  introduced 
and  highly  approved  in  Europe,  has 
justly  been  pronounced  "  one  of  the 
greatest  improvements  in  practical  as- 
tronomy known   to  the   history  of  the 


0 


TAX   NOSTRAND  S   ENGINEERING   MAGAZINE. 


science,  enabling  the  observer  to  do  in  a 
given  time  quadruple  the  work  possible 
without  it  with  nearly  quadruple  accu- 
racy." 

Among  the  various  instruments,  which 
in  the  hands  of  the  Coast  Survey  have 
been  made  of  especial  value,  is  the  zenith 
telescope.  It  is  justly  regarded  both  on 
account  of  its  facility  for  use  and  the 
precision  of  its  results  as  by  far  the 
most  simple  and  effective  instrument 
known  for  the  determination  of  latitude, 
for  which  purpose  it  was  first  employed 
by  the  late  Captain  Andrew  Talcott,  of 
the  United  States  Engineers.  More  re- 
cently it  has  been  also  employed  for  the 
determination  of  time.  The  accuracy  of 
this  instrument  consists  in  measuring 
very  small  differences  of  zenith  distances, 
instead  of  absolute  zenith  distances.  By 
means  of  the  micrometer  an  arc  of  less 
than  one-twentieth  of  a  second  is  meas- 
ured, and  the  probable  error  of  a  single 
observation  is  only  from  three  to  five- 
tenths  of  a  second. 

The  history  of  this  great  national  un- 
dertaking may  be  thus  briefly  sketched: 
In  1806  (  singularly  enough  the  very 
year  in  which  Prof.  Bache  was  born),  a 
survey  of  the  coast  was  suggested  to 
Mr.  Jefferson.  In  1807,  Congress  passed 
an  act  authorizing  a  survey  to  be  made, 
in  which  the  islands,  shoals  and  places 
of  anchorage  within  twenty  leagues  of 
the  shore,  with  the  courses  and  dis- 
tances of  capes  and  head  lands,  were  to 
be  represented  upon  accurately  made 
charts,  and  Mr.  F.  R.  Hassler,  a  dis- 
tinguished man  of  science,  who  had  been 
engaged  upon  the  triangulation  of  the 
Swiss  Canton  of  Berne,  was  appointed 
to  superintend  the  work.  In  1811,  Mr. 
Hassler  proceeded  to  Europe  to  obtain 
the  necessary  instruments,  but  on  ac- 
count of  the  troubled  condition  of  the 
country  at  that  time,  and  for  several 
years  afterwards,  he  did  not  return  until 
1816.  The  following  year  work  was 
commenced  in  the  neighborhood  of  New 
York,  but  on  account  of  the  difficulty 
of  obtaining  funds  from  Congress  the 
work  was  suspended  shortly  afterwards, 
and  in  1818  the  law  authorizing  the  sur- 
vey was  repealed.  From  1819  to  1832, 
surveys  of  certain  parts  of  the  coast 
were  made  by  the  Navy  Department. 
The  results  thus  obtained,  however,  were 
so  far  from  being  satisfactory  that,  in 


1828,  the  Secretary  of  the  Navy  pro- 
nounced the  charts  thus  made  as  expen- 
sive and  unsafe,  and  recommended  a 
more  systematic  plan  of  operation.  In 
1832  the  Coast  Survey  was-  therefore 
commenced  anew,  and  again  put  in 
charge  of  Mr.  Hassler,  who  continued  to 
direct  its  operation  until  his  death  in 
1S43.  Under  his  management  the  work 
was  organized,  instruments  designed  and 
made,  assistants  trained,  and  the  public 
made  acquainted  to  some  extent  with  the 
nature  and  importance  of  the  undertak- 
ing. His  triangulation  fixed  the  position 
of  some  twelve  hundred  stations,  em- 
bracing the  coast  from  Rhode  Island  to 
Chesapeake  Bay,  while  the  Topography 
and  Hydrography  were  well  advanced. 
"  Mr.  Hassler,"  says  one  who  fully  under- 
stood his  character,  "  was  a  man  of  high 
attainments  and  ability,  whose  scientific 
management  of  the  work  which  he  had 
himself  initiated  had  won  universal  ap- 
probation. He  had  emigrated  to  this 
country  from  Switzerland  at  the  begin- 
ning of  the  century,  and  had  brought 
with  him  ideas  of  scientific  accuracy  and 
thoroughness  which  the  public  mind  in 
America  was  not  yet  sufficiently  enlight- 
ened to  appreciate  or  even  to  understand. 
He  gave  to  the  Survey  the  chief  ener- 
gies of  his  life,  and  undeterred  by  its 
suspension  for  fifteen  years,  resumed  its 
prosecution,  when  permitted,  anew  with 
the  same  zeal  which  had  marked  its  in- 
ception. On  the  other  hand,  he  was  a 
man  of  great  eccentricity  of  manner,  and 
not  endowed  with  administrative  ability. 
At  the  time  of  his  death,  the  condition 
of  the  Coast  Survey  was  anomalous  and 
Ishmaelitish.  Every  man's  hand  was 
against  his  neighbor.  The  Secretary  of 
the  Treasury  was  the  real  head  of  the 
Survey,  and  the  principal  assistants  re- 
ported directly  to  him  and  not  to  Mr. 
Hassler."  In  brief,  while  under  a  Euro- 
pean Government,  Mr.  Hassler  would 
have  been  all  that  was  desired  for  his 
position,  under  the  Government  of  this 
country  he  lacked  just  what  his  succes- 
sor possessed  in  so  remarkable  a  degree, 
wonderful  executive  power,  and  the 
ability  of  securing  the  thorough  recogni- 
tion of  the  importance  of  the  work  from 
Congress  and  from  the  people,  and  of 
inspiring  them  with  the  utmost  confi- 
dence in  his  management. 

The  appointment  of  Prof.  Bache  brings 


THE   UNITED   STATES   COAST   SURVEY. 


11 


us  to  the  most  important  and  interesting 
period  in  the  history  of  the  Coast  Sur- 
vey. This  eminent  man  was  born  hr 
Philadelphia  in  1806,  being  maternally 
a  grandson  of  Benjamin  Franklin.  He 
entered  West  Point  at  fifteen  years  of 
age,  and  graduated  in  1825,  first  in  a 
class  of  extraordinary  ability,  and  what 
is  remarkable,  having  never  in  his  four 
years'  course  received  a  single  demerit. 
He  remained  after  graduating  for  a  short 
time  as  an  assistant  to  Prof.  Mahan,  and 
afterwards  served  as  an  assistant  to 
Colonel  Totten  in  the  construction  of 
Fort  Adams  at  Newport.  In  1828 
he  was  appointed  ■  Professor  of  Natural 
Philosophy  in  the  University  of  Pennsyl- 
vania, at  Philadelphia,  where  he  re- 
mained seven  years.  In  1 836  he  was  made 
President  of  Girard  College,  and  visited 
Europe  for  the  purpose  of  examining  the 
principal  educational  institutions  below 
the  grade  of  universities,  and  in  1838 
prepared  an  elaborate  report  of  over  six 
hundred  pages,  being  the  result  of  a 
thorough  examination  of  two  hundred 
and  eighty  several  schools  in  Great 
Britain,  France,  Switzerland,  Holland, 
Italy,  and  the  German  States.  The 
opening  of  Girard  College  being  so  long 
delayed,  he  assumed  the  position  of 
Principal  of  the  High  School  and  Super- 
intendent of  Public  Schools  in  Philadel- 
phia, in  which  position  he  rendered  ines- 
timable services  to  his  native  city.  In 
1842  he  was  again  appointed  to  his  old 
position  in  the  University  of  Pennsylva- 
nia, which  he  held  until  November,  1843, 
when  at  the  unanimous  call  of  the  vari- 
ous colleges,  learned  societies,  and  men 
of  science  of  America,  endorsed  by  such 
names  as  Humboldt-  and  Arago  in 
Europe,  he  was  at  the  age  of  thirty- 
seven  years  appointed  Superintendent  of 
the  United  States  Coast  Survey,  a  posi- 
tion for  which  by  natural  endowments 
and  extraordinary  scientific  attainments 
he  was  so  admirably  fitted,  and  which 
he  retained  until  his  death,  which  oc- 
curred at  Newport  in  1867. 

From  this  time  the  work  was  im- 
mensely expanded  and  driven  on  with 
the  most  untiring  activity.  In  order 
that  the  progress  might  the  sooner  meet 
the  pressing  and  rapidly  increasing  de- 
mands of  commerce,  and  that  the  truest 
economy  might  be  secured,  the  coast 
was   divided   into  eleven   different  sec- 


tions, each  having  as  nearly  as  might  be 
the  same  length  of  shore,  and  each  hav- 
ing its  own  base  line,  but  the  whole 
forming  a  single  system  of  triangles 
reaching  from  Maine  to  Texas,  each 
division  thus  verifying  the  next.  By 
this  system,  according  to  the  report  of 
the  Secretary  of  Treasury,  a  double 
expenditure  produced  a  threefold  result, 
the  same  parties  working  in  the  North 
during  the  summer  and  in  the  South 
during  the  winter. 

The  extent  of  the  work  thus  brought 
into  one  system  may  be  thus  briefly 
stated: 

Length  in  miles  of     Length  of  the 
general  coast  line.  shore  line. 

Atlantic  Coast. . .  .3,036  14,723 

Gulf  Coast 2,162  10,406 

Pacific  Coast 1 ,  866  4, 252 


7,064  29,381 

If  we  suppose  the  whole  time  necessaiy 
for  the  completion  of  the  work  to  extend 
from  1840  to  1880,  or  forty  years,  and 
the  annual  expense  to  be  five  hundred 
thousand  dollars,  we  shall  have  paid  for 
our  whole  thirty  thousand  miles  of  shore 
line  twenty  millions  of  dollars,  a  sum 
greatly  less  than  any  other  government 
has  paid  for  the  like  amount  of  work. 
It  has  been  stated,  and  correctly,  that 
the  annual  cost  of  the  Coast  Survey 
never  exceeded  the  cost  of  a  first-class 
steamer.  Certainly  the  whole  cost  from 
the  commencement  has  not  surpassed 
the  value  of  a  dozen  first-class  Indiaman 
with  their  cargoes. 

"  The  rule  of  Professor  Bache  in  the 
work  of  the  Coast  Survey,"  says  his 
memorialist,  "  was  that  all  of  the  scien- 
tific work  should  be  executed  in  the 
most  thorough  and  accurate  manner 
which  the  resources  of  science  and  art 
would  permit.  He  never  shunned  a  ten- 
fold labor  if  it  was  to  be  repaid  by  a, 
double  precision,  accepting  the  great 
principle  which  prescribes  a  higher  rate 
of  effort  as  we  climb  to  higher  degrees 
of  refinement."  Under  his  guidance  for 
twenty-four  years  the  best  scientific 
talent  of  the  country  was  drawn  into 
the  service  of  the  Coast  Survey.  The 
nineteen  quarto  volumes  of  the  Coast. 
Survey  Reports  from  1852  to  1870,  con- 
taining no  less  than  six  thousand  pages 
and  eight  hundred  plates,  besides  one 
hundred  and  twenty  -  three  scientific 
papers  presented  to  different  associations 


12 


TAN   NOSTRAND'S   ENGINEERING   MAGAZINE. 


from  1829  to  1864,  with  his  annual  re- 
ports as  Superintendent  of  "Weights  and 
Measures,  and  twenty-one  several  reports 
upon  various  harbors,  the  last  made 
jointly  with  Messrs.  Davis  and  Totten, 
all  testify  to  the  immense  activity  of  the 
man.  Not  the  least  laborious  part  of 
his  work,  but  certainly  the  least  agree- 
able, was  the  perpetual  exertion  necessa- 
ry to.  counteract  the  attempts  of  evil- 
minded  people  at  "Washington.  Hardly 
a  session  of  Congress  passed  in  which 
personal  spite,  local  jealousy,  prejudice, 
or  envy,  did  not  show  its  hundred-headed 
"  bad-visaged  front,"  striving  always  to 
sap  the  foundations  of  the  noble  struct- 
ure which  was  steadily  rising  to  the 
public  view,  until  at  last  so  virulent 
were  these  attacks  and  so  apparent  their 
animus  that  the  learned  societies,  cham- 
bers of  trade  and  commerce,  insurance 
companies,  and  private  individuals,  all 
over  the  country  united  in  one  grand 
protest  against  interference. 

The  opinions  of  European  savans  in 
regard  to  the  Coast  Survey  and  its  di- 
rector, may  be  gathered  from  very  nu- 
merous letters  from  such  men  as  Arago, 
Humboldt,  Admiral  Smyth,  and,  lastly, 
from  Sir  Roderick  Murchison,  who  in  pre- 
senting the  Victoria  Gold  Medal  of  the 
Royal  Geographical  Society  of  London, 
to  Prof.  Bache,  remarks,  that  whether 
we  regard  the  scientific  skill  and  zeal  of 
the  operators,  the  perfection  of  the  in- 
struments, or  the  able  manner  in  which 
the  Superintendent  has  enlisted  all  mo- 
dern improvements  into  his  service,  all 
must  agree  that  the  Trigonometrical  Sur- 
vey of  the  United  States  stands  without 
a  superior." 

"When  it  is  considered  that  the  Coast 
Survey  organization  embraces  not  only 
civilians,  but  at  the  same  time  officers  of 
both  Army  and  Navy,  it  will  be  seen 
that  the  chief  who  could  so  direct  these 
somewhat  discordant  elements  as  to  pro- 
duce a  maximum  of  progress  with  a 
minimum  of  internal  dissatisfaction  must 
be  no  ordinary  man.  We  may,  there- 
fore, well  understand  and  believe  the 
truth  contained  in  the  following  eulo- 
gistic words  of  his  memorialist  : 

"  It  was  not  merely  by  his  ardent  love 
of  science,  and  his  disinterested  devotion 
to  her  welfare  that  he  accomplished  so 
much.  His  fertility  of  device,  uncon- 
querable assiduity,  large  policy,  generous 


impulses,  patriotic  devotion,  might  well 
have  co-existed  without  yielding  such 
fruits  in  the  development  of  the  Coast 
Survey,  or  such  a  mighty  power  for 
good  in  the  promotion  of  science  through- 
out the  United  States.  More  was  needed 
than  these ;  far  more  than  these  he  pos- 
sessed. The  greatest  of  all  his  mental 
gifts,  or  attainments,  were  his  marvelous 
knowledge  of  human  nature  and  his  un- 
rivaled skill  in  using  it.  He  had  studied 
men  as  he  would  study  physical  phe- 
nomena. To  a  faculty  of  persuading 
the  most  obstinate,  of  soothing  the  most 
irritable,  of  encouraging  the  most  dis- 
heartened; to  a  power  of  stimulating  the 
most  indolent,  controlling  the  impulsive, 
winning  over  opponents  by  the  charm  of 
his  manner,  and  confirming  friends  by 
the  truthfulness  and  sincerity  of  his  na- 
ture, he  added  that  rare  endowment, 
which  imbued  others  unconsciously  with 
his  own  zeal.  His  companionship  evoked 
latent  aspirations,  and  pointed  to  noble 
aims.  He  knew  the  secret  of  obtaining 
work  from  his  subordinates,  by  doing 
more  than  they  did.  By  no  act  of  his 
life  did  he  ever  curtail  any  man's  means 
of  usefulness,  or  fail,  whenever  it  was 
within  his  po  wer,to  render  available  what- 
ever abilities  might  be  disclosed.  Justice 
and  even-handed  firmness  controlled  his 
action.  Cautious  in  plan,  bold  in  action, 
as  courteous  to  his  assistants  and  as  con- 
siderate of  his  subordinates  as  though 
they  had  been  his  superiors,  ever  as  open 
to  conviction  as  to  argument — such  was 
his  noble  character.  The  progress  of 
education,  the  development  of  scientific 
research,  the  extent  of  scientific  discovj 
ery,  the  growth  of  the  arts  and  the 
spread  of  commerce  have  all  been  greater 
in  America  because  he  has  lived." 

It  is  almost  impossible  to  do  justice  to 
the  chief  of  an  important  undertaking 
without  doing  a  seeming  injustice  to  his 
associates  and  assistants.  Many  of  Na- 
poleon's Marshals  were  great  men,  but 
Napoleon's  greatness  overshadowed  them 
all.  Great  as  Prof.  Bache  was,  he  never 
could  have  accomplished  the  vast  work 
of  the  Coast  Survey  unaided.  Without 
the  labor  of  his  assistants — most  of 
whom  are  yet  active  workers  in  the  field 
— the  admirable  results  which  we  now 
see  would  never  have  been  reached,  nor 
should  we  have  had  the  declaration  from 
one  of  England's  foremost  men  of  sci- 


DOMESTIC   MOTOES. 


13 


ence,  that   "The    Coast   Survey  of  the 
United  States  is  one  of  the  most  perfect 


exemplifications 
modern  times." 


of    applied  science    of 


DOMESTIC  MOTORS. 

From  "The  Engineer." 


Let  it  not  be  thought  that  the  subject 
dealt  with  in  this  article  is  too  insignifi- 
cant to  deserve  the  attention  of  me- 
chanical engineers  ;  nothing  which  can 
add  to  the  comfort  of  a  civilized  com- 
munity is  too  trifling  to  claim  the  exer- 
cise of  the  talent  for  invention.  Who 
will  supply  a  want  long  felt,  and  give 
the  world  a  really  good  domestic  motor, 
an  engine  of  some  kind  which  will  drive 
any  or  all  of  the  machines  now  common 
in  almost  every  household?  At  first 
sight  it  would  appear  that  thore  can  be 
no  great  difficulty  in  producing  a  small 
apparatus  which  would  suffice  to  drive  a 
sewing  machine,  a  knife  cleaner,  or  a 
washing  machine  ;  but  a  little  examina- 
tion of  the  subject  will  show  that  it  is 
rather  more  complex  than  appears  at 
first  sight.  Attempts  have  been  made 
to  solve  the  problem,  but  we  question  if 
those  who  have  made  these  attempts 
have  gone  quite  the  right  way  to  work. 
As  the  conditions  are  not  easy  of  fulfill- 
ment, we  shall  first  state  these  condi- 
tions, and  then  indicate  the  direction 
which  inventors  should  take  to  satisfy 
them.  In  the  first  place,  then,  a  domestic 
motor  must  be  safe — that  is,  it  must  be 
absolutely  free  from  risk  of  explosion  or 
fire.  In  the  second  place,  it  must  be 
generally  applicable.  In  the  third,  it 
must  not  be  likely  to  get  out  of  order. 
Fourthly,  it  must  be  perfectly  under 
control,  and  require  no  special  skill  to 
manage  it.  Fifthly,  it  must  be  cleanly 
in  its  operation ;  and  lastly,  it  must  be 
cheap.  One  or  two  minor  requirements 
might  be  stated,  but  we  believe  we  have 
enumerated  all  that  are  essential.  It  is 
obvious  that  what  applies  to  the  produc- 
tion of  motive  power  in  the  abstract  will 
apply  to  all  motive  power  engines,  small 
or  great.  "We  cannot  create  power,  and 
so,  whether  we  want  to  propel  an  ocean 
steamship  or  to  drive  a  sewing  machine, 
we  must  call  in  some  of  the  forces  of 
nature  to  aid  us.  Before  going  further, 
therefore,   we  may  at  once   dismiss  all 


such  schemes  as  the  winding  up  of 
springs  or  weights  to  produce  motion. 
The  power  to  be  thus  obtained  must  first 
be  got  by  the  exercise  of  manual  labor, 
and  it  would  be  better  to  apply  this 
labor  directly  to  the  machine  to  be  driven 
than  indirectly  to  springs  or  weights,  for 
reasons  very  well  understood  by  engin- 
eers, at  all  events.  The  forces  of  nature 
available  for  our  purpose  are  gravity, 
heat  and  electricity.  They  can  be  ap- 
plied in  various  ways  as  follows  :  First- 
ly, gravity  is  available  under  certain 
conditions  in  the  fall  of  a  body  of  water; 
heat  can  be  utilized  by  a  steam,  hot  air, 
or  gas  engine  ;  and  electricity  can  be 
made  to  serve  our  purpose  by  the  aid  of 
the  magnet.  From  this  list  our  domestic 
motor  must  be  selected.  It  remains  to 
be  considered  which  is  most  like  to  serve 
our  purpose. 

Where  a  constant  supply  of  water 
under  pressure  is  available,  it  would 
seem  that  nothing  is  so  suitable  for  chiv- 
ing a  domestic  motor.  It  is  not  beyond 
the  skill  of  the  engineer  to  construct  a 
little  turbine,  for  example,  which  could 
be  fixed  in  a  neat  case  against,  or  even 
sunk  into,  the  wall  of  a  drawing-room, 
and  to  which  a  pipe,  concealed  like  a  gas 
pipe,  behind  the  wall-paper,  could  be 
laid  from  the  cistern  on  top  of  the  house, 
while  the  discharge  pipe  could,  similarly 
concealed,  be  led  to  the  most  convenient 
place  where  it  might  be  discharged  into 
a  drain.  The  space  occupied  by  a  little 
turbine  of  this  kind  would  be  quite  in- 
significant. The  covering  might  be  ren- 
dered  very  ornamental,  and  the  power 
could  be  taken  off  by  a  small  belt  or  gut 
line.  In  this  way  every  drawing-room 
or  boudoir  might  contain  a  motor  avail- 
able at  any  time  to  drive  a  sewing  ma- 
chine. Its  operation  would  be  quite 
silent,  danger  there  would  be  none,  and 
to  start  or  stop  it  would  be  as  simple  an 
operation  as  turning  gas  on  or  off.  If 
necessary,  the  same  plan  might  be  car- 
ried out   to  drive   a  washing   machine, 


14 


van  nostrand's  engineering  magazine. 


knife  cleaner,  &c,  in  the  basement  of  a 
house,  a  somewhat  larger  and  coarser 
machine  being  used.  But  in  no  case 
would  the  turbine  take  up  much  room  or 
use  a  great  deal  of  water — about  one- 
fifth  of  a  horse-power  is  the  maximum 
that  would  be  required.  This  would  be 
obtained  by  the  expenditure  of  about 
2,000  gallons  of  water  per  hour  under  a 
head  of  20  feet,  or  half  that  quantity 
under  a  head  of  40  feet.  This  would 
practically  represent  the  work  of  a  couple 
of  strong  men.  To  drive  a  sewing  ma- 
chine, of  course  very  much  less  would 
suffice.  "Where  water  under  a  sufficient 
head  is  available  in  the  requisite  volume 
nothing  better  than  the  arrangement  we 
have  sketched  out  can  be  desired.  It  is 
evident,  however,  that  in  London,  at  all 
events,  and  indeed  in  most  large  cities, 
water  cannot  be  had  in  this  way  in  suffi- 
cient quantities,  and  we  must  reluctantly 
reject  the  turbine  as  not  fulfilling  all  the 
requirements  of  an  almost  universally 
applicable  domestic  motor. 

Steam  may  be  used  for  the  required 
purpose,  and  an  apparently  not  unsuc- 
cessful attempt  is  now  being  made  by  a 
London  firm  to  introduce  miniature 
steam  engines  for  driving  sewing  ma- 
chines. The  little  engines  are  on  the 
oscillating  principle,  are  extremely  sim- 
ple, and  well  made.  Steam  is  supplied 
by  little  vertical  boilers,  heated  by  a 
Bunsen  burner  or  ring.  No  chimney  is 
required,  and  the  exhaust  steam  is  car- 
ried off  by  india-rubber  pipes.  Although 
the  pressure  used  is  low  and  the  boilers 
small,  the  arrangement  cannot  be  pro- 
nounced quite  free  from  danger;  and 
the  heat  and  smell  inseparable  from  the 
use  of  steam,  and  the  difficulty  of  satis- 
factorily disposing  of  the  exhaust,  must 
always  tell  against  the  popularity  of 
this,  or  any  other  form  of  steam  engine, 
as  a  motor  suitable  for  drawing-room 
use,  although  it  would,  no  doubt,  prove 
serviceable  in  tailoring  establishments, 
and  other  places  where  a  considerable 
number  of  sewing  machines  have  to  be 
worked;  and  it  would  probably  do  good 
service  in  small  laundries.  It  will  be 
seen,  then,  that  neither  water  nor  steam 
is  likely  to  supply  what  we  want.  We 
may  take  electricity  out  of  its  order,  to 
dismiss  it  at  once,  as  being  too  costly, 
delicate,  and  troublesome  to  satisfy  our 
requirements.     Nothing  is  left,  then,  as 


likely  to  furnish  motive  power,  but  hot- 
air  engines,  gas  engines,  or  petroleum 
engines.  Hitherto  hot-air  engines  have 
not  been  successful;  but  this  is  due  to 
causes  which  would  hardly  operate  in 
the  case  which  we  are  considering.  It 
ought  to  be  possible  to  produce  a  little 
hot-air  engine  which  would  drive  a 
sewing  machine  silently  and  without 
trouble,  the  heat  being  supplied  by  a 
gas  jet.  The  little  engine  need  not 
weigh  more  than  a  few  pounds;  economy 
would  not  be  sought,  and  the  regener- 
ator could  be  wholly  left  out.  The  gas 
could  be  taken  from  the  gaselier  over- 
head by  an  india-rubber  tube,  and  as  it 
would  not  be  necessary  to  wait  for  a  fire 
to  burn  up,  the  machine  should  be  ready 
to  operate  in  five  minutes  after  the  gas 
was  lit.  There  would  be  little  that  was 
objectionable  about  the  machine.  It 
would  be  perfectly  safe,  easily  managed, 
and  the  hot  air  discharged  would  be 
small  in  quantity,  and  readily  disposed 
of  by  the  ordinary  ventilation  of  the 
apartment.  Larger  machines,  but  still 
small,  could  be  used  for  heavier  domes- 
tic work.  We  are  disposed  to  regard 
the  hot-air  engine  as  presenting  an  ex- 
cellent solution  of  the  problem ;  but 
something  still  better  may,  perhaps,  be 
found  in  the  gas  engine.  Lenoir's  en- 
gine, apart  from  the  electrical  apparatus, 
which  is  not  essential,  we  need  hardly 
say,  was  simple  enough,  and  we  see  no 
difficulty  in  constructiug  little  engines 
on  this  principle  modified,  of,  say,  one- 
tenth  of  a  horse-power,  which  might  be 
elegant  in  design,  simple,  and  easily 
managed.  Petroleum  engines  the  world 
knows  too  little  about  at  present  to 
enable  us  to  present  any  opinion  on 
their  suitability  for  the  required  pur- 
pose; but  while  gas  is  available,  as  it 
now  is,  in  every  town  and  in  many 
country  houses,  we  see  no  reason  for 
abandoning  it  in  favor  of  petroleum. 

One  point  remains  to  be  dealt  with, 
namely,  the  cost  of  a  domestic  motor; 
this  must  be  small.  It  should  not  much 
exceed  £5,  if  a  large  sale  is  expected, 
and  we  venture  to  think  that  the  very 
magnitude  of  the  sale  which  would  be 
secured  for  a  really  satisfactory  domestic 
motor  would  enable  the  price  to  be  kept 
within  the  limits  we  have  named.  It 
may  be  argued  that  to  produce  an  effi- 
cient  motor,  however   small,  for   £5   is 


NAVAL   GEEAT   GUNS   AND   GUNNERY. 


15 


absurd,  but  we  cannot  agree  to  this.  A 
.steam  engine,  for  example,  is  by  no 
means  so  complex  as  a  sewing  machine, 
but  the  latter  can  be  sold  for  £5,  allow- 
ing a  good  margin  for  profit.  Not  many- 
years  since  we  heard  it  argued  that  it 
was  impossible  to  produce  a  lawn  mower, 
which  would  be  of  use,  for  less  than  £5. 
Excellent  little  lawn  mowers  are  now 
sold  literally  by  the  thousand  for  25s. 
If  a  good  design  is  once  obtained  every 
portion  of  the  domestic  motor  might  be 
turned  out  by  machinery,  and  fitting  re- 
duced to  a  minimum.  No  engineer,  it 
would  seem,  really  knows  what  he  can 
do  till  he  tries,  and  we  are  certain  that 
by  trying,  not  only  may  a  motor  be  sup- 
plied, but  that  it  can  be  sold,  if  not 
for  £5,  for  something  very  near  that 
sum. 

Whether  a  sufficient  demand  would  ex- 
ist to  make  it  worth  while  to  invest  capi- 
tal in  the  requisite  plant  for  turning  out 
domestic  motors  by  the  thousand,  is  a 
question  which  we  cannot  answer  decid- 


edly, nor  can  anyone  else.  If  we  reason 
by  analogy,  it  would  appear  that  the 
same  laws  would  apply  to  such  machines 
as  to  several  others.  The  first  man  who 
made  portable  engines  gave  up  the  busi- 
ness after  he  had  turned  out  twelve,  be- 
cause, he  argued,  that  more  than  a  dozen 
portable  engines  could  not  possibly  be 
wanted  in  England.  When  the  sewing 
machine  was  first  produced  it  was  held 
that  the  demand  for  it  must  always  be 
limited.  Sewing  machines  are  now  made 
by  the  million.  We  might  cite  a  great 
many  other  instances  to  prove  that  the 
possibility  of  obtaining  a  given  machine 
appears  to  create  a  demand  for  it,  and 
we  think  this  would  apply  in  the  case  of 
the  little  engines  with  which  we  are 
dealing.  However,  it  is  perhaps  prema- 
ture to  speak  of  the  possible  demand  for 
a  machine  which  does  not  as  yet  exist ; 
although  we  have  no  doubt  that  it  is 
practicable  to  produce  it,  some  exercise 
of  inventive  ability  will  be  needed  in  the 
production. 


NAVAL  GREAT  GUNS  AND   GUNNERY. 


From  "Iron  " 


A  paper  on  this  subject  was  read  re- 
cently by  Mr.  J.  Scott  Russell  at  the 
Royal  United  Service  Institution.  Mr. 
Russell  said :  "  What  I  propose  to  lay 
before  you  to-night  is  the  special  ques- 
tion— What  should  be  our  new  navel 
gun,  to  take  the  place  of  my  favorite 
old  8-inch  guns  ?  The  two  important 
points  I  first  want  you  to  settle  are 
these:  What  weight  of  gun  can  you 
accept  as  the  (handleable  weight)  man- 
ageable weight  of  gun?  Next,  what 
work  do  you  want  the  gun  and  its  pro- 
jectile to  do?  If  you  settle  these  two 
leading  points,  I  think  I  can  see  how  all 
the  rest  can  be  done.  To  secure  most 
execution  at  moderate  and  sure  range 
seems  to  me  the  essential  character  of 
naval  gunnery  as  distinguished  from 
land  gunnery.  If  that  be  agreed,  I  now 
proceed  to  see  how  we  can  get  most  use 
for  that  end  out  of  our  12-ton  gun.  I 
say  then  at  once  that  you  will  get  much 
more  practical  good  out  of  your  12-ton 
gun  by  giving  it  a  large  bore  of  12 
inches  than  a  smaller  bore  of  8^  inches. 
In  a  12-inch  bore  the  powder-power 
propelling  the  shot  is  144.  In  an  Sc- 
inch bore  the   propelling  power  is   72. 


Or  the  work  done  by  the  12-inch  bore  is 
double  the  8-J-inch  bore.  For  the  pres- 
ent I  confine  myself  to  this  statement;  I 
will  prove  it  later  on.  Next,  I  will  take 
the  question,  how  shall  we  turn  this 
double  propelling  question  to  account? 
We  have  two  ways,  to  send  out  a  heavier 
shot,  or  to  send  out  the  same  shot  with 
higher  speed.  Now,  in  regard  to  weight 
of  shot,  I  may  observe  that  as  you  have 
fixed  weight  of  gun  I  shall  consider  the 
weight  of  shot  as  fixed  also.  Your  gun 
weighs  12  tons,  that  is,  240  cwt.  Now, 
according  to  the  best  practice  in  all 
countries,  the  normal  shot  is  1  lb.  of 
shot  to  each  112  lb.  of  gun.  This  gives 
for  the  12-ton  gun  240,  or  12-ton  gun 
(240  cwt.)  240  lb.  shot.  Taking,  then, 
240  lb.  shot  in  8^-inch  gun,  and  240  lb. 
shot  in  12-inch  gun,  we  have  double  the 
powder  -  power  propelling  the  same 
shot;  or  double  the  propelling  force 
pushing  forward  the  base  of  the  shot. 
Therefore,  the  same  weight  of  shot  will 
be  discharged  with  much  higher  speed. 
Now  speed  of  shot  is,  as  you  know,  a 
much  more  effectual  means  of  destruc- 
tion and  penetration  than  mere  weight; 
double  weight  of  shot  has  double  pene- 


16 


VAN   NOSTRAND'S   ENGINEERING   MAGAZINE. 


trating  power;  double  speed  of  shot  has 
fourfold  penetrating  power.  The  larger 
bore  has,  therefore,  the  great  advantage  of 
giving  higher  speed  of  shot  and  greater 
penetrating  power.  Double  weight  gives 
double  destruction.  Double  speed  gives 
fourfold  destruction.  The  next  element 
of  efficiency  is  the  power  of  the  hollow 
shot  as  an  explosive  shell.  I  need  not 
prove  that  with  the  same  weight  of 
piercing  shell,  the  larger  bore  admits 
of  much  larger  explosive  effect  of  the 
shell.  Shell  has  much  larger  capacity 
for  explosive  charge.  Thus,  then,  in  all 
these  ways  greater  initial  speed,  greater 
destroying  power,  greater  explosive  ef- 
fect, the  large  bore  12 -ton  gun  is  more 
effectual  for  naval  use  than  the  smaller 
bore.  So  much  for  the  power  of  the 
larger  gun  for  more  work.  I  now  pro- 
ceed to  show  how,  by  wise  arrangement, 
this  larger  bore  gun  of  1 2  tons  may  have 
more  endurance  than  the  small  bore  gun 
also  of  12  tons.  I  shall  be  told  at  once 
that  it  is  quite  true  that  my  large  bore 
has  greater  propelling  power  on  the  shot 
than  my  small  bore;  but  that  the  powder 
in  my  large  bore  has  greater  bursting 
power  on  the  gun  barrel  than  in  the 
small  bore.  This  is  quite  true,  but  it  is 
true  in  quite  different  proportions.  The 
propelling  power  is  as  72  to  144.  The 
bursting  power  is  as  102  to  144. 

This  gives  a  clear  balance  in  favor  of 
the  large  bore  of  144  to  102,  or  of  42 
per  cent.  gain.  Propelling  powers  72  to 
144.  Bursting  powers  102  to  144.  The 
larger  bore  is  the  more  lasting  gun. 
Thinner  metal,  21  to  24  ;  more  effective 
distribution,  26  to  18  ;  gain,  54  to  43. 
The  next  question  is  mode  of  rifling. 
On  this  I  have  merely  to  say  that  I  have 
always  been  the  consistent  advocate  of 
accelerating  twist  for  small  bore  guns 
with  common  powder  charges.  But  for 
large  guns  with  new  and  well-regulated 
powder  charge,  I  am  of  the  opposite 
opinion.  For  large  guns,  with  regulated 
powder  charge,  we  must  lay  aside  accel- 
erating twist  and  come  to  uniform  twist. 
My  reasons  are  two.  First,  accelerating 
twist  injures  large  guns  ;  second,  it  is 
rendered  quite  unnecessary  with  a  regu- 
lated powder  charge.  What  we  want  is 
not  slow  burning  powder,  nor  quick 
burning  powder  ;  but  powder-charges 
that  will  burn  quick  when  we  want  it 
quick,  and  slow  when  we  want  it  slow. 


Or  what  I  call  a  regulated  charge,  slow 
burning  of  powder  at  first,  gradually 
growing  quicker  and  quickest  at  last. 
Now,  if  you  can  get  that  done,  your 
guns  will  last  longer  than  they  have  ever 
done,  your  shot  will  go  further,  and  fast- 
er, and  steadier  than  they  have  ever 
done,  and  your  whole  work  will  be  bet- 
ter done  than  ever.  We  now  meet  face 
to  face  the  next  question,  Have  we  got 
such  regulated  powder  charge  as  I  speak 
of  ?  The  answer  is,  No,  very  much  the 
reverse;  and  then  the  next  question,  Can 
we  get  them  ?  I  answer,  "  Say  you  wish 
it,"  and  you  will  get  it.  As  to  the  ma- 
terial of  which  our  naval  gun  should  be 
made,  there  need  now  be  no  doubt.  Steel 
and  iron  can  now  be  made  of  any  requir- 
ed quality,  and  nearly  any  quantity  in 
one  piece  I  know  that  the  12-ton  12- 
inch  gun  we  have  been  discussing  can  be 
made  of  Whitworth's  condensed  tough, 
powerful  steel,  in  two  concentric  tubes 
or  cylinders,  an  outer  and  an  inner 
tube.  I  dare  say  that  our  engineers  at 
Woolwich  will  be  able  to  make  you  the 
outer  body  of  that  gun  in  one  piece  of 
wrought  iron,  with  an  inner  single  tube 
of  Frith's  steel.  By  and  by,  if  you  de- 
sire it,  the  gun  may  be  one  whole,  but  at 
present  I  prefer  to  have  it  in  two  layers, 
outer  and  inner,  but  each  extending  the 
whole  length,  and  not  in  patches. 
Cheaper  shells  might  be  good  enough  for 
practice,  but  I  consider  that  when  you 
come  within  shot  range  of  your  enemy, 
there  is  no  shell,  however  costly,  that 
should  be  reckoned  "  too  good  "  for  him. 
In  short,  the  most  effective  would  be 
really  the  cheapest.  In  regard  to  gun- 
nery and  gun  carriages,  I  think  that 
when  you  have  resolved  to  adopt  breech- 
loading  matters  are  simplified  very 
much.  I  think  the  existing  naval  gun- 
carriage,  as  designed  by  Captain  Scott, 
is  an  extremely  good  one.  I  also  am  of 
opinion  that  for  certain  special  ships  of 
war  the  gun-carriage  of  Major  Moncrieff 
offers  very  important  advantages  in  use, 
and  facilities  in  application.  But  the 
most  important  of  all  gun  carriages  is 
the  ship  herself,  which  carries  the  great 
guns  we  are  now  discussing.  Unless  the 
ship  herself  possesses  all  the  qualities  of 
a  handy,  quick,  steady,  secure  gun-car- 
riage, nothing  we  can  put  on  board  of 
her  will  enable  her  to  win  a  battle  at 
sea. 


SUBMEESIBLE   LANDS   OF   THE    MISSISSIPPI  VALLEY. 


17 


RECLAMATION    OF    THE    SUBMERSIBLE    LANDS    OF    THE 
MISSISSIPPI  VALLEY. 

By  J.  P.  FRIZELL. 

Written  for  Van  Nostrand's  Engineering  Magazine. 


By  an  Act  of  Congress,  approved  June 
22,  18 74,  the  President  of  the  United 
States  was  authorized  and  directed  to 
appoint  a  Commission  "  To  make  a  full 
report  to  the  President  of  the  best  sys- 
tem for  the  permanent  reclamation  and 
redemption  of  said  alluvial  basin  from 
inundation." 

The  Commission  consisted  of  three  en- 
gineer officers,  viz.  : 

Major  G.  R.  Warren. 
Major  H.  L.  Abbott. 
Captain  W.  H.  H.  Benyaurd. 

And    two   civil    engineers  "  eminent  in 
their  profession,"  viz.  : 


Jackson  E.  Sickels 
P.  O.  Hebert. 


and 


This  Commission  presented  a  report 
under  date  of  January  22, 1875,  in  which 
they  advert  to  the  several  methods  of 
protection  that  have  at  different  times 
occupied  the  public  attention,  and  indi- 
cate the  following  as  their  conclusions  : 

The  attempt  to  control  the  height  of 
floods  by  cut-offs  is  fraught  with  such 
danger  to  the  banks  that  it  should  never 
be  made  ;  then  spontaneous  occurrence 
should  even  be  prevented  when  practic- 
able. 

Division  of  tributaries  is  not  thought 
worthy  of  serious  consideration. 

The  Commission  summarily  condemns 
the  project  of  a  system  of  reservoirs  as 
"  chimerical. 

"  The  "  Commission  is  forced  unwill- 
ingly to  the  conclusion  that  no  assistance 
in  reclaiming  the  alluvial  region  from 
overflow  can  judiciously  be  anticipated 
from  artificial  outlets.  They  are  correct 
in  theory,  but  no  advantageous  sites  for 
their  construction  exist." 

After  considering  some  objections 
urged  against  a  completed  system  of 
levees,  and  pronouncing  them  unfound- 
ed, they  proceed  to  recommend  this  mode 
of  protection.  The  report  goes  on  to 
prescribe  the  height  of  levees  for  differ- 
ent parts  of  the  river,  with  reference  to 
Vol.  XIII.— No.  1—2 


the  highest  known  flood  occurring  in  the 
uncompleted  state  of  the  levees,  viz.  :  ,? 
feet  near  the  mouth  of  the  Ohio,  increas- 
ing to  7  feet  at  Osceola ;  thence  to 
Helena  this  latter  height  should  be  main- 
tained ;  thence  to  Island  71  gradually 
increasing  to  10  feet,  gradually  diminish- 
ing to  8  feet  at  Napoleon ;  thence  to  Lake 
Providence.it  must  be  gradually  increas- 
ed to  11  feet ;  thence  to  the  mouth  of 
the  Yazoo  it  must  be  gradually  reduced 
to  6  feet,  and  it  should  thus  be  maintain- 
ed to  Natches  ;  thence  to  Red  River 
Landing  it  must  be  gradually  increased 
to  7  feet;  thence  to  Baton  Rouge  it  may 
be  gradually  reduced  to  5  feet ;  thence 
to  Donaldsonville  this  height  must  be 
maintained.  At  Canolton,  4.7  feet  will 
suffice,  &c.  The  levees  should  be  located 
at  a  sufficient  distance  from  the  river 
bank  to  guard  against  caving.  An  ap- 
proximate estimate  is  presented  of  the 
cost  of  a  completed  system  amounting 
to  about  45  millions  of  dollars. 

Upon  completion  of  the  works  they 
propose  to  intrust  their  maintenance  and 
care  to  a  board  of  engineers,  or  superin- 
tendents, each  of  whom  will  exercise 
authority  in  a  certain  district,  and  who 
will  have  a  mutual  organization  with 
powers  and  functions  analogous  to  those 
of  the  river  syndicates  of  France  and 
Spain.  They  recommend  further  an  ac- 
curate instrumental  survey  of  the  entire 
alluvial  region  subject  to  overflow.  It  is 
very  much  to  be  regretted  that  this  sur- 
vey was  not  authorized  by  Congress. 

Without  denying  the  general  conclu- 
sions of  this  Commission,  I  nmst  be  per- 
mitted to  say  that  they  would,  in  my 
opinion,  have  been  entitled  to  more 
weight  had  the  report  more  fully  met 
certain  grave  objections  to  which  a  com- 
pleted levee  system  is  liable. 

What  is  said  of  the  tendency  of  dyked 
rivers  to  elevate  their  beds,  is  substan- 
tially a  repetition  of  the  views  contained 
in  Humphrey's  and  Abbott's  report.  It 
appears  to  me  that  the  true  source  of 
danger  is  not  discussed  hi  either  of  these 


18 


VAN   N03TRAND  S   ENGINEERING  MAGAZINE. 


reports.  "We  need  not  ascribe  to  rivers 
dyked  or  undyked  any  tendency  to  ele- 
vate their  bottoms  or  their  low  water 
surfaces.  It  is  none  the  less  true  that  a 
completed  system  of  dykes  does  set  in 
motion  causes  tending  inevitably  to  the 
progressive  contraction  of  the  high  water 
section  of  the  river,  and  the  progressive 
elevation  of  its  flood  surface. 

That  the  deposits  resulting  from  the 
overflows  of  the  Mississippi,  in  its  nat- 
ural state,  have  elevated  the  ground  in 
its  immediate  vicinity,  is  evident  from 
the  fact  that  the  ground,  in  all  cases, 
descends  as  you  recede  from  the  river  ; 
the  river  banks  being  often  10  or  15  feet 
higher  than  the  swamps  which  lie  paral- 
lel with,  and  at  some  distance  from,  the 
river.  Upon  the  completion  of  the  sys- 
tem of  dykes,  it  is  equally  evident  that 
this  process  must  cease  inside  the  dyke, 
while  continuing  with  increased  vigor 
outside.  The  exposed  ground  {vorland 
as  it  is  called  in  Germany)  is  withdrawn 
from  cultivation.  Every  overflow  is  suc- 
ceeded by  a  rank  growth  of  bushes  and 
reeds  whose  roots  hold  fast  the  material 
deposited,  and  whose  stems  operate  to 
check  the  water  and  increase  the  depos- 
its of  the  next  year.  The  evil  is  greatly 
aggravated  if  the  vorland  is  protected 
"by  a  low  dyke  as  suggested  in  the  report. 
In  this  case,  at  every  overflow  of  the  low 
dyke,  the  vorland  is  filled  with  turbid 
water  moving  with  a  very  moderate  vel- 
ocity, a  condition  favorable  to  enormous 
deposits.  I  have  seen,  on  the  Mississippi, 
in  the  analogous  case  of  a  flooded  coffer 
dam,  a  deposit  of  more  than  12  inches 
in  the  course  of  a  single  flood. 

The  contraction  of  the  flood  water 
way,  from  these  causes,  tends,  of  course, 
to  increase  the  height  of  the  floods,  and 
levees  originally  sufficiently  high  will 
require  to  be  progressively  raised  and 
strengthened. 

In  swampy  regions,  another  cause 
comes  into  operation  to  increase  the 
height  of  floods  with  reference  to  the 
reclaimed  ground,  i.  e.  the  subsidence  of 
the  latter  in  consequence  of  the  better 
drainage  permitted  by  the  levees.  Re- 
claimed polders  in  Holland  usually  sink 
one  or  two  feet  from  this  cause. 

It  is  not  alone  with  reference  to  the 
Po,  as  the  report  appears  to  assume,  that 
apprehensions  of  gradual  elevation  have 
been  entertained.     Such  fears  have  been 


felt  with  reference  to  the  Rhine,  and  this 
not  alone  by  speculative  physicists,  but 
by  engineers  specially  conversant  with 
this  branch  of  their*  profession. 

Hagen*  considers  the  fact  of  such  pro- 
gressive elevation  well  established.  He 
cites  two  papers  bearing  upon  this  point. 
One,  a  memoir  presented  by  Blankenf  to 
the  Institute  of  the  Netherlands  in  1818, 
in  which  he  shows  that  dyke-breaks  up- 
on the  Rhine  and  Waal  had  increased  in 
frequency,  as  compared  with  the  preced- 
ing century,  notwithstanding  the  raising 
and  strengthening  of  those  dykes  which 
were  then  much  higher  than  formerly. 
The  other,  a  report  by  Rechtereu,J  in 
1830,  in  which  he  goes  so  far  as  to  re- 
commend the  flooding  of  the  country  in 
the  winter  as  the  only  means  of  avoid- 
ing ultimate  ruin. 

The  Commissioners  say  :  "The  pro- 
longation of  the  delta  into  the  gulf  by 
the  aggregation  of  sedimentary  matter 
is  also  assigned  as  a  cause  for  the 
ultimate  rise  of  the  bed,  and  hence 
for  a  future  necessary  increase  in  the 
height  of  the  levees.  A  possible  secu- 
lar change  of  this  nature  is  quite  too  re- 
mote in  its  effects  to  merit  attention 
from  practical  men  of  the  present  day. 
Simple  calculation  will  show  that  hun- 
dreds of  years  will  be  required  to  raise 
the  flood  height  at  New  Orleans  an  inch 
from  this  cause." 

Here,  again,  it  appears  to  me  that  the 
Commissioners  have  failed  to  note  the 
real  danger  to  be  apprehended  from 
changes  at  the  mouth  of  the  river.  A 
passage  in  the  physical  history  of  the 
lower  Rhine  may  be  interesting  in  this 
connection.     I  translate  from  Hagen  :§ 

"  At  what  time  the  old  Rhine  was  en- 
tirely closed,  and  when  the  numerous 
connections  between  the  Waal  and  the 
Maas,  either  spontaneously  originated  or 
were  artificially  opened,  is  unknown. 
Many  dyke-projects,  however,  were  exe- 
cuted in  the  twelfth  and  thirteenth  cen- 
turies at  which  time  the  entire  existing 
dyke-system  originated.  Whether  this 
was  done  in  the  immediate  interest  of 
agriculture,  without  reference  to  its  ef- 

*  Handbuch  der  Wassenbankunst.  Theil  3  Band.  8,  p. 
704. 

t  Beschouwingover  de  Uitsrooming  der  Opper  Rija  en 
Maas-Wateren.    Amsterdam,  1S19. 

t  Verhandelingen  over  den  Staat  van  den  Eijn,  de  Wftftl, 
etc.    Nijmegen,  1830. 

5  Handb.  d.  Wassenbankunst.    Theil  2  B.  p.  423. 


SUBMERSIBLE   LANDS   OF   THE   MISSISSIPPI  VALLEY. 


19 


feet  upon  the  regimen  of  the  rivers,  can- 
not now  be  ascertained.  Certain  it  is 
that  the  dykes  became  a  new  cause  of  de- 
rangement to  the  rivers,  and  many  new 
channels  were  opened  by  dyke-breaks. 
The  most  frightful  instance  of  this  kind 
was  the  overflow  of  the  Waal  and  Maas 
in  the  South  Holland  Waard,  or  the 
JBergsche  Feld.  The  Maas  had  already, 
in  the  lower  part  of  its  course,  united 
itself  with  the  Waal,  and  both,  on  the 
18th  of  November,  1421,  broke  through 
the  left  dyke,  between  Woudrichem  and 
Bortreckt,  and  flooding  the  low  lands, 
destroyed  a  surface  of  many  square* 
miles.  The  water  thereby  opened  for 
itself  a  new  mouth  in  the  sea,  through 
the  deep  and  wide  bay  of  the  Beisbosch, 
through  the  Holland's  deep,  and  through 
the  Krammer.  Seventy-twof  villages 
were  destroyed  by  the  water  together 
with  the  ground  on  which  they  stood. 
This  devastation  is  only  explainable  upon 
the  supposition  that  the  sea,  being  put 
in  communication  with  the  dyked  land, 
entered  it  at  every  flood  and  receded  at 
every  ebb.  Thus  originated  the  power- 
ful currents  which  led  to  the  widening 
and  deepening  of  the  channel.  A  natu- 
ral consequence  of  this  dyke-break  was 
that  the  Waal  now  took  the  level  of  the 
North  Sea  at  the  Beisbosch,  that  is,  10 
miles  (about  45  English  miles)  from  its 
former  mouth,  and  its  course  was,  there- 
after, shortened  by  that  distance.  The 
relative  fall  thereby  augmented,  as  far 
as  the  point  of  separation  (from  the 
Rhine),  at  Lobit.  The  rush  of  waters 
increased,  and  in  proportion  as  the  chan- 
nel was  extended  and  deepened,  those 
■of  the  Rhine,  the  Leek  and  the  Issel 
were  shoaled  by  \ he  diminished  velocity. 
This  relation  which  promised  the  entire 
closing  of  the  weaker  arms  and  the  ulti- 
mate reunion  of  the  streams  in  a  single 
channel,  disappeared,  however,  and  a  re- 
markable change  was  allowed  to  develop 
itself  in  the  course  of  some  centuries. 
The  Beisbosch  was,  by  the  sediment  of 
the  river,  and  possibly  also  by  tidal  ac- 
tion, gradually  filled  up,  and  the  broad 
bay  was  replaced  by  a  marshy  region  in 
which  isolated  islands  already  raised 
themselves   above  the  ordinary  level  of 


*  A  square  German  mile  is  about  twenty  square  Eng- 
lish miles. 

t  Blanken.  Memorie  betrekkelligk  den  Staat  derKivier- 
-en.    Utrecht,  1823,  page  22. 


the  water.  They  were  overgrown  with 
grass  and  bushes,  and  were  soon  provid- 
ed with  dykes.  Between  them  were  a 
great  number  of  shallow  water  courses, 
which  were  naturally  no  longer  in  a  con- 
dition to  carry  off  the  greater  part  of 
the  volume  of  the  Rhine,  and  still  less 
could  the  level  of  the  sea  establish  itself 
therein.  The  low  water-level  in  the 
Waal  thus  disappeared,  and  with  it  the 
former  large  (relative)  fall.  The  Rhine 
and  the  Leek,  and  likewise  the  Merwede 
or  lower  part  of  the  Waal,  thereupon 
took  a  stronger  current,  and  the  entire 
volume  of  the  Rhine  resumed  its  course 
through  these  arms,  while,  in  consequence 
of  the  previous  diminished  current,  the 
depth  therein  had  diminished  in  a  re- 
markable degree,  and  they  had  become 
entirely  insufficient  for  carrying  off  the 
waters.  The  streams  could  only  be  con- 
fined to  their  beds  by  raising  the  dykes, 
but  they  filled  these  to  such  an  alarming 
height  that  not  only  did  the  natural 
drainage  in  great  part  fail,  but  the  dan- 
ger of  dyke-breaks  ever  increased  and 
the  existence  of  many  important  places 
was  continually  threatened." 

We  see,  then,  that  apprehensions 
founded  upon  possible  changes  at  the 
mouth  of  the  river  are  not  so  groundless 
as  the  Commissioners  suppose.  The  com- 
pletion of  a  system  of  dykes  is  very 
liable  to  cause  changes  in  the  course  of 
the  lower  river  by  curasses,  and  these 
changes  are  liable  to  necessitate  an  in- 
crease in  the  height  of  the  dykes. 

I  pass  now  to  another  point  of  most 
vital  importance,  which,  strange  to  say, 
has  not  been  touched  upon,  either  in  this 
report  or  in  the  very  voluminous  and 
valuable  report  of  Humphrey's  and  Ab- 
bott. How  is  it  proposed  to  deal  with 
the  rainfall  in  the  reclaimed  district  ? 

In  the  history  of  the  levees,  thus  far, 
this  question  has  attained  no  practical 
significance.  They  have  been  built  to 
meet  immediate  and  local  wants,  with 
but  slight  consideration  of  ultimate  ef- 
fects consequent  upon  the  completion  of 
the  system.  They  have  afforded  protec- 
tion only  to  the  higher  grounds  near  the 
river,  leaving  always  extensive  swamps 
in  the  rear  to  receive  and  convey  away 
their  surface  water.  Upon  the  comple- 
tion of  the  system,  the  swamps  above 
Red  River  will  no  longer  afford  this  re- 
lief.    Their  outlets  are  liable  to  be  back- 


20 


van  nostrand's  engineering  magazine. 


ed  up  from  four  to  ten  feet  above  the 
highest  flood  hitherto  known.  The  flood 
stage  of  the  river  lasts  sometimes  three 
or  more  months,  during  which  time  the 
alluvial  districts  are  liable  to  receive  a 
rainfall  of  two  feet  or  more.  Without 
efficient  drainage,  their  condition  will 
hardly  be  improved  by  the  levees.  In 
fact,  extensive  tracts  will  be  liable  to 
overflow  several  feet  deep,  which,  with- 
out levees,  would  have  been  above  water. 
Claims  for  protection  will  be  urged  with 
redoubled  vehemence,  claims  which  the 
Government  cannot  in  justice  disregard, 
the  evils  being  of  its  own  creation.  I 
can  conceive  of  no  effectual  remedy  for 
these  evils  other  than  a  vast  establish- 
ment of  steam  -  pumping  machinery. 
Such  an  establishment  is  ultimately  in- 
separable from  a  perfected  system  of 
levees.  If  the  Government  commits  it- 
self to  the  first,  it  cannot  reasonably  or 
justly  evade  the  second. 

Let  the  reader  endeavor  to  form  an 
idea  of  the  cost  of  such  an  establish- 
ment, capable,  for  instance,  of  relieving 
a  district  20,000  square  miles  in  extent, 
of  12  inches  of  rain-water  in  the  course 


of  30  days,  the  water  to  be  raised  12 
feet.  The  result  is  absolutely  appalling. 
More  than  three  times  the  sum  assigned 
as  the  entire  cost  of  the  levees. 

It  is  not  the  purpose  of  this  communi- 
tion  to  offer  anything  in  the  way  of  prac- 
tical suggestion,  but  rather  to  urge  the 
importance  of  a  more  thorough  consider- 
ation of  the  subject  than  it  appears  to 
have  received  from  this  Commission. 
The  method  of  protection  by  levees,  once 
resolved  on  and  undertaken  by  the  Gov- 
ernment, must  be  persevered  in,  however 
great  the  difficulties  in  their  maintenance 
developed  by  time.  The  longer  they 
afford  protection  to  the  country,  the 
more  important  become  the  interests  to 
be  protected,  the  more  deplorable  results 
of  failure,  and  the  stronger  the  obliga- 
tion to  maintain  the  system.  The  Gov- 
ernment should  not  be  committed  to  ac- 
tion so  momentous  and  irrevocable  with- 
out all  the  light  that  the  history  of  simi- 
lar works  can  afford,  lest  the  difficulties, 
now  but  dimly  to  be  foreseen,  should 
progressively  acquire  such  strength  as  to 
become  utterly  overwhelming. 


LIME. 


From  "The  Builder.' 


Or  all  the  materials  used  in  construc- 
tion, lime  is  perhaps  the  most  important, 
and  the  following  resume  of  several 
series  of  experiments  made  by  French 
engineers  and  others  into  its  nature  and 
treatment  cannot  fail  to  be  acceptable. 

I.  Pure  or  quick  Lime,  Oxide  of  Cal- 
cium, is  composed  of  28.58  parts  of 
oxygen,  and  71. 42  parts  of  calcium,  a 
substance  white  in  color,  caustic,  pulveru- 
lent, absolutely  infusible  in  the  fiercest 
fire,  susceptible  of  crystallization  in 
rhomboidal  prisms,  and  of  a  burning 
and  acrid  taste;  it  quickly  disorganizes 
animal  substances  brought  into  contact 
with  it,  turns  syrups  of  violets  green, 
and  gives  to  turnsole  the  same  reddish 
blue  color  as  an  acid. 

Its  specific  gravity  is  2.30.  It  dis- 
solves in  900  or  1,000  times  its  weight 
of  cold  water,  or  in  twice  that  quantity 
of  boiling  water.     It  is   scarcely   ever 


found  in  nature  in  a  state  of  purity, 
except  in  some  volcanic  prodiictions. 

Brought  into  contact  with  water,  it  is 
transformed  into  hydrate;  it  gives  out  a 
quantity  of  heat  which  may  amount  to 
300°centigrade,  and  is  capable  of  igniting 
gunpowder;  a  part  of  the  water  escapes 
in  the  form  of  very  hot  vapor,  slightly 
caustic,  and  a  noise  is  produced  resem- 
bling that  caused  by  plunging  red-hot 
iron  into  water;  it  melts  or  is  reduced 
into  impalpable  powder,  or  into  paste. 
This  hydrate  is  chaux  amortie,  chaux 
coulee,  or  chaux  eteinte,  slaked  lime,  to 
distinguish  it  from  quick  or  anhydrous 
lime. 

LT.  Physical  Characteristics.  —  When 
slaked,  lime  increases  in  volume;  it 
swells  according  to  its  degree  of  purity, 
and  sometimes  attains  a  volume  two  or 
three  times  that  of  the  quicklime  from 
which  it  is  produced.     That  which  has 


LIME. 


21 


absorbed  a  volume  of  water  equal  to 
2.60  to  3.60  for  one  of  lime  is  called 
chaux  grasse,  or  fat  lime ;  and  which  has 
only  taken  up  1  to  2.30  per  cent,  of  water, 
chaux  maigre.  When  the  latter  hardens, 
not  only  in  the  air  but  under  water,  it  is 
called  hydraulic  lime. 

III.  Limestone. — Lime  is  obtained  for 
industrial  purposes  by  the  calcination  of 
calcareous  stone,  a  substance  composed 
of  lime  and  carbonic  acid,  and  which 
partly  dissolves  in  weak  acid,  with  more 
or  less  effervescence.  The  quantity  of 
lime  which  it  is  capable  of  yielding  is  in 
proportion  to  the  carbonate  of  lime  con- 
tained within  it. 

Pure  carbonate  of  lime  is  very  rare;  it 
contains  55.98  parts  of  lime,  and  44.02 
of  carbonic  acid.  When  calcined  at  a 
high  temperature,  it  yields  pure  caustic 
lime. 

Calcareous  matter  is  one  of  the  most 
common.  In  nature,  it  is  usually  mixed 
with  silica,  alumina,  magnesia,  quartz  in 
grains,  or  sand,  clay,  oxide  of  iron,  man- 
ganese, bitumen,  and  sulphur,  or  pyrites. 
The  combination  of  these  various  sub- 
stances constitutes  several  kinds  of  lime- 
stone, which  are  subdivided  into  many 
varieties. 

Mineralogists  distinguish  several  kinds 
of  limestone,  and  point  out  varieties  of 
form  and  texture  in  each;  but  that 
which  is  important  for  the  builder 
to  know  is,  that  each  kind  furnishes  a 
special  line  different  in  color,  density, 
greediness  for  water,  and  especially  in 
its  practical  results  when  mixed  with 
sand. 

The  physical  characteristics  of  calcare- 
ous stones  furnish  no  certain  data  with 
respect  to  the  kind  of  lime  they  will 
yield,  and  even  chemical  analysis  affords 
but  approximate  results.  Formerly  it 
was  maintained  that  the  hardest,  heavi- 
est, most  compact,  and  most  homogene- 
ous stones,  with  the  finest  grain,  made 
the  best  lime;  it  is  now  admitted  that 
these  characteristics  are  not  sufficient 
indices  of  the  quality  of  the  products  to 
be  obtained  from  them.  It  is  only  by 
trials  and  experiments  that  their  value 
can  be  determined.  The  purer  the  lime- 
stone, the  more  the  lime  obtained  will 
swell ;  if  the  carbonate  of  lime  contain 
foreign  matter  to  the  extent  of  ten  or 
twenty  per  cent.,  the  lime  after  being 


slaked  will  swell  very  little  or  not  at  all, 
it  is  poor. 

IV.  Hydraulic  JOvmeetone.  —  As  hy- 
draulic limestone  is  the  most  valuable 
on  account  of  its  peculiarity  of  harden- 
ing rapidly  under  water,  it  is  most 
important  to  ascertain  what  limestone 
will  furnish  it.  For  a  long  period  scien- 
tific men  were  not  agreed  as  to  the 
causes  which  rendered  lime  more  or  less 
hydraulic;  some  attributed  this  peculiar 
property  to  the  presence  of  metallic 
oxides,  others  to  a  combination  of  silica 
and  alumina.  Smeaton,  in  1756,  discov- 
ered that  the  hardening  by  immersion 
was  due  to  a  certain  quantity  of  clay 
contained  in  the  limestone  possessing 
that  quality.  MM.  de  Saussure,  General 
Freussard,  Berthier,  and  Fuchs,  of 
Munich,  have  published  remarkable 
papers  on  this  subject,  but  no  one  has 
done  so  much  for  it  from  a  scientific 
point  of  view  as  M.  Vicat.  Before  his 
time  there  were  not  ten  quarries  in 
France  in  which  hydraulic  limestone 
was  known  to  exist,  but  after  traveling 
the  country  on  foot  for  years,  he  discov- 
ered more  than  three  hundred,  and  there 
is  not  a  department  in  all  France  that 
does  not  owe  to  him  the  discovery  of  a 
mass  of  mineralogical  wealth. 

V.  How  to  recognize  hydraulic  Lime- 
s£cme.— Hydraulic  lime  being  produced 
from  the  mixture  of  carbonate  of  lime 
with  clays,  it  is  important  to  know  the 
quarries  in  which  the  variety  is  to  be 
found.  M.  Vicat  recommends  that  the 
strata  should  be  deeply  sounded,  as  the 
chemical  composition  of  the  lower  layers 
may  differ  sensibly  from  that  of  the 
layers  more  exposed  to  the  influence  of 
the  atmosphere.  It  has  been  remarked 
in  general,  that  limestone  of  a  dirty 
grey,  ashy,  or  bluish  tint,  contains  much 
more  of  the  argillaceous  or  silicious 
principles  than  that  of  a  compact  or 
crystalline  texture.  The  information 
obtained  from  miners  and  masons  is 
very  useful;  and  we  must  not  be  discon- 
certed by  failures ;  they  arise,  generally, 
simply  from  misdirection  of  research. 
M.  Chateau  relates  that  for  a  long-time 
Paris  obtained  her  hydraulic  lime  from 
Senonches,  at  the  cost  of  80  francs  the 
cubic  metre,  while  the  quarries  of  the 
Buttes  -  Montmartre,   the   Buttes-Chau- 


22 


VAN   NOSTrAsTD'S   ENGINEERING   MAGAZINE. 


mont,  and  Romainville,  which  yield 
limestone  that  produces  all  the  varieties 
of  hydraulic  lime,  remained  unexplored. 
For  the  testing  of  limestone,  M.  Vicat 
recommends  the  burning  first  of  a  small 
quantity,  and  afterwards  on  a  large 
scale.  The  difference  of  the  weight  and 
the  value  of  the  products  will  thus  set 
all  doubt  at  rest. 

VI.  Mode  of  Trial. — The  method  pro- 
posed by  Mr.  Berthier  is  as  follows: 

Crush  the  limestone,  pass  the  powder 
through  a  silk- sieve  and  pour  upon  it 
little  by  little  muriatic  acid,  or,  in  the 
absence  of  that,  sulphuric  acid,  or  vine- 
gar, diluted  with  a  small  quantity  of 
water,  stirring  it  continually  with  a 
glass  rod  or  a  stick,  and  continuing  the 
application  of  the  acid  until  all  efferves- 
cence ceases ;  evaporate  the  mixture  with 
a  gentle  heat,  and  when  all  is  reduced  to 
a  soft  paste  mix  this  up  with  about  a 
pint  of  water  and  filter  it;  the  clay, 
which  will  remain  on  the  filter,  must 
then  be  dried,  either  in  the  sun  or  before 
the  fire,  and  weighed;  or,  which  is  better, 
calcine  the  clay  to  redness  in  an  earthen 
or  metal  crucible  before  weighing  it, 
then  pour  lime-water  on  the  filtered 
solution  so  long  as  any  precipitate  con- 
tinues to  fall;  collect  this  precipitate, 
which  is  magnesia,  sometimes  mixed 
with  iron  and  manganese,  as  quickly  as 
possible  on  a  filter,  wash  it  with  pure 
water,  dry  it  as  completely  as  possible, 
and,  finally,  weigh  it.  The  weight  of 
the  clay  compared  with  that  of  the 
calcareous  substance  dissolved  gives  ap- 
proximatively  the  rank  which  the  min- 
eral should  fill  amongst  hydraulic  lime- 
stones. It  is  important  to  note  that 
after  the  first  filtration  no  clay  may  be 
found,  or  only  a  mixture  of  fine  sand 
with  clay;  in  the  former  case,  the  lime- 
stone will  only  furnish  poor  lime;  in  the 
latter,  the  sand  must  be  separated  from 
the  clay  by  washing  and  decantation,  to 
ascertain  the  resj^ective  weight  of  each. 

VII.  Lime-burning. — In  the  burning 
of  lime,  all  kinds  of  fuel  are  employed, 
according  to  the  locality — wood,  heather, 
peat,  coal;  coke  gives  excellent  results, 
charcoal  not  so  good,  besides  being  \rery 
dear.  The  form  of  the  kirns  varies  with 
the  customs  of  the  place,  and  the  kind  of 
fuel  employed:  it  should  tend  to  econo- 


mize the  latter,  but  without  endangering 
the  quality  of  the  product.  In  those 
regions  where  wood  is  abundant,  the 
kiln  is  often  a  simple  square  or  circular 
excavation,  about  6  ft.  wide  by  10  ft.  to 
11  ft.  in  height,  the  interior  being  lined 
with  dry  stones,  or,  still  better,  fire-clay 
bricks.  The  limestone  is  thrown  in,  but 
not  too  compactly,  so  that  the  flame 
may  circulate,  and  the  smoke  escape;, 
the  fuel  is  then  placed  in  a  space  left  in 
the  upper  part  of  the  mass.  No  arrange- 
ment whatever  is  made  to  concentrate 
the  heat,  the  loss  of  which  is  enormous, 
and  the  burning  of  the  limestone  is  un- 
equal. 

The  forms  employed  for  better  con- 
structed kilns  are  the  right-angled  prism, 
the  cylinder,  the  cylinder  surmounted 
by  a  truncated  cone,  the  reversed  trun- 
cated cone,  and  the  ellipsoid  ovoide, 
with  variations.  The  rectangular  forms 
are  used  in  the  centre,  south  and  east  of 
France.  Bricks  and  lime  are  burned  in 
them  at  the  same  time.  The  limestone 
is  placed  below,  filling  up  half  the  kiln, 
and  the  upper  part  is  filled  with  brick& 
or  tiles.  When  a  large  quantity  of  lime 
is  required  rapidly,  the  cylindrical  form 
is  employed;  their  construction  is  eco- 
nomical and  easy,  but  they  do  not  last 
long.  The  limestone  is  built  up  like  a 
tower,  and  covered  with  beaten  earth, 
the  fire  being  introduced  below. 

The  other  kilns  are  built  in  a  solid 
and  durable  manner;  no  bricks  are  burnt 
in  them;  the  large  stones  are  placed 
below,  and  the  small  upon  them  in  the 
upper  cone.  The  ellipsoidal  and  ovoidal 
kilns  are  for  burning  by  means  of  coal 
or  coke;  their  linings  are  of  brick,  16 
in.  to  20  in.  in  thickness,  set  in  mortar 
made  of  refractory  clay  and  sand. 

In  the  long-flame  kilns,  fed  by  wood 
and  heather,  the  charge  rests  on  one  or 
two  arches  constructed  of  the  same  ma- 
terials as  the  kiln ;  the  fire  increases 
with  the  draught,  the  mouth  is  kept, 
filled  with  fuel,  the  flame  makes  its  way 
gradually  until  the  whole  mass  is  in  a, 
state  of  incandescence  to  the  very  sum- 
mit. 

VIII.  The  Kilns. — A  crowd  of  cir- 
cumstances may  affect  the  burning — the 
quality  of  the  fuel,  the  direction  of  the 
wind,  etc.  Generally  it  takes  120  to  150 
hours  to  calcine  properly  70  to  80  tons 
of  limestone. 


LIME. 


23 


It  is  almost  impossible  in  long-flame 
kilns,  20  ft.  to  25  ft.  high,  to  burn  the 
paper  layers  of  limestone  sufficiently 
without  overburning  the  lower;  in  the 
case  of  rich  lime  this  is  not  a  matter  of 
much  importance,  but  in  that  of  argilla- 
ceous limestone  it  is  fatal,  because  if 
overburned  it  falls  into  powder  and 
becomes  good  for  nothing.  The  steam 
of  the  water  contained  in  the  limestone 
aids  by  its  expansion  in  the  burning  of 
the  upper  layers:  thus  the  limeburner 
prefers  the  stone  just  out  of  the  quarry 
to  that  which  has  lost  its  water. 

The  burning  of  argillaceous  limestone 
is  also  very  difficult  in  kilns  heated  with 
coal,  the  latter  being  mixed  with  the 
stone,  The  draught  is  affected  in  many 
ways,  by  changes  in  the  direction  or  in 
the  force  of  the  wind,  by  any  damage 
done  to  the  sides  of  the  kiln,  by  the  fact 
of  the  pieces  of  limestone  being  too  un- 
equal in  size,  and  thus  not  being  equally 
mixed  with  the  coal,  and  many  other 
accidents  which  cause  the  lime  to  be 
burnt  too  much  or  insufficiently. 

IX.  MM.  Donopp  and  Deblinne  set 
forth  the  differences  which  exist  in  lime 
calcined  by  means  of  wood,  coal,  and 
peat. 

1.  Lime  burned  with  wood  is  gener- 
ally whiter  than  that  produced  with 
other  fuel. 

2.  Lime  calcined  with  peat,  slaked 
and  mixed  with  an  equal  quantity  of 
water,  always  precipitates  more  rapidly 
than  that  which  has  been  burned  with 
wood. 

3.  The  calcination  with  coal  produces 
lime  which  precipitates  very  promptly, 
when,  after  having  been  slaked,  it  is 
mixed  with  a  certain  quantity  of  water. 

Consequently,  it  is  in  the  interest  of 
builders  to  employ  lime  burned  with 
peat  or  coal,  because  as  its  residue  does 
not  contain  the  alkaline  principles  of 
lime  burnt  with  wood  by  the  mixture  of 
the  ashes,  the  mortars  of  which  they 
form  part  will  be  of  superior  quality. 

X.  Rich  lime  is  obtained  from  the 
purest  limestone;  it  is  called  chaux 
grasse,  because  when  slaked  the  paste  is 
fine  and  greasy  to  the  touch.  This 
kind  swells  and  throws  out  more  heat 
than  the  others.  Reduced  to  a  paste 
and  exposed  to  the  air,  it  dries  by  the 


evaporation  of  the  water  which  is  not 
in  combination  with  it,  absorbs  a  portion 
of  the  carbonic  acid  contained  in  the  air, 
and  in  time  acquires  considerable  hard- 
ness; this  hardness  is  much  accelerated 
by  the  substitution  of  a  current  of  car- 
bonic acid  gas  for  atmospheric  air.  In  this 
state,  and  with  the  aid  of  small  mould?, 
tiles  and  slabs  may  be  made  which  take 
a  polish  when  rubbed  upon  a  fine  stone, 
and  resemble  the  finest  white  marble. 

The  following  analyses  of  the  compo- 
sition of  several  materials  producing 
rich  lime  are  by  M.  Berthier,  engineer: 

Iceland  Spar.  —  Pure  carbonate  of 
lime.     The  elements  are: 

Lime 0.564 

Carbonic  Acid 0.436 

1.000 

Carrara  White  Statuary  Marble. — 
The  matter  which  is  insoluble  in  acid  is 
pure  quartz.     The  elements  are: 

Lime 0 .  554 

Magnesia 0 .  001 

Clay  and  quartz 0.010 

Carbonic  acid 0.435 

1.000 

Limestone  of  Saint  Jacques,  Jura. — 
Compact,  yellowish  in  color,  forms  the 
basis  of  the  Jura  mountains.  The  ele- 
ments are: 

Lime 0.546 

Magnesia 0.009 

Clay  and  quartz 0 .  01 5 

Carbonic  acid 0.430 

1.000 

Limestone  of  the  Jurassic  formation, 
forming  the  superstratum  of  the  iron 
mine  of  La  Voulte  in  the  Ardeche — 
compact,  yellowish,  shelly,  density,  2.67. 
The  elements  are: 

Lime 0.541 

Magnesia 0 .  006 

Oxide  of  iron 0.005 

Clay  and  quartz 0.023 

Carbonic  acid 0.426 

1.000 

Coarse  Limestone,  tertiary  formation 
in  the  environs  of  Paris,  very  shelly. 
The  elements  are: 

Lime 0.556 

Clay  and  quartz 0.015 

Carbonic  acid 0.429 

1.000 


24 


VAN   NOSTRAND  S   ENGINEERING   MAGAZINE. 


Fresh-water  Limestone  of  the  environs 
Nemours,  Seine,  and  Marne — compact, 
yellow,  rather  cellular,  and  very  sono- 
rous.    The  elements  are: 

Lime 0.548 

Magnesia 0.009 

Clay  and  quartz 0.010 

Carbonic  acid 0 .  433 

1.000 

Fresh  -  water  Limestone  of  GEnigen, 
near  Constance,  Algeria — composed  of 
remains  of  birds,  saurians,  and  fish,  con- 
tains a  large  proportion  of  organic 
matter.     The  elements  are: 

Lime 0.504 

Magnesia 0.018 

Clay  and  quartz 0.069 

Carbonic  acid 0 .  409 

1.000 

The  two  following  are  due  to  M. 
Vicat : 

Vichy  Limestone. — This  stone,  from 
the  amount  of  clay  which  it  contains, 
forms  the  limit  of  rich  limestones.  The 
elements  are: 

Lime 48.80 

Magnesia 4 .  76 

Oxide   of   iron,  clay,   and 

quartz 2 .  80 

Carbonic  acid 43.64 

100.00 

The  composition  of  the  lime  produced 
from  the  above  stone  is  as  follows: 

Lime 86.00 

Magnesia 4.76 

Oxide  of    iron,   clay,   and 
quartz 5.00 

100.00 

The  rich  lime,  which  swells  most,  is 
evidently  the  most  profitable;  but  its 
employment  should  be  restricted  to  ordi- 
nary masonry  in  elevations;  if  used  for 
underground  or  water  work,  the  mortar 
in  which  it  enters  will  not  harden,  but 
crumble  away. 

XI.  Ghaux  Maigre,  or  poor  lime,  so 
called  from  the  fact  that  when  mixed 


with  water,  of  which  it  absorbs  but  a 
small  proportion,  it  is  short  and  hard, 
not  sticky  and  unctuous,  like  chaux 
grasse — it  scarcely  effervesces  at  all.  It 
is  produced  from  limestone  containing 
mineral  oxides  and  magnesian  products 
in  considerable  proportions.  Like  the 
preceding,  it  is  quite  unfit  for  use  under 
water  or  in  damp  places. 

XII.  Hydraulic  Lime. — When  chaux 
maigre  possesses  the  special  property  of 
hardening  under  water,  it  is  called  hy- 
draulic lime.  M.  Vicat  subdivides  the 
various  kinds  under  three  heads,  accord- 
ing to  their  rapidity  of  hardening: 

1st  Class. — Medium  Hydraulic,  con- 
taining 82  per  cent,  of  lime  and  18  per 
cent,  of  clay. 

2d  Class. — Hydraulic  Lime,  contain- 
ing 74  per  cent,  of  lime  and  26  per  cent, 
of  clay. 

3d  Class. — Eminently  Hydraulic,  com- 
posed of  70  per  cent,  of  lime  and  30  per 
cent,  of  clay. 

The  first  sets  after  immersion  for 
fifteen  to  twenty  days;  the  second,  in 
six  to  eight  days;  and  the  third  in  two 
to  four  days.  The  lime  is  considered  to 
have  set  when  it  will  support  a  knitting- 
needle,  filed  square  at  one  end,  and 
loaded  with  a  weight  of  10  ounces, 
without  any  sensible  depression  being 
produced.  In  this  state  it  will  resist  the 
finger  with  a  pressure  of  10  to  12 
pounds.  A  fragment  of  it  will  not  bend, 
but  break. 

The  hydraulic  limes  have  little  color. 
They  have  generally  a  muddy  grey,  un- 
burnt  brick,  or  yellow  tint.  Their 
swelling,  as  compared  with  the  unctuous 
limes,  is  scarcely  noticeable.  The  best 
and  dearest  of  all  the  kinds  known  in 
France  is  that  of  Saint  Quentin. 

XIII.  Analyses  of  the  Limes. — The 
following  table  contains  the  results  of 
analyses  by  MM.  Berthier,  Rivot,  De- 
lesse,  and  H.  Deville,  of  the  best  known 
hydraulic  limes,  ten  being  of  the  class 
called  "hydraulic,"  and  six  of  the  de- 
nominated "eminently  hydraulic:" 


NITRO-GLYCEKINE   EXPLOSIONS. 


25 


Percentage  of  the  Elements  of  tJiese  Limestones. 


"Hydraulic." 

"  Eminently  Hydraulic." 

Carbonate  of  lime 

61.33  to  89.2  per  cent. 

52.47  to  82.5  per  cent. 

magnesia 

In  1  case  40.91 ;  gen.  2  to  3  per  cent. 

44.25  in  1  case;  gen.  1.5  to  4.5  p.  c. 

Clay 

5.50  to  15  per  cent. 

3.25  to  23  per  cent. 

15.3  in  1  specimen  only. 

None. 

Quartz  sand  and  clay- 

15.0 

Alumina,  with  a  little 

oxide  of  iron 

2.6 

Oxide  of  iron 

Trace     "            " 

Carbonate  of  iron. . . . 

0.58  in  1,  and  6.2  in  another. 

3.0  per  cent,  in  1  case. 

"         manganese 

None. 

1.5 

Iron  pyrites ... 

0.80  in  1  specimen. 

None. 

Soda  and  potash 

0.12 

«i 

1.0  to  4.5  per  cent. 

Percentage  of  the  Elements  in  the  Limes  made  from  the  above. 


Lime 

pt,      |  Silica 

C1*y}  Alumina 

Quartz  sand 

Magnesia 

Oxide  of  iron 

' '       manganese. 
Sulphate  of  lime. . . . 


'Hydraulic." 


53.82  to  78.29  per  cent. 

10.25  to  26.14      " 

1.54  to    8.69      " 

1.71  in  1  case  ;  35.93  in  another. 

From  a  trace  to  1.34  per  cent. 

Traces. 

None. 

1.15  in  1  case  ;  1.24  in  another. 


"  Eminently  Hydraulic." 


53.05  to  70  per  cent. 

13.40  to  29 

Traces  in  1  instance  only. 

Trace  to  39.71,  in  3  cases  only. 
1  to  4.10  percent,  in  3 
4  per  cent,  in  1 
None. 


The  best  manner  of  preserving  these 
hydraulic  limes,  when  they  come  from 
the  kilns,  is  to  strew  the  bottom  of  the 
receptacle,  which  mast  be  perfectly  dry, 
with  slaked  and  sifted  lime,  to  the  depth 
of  about  3  in.,  and  to  place  about  the 
same  quantity,  or  rather  more,  of  the 
same  over  the  top  of  the  lime  when  the 
receptacle  is  filled. 

When  the  proportion  of  clay  exceeds 


30  per  cent,  in  hydraulic  lime,  it  can 
only  be  slaked  by  means  of  boiling 
water.  Powdered  and  mixed,  this  lime 
sets  immediately.  It  does  not,  however, 
retain  its  hardness,  but  falls  into  powder 
or  paste,  according  to  the  state  of  the 
atmosphere.  This  is  called  chaux  limite, 
but  it  constitutes  by  comparison  the 
limit  between  lime,  the  cements,  and  the 
puzzolanos. 


NITRO-GLYCERINE  EXPLOSIONS. 

Bt  chas.  l.  kalmbach,  m.  e. 

Written  for  Van  Nostrand's  Engineering  Magazine. 


Having  manufactured,  solely  for  my 
own  use,  nitro-glycerine,  fulminate,  gun- 
cotton,  and  the  dynamites,  for  nearly 
nine  years,  and  having  expended  these 
materials  under  a  great  variety  of  cir- 
cumstances, on  land,  in  mines,  and  under 
water,  I  have  been  enabled  to  accumu- 
late a  great  number  of  facts  concerning 
their   character.      This   experience    has 


forced  me  to  dissent  from  many  import- 
ant and  universally  received  maxims, 
governing  the  storage,  transportation, 
and  use  of  nitro-glycerine,  and  the  com- 
pounds made  of  the  same.  The  fact 
that  during  all  that  time  I  have  never 
met  with  the  slightest  so-called  accident, 
confirms  my  faith  in  the  deductions  I 
have    made    from    these    observations. 


26 


VAN   NOSTRAND'S   ENGINEERING   MAGAZINE. 


Incidentally,  while  engaged  in  these 
labors,  I  discovered  some  improvements 
in  the  economical  application,  as  well  as 
in  the  compounding,  of  nitro-glycerine 
with  absorbent  materials,  which  im- 
provements are  covered  by  letters 
patent.  Since,  however,  the  specifica- 
tions cannot  relate  my  experience  nor 
give  the  reasons  for  the  system  of  rules 
I  employ,  I  am  induced  to  publish  these, 
notes  to  the  end  that  the  attention  of 
others  may  be  drawn  to  a  system  which 
has  proved  so  eminently  successful  in 
my  hands. 

On  the  14th  of  April,  1S66,  an  explo- 
sion of  nitro  -  glycerine  occurred  in 
Wells,  Fargo  &  Co.'s  office,  San  Fran- 
cisco, resulting  in  great  loss  to  life  and 
property.  A  suit  for  damages  arose, 
which  is  on  record  in  vol.  15,  p.  524,  of 
Wallace's  Reports,  United  States  Su- 
preme Court.  From  the  testimony  of  the 
experts  examined  I  quote:  "Explosion  of 
nitro-glycerine  is  produced  by  percussion 
and  concussion,  by  a  high  degree  of  pres- 
sure^ but  not  by  contact  with  fire.  If 
flame  be  applied  it  will  burn  slowly, 
without  exploding,  and  when  the  flame 
is  withdrawn  it  will  cease  to  burn.  It 
will  also  explode  when  subjected  to  a  heat 
of  360  degrees  Fahrenheit.^ 

I  believe  that  the  causes  of  explosion 
enumerated  in  the  above  quotation  are 
to  this  day  universally  received  as 
axioms,  and  that  the  fact  of  their  un- 
questioned reception  is  the  fruitful 
source  of  many  accidents.  I  assert  that 
but  one  of  them  is  true  and  worth 
guarding  against,  namely:  Nitro-gly- 
cerine will  explode  when  heated  to  about 
360  Fahrenheit.  I  will  also  state  that 
all  compounds  containing  nitro-glycerine 
will  explode  when  heated  to  that  degree. 
Simple  concussion  or  percussion  will  not 
explode  nitro-glycerine  nor  the  dy- 
namites. 

A  bottle  or'  other  frangible  vessel  par- 
tially filled  with  nitro-glycerine  may  be 
thrown  with  great  violence,  or  from  a 
height  on  rock  and  shattered  without 
producing  explosion.  Surely  here  we 
have  concussion  or  percussion.  But 
what  happens  if  a  tin  can  or  other 
strong  flexible  vessel  filled  with  nitro- 
glycerine is  subjected  to  such  an  ordeal  ? 
Such  can  will  invariably  explode  when 
it  strikes.  The  reason  is  evidently  this: 
Arrested   motion    converted    into   heat. 


The  glass  bottle  breaks  by  first  contact, 
releasing  the  contents  and  allowing  them 
to  scatter,  thus  measurably  continuing 
the  motion;  The  flexible  vessel,  how- 
ever, if  strong  enough,  does  not  release 
them,  but  dents  or  flattens  in  the  direc- 
tion of  the  line  of  motion,  thus  reducing 
its  cubical  internal  measure  and  produc- 
ing on  the  contents  rapid  or  rather  per- 
cussive compression.  This  compression 
evolves  an  amount  of  heat  exactly  de- 
pending on  the  weight  of  the  canister 
and  the  rapidity  of  its  motion.  For  this 
reason  it  is  difficult  to  explode  the  dy- 
namites by  similar  force  and  under  iden- 
tical conditions.  Being  porous  and 
capable  of  yielding  to  compression  to  a 
degree,  they  are  incapable  of  evolving 
the  necessary  amount  of  heat  for  such 
explosion.  It  is  possible,  of  course,  to 
compact  them  sufficiently  to  neutralize 
that  elasticity  and  evolve  the  heat  neces- 
sary— in  fact  they  are  so  compacted 
every  time  they  are  exploded  in  a  mine, 
but  it  is  evident  that  the  conditions 
necessary  are  difficult  to  attain  in  the 
ordinary  circumstances  attending  their 
storage,  handling,  and  shipment. 

Flame  may  be  applied  to  nitro-gly- 
cerine, and  it  may  thus  be  burned  on  its 
surface  without  explosion,  provided: 
that  the  burning  be  interrupted  before 
the  unburned  mass  attains  the  explosive 
360°  of  heat.  The  dynamites  may  be 
burned  safely,  because,  being  porous, 
they  are  poor  conductors  of  heat  and  do 
not  absorb  it  readily  from  the  burning 
surface  as  the  pure  nitro-glycerine  does. 
But  it  would  be  unsafe  to  burn  a  con- 
siderable amount  of  them  in  a  thick 
metallic  vessel,  as  the  metal  would  carry 
the  heat  from  the  upper  burning  portion 
to  the  bottom  and  thus  cause  explosion. 

The  report  next  mentions  "  high  pres- 
sure "  as  a  factor  of  explosion.  It  is 
true  that  every  explosion  is  attended,  or 
rather  preceded,  by  a  high  pressure,  but 
it  is  a  pressure  developed  instantaneous- 
ly and  the  most  efficient  generator  of  the 
heat  required.  Pressure  applied  so 
slowly  as  to  allow  the  dissipation  of  the 
heat,  generated  cannot  produce  explosion. 
For  this  reason  I  doubt  whether  nitro- 
glycerine can  be  exploded  in  a  vacuum. 

The  report  then  stated  that:  "It  does 
not  explode  by  the  application  of  fire," 
which  is  true  enough,  if  the  fire  be  ap- 
plied   to    the    open    surface    of    nitro- 


NiTRO-GLYCERINE   EXPLOSIONS. 


27 


glycerine  of  normal  temperature,  but 
that  is  certainly  the  only  way  in  which 
fire  may  be  applied  to  it  without  produc- 
ing an  explosion.  A  glowing  coal,  a 
hot  iron,  or  a  gas  jet,  applied  to  the 
bottom,  or  even  the  side,  of  a  tin  can, 
will  explode  it,  for  it  will  heat  the  film 
in  immediate  contact  to  the  explosive 
point,  producing  an  initial  explosion.  I 
say  "initial,"  because  if  the  vessel  is 
entirely  open  and  the  point  of  contact 
small,  the  gases  produced  by  the  explo- 
sion of  the  film  will  merely  throw  the 
other  fluid,  jritro-glycerine,  aside  and 
escape  with  a  crackling  noise.  If  the 
can  be  full,  or  closed,  or  if  the  mass  be 
frozen,  or  of  great  height  above  the  point 
of  contact,  the  whole  will  explode,  be- 
cause it  cannot  get  out  of  the  way  of 
the  pressure  of  the  first  or  initial  explo- 
sion, and  this  "  initial "  produces  the  re- 
quired compression  for  the  necessary 
instantaneous  evolution  of  heat.  On  the 
other  hand,  a  pan  holding  a  moderate 
depth  of  nitro-glycerine  may  be  set  over 
a  slow  fire  and  entirely  evaporated  with- 
out an  explosion,  because  the  lire  evapo- 
ration keeps  the  temperature  below  the 
explosive  degree.  Dynamite  is  subject 
to  the  same  law,  and  differs  only  to  the 
extent  of  its  porosity. 

Nitro-glycerine,  if  ever  so  carefully 
prepared  and  washed,  will  slowly  decom- 
pose, yielding  fumes  of  nitrous  acid.  If 
strictly  confined  these  fumes  accumulate 
and  exert  pressure,  which  pressure  makes 
it  peculiarly  sensitive  to  percussion. 
This  fact  has  been  (doubtless)  the  sole 
cause  of  many,  apparently  mysterious, 
accidents. 

I  find,  then,  but  a  single  primary 
cause  for  the  explosion  of  nitro-glycerine, 
viz.:  Heat  of  not  less  that  360  degrees 
Fahrenheit. 

I  also  find  that  the  most  direct  and 
efficient  way  to  produce  such  a  degree 
of  heat  is  by  percussive  compression. 

Knowing  the  primary  cause  of  its  ex- 
plosion, it  should  be  comparatively  easy 
to  make,  store,  transport,  and  use,  nitro- 
glycerine in  such  a  manner  as  to  avoid 
all  conditions  favoring  that  cause. 

It  being  important  to  give  free  access 
of,  or  rather  to  the,  air,  it  should  be 
stored  in  shallow,  open,  non-metallic 
vessels,  which  should  not  be  filled  to  a 
greater  depth  than  their  diameter. 

Stone,   or  earthenware,  glazed  inside, 


is  the  best  material  for  such  vessels, 
because :  It  is  not  affected  by  acids,  not 
a  good  conductor  of  heat,  and  it  is  strong, 
stiff,  and  brittle.  Such  vessels  are  cheap 
and  easily  obtained  everywhere,  lasting 
an  indefinite  time.  The  flexible  metallic- 
can  is  supremely  dangerous  and  unfit 
for  the  same  reasons. 

The  shallow,  op#n  vessel  gives  an  other- 
material  advantage  in  the  fact  that  the 
contents  are  always  fully  visible,  and 
any  change  in  appearance  indicating 
dangerous  decomposition  may  be  at  once 
observed  and  provided  for,  for  it  always 
does  change  in  appearance  long  before  a 
dangerous  stage  is  reached. 

When  during,  or  rather  immediately 
after,  manufacture,  the  acids  containing 
the  nitro-glycerine  are  washed  in  an 
abundance  of  well  agitated  water  of  a 
low  temperature,  the  precipitated,  heavy 
oil  has  a  white,  curdy  appearance  not 
unlike  buttermilk.  It  is  then  in  its  very 
safest  condition,  as  it  is  impossible  to 
explode  it  .by  any  ordinary  degree  of 
compression.  It  is,  however,  just  as 
strong  as  it  ever  is  under  other  and 
more  sensitive  conditions.  I  have  sent  a 
rifle  ball  through  a  tin  canister  of  it 
without  producing  explosion,  and  have 
fired  a  strong  fulminate  primer  in  anoth- 
er with  the  same  result,  viz.,  tearing  the 
vessel  and  spilling  the  contents.  When 
the  latter  experiment,  however,  was  re- 
peated with  a  strong  champagne  bottle 
the  explosion  occurred,  because  the  sides 
of  the  bottle  were  strong  enough  to 
enable  the  primer  to  exert  the  requisite 
compression.  Such  nitro-glycerine,  in  a 
temperature  of  70°  F.,  will  retain  this 
appearance  and  this  quality  for  one  and 
even  two  months.   # 

Since  it  adds  so  much  to  the  safety  it 
is  worth  the  trouble  to  store  a  supply 
sufficient  only  for  that  length  of  time. 

Such  nitro-glycerine  is  peculiarly  fitted 
for  shipment  and  is  safest  to  carry  hi 
boxed  stone  jugs,  which  are  not  to  be 
filled  quite  full,  say  3  gallons  in  a  5-gal- 
lon  jug.  Only  a  very  gradual  raising  of 
the  temperature  will  explode  such  jugs — 
no  amount  of  crushing  force  being  able 
to  cause  explosion,  provided  the  nitro- 
glycerine remain  fluid.  As  soon  as  it 
freezes  it  separates  from  the  water  and 
will  remain  so  after  thawing.  Thus  it 
can  be  made  highly  sensitive  by  repeated 
freezing:    and    thawing;.     Frozen    nitro- 


38 


VAN  nostrand's  engineering  magazine. 


glycerine  is  dangerous  to  handle  and 
transport,  because  it  is  rigidly  confined 
in  its  crystals  which  occupy  a  less  space 
than  the  fluid  they  are  formed  of.  The 
fracture  of  a  dry  crystal  will  often  cause 
explosion.  There  is,  however,  one  ad- 
vantage in  keeping  nitro-glycerine  frozen 
in  store  and  it  is  this:  When  frozen  the 
acidulous  decomposition  noticed  on  page 
27  cannot  possibly  take  place,  but  the 
nitro-glycerine  remains  perfectly  unalter- 
ed as  long  as  it  remains  hard.  Since 
such  decomposition  is  so  slow  as  to  be 
almost  imperceptible,  and  since  it  is  so 


easily  checked  and  provided  for  by  sim- 
ple washing  and  a  superposed  film  of 
water,  I  have  always  avoided  freezing 
because  of  the  risk  involved. 

I  have,  in  the  above,  tried  to  give  a 
full  and  intelligible  exposition  of  the 
true  cause  of  the  explosion  of  nitro- 
glycerine and  the  means  I  have  success- 
fully applied  to  avoid  unintentional 
explosion.  I  only  hope  that  I  have 
avoided  all  obscurity  of  expression,  as 
that  is  the  only  chance  for  misapprehen- 
sion. 


CLEVELAND  AND  THE  WORLD'S  IRON  TRADE.* 

From  the  "  London  Mining  Journal." 


Duration  of  Supply. — The  Cleveland 
ironstone  has  been  estimated  by  Bewick 
to  extend  over  an  area  of  not  less  than 
420  miles.  Allowing  a  yield  of  20,000 
tons  per  acre,  it  has  been  calculated  that 
the  main  seam  of  the  district  contains 
close  on  5,000,000,000  tons.  Not  a  few 
estimates  have  been  made  regarding  the 
probable  duration  of  this  supply.  Mr. 
Cockburn,  manager  of  the  Upleatham 
Mines,  in  a  paper  read  before  this  Insti- 
tute in  the  year  1869-70,  calculated  that 
Urst-class  stone  would  be  found  in  the 
Cleveland  hills  for  73  years  to  come, 
allowing  an  average  weekly  consumption 
of  75,000  tons.  It  is  pretty  well  known 
that  this  consumption  has  already  been 
surpassed.  Including  the  ironstone  vend- 
ed from  the  Rosedale  Mines  of  Messrs. 
Morrison  and  Leema*i,  and  the  Hinder- 
well  Mines  of  Palmer's  Shipbuilding 
Company,  the  total  average  weekly  out- 
put of  ore  is  now  over  100,000  tons,  so 
that,  according  to  Mr.  Cockburn's  esti- 
mate, the  period  of  the  exhaustion  of 
our  best  mineral — assuming  a  continued 
ratio  of  increase — is  likely  to  be  arrived 
at  within  (say)  the  next  60  years.  Mr. 
Cockburn's  calculation,  I  believe,  leaves 
the  top  seam,  as  well  as  the  upper  and 
lower  oolitic,  intact,  and  yet  Bewick 
placed  the  duration  of  the  same  source 
of  supply  at  680  years,  and  allowed  800 
■or   900  years  as  the   limit   of   duration 


*  From  a  paper  read  by  Mr.  J.  S.  Jeans  before  the 
43  ociety  of  Cleveland  Engineers. 


over  which  the  inferior  seams  would  be 
capable  of  extending.  Mr.  Jones,  secre- 
tary of  the  Cleveland  Ironmasters'  Asso- 
ciation, is  reported  to  have  stated  in 
1872  to  the  committee  on  the  Cleveland 
Extension  Railway  Bill,  that  the  supply 
of  ironstone  in  the  Cleveland  district 
would  last  for  a  hundred  years  at  an 
increasing  ratio  of  consumption,  and  it 
was  calculated  by  the  same  gentleman 
at  that  time  there  were  about  300,000,000 
tons  under  lease  and  worked,  being  equal 
to  37  years'  consumption  at  the  rate  of 
7,740,000  tons  per  annum.  It  is  of  little 
use  taking  into  account  the  thin  and 
inferior  seams,  as  they  are  nearly  all  too 
coarse  and  silicious,  and  contain  too 
small  a  percentage  of  iron  to  defray  the 
cost  of  working.  It  is,  therefore,  on 
the  main  seam  that  the  prospects  and 
prosperity  of  Cleveland  must  depend. 
It  would  probably  be  found  that  with  a 
more  exact  definition  of  the  area  of  the 
ironstone  field  embraced  within  their 
calculations  the  figures  given  by  Messrs. 
Bewick  and  Cockburn  would  more  nearly 
coincide  than  they  now  appear  to  do; 
but  whichever  estimate  we  accept,  the 
period  of  the  exhaustion  of  our  supplies 
of  ironstone  is  placed  at  so  remote  a 
date  that  it  need  not  further  enter  into 
our  calculations.  It  has  hitherto  been, 
and  still  is,  the  custom  to  '  speak  of  the 
ironstone  of  Cleveland  as  practically 
inexhaustible,  and  this  we  may  here 
confidently  assume  to  be  the  fact. 


CLEVELAND   AND   THE   WORLD'S   IRON   TRADE. 


29 


Compared  "with  other  Iron  Fields, 
the  ironstone  can  be  worked  at  a  cheap 
cost.  Until  within  the  last  three  years 
its  price  did  not  generally  exceed  3s.  6d. 
per  ton,  and  it  could  be  mined  for  lOd. 
per  ton.  There  is  scarcely  any  other 
district  in  which  more  economical  results 
are  obtained.  In  Lincolnshire,  it  is  true, 
the  ore  is  quarried  at  a  cost  of  6d.  to  8d. 
per  ton,  and  is  sold  at  the  mine  for  2s. 
6d.  to  3s.,  but  then  the  ironmakers  of 
Cleveland  will  not  hesitate  to  affirm  that 
the  Lincolnshire  ore  is  not  so  uniformly 
well  adapted  for  smelting  purposes  as 
the  ore  of  Cleveland;  and  when  it  was 
found  necessary  last  year  to  make  use 
of  it  in  lieu  of  the  native  stone,  it  in- 
volved no  end  of  trouble  in  the  working. 
Scotland  has  what  seems  at  first  sight  a 
superior  advantage  to  Cleveland  in  the 
closer  juxtaposition  of  its  minerals,  the 
splint  coal  being  found  not  unfrequently 
in  the  same  measures  that  yield  the  iron 
ore;  but  both  the  splint  or  smelting  coal 
and  the  blackband  ironstone  of  Scotland 
are  near  exhaustion,  and  retrogression 
has  consequently  marked  the  course  of 
the  Scotch  iron  trade  during  the  last 
two  years.  Staffordshire  and  Wales  have 
such  inadequate  supplies  of  local  ore 
that  they  are  compelled  to  import  the 
great  bulk  of  what  they  consume  from 
foreign  sources.  Northampton  has  of 
late  been  brought  into  considerable 
prominence  as  a  source  of  supply,  but 
the  position  of  the  district  is  even  worse 
than  that  of  either  of  the  three  older 
districts  here  enumerated,  seeing  that  it 
labors  under  the  insuperable  want  of  a 
proximate  source  of  coal  supply.  It  is 
scarcely  necessary  to  extend  our  com- 
parison into  North  Lancashire  and  Cum- 
berland, for  in  addition  to  the  great  cost 
and  uncertainty  attached  to  the  mining 
of  iron  ore  in  these  districts,  the  former 
with  an  ample  supply  of  hematite  is 
compelled  to  bring  the  great  bulk  of  its 
fuel  from  South  Durham,  at  a  freightage 
rate  of  8s.  to  9s.  per  ton,  while  the 
latter,  with  a  proximate  supply  of  infe- 
rior coal,  is  chiefly  dependent  on  the 
Cleator  Moor  district — a  restricted  and 
rather  precarious  source  of  supply — for 
its  ironstone.  Unaided  and  alone,  the 
ironstone  of  Cleveland  would  never  have 
placed  that  district  in  the  proud  indus- 
trial position  it  now  occupies.  The  con- 
tiguity of  the  South  Durham  coal  field, 


with  boundless  supply  of  the  finest  fuel 
yet  found  to  be  available  for  iron  smelt- 
ing purposes,  has  been  the  ladder  on 
which  Cleveland  has  mounted  to  excep- 
tional prosperity.  The  Durham  coal 
field  is  within  Is.  6d.  or  2s.  per  ton  of 
Middlesborough,  and  the  development 
of  the  Durham  coal  trade  has  followed 
that  of  the  iron  trade  of  Cleveland  in  an 
unvarying  ratio  of  increase. 

Iron  Manufacture  on  the  Conti- 
nent.— Spain  has  large  tracts  of  iron 
ore  in  the  district  around  Bilboa,  now 
being  largely  developed  by  English  capi- 
tal, but  there  is  no  sufficiently  contiguous 
coal  field  to  favor  the  erection  of  iron- 
works on  the  spot.  Besides  the  coal  of 
Spain  is  very  inferior  in  quality,  contain- 
ing a  low  proportion  of  carbon,  ranging 
from  45.5  to  82.0  per  cent.  Russia  also 
has  to  combat  the  difficulties  of  a  limited 
and  inferior  coal  supply,  the  total  area  of 
its  coal  field  being  not  more  than  100 
square  miles,  while  the  coal  often  contains 
as  much  as  17.1  per  cent,  of  ash  to  38.7 
per  cent,  of  carbon.  A  good  deal  has 
recently  been  done  to  develop  the  miner- 
al resources  of  Russia,  for  we  find  in  a 
recently  published  return  it  is  stated  that 
there  were  1174  iron  mines  in  operation, 
and  that  the  production  of  pig-iron  was 
at  the  rate  of  354,000  tons  per  annum  ; 
but,  notwithstanding  that  there  are  nu- 
merous rich  deposits  of  iron  ore,  the 
scarcity  and  inferiority  of  the  supplies 
of  fuel  must  always  operate  to  the  detri- 
ment of  its  metallurgical  industry.  Com- 
mencing in  Luxemberg  and  terminating 
in  France,  there  is  a  field  of  ironstone 
150  miles  in  extent,  which  corresponds  in 
geological  position  with  our  own.  The 
ore  varies  from  6 J  to  16-g-  feet  in  thick- 
ness, and  yields  about  32  per  cent,  of 
iron.  The  same  field  may  be  followed 
into  Alsace-Lorraine,  where  it  attains  a 
uniform  thickness  of  13  feet,  and  where 
the  mines  are  close  to  the  furnaces.  Mr. 
I.  L.  Bell  has  found  that  iron  can  be 
made  here  more  cheaply  than  on  the 
banks  of  the  Tees,  but  the  fuel  available 
for  smelting  purposes  in  this  part  of  the 
Continent  is  so  deficient  alike  in  quantity 
and  quality  that,  in  spite  of  cheaper 
labor  and  other  collateral  advantages, 
there  is  not  much  scope  for  any  great  de- 
velopment of  production  unless,  indeed, 
there  shall  meanwhile  be  found  greater 


30 


VAN   NOSTRAND  S   ENGINEERING   MAGAZINE. 


capabilities  of  fuel  supply  than  are  now 
known  to  exist.  There  is  no  other  Euro- 
pean country  that  threatens  to  come 
within  sight  of  England  in  the  manufac- 
ture of  iron,  if  avc  except  Belgium,  which 
has  long  been  held  up  as  the  bete  noir  of 
the  British  industrial,  and  of  whose  riv- 
alry we  are  still  hearing  reports  from  day 
to  day.  No  one  who  knows  anything 
about  the  relative  industrial  conditions 
of  the  two  countries  will  seriously  admit 
that  any  ultimate  danger  is  threatened 
to  England  from  Belgian  competition. 
Here  and  there  a  Belgian  firm  has  wrest- 
ed an  order  from  the  English  iron  trade ; 
and  the  opposition  thus  confronting  us 
has  been  more  seriously  felt  since  the 
tide  of  industrial  prosperity  commenced 
to  ebb,  some  15  or  18  months  ago.  But 
there  can  be  no  permanency  in  the  hold 
which  the  Belgians  have  been  able  to 
seize  upon  the  markets  of  Europe.  So 
far  as  its  natural  resources  are  concerned, 
Belgium  is  one  of  the  most  impoverished 
nations  in  Europe.  Its  coal  field  does 
not  cover  an  area  of  more  than  510  square 
miles,  as  compared  with  5,400  square 
miles  of  coal  area  in  Great  Britain.  Its 
collieries  are  generally  worked  under 
very  great  difficulties,  and  its  ironstone 
is  all  but  exhausted.  Out  of  700,000 
tons  of  iron  ore  required  to  produce  the 
610,000  tons  of  pig-iron  made  in  Bel- 
gium in  1871,  not  more  than  100,000  tons 
were  raised  in  Belgium  itself,  the  residue 
being  almost  entirely  from  the  Grand 
Duchy  of  Luxembourg,  so  that  the  bulk 
of  the  ore  has  to  be  carried  a  distance  of 
over  100  miles,  while  much  of  the  ore 
does  not  contain  more  than  26  to  27  per 
cent,  of  iron.  But,  in  addition  to  these 
drawbacks,  neither  the  ironstone  nor  the 
fuel  supplies  of  Belgium  are  equal  in 
quality  to  those  of  England.  The  fact 
is  that  the  Belgians  hold  their  high  posi- 
tion among  industrial  nations  not  because 
but  in  spite  of  the  natural  resources  of 
their  country.  Cheap  labor,  an  avoid- 
ance of  all  avoidable  waste,  contentment 
with  small  profits,  and  patient  industiy 
have  really  and  solely  made  Belgium 
what  it  is  ;  and  I  hope  that  I  shall  not 
be  considered  presumptuous  if  I  venture 
to  add  my  opinion  that  it  has  reached  its 
utmost  limit  of  development  so  far  as  the 
iron  trade  is  concerned.  Already  it  im- 
ports from  England  a  great  deal  of  the 
pig-iron  and  fuel  required  for  its  manu- 


factures, and  so  long  as  it  is  handicapped 
to  this  extent  it  is  manifest  that  "if  Eng- 
land to  herself  do  prove  but  true,"  no- 
thing that  Belgium  can  do  need  furnish 
cause  for  alarm  or  aiqjrehension. 

American  Competition. — And  now  I 
approach  what  is  to  me  the  most  inter- 
esting, and  to  others  will  appear  the  most 
important,  part  of  my  subject — the  con- 
sideration of  the  rivalry  that  the  iron 
trade  of  England  is  henceforth  to  ex- 
perience from  America,  and  probable  ex- 
tent to  which  American  ironmakers  will 
in  the  future  supplement  or  supersede 
the  iron  production  of  this  country. 
Hitherto,  it  must  be  admitted,  the  iron 
trade  of  America  has  not  made  the  pro- 
gress that  was  reasonably  to  be  expected, 
notwithstanding  that  it  has  been  un- 
naturally stimulated  by  a  protective  tariff 
of  import  duties.  There  are  five  iron- 
making  regions  in  the  United  States,  of 
various  extent  and  importance.  Chief 
among  these  is  the  region  of  Lake  Su- 
perior, the  great  tract  of  country  lying- 
west  of  the  Alleghanies.  It  extends  by 
Lakes  Superior,  Huron,  and  Erie  towards 
New  York  State,  and  by  Lake  Michigan 
into  Wisconsin,  Illinois,  and  Indiana,  and 
abounds  in  ores  yielding  from  50  to  60 
and  even  70  per  cent,  of  iron.  In  the 
Michigan  iron  range  there  is  an  immense 
deposit  of  the  best  black  magnetic  ore, 
which  yields  from  65  to  69  per  cent,  of 
iron.  For  the  most  part  these  deposits 
lie  within  easy  reach,  and  mining  is  never 
deep  and  difficult  as  in  this  country. 
Often  it  is  mere  quarrying,  and  the 
"  bluffs "  which  contain  the  ores  fre- 
quently allow  of  tunneling,  with  a  slope 
under  the  ground.  All  through  the 
States,  indeed,  there  is  an  abundance  of 
iron  ore  of  a  quality  rarely  found  in  this 
country,  and  in  the  Lake  Superior  region 
alone  1,197,000  tons  of  iron  ore  were 
raised  in  1873,  valued  at  the  mines  at 
over  $8,000,000.  The  fuel  of  America 
is  generally  well  adapted  for  smelting 
purposes,  and  distinguished  for  a  high 
degree  of  purity.  It  is  not,  however,  so 
much  in  the  superior  quality  of  its  re- 
sources as  in  their  magnitude  that  Amer- 
ica will  probably  overtake  and  ultimately 
surpass  Great  Britain.  The  coal  fields 
of  the  United  States  are.  estimated  by 
Prof.  Rogers  to  cover  an  area  of  196,650 
square  miles,  while  a  further  coal  area  of 


CLEVELAND   AND   THE   WORLD'S   IRON   TRADE. 


31 


7,530  square  miles  is  contained  in  the 
British  Provinces  of  North  America, 
making  together  a  total  coal  area  of 
200,000  square  miles,  as  against  5,400 
square  miles  of  coal  area  in  Great  Brit- 
ain. These  figures  simply  represent  the 
difference  between  an  easily  exhaustible 
and  a  practically  inexhaustible  supply, 
for  although  much  of  the  coal  of  the 
United  States  may  not  be  within  reach 
of  working,  there  will  be  millions  upon 
millions  of  tons  left  unworked  when  the 
last  ounce  of  available  coal  has  been  ex- 
tracted from  the  coal  fields  of  Great 
Britain  ;  and  if  ever  England  is  reduced 
to  the  necessity  of  importing  her  fuel 
from  America  or  China,  "  the  day  of  her 
manufacturing  prosperity  —  to  say  no- 
thing of  her  supremacy — will  have  gone 
for  ever."  At  the  present  moment  the 
production  of  pig  iron  in  America  is  a 
little  over  a  third  of  the  total  produc- 
tion of  Great  Britain. 

The  total  number  of  blast  furnaces 
available  for  use  in  the  United  States, 
according  to  the  most  recent  statistics,  is 
575,  and  of  that  number  348  only  were 
in  blast.  It  is  rather  remarkable  that, 
notwithstanding  the  abundant  coal  re- 
sources of  the  country,  more  than  200 
of  these  furnaces  burn  nothing  but  char- 
coal ;  of  the  remainder  181  burn  coke, 
and  187  burn  anthracite.  One  of  the 
greatest  difficulties  in  the  way  of  the  de- 
velopment of  the  American  iron  trade  is 
the  general  absence  of  a  proximate  coal 
field  to  the  ironstone  measures.  In  some 
cases  the  coal  has  to  be  brought  a  dis- 
tance of  many  hundred  miles  to  be 
smelted  on  the  spot  where  the  ironstone 
is  found  ;  and  in  other  cases  the  iron 
stone  is  brought  a  long  distance  to  the 
coal.  The  drawback  incidental  to  the 
geographical  association  of  coal  and  iron 
ore  is,  to  a  large  extent,  discounted  by 
the  splendid  facilities  of  transport  that 
exist  throughout  nearly  the  whole  of  the 
United  States.  Minerals  can  be  carried 
at  a  cheap  rate  along  the  Ohio,  the  Dela- 
ware, Lake  Michigan,  the  Mississippi, 
.  #  and  other  inland  seas,  to  the  advantages 
of  which,  in  this  country,  we  are  com- 
plete strangers.  It  is  undoubtedly  true 
that  labor  is  at  the  present  time  cheaper 
in  this  country  than  in  America,  but 
labor  is  an  item  of  cost  that  can  be 
adapted  to  circumstances,  whereas  natur- 
al resources  are  not.     There  is  a  want  of 


definite   information  respecting  the  fuel 
supplies  of  America  ;  and  in  the  last  re- 
port of  Her  Majesty's  Secretaries  of  Em- 
bassy and  Legation  a  doubt  is  expressed 
as   to   whether    the    coal    resources    of 
America  are  equal  to  keeping  pace  with 
her  requirements  in  iron  smelting.     But. 
every  accession  to  our  knowledge  on  this 
matter  only  tends  to  strengthen  the  con- 
viction that  the  fuel  of  America  is  not 
only  practically  illimitable,  but   in  the 
main    admirably   adapted   for   smelting 
purposes.     Americans  have  also  of  late 
years  essayed  to  excel  the  manufacturers 
of    Cleveland  in  their  greatest  achieve- 
ments.      The     "  Cambria "    furnace    at 
Johnstown,  with   a   capacity  of   15,020 
cubic  feet,  and  the  "Lucy"  furnace  at 
Pittsburg,  yielding  475  tons  of  Bessemer 
pig-iron  per   week,   have  become  quite 
historical ;   but  these  furnaces  have  re- 
cently been  left  in  the  shade  by  one  built 
on  the  banks  of  the  Alleghany,   which 
sometimes  produces  as  much  as  101  tons 
of  pig-iron  in  a  day,  and  can  yield  with 
unvarying   regularity   from   6§0  to  660 
tons  of    foundry  iron  in  a  week.     We 
have  never  heard  of  a  blast  furnace  in 
Cleveland  that  yielded  anything  like  this 
result,  despite  the  fact  that  we  have  long 
boasted  of  having  the  biggest  and  most 
productive  furnaces  in  the  world.     Hab- 
itual optimists  on  the  one  hand,  and  rest- 
and-be-thankful  economists  on  the  other, 
have  been  diligently  trying  to  explode 
the  notion  that  America  will  one  day  be- 
come   a   competitor  with   England,  not 
only  in  United  States  markets,  but  in  all 
other  markets  in  the  world.     They  say 
that  America  has  not  the  capital  neces- 
sary to  enable  her  to  overtake  and  rival 
England,  forgetting  that  the  accumula- 
tion of  capital  is  only  a  work  of  time. 
They  say  also  that  the  purchasing  power 
of  money  is  so  much  less  in  the  United 
States  than  in  Europe,  that  the  manufac- 
turers of  the  former  could  never  success- 
fully compete  in  the  markets  of  the  lat- 
ter ;  but  it  is  easy  to  perceive  that  closer 
assimilation  in  this  essential  is  not  only 
attainable,  but  certain,  sooner  or  later, 
to  be  attained  through  the  exigencies  of 
commercial  intercourse.     It  was,   more- 
over, believed  not  long  ago  that,  owing 
to   some    defect   in   the   clay  of    which 
American  blast-furnaces  were  built,  the 
cost  of  providing  plant  and  keeping  it 
in  repair  would  seriously  handicap  Arner- 


32 


VAN  nostrand's  engineering  magazine. 


ican  manufacturers  ;  but  we  now  learn 
that  the  "Mount  Savage"  brick  of  the 
States  excels  the  Scotch  or  German,  or 
even  the  famous  Stourbridge,  so  that  un- 
less the  rich  ores  of  America  prove  too 
much  for  any  clay,  the  building  of  mon- 
ster blasts  will  probably  become  the  rule 
of  the  future.  Taken  as  a  whole,  there- 
fore, it  may  fearlessly  be  maintained 
that  America  lacks  none  of  the  essential 
elements  of  manufacturing  greatness, 
while  her  ultimate  resources  surpass 
those  known  in  Europe  by  as  much  as  a 
mountain  surpasses  a  mole-hill. 

General  Conclusions. — Cleveland  is 
now  the  only  known  iron-producing  dis- 
trict in  Europe  likely  in  the  future  to 
come  into  active  competition  with 
America,  and  that  if  the  resources  of 
America  were  less  than  they  are,  the 
development  of  the  Cleveland  iron  trade 
would  probably  proceed  at  a  much  more 
rapid  pace.  Hitherto  the  American  iron 
trade  has  been  defensive  rather  than  ag- 
gressive in  its  tendencies.  It  has  been 
content  with  seeking  to  supply  home  re- 
quirements. But  this  endeavor  it  has 
realized  with  a  success  at  once  startling 
and  inimical  to  the  manufacturers  of 
Europe.  Within  the  last  three  years 
the  "United  States  have  fully  doubled 
their  resources  for  the  production  of 
pig-iron,  and  they  have  increased  their 
production  of  malleable  iron  from 
1,500,000  in  1871  to  2,000,000  tons  in 
1873.  It  is  not  necessary  to  weary  you 
with  figures  showing  you  how  the  ex- 
ports   of  all  kinds   of    iron  from   this 


country  to  America  have  fallen  off 
within  recent  years,  or  how  that  falling 
off  has  affected  Cleveland  in  particular. 
It  is  abundantly  evident  that  America 
has  learned  to  depend  upon  herself,  and 
year  by  year  we  will  continue  to  lose 
,,our  hold  upon  American  markets  until 
we  are  shut  out  altogether.  But  while 
America  will  become  her  own  ironmaster, 
she  is  not  likely  for  many  years  to  seek 
for  custom  outside  her  own  territories. 
She  may  produce  iron  more  cheaply  than 
it  can  be  imported  from  England  with  a 
high  protective  tariff  in  her  favor;  but 
she  will  not  be  able  to  undersell  the 
British  manufacturer  in  the  markets  of 
Europe.  This,  then,  is  the  field  in  which 
the  Cleveland  ironmasters  must  labor  in 
the  future;  and  we  think  we  have 
already  shown  that  his  resources  are 
such  as  to  enable  him  to  cultivate  this 
field  more  successfully  than  any  visible 
competitor.  In  this  field  the  sun  of  his 
prosperity  will  only  set  when  the  fuel 
available  for  smelting  the  ironstone  of 
this  district  becomes  exhausted.  That, 
however,  must  be  regarded  as  a  very  re- 
mote event,  notwithstanding  the  calcu- 
lations of  Mr.  Jevons  and  other  statisti- 
cians; and  if  there  is  any  truth  in  the 
commonly  accepted  estimate  that  there 
is  just  about  sufficient  fuel  left  in  the 
Durham  coal-field  to  smelt  the  ironstone 
contained  in  the  main  bed  of  Cleveland, 
our  capitalists  may  rest  in  undisturbed 
security,  for  no  one  will  wake  up  in  their 
generation  to  find  that  exhaustion  has  at 
length  overtaken  us. 


THE  SEWAGE  OF  PAKIS. 

From  "The  Engineer." 


In  certain  respects  Paris  is  in  a  worse 
position  for  the  satisfactory  disposal  of 
her  sewage  than  London.  It  is  true 
that  her  population  is  much  smaller,  and 
the  area  of  collecting  ground  more  man- 
ageable; but,  on  the  other  hand,  the 
great  distance  of  Paris  from  the  sea  ren- 
ders it  impossible  to  use  the  latter  as  a 
recipient  of  the  sewage  sent  down  from 
the  former.  Thus  the  cost  of  construct- 
ing anything  like  the  terminal  canals  of 
our  own  metropolitan  main  drainage 
system  would  be  so  enormous  that  the 


idea  could  not  be  entertained  for  a 
moment.  In  one  word,  Paris  sewage 
cannot  be  sent  to  sea  in  special  channels. 
For  years  it  was  poured  into  the  Seine 
almost  without  protest,  but  the  extension 
of  the  city,  and  the  consequent  augmen-  • 
tation  in  the  volume  of  sewage  to  be 
disposed  of,  at  last  became  so  great  that 
the  conditio  n  of  the  river  coiild  no  long- 
er be  tolerated.  The  construction  of  a 
fine  system  of  main  sewers,  tolerable 
perfect  in  every  respect  except  that  they 
lacked   a  satisfactory  outfall,  supplied, 


THE   SEWAGE   OF   PARTS. 


33 


no  doubt,  an  additional  stimulus  to  exer- 
tion. It  became  possible  at  least  to  col- 
lect the  sewage  of  Paris,  a  thing  which 
was  impossible  while  thousands  of  sub- 
sidiary sewers  debouched  into  the  river. 
Then  came  a  period  during  which  ex- 
periments were  carried  out  with  various 
processes  for  the  purification  of  sewage,  all 
with  more  or  less  unsatisfactory  results. 
A  farm  was  established,  however,  on 
which  a  considerable  quantity  of  sewage 
was  distributed  with  fair  promise  of 
success,  and  at  last  a  commission  was 
appointed  on  the  27th  of  August,  1874, 
to  investigate  and  report  on  the  condi- 
tion of  the  Seine,  and  suggest  means  for 
insuring  its  purification.  The  commis- 
sion have  just  published  their  report, 
which  we  have  much  satisfaction  in 
stating  confirms  the  views  which  we  have 
all  along  expressed.  They  find  that  the 
only  satisfactory  mode  of  disposing  of 
the  sewage  of  Paris  is  to  run  it  on  to 
land;  in  other  words,  the  system  to  be 
adopted  is  a  combination  of  irrigation 
and  Mr.  Bailey  Denton's  method  of 
downward  filtration.  The  extent  of 
land  is  to  be  much  larger  than  Mr.  Den- 
ton would  probably  deem  necessary;  but 
"it  is  certainly  smaller  than  we  think 
would  suffice  if  the  soil  were  not  of  great 
depth,  and  so  porous  that  the  sewage 
would  be  fairly  puiified  even  if  no  crops 
were  grown.  Having  premised  this 
much,  we  shall  now  proceed  to  consider 
the  report  more  in  detail. 

The  commissioners  commence  by  de- 
scribing the  existing  state  of  the  river. 
The  Seine  is  joined  before  entering  Paris 
by  the  Marne,  the  Yonne,  arid  several 
smaller  streams,  all  exposed  to  certain 
chances  of  pollution.  Yet  the  condition 
of  the  water  is  stated  to  be,  on  the 
whole,  good.  Fish  flourish  in  the  stream, 
which  runs  over  a  bed  of  white  sand 
visible  through  the  clear  water.  Pollu- 
tion commences  as  soon  as  the  stream 
fairly  enters  the  city,  but  it  is  limited 
in  character  and  of  small  importance 
until  the  bridge  at  Asnieres  has  been 
reached.  The  great  main  sewer  running 
.north  through  Paris  discharges  itself 
close  by  at  Ulichy,  and  the  contents  of 
this  conduit  appear  to  be  incredibly 
nasty.  The  report  goes  a  good  deal 
into  detail  about  dead  dogs  and  cats, 
and  scum,  and  organic  refuse.  The 
picture  drawn  leaves,  indeed,  little  if 
Vol.  X1H.— No.  1—3 


anything  to  the  imagination,  and  nothing 
to  be  desired.  In  moderate  weather  the 
Stygian  flood  keeps  the  middle  of  the 
stream,  but  in  heavy  rains  the  force  of 
the  current  in  the  river  is  too  much  for 
that  issuing  from  the  sewer,  and  the 
sewage  is  compelled  to  run  close  to  the 
left  bank.  On  this  bank  a  filthy  deposit 
is  left  as  the  river  falls.  Of  this  we 
shall  say  nothing  in  the  way  of  descrip- 
tion. It  will  suffice  to  state  that  nothing 
that  we  have  ever  read  or  heard  of  can, 
apparently,  be  more  insufferably  dis- 
gusting. The  pollution  extends  a  long 
way  down  the  stream — how  far  we  do 
not  know  with  precision.  Oxidation  and 
deposition  do  their  work  by  degrees, 
and  the  nuisance  is  abated  after  miles 
have  been  traversed.  But  the  Seine,  we 
need  hardly  say,  is  never  really  pure — 
we  use  the  word  in  the  mildest  sense — 
after  it  has  passed  through  the  bridge 
at  Asnieres.  Such  being  the  position  of 
affairs,  the  commission  had  to  consider 
how  best  to  improve  matters.  Five  dis- 
tinct schemes  for  effecting  this  object 
appear  to  have  been  carefully  weighed. 
The  first  was  the  extension  of  the  main 
sewers  to  the  sea — which  was  at  once 
set  aside  because  of  the  expense.  The 
second  contemplated  the  extension  of 
the  sewers  to  the  confluence  of  the  Oise. 
But  this  would  only  carry  the  nuisance 
to  the  banks  of  the  Oise  and  was  accord- 
ingly rejected.  The  third  scheme  was 
essentially  novel.  The  sewage  was  to 
be  diluted  by  the  addition  of  pure  water 
near  the  outfalls,  and  still  suffered,  as 
before,  to  escape  into  the  Seine.  We 
need  hardly  say  that  this  ingenious 
proposition  was  rejected.  Fourthly,  it 
was  proposed  that  the  sewage  should 
be  passed  through  large  filtering  beds, 
and  the  clear  water  delivered  into  the 
Seine.  This  scheme  was  rejected  be- 
cause, as  the  commissioners  point  out, 
filters  require  incessant  attention,  and, 
after  all,  they  only  remove  solid  impu- 
rities. The  fifth  scheme  was  to  construct 
immense  settling  tanks  near  the  outfalls, 
to  collect  the  dead  dogs  and  other  solid 
matters.  This  would  obviously  only 
eliminate  a  portion  of  the  evil,  while  the 
settling  tanks,  which  would  need  to  be 
very  large,  would  prove  a  dangerous 
nuisance  in  hot  weather,  and  this  idea 
was  accordingly  abandoned.  Xothing 
remained  but  irrigation,  downward  filtra- 


34 


VAN  NOSTKAND'S  ENGINEERING  magazine. 


tion  on  Denton's  system,  or  purification 
by  some  of  the  numerous  patented 
schemes  before  the  world.  That  which 
appeared  most  likely  to  succeed  was  the 
precipitation  system.  To  test  its  value, 
a  series  of  experiments  were  carried  out 
at  the  suggestion  of  M.  Chatcher,  In- 
spector-General of  Mines.  Reservoirs 
were  established  at  Clichy  on  a  great 
scale,  and  on  the  11th  of  October  the 
commissioners  saw  as  much  as  600,000 
tons  of  sewage  treated  by  the  sulphate 
of  alumina  process.  The  result  was, 
that  the  water  was  discharged  clear;:but 
not  pure.  Careful  experiments  made  in 
1868,  showing  that  two-thhds  of  the 
nitrogen  and  one-third  of  the  volatile  or 
combustible  materials  of  the  sewage 
were  left  in  the  water,  which  was  unfit 
for  any,  even  the  commonest  domestic 
uses,  and  could  not  possibly  be  dis- 
charged into  a  river  without  contami- 
nating it.  What  was  true  in  1868  is,  of 
course,  equally  true  of  the  process  in 
1815.  The  report  deals  very  fairly  with 
this  question,  and  shows'  honestly  and 
dispassionately  why  it  is  that  all  these 
sewage  processes  must  fail,  except  as 
palliative  measures.  It  is  estimated  that 
Paris  discharges  annually  about  260,000 
cubic  yards  of  solid  matter  suspended  in 
the  sewage.  Now,  a  depositing  process 
would  have  to  provide  for  the  disposal 
of  this  huge  mass  of  mud.  How  can 
this  possibly  be  effected  ?  If  by  artificial 
heat,  the  cost  would  be  enormous.  If  by 
natural  means,  the  space  occupied  by  the 
filthy  mass  would  be  very  great — not 
much  less  than  150  acres.  A  nuisance 
would  be  unavoidable;  and  the  process 
of  desiccation  could  scarcely  be  carried 
on  at  all  in  winter.  But  when  the  mud 
had  been  so  far  dried  that  it  could  be 
carted  or  otherwise  manipulated,  what 
would  become  of  it  ?  The  theory  of  the 
believers  in  "processes"  is, that  it  would 
constitute  a  very  valuable  manure,  worth 
as  much  as  50s.  a  ton,  or  more.  The  re- 
port before  us  explodes  this  fallacy.  In 
France,  at  all  events,  dry  sewage  mud  is 
only  worth  from  6f.  to  lOf.  a  ton,  which 
is  just  about  the  cost  of  the  chemicals 
used.  The  expense  of  pumping,  drying 
the  mud,  and  otherwise  manipulating 
the  sewage,  remains  undefrayed,  even  if 
a  ready  sale  could  be  had  for  the  mud. 
So  that  the  cost  of  carrying  out  the  pro- 
cess would  be  very  heavy,  even  if  the 


value  of  the  residitum  were  maintained, 
which  is,  we  may  add,  to  the  least  degree 
unlikely,  as  it  would  not  pay  to  trans- 
port so  worthless  a  material  to  any  dis- 
tance by  road  or  rail,  and  the  landowners 
in  the  vicinity  of  the  purification  works 
would  soon  find  that  they  could  dictate 
their  own  terms,  because  the  authorities 
would  be  compelled  to  sell  the  product 
at  any  price,  and  rest  content  so  long  as 
they  get  rid  of  it.  The  commissioners 
estimate  that  the  adoption  of  the  sul- 
phate of  alumina  process  would  cost  the 
ratepayers  of  Paris  and  its  environs 
£40,000  a  year,  and  very  wisely  rejected 
it  without  further  scruple,  as  being  at 
once  unsatisfactory  as  regarded  the  efflu- 
ent, unmanageable  on  a  large  scale,  and 
expensive. 

After  a  review  of  the  various  schemes 
we  have  cited,  the  commissioners  go  on 
to  state  that  the  solution  of  the  question 
must  be  sought  not  in  chemical  processes 
of  purification,  but  in  the  combined 
action  of  the  soils  and  plants  on  sewage. 
They  are  very  careful,  however,  to  qual- 
ify this  statement  by  adding  that  the 
soil  must  be  peimeable.  They  thus  evi- 
dently clearly  appreciate  the  conditions 
under  which  sewage  can  best  be  applied 
to  irrigation  purposes.  Experiments 
were  carried  out  by  the  commission  to 
test  the  advantages  of  downward  filtra- 
tion; and  Mr.  Denton  will  rejoice  to 
learn  that  the  results  obtained  were  emi- 
nently satisfactory.  A  glass  vessel  half 
a  metre  high,  filled  with  earth  and  sand 
from  the  plain  of  Gennevilliers,  clarified 
for  a  long  period  sewage  discharged  on 
the  surface.  The  commission  analyzed 
the  sewage  with  which  they  had  to  deal, 
and  the  variety  of  plants  which  they 
proposed  to  cultivate,  and  they  have 
arrived  at  the  conclusion  that  for  each 
crop  7,800  cubic  yards  of  sewage,  or, 
say,  1,306,000  gallons,  should  be  applied 
per  acre.  On  this  point  the  commission- 
ers are  probably  wrong  in  principle,  as  the 
quantity  appears  to  be  excessive,  but  they 
are  apparently  right,  taking  into  consid- 
eration the  nature  of  the  soil  with  which 
they  have  to  deal,  in  assuming  that  each 
acre  of  irrigated  land  will  purify  about 
24,000  cubic  yards  of  sewage  per  annum. 
We  shall  hot  attempt  to  reproduce  here 
a  description  of  the  existing  works  at 
Gennevilliers,  where  the  irrigation  sys- 
tem has  for  two  years  been  at  work;  it 


MINES   AND   IRONWORKS   IN   THE   UNITED   STATES. 


35 


must  suffice  to  say  that  about  fourteen 
miles  of  ditches  distribute  sewage,  raised 
at  Clichy  by  centrifugal  pumps,  over  a 
farm  of  about  353  acres.  The  commis- 
sioners carefully  examined  the  farm,  and 
investigated  all  the  particulars  connected 
with  it,  and  they  finally  arrive  at  the 
conclusion  that  the  only  remedy  for  the 
pollution  of  the  Seine  is  the  direct  appli- 
cation of  the  sewer  water  to  agricultural 
purposes,  and  that  a  permeable  soil,  like 
that  at  Gennevilliers,  is  favorable  to  the 
cultivation  of  market  garden  produce, 
plants  for  manufacturing  purposes,  and 
grass,  and  that  no  injury  to  the  health 
of  those  living  near  the  sewage  farm  is 
to  be  feared.  We  cannot,  for  lack  of 
space,  enter  into  a  detailed  consideration 
at  this  moment  of  the  arrangements  pro- 
posed by  the  commissioners  for  carrying 
out  their  scheme.  The  works  existing  at 
Gennevilliers  were  constructed  with  a 
grant  of  £40,000,  made  for  the  purpose 
in  1872.  In  1874  a  similar  sum  was 
voted  for  extension  of  the  works,  and, 
when  these  are  constructed,  about  2,470 
acres  will  be  available  for  irrigation, 
and  these  will  dispose  of  about  fifty 
millions  of  tons  of  sewage  per  annum, 
or  half  the  total  volume  of  water  now 
collected  by  the  sewers  of  Paris.  As 
regards  the  other  half,  it  appears  that 
west  of  the  present  farm  more  land  can 
be  obtained  at  Gennevilliers,  to  the  ex- 
tent of  nearly  3,000  acres,  and  it  is  esti- 
mated that  all  this  might  be  brought 


into  use  by  an  outlay  of  £200,000. 
This  would  dispose  of  the  whole  of  the 
sewage  of  Paris.  Land  might  also  be 
obtained  near  St.  Germain,  and  the 
commissioners  think  that  it  would  be 
well  that  this  should  be  examined  before 
taking  another  tract  at  Gennevilliers. 

We  have  done  little  more,  it  will  be 
seen,  than  give  the  heads  of  one  of  the 
most  interesting  documents  yet  contrib- 
uted to  the  literature  of  sewage;  we 
shall  return  to  the  subect.  Meanwhile, 
we  would  express  the  hope  that  the 
publication  of  this  report  may  do  some- 
thing to  place  matters  on  a  more  satis- 
factory footing  in  this  country.  If  it  is 
once  proved  that  there  is  no  way  of  dis- 
posing satisfactorily  of  sewage  but  by 
turning  it  on  land,  we  may  hope  that 
the  Legislature  will  interfere,  to  such  an 
extent  as  will  simplify  the  present  pro- 
cess of  obtaining  sewage  farms.  The 
energies  of  corporations  are  too  often 
wasted  now  on  various  schemes  more  or 
less  conflicting,  and  it  is  too  commonly 
argued  that  it  is  much  better  to  try  a 
process  than  incur  the  cost  of  purchasing 
a  sewage  farm.  While  an  alternative 
remains  for  adoption,  time  and  money 
are  certain  to  be  wasted  by  local  boards. 
The  report  of  the  Paris  Commission  has 
done  much  to  prove  that  irrigation  with- 
out alternative  must,  in  the  long  run,  be 
adopted,  and  we  trust  the  conclusion  will 
be  accepted  as  nearly,  if  not  absolutely, 
final. 


NOTES  OF  A  VISIT  TO  MINES  AND  IRONWORKS  IN  THE 

UNITED  STATES.* 

By  I.  LOWTHIAN  BELL,  F.  K.  S. 
From  "Iron." 


Mb.  Bell  began  by  saying  that  in  the 
year  1871,  one-half  of  the  iron  produced 
in  England  was  exported  to  foreign 
countries,  and  one-fourth  of  this  half 
was  despatched  to  the  United  States,  in 
all  about  750,000  tons.  In  the  year  1874, 
however,  the  States  only  took  130,000 
tons,  and  it  was  stated  that  during  the 
three  years  the  producing  power  of  that 
country  had  risen  from  two  and  a  half 
millions  to  four  millions  of  tons.     It  is  a 


!  Bead  before  the  Iron  and  Steel  Institute. 


matter  of  great  interest  to  the  British 
ironmasters  to  learn  whether  this  extra- 
ordinary growth  is  due  to  the  stimulus 
of  our  own  excited  markets,  and  whether 
the  increase  can  be  actively  employed 
when  iron  falls  in  value  to  what  experi- 
ence has  accustomed  the  world  to  pay 
for  this  commodity.  Li  touching  upon 
the  question  of  transport,  which  so  near- 
ly relates  to  the  manufacture  of  iron,  he 
said  that  the  raw  material  in  America 
has  to  be  carried  over  distances  quite 
unknown  in  this  country.     This  applies 


36 


YAN  NOSTRAND  S  ENGINEERING-   MAGAZINE. 


also  to  the  manufactured  product.  A 
great  deal  is  done  by  water,  and,  as  an 
instance,  he  gave  the  cost  of  conveyance 
of  coal  from  Pittsburg  down  the  Ohio. 
Twenty  thousand  tons  of  this  mineral 
are  sometimes  embarked  on  board  a  flo- 
tilla of  flat-bottomed  boats,  and  conduct- 
ed by  one  steamer,  for  a  distance  of  1,600 
miles  at  something  under  Is.  per  ton, 
which  includes  the  cost  of  bringing  back 
the  empty  barges.  The  entire  question 
of  internal  intercommunication  of  the 
United  States  has  experienced  great 
changes  in  consequence  of  the  enormous 
development  of  the  railway  system.  The 
Hudson  River,  which  is  accessible  by  the 
Great  Eastern  Railway  for  seventy-five 
miles  above  New  York,  has  a  double  line 
of  rails  running  alongside  its  stream  be- 
yond the  city  of  Albany.  Thus  the  lo- 
comotive has  not  only,  in  many  cases, 
displaced  the  marine  engine,  but  it  has 
brought  mineral  districts  into  communi 
cation  with  each  other,  which,  without 
it,  would  in  a  great  measure  have  remain- 
ed useless.  A  limited  quantity  of  char- 
coal iron  can  be,  and  is,  produced  from 
the  rich  ores  of  Lake  Superior,  the  Iron 
Mountain  of  Missouri,  and  Lebanon  in 
Pennsylvania  ;  but  the  quantity  would 
have  remained  insignificant  had  the  rail 
not  enabled  these  minerals  to  be  convey- 
ed to  the  coal  of  the  Shenango  and  Ma- 
honing Valleys,  and  to  those  of  the  Le- 
high, Delaware,  Ohio,  and  others.  The 
railway  system  has  grown  into  dimen- 
sions far  exceeding  those  in  England,  the 
land  of  its  birth.  At  the  end  of  1873 
the  United  States  had  76,651  miles  of 
road,  against  only  16,082  miles  in  Eng- 
land. The  average  cost  per  mile  in  the 
latter  has  been  £36,582,  and  in  America 
not  one-third  of  that  sum.  In  the  latter 
case,  however,  the  Americans  have  had 
the  advantage  of  getting  their  land  for 
a  mere  trifle,  but  they  have  had  to  con- 
tend with  scarce  and  dear  capital,  and 
with  materials  and  labor  far  more  costly 
than  in  England.  They  have  not  con- 
structed such  substantial  lines,  however 
— the  convenience  of  the  many  being  al- 
lowed to  override  the  possible  injury  to 
the  interest  of  the  few.  The  working 
charges  in  the  States  absorb  65.1  per 
cent,  of  the  gross  earnings,  and  in  this 
country  only  53  per  cent.  The  rates  of 
carriage  also  vary,  some  charging  l£d. 
per  ton  per  mile,  and   others   only  ^d. 


Looking  at  the  fuel  consumed  in  the 
manufacture  of  iron  in  America  Mr.  Bell 
first  referred  to  charcoal,  and  remarked 
upon  the  large  quantity  of  fox*est  land  to 
be  found.  In  the  earlier  history  of  the 
iron  trade  it  was  almost  exclusively  used 
in  the  blast-furnace,  and  even  in  1854 
one-third  of  the  pig-iron  produced  in  the 
United  States  was  smelted  in  the  char- 
coal furnace,  or  about  300,000  tons;  now 
it  is  500,000  tons,  or  one-fifth  of  the  en- 
tire make.  It  is  mostly  used  for  railway 
carriage  wheels.  The  prices  of  charcoal 
vary  according  to  the  district,  and  Mr. 
Bell  gave  instances.  He  spoke  of  the 
system  of  weights  and  measures  employ- 
ed in  the  American  ironworks,  and  said 
that  this  is  one  of  the  few  things  which 
the  people  there  had  done  badly.  Not 
content  with  introducing  our  unmean- 
ing ton  of  20  cwt.  of  112  lbs.,  they  have 
two  distinct  tons,  one  of  2,000  lb.,  and 
the  other  of  2,440  lb.  Mr.  Bell  calcu- 
lates that  46,000  acres  of  timber  fall  an- 
nually to  provide  fuel  for  the  charcoal 
furnace.  Less  than  200  acres  of  a  four- 
feet  seam  of  coal,  in  the  county  of  Dur- 
ham, would  produce  the  same  weight  of 
coke  as  is  obtained  from  46,000  acres  of 
American  forest.  Coal  is  more  abundant 
in  the  United  States  than  in  any  other 
part  of  the  world,  and  all  kinds  are 
found.  In  some  places  natural  gas  is 
used  for  puddling,  reheating,  &c.  Of 
pit-coal  itself  there  are  192,000  square 
miles,  as  compared  with  8,000  square 
miles  in  the  United  Kingdom  ;  and .  Mr. 
Bell  thinks  it  may  be  doubted  whether 
there  is  any  similar  area  in  the 
world  in  which  a  larger  proportion  of 
the  surface  is  occupied  by  coal-bear- 
ing strata.  The  anthi-acite  fuel  is  much 
used  in  the  blast-furnace,  indeed,  out  of 
two  and  a  half  millions  of  tons  of  pig- 
iron  smelted  last  year,  about  one-half 
was  the  product  of  furnaces  burning 
anthracite.  From  the  position  which 
these  beds  of  anthracite  coal  occupy,  it 
would  appear  as  if,  after  their  original 
formation,  an  enormous  amount  of  later- 
al compression  had  been  experienced  by 
the  districts  in  which  they  lie.  This 
force  has  raised  the  strata  into  a  succes- 
sion of  waves,  as  it  were,  the  slopes  of 
which  vary  from  an  angle  of  20  to  45 
degs.,  and  occasionally  descending  to  a 
depth  of  200  to  250  fathoms  or  more. 
In  some  cases,  this  compressive  power 


MINES  AND   IRONWORKS   IN   THE   UNITED   STATES. 


37 


has  been  so  great  as  to  have  forced  one 
ridge  back  over  its  neighbor,  to  such  an 
extent  as  to  convert  what  is  the  floor  of 
the  seam  of  one  place  into  the  roof  at 
another,  and,  from  a  similar  cause,  the 
quantity  of  coal  which  has  accumulated 
at  the  anticlinal  axes  of  some  of  these 
coal  undulations  is  so  great  as  to  afford  a 
face  of  40  to  60  feet,  or  even  more,  in 
thickness.  In  some  cases  denudation  has 
carried  off  not  only  the  sandstones  and 
shales,  but  a  portion  of  the  coal  itself, 
the  bared  edge  of  the  seam  is  found  im- 
mediately under  the  alluvial  matter  of 
the  surface.  The  coal  is  sometimes  quar- 
ried ;  indeed,  at  Mauch  Chunk,  there  is 
an  open  quarry  of  coals  10  acres  in  ex- 
tent, the  face  of  the  seam  having  a 
height  of  70  feet.  Peculiar  appliances 
are  necessary  for  extracting  this  coal, 
and  Mr.  Bell  described  them  briefly. 
The  largest  blocks  known  as  "  lump " 
coal  are  chiefly  consumed  in  the  blast- 
furnaces, the  others  go  for  various  pur- 
poses. The  "  stove "  coal  is  that  used 
for  domestic  fires,  and  commands  the 
highest  price.  Anthracite  coal  is  regard- 
ed as  a  natural  coke,  as  it  often  contains 
as  much  as  93  pe"r  cent,  of  solid  carbon. 
The  height  of.  the  seams  and  the  nature 
of  the  "  thrust "  by  working  out  the  sup- 
port of  a  roof  lying  at  a  high  angle,  is 
the  cause  of  great  loss  in  "pillars,"  25 
per  cent,  of  the  whole  contents  of  the 
seam  being  the  average.  The  American 
coal  master  has  also  to  contend  with  a 
considerable  quantity  of  small,  which  is 
entirely  valueless,  and  many  acres  of 
land,  near  the  older  pits,  are  covered 
with  it.  Sometimes  as  much  as  one-half 
of  the  whole  produce  of  the  mine  is  thus 
rejected,  but  the  average  is  about  20  per 
cent,  of  the  coal  actually  drawn.  The 
men  engaged  in  the  anthracite  mines 
work  from  eight  to  ten  hours  per  day, 
and  are  paid  on  a  sliding  scale,  accord- 
ing to  the  selling  price  of  coal.  Des- 
cribing bituminous  coal,  Mr.  Bell  stated 
that  this  is  worked  without  producing 
much  small,  and  is  largely  used  in  a  raw 
state  in  the  blast-furnaces  in  the  Mahon- 
ing and  Shenango  Valleys.  In  the  east- 
ern coal-fields,  near  Pittsburg,  a  cele- 
brated coking  coal  is  raised.  Near  Con- 
nellsville  the  seam  is  10  or  11  feet  thick, 
and  the  coal  lies  so  soft  in  the  ground 
that  a  man  without  the  use  of  powder 
can  shovel  a  ton  an  hour  into  the  trams. 


The  entire  produce  of  the  mines  is  con- 
verted into  coke,  and  this  is  considered 
the  best  of  any  in  the  United  States. 
Mr.  Bell,  however,  thinks  that  it  is  great- 
ly inferior  to  Durham  coke.  The  cheap- 
est coal  he  heard  of  is  obtained  for  sup- 
plying one  of  the  large  ironworks,  and, 
exclusive  of  royalty,  it  is  delivered  at 
the  furnaces  for  about  3s.  per  ton.  After 
describing  the  coal  in  the  various  fields, 
he  went  on  to  consider  another  item  of 
iron  manufacture,  viz.,  the  supply  of  flux 
for  blast-furnaces.  He  stated  that  there 
is  avast  extent  of  carboniferous  or  moun- 
tain limestone  in  America,  frequently 
very  near  the  pig-iron  works.  Near  Bal- 
timore the  shells  of  oysters,  which  are 
found  in  great  abundance  at  Chesapeake 
Bay,  are  used.  They  contain  95  per  cent, 
of  carbonate  of  lime,  and  are  a  very  inex- 
pensive substitute  for  lime  itself.  The 
United  States  contains  abundant  quanti- 
ties of  iron  ore  of  all  kinds  except  the 
spathose  ore,  which  is  very  scarce  even 
in  Europe.  The  ironstone  of  the  liassic 
and  oolitic  seams,  which  furnish  about 
one-third  of  the  pig-iron  made  in  the 
United  Kingdom,  seems  to  be  entirely 
wanting  in  the  States.  The  speaker  des- 
cribed first  the  magnetic  iron  ore  of  Lake 
Champlain,  its  peculiarities,  mode  of  de- 
position, &c.  Relative  to  the  specular 
ore  of  Lake  Superior,  which  is  valuable 
from  the  cheapness  of  its  extraction,  its 
abundance,  and  its  freedom  from  dele- 
terious ingredients,  he  remarked  that 
the  contents  of  the  mines  are  chiefly  ob- 
tained by  open  quarry  work.  The  ore 
yields  something  like  67  per  cent,  in  the 
blast-furnace,  and  is  pure  enough  for  the 
manufacture  of  Bessemer  iron.  Mr. 
Bell  next  noticed  the  Iron  Mountain  de- 
posit. It  is  of  easy  reduction;  indeed,  a 
furnace  only  40  feet  high,  with  boshes  of 
9£  feet,  blown  with  cold  air,  "will  make 
100  or  120  tons  per  week  of  grey  iron, 
with  less  than  24  cwt.  of  charcoal  ;  with 
moderately  hot  air  150  tons  per  week 
can  be  run  with  20  cwt.  of  fuel.  The 
yield  of  the  ore  may  be  taken  at  65  per 
cent.  The  author  then  described  in  de- 
tail, various  deposits  of  limonite.  or 
brown  haematite,  which  he  saw,  and' 
afterwards  touched  upon  those  of  red 
haematite  ;  clay  and  blackband  ores  also 
came  in  for  a  share  of  attention.  Mr. 
Bell,  in  treating  of  the  blast-furnaces, 
referred  first  to  the  establishments  which 


VAN   NOSTRAND'S   ENGINEERING   MAGAZINE. 


have  been  founded  for  promoting  scien- 
tific training  and  education,  and  he  spoke 
very  highly  of  the  earnestness  and  de- 
votion which  characterizes  those  engaged 
in  the  mining  and  metallurgical  indus- 
tries of  the  States.  He  criticised  the 
various  matters  in  which  he  thinks  an 
improvement  might  be  made,  and  recom- 
mended those  worthy  of  adoption  in 
this  country.  He  stated  that  the  Lehigh 
makers  are  a  little  behind  the  age  in  the 
question  of  fuel.  In  furnaces  55  feet 
high,  with  boshes  of  from  17  feet  to  IS 
feet,  the  anthracite  used  in  smelting  an 
ore  yielding  50  per  cent,  with  1 2  cwt.  of 
ironstone  was  about  35  cwt.  Perhaps 
this  was  due  to  a  want  of  sufficient  tem- 
perature of  the  blast,  and  so  the  insuffi- 
cient height  of  the  furnace.  Where 
ironmasters  had  been  bold  enough  to 
erect  furnaces  of  72  feet  high,  their  ex- 
perience has  proved  eminently  success- 
ful, for  the  fuel  consumed  has  been  re- 
duced to  25  cwt.  per  ton  of  iron.  In 
the  matter  of  wages,  skilled  men  are 
paid  at  rates  below  their  brethren  in 
England.  The  furnace-keepers  in  1874 
received  8s.  6d.,  against  10s.  and  12s. 
paid  last  year  in  the  North  of  England. 
As  a  rule,  in  the  States,  they  have  more 
men  employed  to  do  the  same  work,  and 
this,  added  to  some  superiority  in  ar- 
rangements, enables  English  makers  to 
smelt  a  ton  of  iron  for  considerably  less 
than  the  amount  paid  in  wages  in  Penn- 
sylvania. Mr.  Bell  spoke  highly  of  their 
blowing  machinery.  He  stated  that  the 
make  of  the  55  feet  and  60  feet  furnaces 
of  grey  iron  may  be  taken  at  200  tons, 
and  that  of  the  larger  at  300  tons  per 
week.  Remarking  on  the  very  large 
make  of  some  of  the  Pittsburg  blast- 
furnaces, Mr.  Bell  stated  that  their  whole 
secret  lies  in  forcing  the  air  into  the  fur- 
nace at  a  high  pressure,  8  lb.  to  9  lb.,  and 
in  immense  volume.  The  ready  reduci- 
bility  of  the  ores  is  also  favorable  to  a 
large  make.  Going  on  to  the  malleable 
ironworks,  Mr  Bell  remarked  that  the 
quantity  of  pig-iron  puddled  is  less  than 
in  this  country,  as  a  large  quantity  of  old 
rails  are  annually  worked  up  in  the  mills. 
The  greatest  number  of  puddling  fur- 
naces in  any  one  establishment  is  at  the 
Cambria  Works,  at  Johnstown,  Pennsyl- 
vania, but  they  cannot  turn  out  above 
600  tons  of  puddled  iron  per  week,  al- 
though their  make  is  equal  in  steel  and 


iron  rails  to  100,000  tons  a  year.  In  the 
States  there  are  899  double  and  2,063 
single  puddling  furnaces,  which  together 
only  produce  about  2,000,000  tons  of 
puddled  iron,  or  1,750,000  tons  of  finish- 
ed iron.  The  prices  for  puddling  vary 
considerably  in  different  localities.  In 
Troy,  the  rate  is  as  low  as  19s.  per  ton, 
in  the  Lehigh  Valley  21s.  9d.  is  paid,  and 
at  St.  Louis  and  Chattanooga  24s.  6d. 
At  Pittsburg  22s.  7-|d.  was  paid  at  the 
time  of  Mr.  Bell's  visit.  He  could  not 
give  a  very  satisfactory  account  of  the 
progress  of  mechanical  puddling  in 
America.  He  referred  at  length  to  the 
Danks'  progress,  and  stated  that  during 
his  visit  to  Messrs.  Graff,  Bennet  &  Co.'s, 
where  they  are  in  operation,  the  work 
was  going  on  in  a  satisfactory  way,  but 
the  furnaces  were  not  used  at  nights. 
Mr.  Bell  believes  that  rotatory  puddling 
will  ultimately  be  achieved,  and  it  may 
be  the  result  of  some  modification  of  the 
apparatus  invented  by  Mr.  Danks. 
Whenever  hand  puddling  is  superseded 
by  mechanical  means,  Mr.  Danks  will 
deserve  great  credit  for  the  assistance  he 
has  already  rendered,  not  only  in  per- 
fecting the  furnace  itself,  but  in  devising 
other  appliances  required  in  manipulating 
large  masses  of  iron.  Mr.  Bell  noticed 
the  three-high  rolls  in  finishing  mills, 
wdiich  are  in  the  United  States  very  gen- 
erally adopted.  The  next  subject  for 
remark  is  that  of  the  manufacture  of  steel. 
The  make  last  year  of  Bessemer  steel 
reached  175,000  tons,  of  which  135,000 
tons  were  used  for  Bessemer  rails.  At 
the  Bethlehem  Iron  Works  Mr.  Bell  saw 
hot  ingots  of  steel  weighing  a  ton  each, 
taken  direct  to  Siemens'  furnace,  out  of 
which  they  were  charged  and  drawn  by 
means  of  hydraulic  cranes.  When  at  a 
suitable  temperature,  the  ingots  were 
brought  to  the  cogging-mill,  which  was 
provided  on  each  side  with  feeding  tables, 
the  invention  of  Mr.  Fritz.  These 
tables  consist  of  two  strong  frames,  the 
breadth  of  the  rolls,  and  long  enough  to 
support  the  ingot  when  rolled  out.  The 
frame  is  furnished  with  a  series  of  rollers, 
and  supported  on  the  standards  them- 
selves is  also  a  roller,  the  latter  forming 
thus  a  continuation  of  the  platform  of 
rollers  placed  on  the  frames.  A  man  at 
a  small  double-cylinder  engine  is  able  to 
set  the  whole  of  the  rollers  on  the  two 
feeding-tables,  as  well  as  those  carried  on 


MINES   AND   IRONWORKS   IN  THE   UNITED   STATES. 


39 


the  standards,  in  motion,  which  he 
changes  at  will,  by  simply  reversing  his 
engine.  As  soon  as  the  ingot  is  partially 
on  the  table  the  rollers  are  started,  and 
the  ingot  is  propelled  towards,  and 
drawn  through  the  rolls,  when  it  is  re- 
ceived on  the  table  behind  the  rolls.  The 
moment  this  is  done,  a  second  man,  by 
means  of  hydraulic  machinery,  raises 
the  two  tables  to  the  level  of  the  grooves 
formed  by  the  middle  and  top  roll. 
While  this  is  being  done,  powerful  screws 
reduce  the  aperture  in  the  rolls,  and  the 
ingot,  by  reversing  the  rollers,  is  passed 
to  the  front,  when  the  feeding-tables  are 
lowered  again  to  their  original  position. 
Underneath  the  front  feeding-table  is  a 
traversing  frame,  to  which  movement,  by 
hydraulic  pressure,  can  be  communicated 
parallel  to  the  rolls,  and  at  right  angles 
with  the  rollers  of  the  table.  Attached 
to  this  traversing  frame  is  a  row  of  five 
strong  bars  coming  through  between  the 
rollers,  and  bent  at  the  top  ends  at  right 
angles.  By  the  use  of  hydraulic  power, 
these  bars  can  be  raised  and  lowered,  so 
that,  by  means  of  the  traversing  frame, 
they  are  made  to  travel  at  will  between 
the  rollers,  and  pass  up  through  them. 
The  moment  the  ingot  is  lowered  on  the 
front  feeding-table,  the  bent  ends  of  the 
bars  catch  it  on  the  left-hand  edge — look- 
ing towards  the  rolls — and  turn  it  over, 
the  traversing  frame  moves  to  the  right, 
and  the  five  bars,  now  projecting  above 
the  feeding-table,  push  the  ingot  oppos- 
ite the  second  groove.  The  rollers  are 
jset  in  motion,  and  the  ingot  is  passed 
through  the  rolls  as  before,  and  this  is 
repeated  for  each  groove  in  the  rolls. 
In  this  way  the  ingots  are  reduced  to  the 
size  fit  for  the  finishing  mill,  without  a 
man  ever  touching  them.  After  beino- 
cut  in  suitable  lengths,  they  are  charged 
while  hot  into  a  second  Siemens'  furnace, 
and  heated  for  the  rail  mill  also,  with 
three  high  rolls,  and  a  masterpiece  of 
rolling  machinery  for  strength  and  ac- 
curacy. Mr.  Bell  thinks  that  all  that 
can  be  said  of  the  blast-furnace  process, 
and  the  malleable  ironworks  of  America, 
is  that  they  are  keeping  fairly  up  with 
the  British,  but,  in  the  Bessemer  works, 
we  must  look  to  the  United  States  for 
superiority  of  arrangement  and  some 
improvement  in  machinery  over  our  own. 
He  considers  the  Americans,  like  our- 
selves, have  done  nothing  in  imitating 


the  French  by  running  the  iron  from  the 
blast-furnace  direct  into  the  converter. 
Little  or  no  steel  was  being  made  in 
America  by  the  Siemens-  \tartin  steel 
process.  An  establishment  had  been 
erected  on  the  banks  of  the  Mononga- 
hela  River,  near  Pittsburg,  for  carrying 
on  the  Blair  process  of  making  steel.  In 
principle  there  is  no  novelty  in  Mr. 
Blair's  method,  which  cousists  of  de- 
oxydizing  ore  and  melting  the  iron  sponge 
so  obtained  in  an  open  hearth  with  pig- 
iron.  The  first  step  in  the  process  has 
been  tried  over  and  over  again  by  Chenot 
and  others  ;  and  Dr.  Siemens  has  paid 
an  immense  amount  of  attention  to  the 
second.  The  consumption  of  charcoal 
and  fuel  was  considerable,  and  did  not 
seem  to  be  a  good  substitute  for  the 
combined  action  of  the  blast  and  puddling 
furnaces.  Mr.  Bell  thus  describes  the 
Blair  process  : 

"  Mr.  Blair  conducts  the  operation  in 
an  upright  retort,  but  circular  in  section, 
4|-  feet,  in  diameter,  and  40  or  50  feet 
high.  In  the  upper  eight  or  ten  feet, 
however,  is  inserted  a  metal  pipe  about 
3  \  feet  in  diameter,  so  that  for  this  dis- 
tance from  the  top  the  working  space  is 
an  annulus  4^  inches  across.  Heat  pro- 
duced by  burning  carbonic  oxide,  obtain- 
ed from  a  Siemens'  producer,  is  applied 
to  the  outside  of  the  retort,  and  heat  is 
similarly  communicated  to  the  inside  of 
the  3|-feet  pipe.  Ore  and  charcoal  are 
charged  into  the  top  of  the  annular 
space,  which  is  thus  exposed  to  heat 
from  the  outside  and  inside,  instead,  of, 
as  with  Chenot,  having  the  heat  only  ap- 
plied to  the  exterior.  The  sponge  is  re- 
tained by  Mr.  Blair,  as  with  Chenot,  in 
the  lower  portion  of  the  pipe,  which  is 
kept  closed  until  it  cools.  One  such  re- 
tort as  that  described  gives  about  2  tons 
of  sponge  in  the  twenty-four  hours.  The 
difficulty  which  besets  this  and  all  other 
modifications  of  dealing  with  iron  in  so 
fine  a  state  of  division  as  it  exists  in  iron 
sponge  is  its  proneness  to  oxydation. 
Hitherto  it  seems  to  me  the  direct  pro- 
cess, as  it  is  termed,  has  met  with  the 
most  success  at  Laudore.  The  pig-iron, 
after  being  melted,  has  blocks  of  ore 
thrown  in  ;  the  carbon  and  silicon  of  the 
bath  reduce  the  oxyde,  and  the  metallic 
iron  is  instantly  taken  up  by  the  bath  of 
liquid  metal.  Very  different  must  be 
ih^  action  on  sponge,  which,  when  thrown 


40 


VAN  nostrand's  engineering  magazine. 


into  the  furnace,  will  float  on  the  melted 
pig,  and,  heing  exposed  to  carbonic  acid 
at  a  very  high  temperature,  will,  to  some 
extent,  infallibly  be  reconverted  into 
oxyde.  So  far  as  I  was  able  to  learn, 
two  parts  of  pig-iron  and  one  of  sponge 
lost  about  20  per  cent,  in  the  furnace. 
Now,  if  it  be  true,  as  I  have  heard  stated, 
that  a  mixture  of  wrought  and  pig-iron 
can  be  fused  in  an  open  hearth  with  a 
loss  of  6  per  cent.,  it  follows  that  a  con- 
siderable portion  of  the  sponge  used  in 
Mr.  Blair's  process  must  be  reconverted 
or  reoxydized.  The  specimens  of  steel 
I  had  an  opportunity  of  examining  indi- 
cate entire  success,  so  far  as  a  mere  ques- 
tion of  quality  in  the  product  is  concern- 
ed. There  seems  to  be  no  doubt  that, 
in  obtaining  the  sponge-iron,  Mr.  Blair 
has  made  a  notable  step  in  advance  of 
M.  Chenot,  and  I  am  far  from  wishing  it 
to  be  understood  that  I  indicate  an  un- 
favorable opinion  on  the  future  commer- 
cial merits  of  the  scheme." 

Mr.  Bell  then  considered  the  labor 
question,  noticing  the  varying  amounts 
of  the  wages,  paid  in  different  districts. 
While  in  one  locality  an  iron-ore  miner  is 
paid  12s.  9d.  per  day,  in  another  he  is 
satisfied  with  4s.  8d.  In  other  districts, 
particularly  in  the  South,  the  iron  mines 
are  worked  by  convict  labor.  The  wages 
must  necessarily  be  higher  in  the  States 
than  they  are  here,  as  the  cost  of  living 
is  so  much  greater.  Mr.  Bell  referred  at 
length  to  the  question  of  import  and  ex- 
port duties.  He  states  that  he  is  fully 
aware  how  unpopular,  among  a  great 
number  of  the  iron  manufacturers,  the 
present  tariff  would  be — indeed,  they 
rather  seek  to  add  to  the  restrictions  it 
already  imposes.     In  the  United  States 


itself,  the  opinions  are  very  largely  di- 
vided as  to  the  benefit  of  protection,  as 
applied  to  native  industry.  The  protec- 
tionists frequently  argue  that  Ave  our- 
selves retained  protection  to  native  in- 
dustry, until  we  felt  that  we  were  inde- 
pendent of  foreign  competition;  and  now 
that  we  no  longer  fear  this,  and  require 
the  necessaries  of  life  for  our  people  we 
are  found  crying  out  for  free  trade. 
They  appear  to  overlook  the  fact  that 
the  chief  opponents  to  free  trade  in 
England  thirty  years  ago  had  as  much 
reason  to  fear  foreign  competition  as  any 
branch  of  industry  in  the  States  need 
dread  the  importation  of  British  iron. 
Mr.  Bell  gave  instances  of  what  has 
been  the  effects  of  production  in  the 
manufacture  of  iron.  Soon  after  1871, 
the  price  of  iron  commenced  to  rise  in 
England.  At  that  period,  something 
like  one-third  of  the  metal  consumed  in 
the  United  States  was  imported  from 
England.  The  change  in  value  here  at 
once  made  itself  felt  in  America,  and 
foundry  iron  was  commonly  sold  at  £10. 
This  remarkable  change  led  to  an  im- 
mediate increase  in  the  number  of  blast- 
furnaces, many  new  ones  being  added 
by  the  end  of  1873.  Mr.  Bell  concluded 
his  paper  by  dwelling  at  length  on  the 
benefits  of  free  trade,  and  combated  cer- 
tain arguments  enunciated  to  the  con- 
trary by  the  Secretary  of  the  American 
Ironmasters'  Association. 

Mr.  Bell  expressed  his  satisfaction  at 
the  recompense  which  the  meeting  had 
given  him,  and  stated  that  he  had 
brought  specimens  of  some  of  the  ores 
he  had  met  with  in  the  United  States, 
and  they  were  in  the  room  for  inspec- 
tion. 


THE  UTILIZATION  OF  WASTE  STEAM. 


Prom  "The  Engineer." 


The  number  of  non-condensing  station- 
ary engines  in  use  is  very  large,  and  the 
discharge  of  their  steam  into  the  atmos- 
phere instead  of  into  a  condenser  repre- 
sents a  great  expenditure — we  shall  not 
say  waste — of  fuel.  Such  engines  are, 
however,  seldom  adopted  without  rea- 
sons sufficiently  powerful  to  insure  the 
rejection  of  condensing  apparatus.*  Lo- 
comotives and  portable  engines  for  obvi- 


ous reasons  cannot  be  constructed  on  the 
condensing  principle,  and  it  will  be  found 
that  stationary  non-condensing  engines 
are  only  used  where  fuel  is  exceedingly 
cheap,  where  water  is  too  scarce  to  be 
used  for  condensing  purposes,  or  in  iron- 
works, where  all  the  steam  needed  and 
more,  can  be  raised  by  the  heat,  which 
would  otherwise  be-  wasted,  escaping 
from  puddling  and  ball  furnaces.     No- 


THE   UTILIZATION    OF   WASTE   STEAM. 


41 


one  thinks  of  utilizing  waste  steam  under 
st»eh  conditions,  and  we  shall  not  further 
refer  to  the  subject  in  connection  with 
them.  Indeed,  it  is  very  difficult  to  see 
to  what  purpose  the  steam  could  be  ap- 
plied in  such  cases,  with  one  somewhat 
limited  exception — the  warming  of  feed 
water — but  the  conditions  of  its  employ- 
ment to  the  best  advantage  in  this  way 
are  well  understood,  and  we  need  not 
dwell  on  them.  In  large  cotton  mills 
and  weaving  sheds  considerable  quanti- 
ties of  steam  are  required  not  only  to 
heat  the  mill,  but  to  supply  the  damp 
atmosphere  requisite  to  the  successful 
weaving  of  fine  sized  fabrics.  In  paper 
mills  and  calico  printing  establishments 
much  steam  is  used  in  heating  rolls,  and 
the  use  of  steam  for  warming  water  in 
brewing,  etc.,  is  very  common.  The 
question  which  presents  itself,  and  which 
we  propose  to  deal  with  here,  is  this:  Is 
it  better  to  use  the  steam  which  has  left 
an  engine  for  heating  purposes,  or  to 
condense  that  steam  and  provide  a  sepa- 
rate boiler,  or  additional  boiler  power  in 
some  other  way,  io  supply  the  steam 
needed  for  heating  purposes  ?  We  hap- 
pen to  know  that  there  is  a  curious  con- 
flict of  opinion  on  this  point,  which 
renders  it  well  worth  discussion  in  these 
pages.  We  must  regard  the  question 
from  two  distinct  points  of  view.  In 
the  first  place  we  have  to  deal  with  those 
conditions  under  which  much  more  steam 
passes  through  an  engine  than  can  be 
used  for  heating  purposes.  This  is  the 
condition  ordinarily  obtaining  in  cotton 
mills.  In  the  second  place,  we  have 
presented  for  consideration  those  cases 
in  which  as  much,  or  more,  steam  is  re- 
quired for  heating  purposes  as  for  driv- 
ing machinery.  It  will  be  found  on 
examination  that  these  varying  condi- 
tions materially  modify  the  problem  to 
be  solved. 

As  regards  engines  driving  cotton 
mills,  it  will  be  seen  that  the  whole 
question  turns  on  the  value  obtained 
from  the  use  of  a  condenser.  Thus,  if 
we  suppose  that  10  per  cent,  of  all  the 
fuel  burned  to  make  steam  is  expended 
in  heating  the  mill,  and  that  it  could  be 
shown  that  the  gain  from  the  use  of  a 
condenser  represented  but  10  per  cent. 
of  the  whole  consumption  of  coal  by 
the  engine,  then  it  would  be  better  to 
use  a  non-condensino-  than  a  condensing 


engine;  and  it  will  also  be  clear  on  ex- 
amination, that  as  the  volume  of  steam 
required  for  heating  purposes  augment* 
in  proportion  to  the  power  due  to  the 
condenser,  so  will  the  economy  of  con- 
densing as  compared  with  non-condens- 
ing diminish,  until  at  last  a  point  will  be 
reached  when  it  is  a  matter  of  indiffer- 
ence which  system  we  adopt,  while  a 
further  demand  for  heating  steam  would 
render  it  better  to  abandon  condensation 
altogether.  We  are  aware  that  this  is; 
opposed  to  the  views  of  some  engineers, 
who  maintain  that  it  is  better  in  all 
cases  to  keep  heating  and  power  dis- 
tinct. But  our  views  are  nevertheless 
demonstrably  sound,  provided  the  con- 
ditions are  such  that  the  working  of  the 
engine  will  be  no  more  affected  by  the 
use  of  the  steam  in  heating  pipes  than  it 
would  be  if  the  steam»were  discharged 
directly  into  the  atmosphere,  a  condition 
which  we  admit  is  not  always  obtainable. 
As  regards  cotton  mills,  however,  it  will 
be  found  that,  as  a  rule,  the  quantity  of 
steam  required  for  heating  purposes  is 
much  smaller  than  that  given  off  by  the 
engine — probably  amounting  to  about 
one-sixth  only.  In  a  word,  the  engine 
rejects  more  heat  than  can  be  utilized, 
and  this  being  the  case,  it  is  better  to 
use  a  condenser  than  not.  This  proposi- 
tion at  first  sight  appears  anomalous. 
Because  an  engine  gives  out  more  heat 
than  we  require,  why  should  we  refrain 
from  utilizing  that  heat  ?  The  contra- 
diction is  easily  explained  away,  as  will 
be  seen  in  a  moment. 

In  order  to  ascertain  the  power  de- 
rived from  the  use  of  a  condenser,  it  is  a 
very  simple  matter  to  take  an  indicator 
card  and  measure  the  relative  areas  of 
the  condensing  and  non-condensing  por- 
tions; or,  which  comes  to  the  same 
thing,  to  measure  the  average  pressure 
in  each  portion.  Thus,  for  example,  if 
we  take  the  case  of  a  condensing  engine 
using  steam  of  an  absolute  pressure  of 
75  lb.  on  the  square  inch  expanded  five 
times,  we  shall  have  an  average  theoreti- 
cal pressure  of  39  lb.  From  this  must 
be  deducted  back  pressure,  say,  5  lb., 
allowance  being  made  for  imperfect 
vacuum  and  port  resistance.  The  effect- 
ive pressure  will  be  34  lb.  on  the  square 
inch.  If,  however,  the  condenser  were 
suppressed,  the  average  driving  pressure 
would  remain  unaltered,  but  the  back 


42 


VAN  nostra^' s  engineering  magazine. 


pressure  would  be  increased  from  5  11). 
to  about  17  lb.,  and  the  effective  pressure 
would  be  reduced  from  39  lb.  to  22  lb. 
For  the  moment  we  shall  regard  the 
consumption  of  steam  as  remaining  un- 
altered; therefore,  the  loss  of  power  due 
to  the  loss  of  pressure  represents  the 
gain  due  to  the  condenser,  which  in  the 
case  cited  would  be  about  36  per  cent.; 
that  is  to  say,  for  every  100-horse  power 
given  out  by  the  engine  with  the  con- 
denser, it  would  without  it, 'give  out  but 
a  fraction  over  64-horse  power.  It  is 
extremely  improbable  that  any  circum- 
stances could  arise  in  connection  with  a 
cotton  spinning  or  weaving  mill  in  which 
so  large  a  quantity  of  steam  as  that 
representing  36  per  cent,  of  the  whole 
power  employed  would  be  required  for 
heating  purposes,  and,  therefore,  to 
abandon  the  condenser  would  be  false 
economy.  It  may,  however,  be  as  well 
to  state  here  that  the  engine  when  work- 
ing without  a  condenser  would  not  use 
as  much  steam  to  produce  65  horse 
power  as  it  did  when  with  the  aid  of 
the  condenser  it  gave  out  100-horse 
power,  simply  because  the  internal  con- 
densation either  in  the  cylinder  or  jacket 
would  be  sensibly  diminished  when  the 
frigorific  influence  of  the  condenser  was 
withdrawn.  The  temperature  of  steam 
of  75  lb.  pressure  is  307.4  deg. ;  that  of 
steam  of  5  lb.  pressure  is  162.5  deg.  The 
range  of  cylinder  temperature  would, 
therefore,  with  condensation,  be  144.9 
deg.  The  temperature  of  steam  of  17 
lb.  pressure  is  219.45  deg.,  and  without 
condensation  the  cylinder  temperature 
wrould  consequently  range  through  87.95 
deg.  only.  Precisely  how  much  this 
circumstance  would  affect  the  quantity 
of  steam  condensed  in  the  cylinder  it  is 
impossible  to  say  without  direct  experi- 
ment, but  that  it  would  reduce  the  loss 
is  beyond  doubt.  On  the  other  hand, 
however,  if  the  same  conditions  of  ex- 
pansion and  pressure  were  maintained  in 
"both  cases,  the  engine  must  have  a 
larger  cylinder  in  order  to  develop  the 
required  power,  and  a  new  element  of 
waste  would  be  introduced  by  the  exten- 
sion of  the  metallic  surface  with  which 
the  steam  would  come  in  contact.  These 
matters  are,  however,  rather  beside  the 
question  we  are  discussing,  and  we  may 
take  it  as  proved  that  the  engines  used 
in  our  manufactories  owe  over  one-third 


of  their  power  to  the  assistance  rendered 
by  a  condenser — in  many  cases  much 
more — and  that  the  most  economical  use 
to  which  heat  rejected  by  their  cylin- 
ders can  be  applied  is  embodied  in  the 
production  of  a  vacuum. 

It  has  been  proposed  that  the  exhaust 
steam  might  be  utilized  in  heating  mills 
while  the  condenser  was  retained.  In 
other  words,  the  exhaust  pipe  might  be 
led  up  and  down  and  round  about  a 
mill,  and  then  return  to  the  condenser. 
The  steam  would  then  be  partially  con- 
densed in  the  pipes  and  partly  by  the 
jet.  Such  a  scheme  is  eminently  delu- 
sive. In  the  first  place,  the  maximum 
temperature  in  the  pipes  would  not  ex- 
ceed that  due  to  the  pressure  in  them, 
or,  say  about  170  deg.;  in  the  second, 
back  pressure  would  be  occasioned  by 
the  resistance  of  the  pipes  and  their 
bends;  and  lastly,  it  would  be  practically 
impossible  to  maintain  all  the  joints  in 
such  a  heating  pipe  air-tight.  In  one 
word,  we  should  have  a  bad  heating  ap- 
paratus and  a  wretched  vacuum  com- 
bined. It  would  b#  waste  of  time  to 
discuss  this  aspect  of  the  question 
further. 

There  remain  for  consideration  cases 
in  which  it  is  essential  that  large  volumes 
of  high-pressure  steam  shall  be  used  in 
manufacturing  operations,  such  as  boiling 
pulp  for  paper  making.  Whether  the 
supply  is  or  is  not  to  be  had  from  the 
exhaust  pipe  of  an  engine  depends  alto- 
gether on  circumstances.  The  total 
quantity  of  heat  utilized  by  a  steam 
engine  represents  so  small  a  proportion 
of  the  whole  heat  contained  in  steam, 
that  it  is  certain  steam  intended  for 
heating  purposes  will  lose  little  if  it  is 
first  used  to  drive  an  engine.  Cases  may 
arise  in  which  steam  of  a  total  pressure 
of,  say,  70  lb.  on  the  square  inch  is  re- 
quired for  some  manufacturing  purpose. 
Now  the  consumption  of  fuel  in  produc- 
ing 100  lb.  steam  is  practically  the  same 
as  though  the  pressure  were  70  lb.,  and 
it  will  be  very  good  economy  to  generate 
steam  of  the  higher  pressure  named  and 
pass  it  through  a  steam  engine,  which 
will  then  play  the  part  of  a  reducing 
valve,  and  give  out  all  the  power  due  to 
a  pressure  of  30  lb.  on  the  square  inch. 
The  engine  will,  it  is  true,  work  against 
a  back  pressure  of  70  lb.,  but  no  one 
looks  for  economy  here.     As  the  steam 


THE   PROTECTION   OF   BUILDINGS   FROM   LIGHTNING. 


43 


must  be  had  in  any  case,  it  is  as  well  to 
get  all  we  can  out  of  it,  and  in  this  way 
in  many  works  from  five  to  50-horse 
power  might  be  had,  in  one  sense,  for 
nothing.  Under  such  conditions  as  these, 
the  cases  we  have  named,  in  which  en- 
gines are  worked  with  a  heavy  back 
pressure,  become  perfectly  legitimate 
examples  of  the  utilization  of  waste 
steam.  So  long  as  the  pressure  of  the 
steam  required  for  boiling  or  heating  is 
moderate,  but  still  considerably  above 
that  of  the  atmosphere,  it  is  good  policy 
to  use  strong  boilers,  and  carry  the 
pressure  high  enough  to  work  an  engine ; 
but  this  rule  will  only  apply,  as  we  have 
already  pointed  out,  in  another  case, 
when  the  whole  volume  of  steam  required 
for  heating  is  much  greater  than  that 
which  would  be  rejected  by  the  engines. 
In  few  words,  when  the  primary  use  of 
steam  is  to  heat,  then  the  condenser 
may  be  suppressed;  when  the  primary 
use  of  steam  is  to  give  out  power,  then 
the  condenser  cannot  with  advantage  be 
dispensed  with. 

A  somewhat  complex  case  is  presented 


when  the  final  pressure  in  the  cylinder  of 
a  condensing  engine  is  greater  than  that 
of  the  atmosphere.  Under  such  circum- 
stances it  is  obvious  that  more  steam  re- 
mains in  the  cylinder  at  the  end  of  the 
stroke  than  is  required  to  produce  a 
vacuum.  The  surplus  may  be  utilized 
for  heating  purposes  in  many  cases  with 
advantage.  On  some  of  the  American 
river  boats  it  is  employed  very  inge- 
niously to  urge  the  fires.  The  moment 
the  exhaust  *^alve  opens,  the  steam,  of 
perhaps  30  lb.  pressure,  escapes  in  part 
through  a  suitable  secondary  valve,  and 
rushing  up  the  chimney  creates  a 
draught.  The  secondary  valve  instantly 
closes,  however,  and  in  doing  so  opens  a 
free  communication  with  the  condenser, 
to  which  about  one-half  the  whole  vol- 
ume of  steam  goes,  the  remainder  urging 
the  fires  as  we  have  said.  By  a  somewhat 
similar  arrangement  the  steam  could  ob- 
viously be  used  for  heating  purposes.  It 
must  not  be  forgotten,  however,  that  it 
is  very  bad  economy  under  most  circum- 
stances to  discharge  steam  of  30  lb. 
pressure  either  into  the  air  or  a  con- 
denser. 


THE  PROTECTION  OF  BUILDINGS  FROM  LIGHTNING. 

By  E.  J.  MANN,  M.D. 


From  the  "Journal  of  the  Society  of  Arts." 


When  a  lightning  discharge  falls  from 
a  charged  cloud  to  the  earth,  it  of  neces- 
sity takes  the  line  of  least  resistance 
that  is  open  to  it,  whatever  that  may  be, 
and  if  that  line  lies  along  sufficiently 
large  and  absolutely  continuous  metallic 
substance,  the  effective  resistance  to  its 
passage  is  so  small  that  no  mechanical 
violence,  or  heating  effect  of  any  conse- 
quence ensues.  This,  therefore,  at  once 
indicates  what  the  first  expedient  in 
providing  artificial  protection  from  me- 
chanical injury  must  be.  A  continuous 
rod  of  good  conducting  metal  must  be 
carried  from  the  top  of  the  building  to 
the  ground.  Then  when  the  stroke  of 
lightning  chances  to  fall  upon  the  build- 
ing, it  goes  by  the  easy  way,  and  flows 
harmlessly  and  silently  through  the  me- 
tallic rod  to  the  earth,  and  the  less  per- 


fect conducting  materials  of  the  house, 
such  as  bricks,  mortar,  cement,  and 
wood,  are  not  touched.  In  order,  how- 
ever, that  this  desirable  result  may  be 
brought  about,  it  is  essential  that  the 
metallic  rod  shall  be  large  enough  to 
carry  quietly  and  harmlessly  the  largest 
discharge  that  may  have,  under  any 
circumstance,  to  pass  through  it.  As  a 
rain-water  pipe  must  be  made  large 
enough  to  carry  safely  away  the  largest 
rainfall  that  can  occur,  if  flooding  is  to 
be  avoided,  so  the  lightning  conductor 
must  be  made  large  enough  to  carry  the 
heaviest  lightning  that  can  strike.  And 
it  is  even  more  important  that  this 
should  be  secured  in  the  case  of  light- 
ning than  in  the  case  of  rain,  because  an 
overflow  of  fire  is  a  more  serious  matter 
than  an  overflow  of  water.     Some  elec- 


44 


VAN  nostrand's  engineering  magazine. 


tricians  consider  that  an  insufficient 
lighting  conductor  is  better  than  none 
at  all,  because  there  have  been  instances 
again  and  again  where  buildings  have 
been  saved  from  mischief  on  the  dis- 
charge of  lightning,  although  the  light- 
ning conductor  that  has  effected  their 
protection  has  been  burnt  up  and  de- 
stroyed. As  in  such  cases,  however,  a 
new  lightning-rod  has  to  be  immediately 
supplied,  it  would  have  been  obviously 
better  that  the  conductor  %f  double  ca- 
pacity should  have  been  erected  in  the 
first  instance.  The  author  of  this  paper 
must  also  add  that  he  has  some  reason 
to  look  upon  the  conclusion  itself  with 
doubt.  There  is  always  danger  from  fire 
if  a  lightning  conductor  of  insufficient 
dimensions  happens  to  be  carried  along 
near  combustible  materials.  The  light- 
ning stroke  is  certainly  more  likely  to 
fall  where  a  lightning  conductor,  of 
whatever  kind,  is  placed  than  it  would 
be  if  there  were  no  such  appliance.  The 
lightning  conductor,  in  such  circum- 
stances, may  be  "  the  slight  acquisition 
of  power  which  destroys  the  tottering 
equilibrium;  the  last  straw  which  breaks 
the  camel's  back;"  alluded  to  by  Mr. 
Preece.  There  certainly  is  as  much 
danger  in  the  interpolation  of  a  light- 
ning-rod in  such  tottering  equilibrium 
as  there  would  be  in  "  a  horseman  gal- 
loping along  over  the  ground."  What 
the  damage  is  that  a  conductor  of  insuffi- 
cient size  may  effect  is  well  illustrated 
in  the  practice  of  firing  charges  of  gun- 
powder in  mines  by  the  platinum  fuse. 
A  fine  wire  of  platinum  is  made  part  of 
a  current  of  electrical  communication  in 
the  midst  of  a  charge  of  gunpowder. 
When  a  current  of  electricity  is  passed 
through  the  wire  it  becomes  red  hot,  on 
account  of  not  having  sufficient  size  to 
convey  the  electricity  without  derange- 
ment of  its  molecules,  and  the  red  hot 
wire  fires  the  gunpowder.  If  the  plati- 
num wire  had  had  the  thickness  of  a 
pencil,  instead  of  a  hair,  the  same  charge 
of  electricity  would  have  passed  without 
the  explosion  of  the  gunpowder.  Anoth- 
er very  telling  illustration  is  supplied  by 
the  not  uncommon  occurrence,  where  a 
small  soft  metal  gas-pipe  is  attacked  by 
a  powerful  discharge  of  lightning,  and 
the  gas-pipe  is  fused,  and  the  gas  set 
light  to.  What  the  dimensions  in  a 
lightning  conductor  are  that  would  fulfil 


this  essential  condition  of  giving  suffi- 
cient capacity  for  the  safe  transmission 
of  the  largest  possible  discharge  is  yet 
an  unsettled  question.  In  his  excellent 
monograph  already  alluded  to,  Mr. 
Preece  argues  that  a  No.  4  telegraph 
wire  of  galvanized  iron,  which  is  a 
quarter  of  an  inch  in  diameter,  is  suffi- 
cient for  the  protection  of  most  dwelling- 
houses,  because  No.  8  wires,  of  only  half 
this  capacity,  are  found  practically  to 
protect  telegraph  posts  from  damage 
by  lightning.  It  is,  however,  most 
probable  that  in  the  case  of  tele- 
graph wires  a  lightning  discharge 
is  distributed  among  several  of  these 
protectors,  as  several  are  brought  into 
the  system  by  the  conducting  tele- 
graph wires  above.  Mr.  Preece  alludes 
to  two  No.  8  wires  having  been  fused 
and  destroyed  by  lightning  in  one  season. 
M.  Arago  gives  the  case  of  a  chain  128 
feet  long,  formed  of  successive  rods  of 
iron,  one  quarter  of  an  inch  in  diameter, 
which  was  fused  through  its  whole 
length  by  a  lightning  discharge.  On 
the  other  hand,  rods  of  iron,  three- 
quarters  of  an  inch  in  diameter,  have 
been  known  to  convey  very  powerful 
lightning  strokes  to  the  ground  harm- 
lessly and  safely.  In  the  instructions  of 
the  "  Academie  des  Sciences,"  drawn  up 
by  Gay-Lussac  and  Pouillet,  1823  and. 
1824,  a  square  iron  bar,  three-quarters 
of  an  inch  in  diameter,  was  adopted  as 
ensuring  ample  capacity  for  all  practical 
purposes.  An  iron  pipe,  having  the 
same  sectional  mass  of  metal,  is  better 
than  a  solid  rod,  because  the  electrical 
force  is  transmitted  by  the  surface  of 
the  conductor,  and  a  pipe  obviously  has 
more  surface  than  a  solid  rod  of  the 
same  relative  mass.  Galvanized  iron  is 
better  than  uncoated  iron,  in  the  first 
place  because  its  surface  is  protected 
against  rusting;  and  in  the  second  place 
because  the  zinc  conducts  with  three 
times  greater  facility  than  iron.  A  rope 
of  galvanized  iron  consisting  of  42 
strands  of  sixteenth  of  an  inch  wire  is  a 
very  convenient  form  of  conductor,  on 
account  of  its  ready  flexibility,  for  pur- 
poses of  conveyance  and  adaptation  to 
angles  and  irregularities  of  a  buildings 
and  on  account  of  the  long  stretch  that 
can  be  made  in  continuous  lengths.. 
If  a  conductor  is  made  of  several  pieces, 
it    is    indispensable  that    those    pieces- 


THE   PROTECTION   OF   BUILDINGS   FROM    LIGHTNING. 


should  be  joined  together  by  absolutely 
perfect  metallic  union,  or  there  will  be 
greatly  increased  resistance  to  the  pas- 
sage of  the  electric  force  in  consequence 
of  the  gaps.     In  strands  of  galvanized 
iron  the  galvanic  surface  affords  a  very 
easy  path  for  the  electricity,  and  the  iron 
core  is  a  stubborn  metal  in  reference  to 
heat,  and  not  readily  destroyed.     A  42- 
strand   wire  rope  of  the  character  that 
has  bee  n  described  affords  as  much  sur- 
face,  and  is  in  all  respects   as  good  a 
conductor  as  a  strip  of  stout  galvanized 
iron  four  inches  broad.     Copper  is  a  five 
times  better  conductor  than  naked  iron. 
A  rope  of  copper  wire,  one-sixteenth  of 
an   inch    thick,    and   with    28    strands, 
would  be   as  efficient    as   a   galvanized 
iron  wire  rope  of  42  strands.     Dimen- 
sions   of    this   value  are   recommended, 
because  they  are  unquestionably  equal 
to  any  demand  that  can  be  made  upon 
them,    and   because   there   is   yet  some 
measure  of  uncertainty  in  regard  to  the 
possible  intensity  of  the  electrical  dis- 
charge  in   exceptional   cases.     It    may, 
perhaps,   be  necessaiy  to  point   out,  in 
regard  to  this  particular  bearing  of  the 
subject,  that  the  sole  reason  why  tele- 
graph   engineers    incline    towards   con- 
ductors of  smaller  capacity  is  that  reduc-4 
tion  in  cost  virtually  increases  the  number 
of  lightning  conductors  that  are  used. 
This  is  a  very  important  practical  con- 
sideration.    But,  in  the  face  of  it,  and 
after  patient  and  long-continued  weigh- 
ing of  the  whole  subject,  the  author  of 
this  communication,  in  his  experience  as 
a  lightning  engineer    in  South  Africa, 
notoriously    a    favorite    haunt    of    the 
thunder  storm,    adopted   the  42  strand 
rope  of  sixteenth  of  an  inch  galvanized 
iron  wire,  and  never  found  any  reason 
yet  to  regret  his  practice  on  this  point. 
The  provision  is  ample  for  buildings  of 
considerable  elevation.     The  mistake  of 
employing   too  small   a   conductor  is  a 
very  common  one.     Within  the  last  few 
weeks  the  author  of  this  paper  himself, 
in   company  with   his   excellent  friend, 
the   secretary  of  the   Society   of   Arts, 
came   upon   a  lightning   conductor    at- 
tached   to    a   very   handsome    recently 
restored  church  in  the  vicinity  of  London, 
in  which  a  single  very  small  galvanized 
iron  wire  was  used,  where  a  lofty  spire 
was  part  of  the  structure,   and   where, 
apparently,  the  thin  wire  passed  down 


the  face  of  this  spire  along  a  casing  of 
wood  shingles.    The  author  submits  that 
if  this  is  not  one  of  the  "last  straws  that 
might  break  the   camel's   back    in    the 
circumstance  of  a  tottering  equilibrium," 
it  ought  to  be.     The  advantage  of  cop- 
per,  in  contrast  with  iron,  for  employ- 
ment as  a  lightning  conductor,  is  simply 
that  it  heats  less  easily  under  an  electric 
discharge,  is  very  stubborn  to  melt,  and 
that  it  is  the  best  of  all  conducting  sub- 
stances.    Its ,  disadvantages  are,  that  it 
is  much  more  costly  than  the  galvanized 
iron  conductor  which  furnishes  an  equal 
facility  of  passage,  and  that,  as  a  metal, 
it  undergoes  a  molecular   change,  from 
the  frequent  passage  of  strong  currents 
of    electrical     force,    which     materially 
affects  its  conducting  power.     It  must 
also  be  remarked  that  copper  is  a  very 
much  better  conductor  than  brass.    Cop- 
per   costs    about   one-third    more    than 
brass,  but  it  transmits  electrical  currents 
eight  times  as  well.     Messrs.  Sanderson 
and  Proctor,  of  Huddersfield,  and  of  18 
Queen    Victoria    Street,   have    recently 
contrived  a  copper  tape,  or   strap,   for 
lightning  conductors,  which  costs  about 
one   shilling  the  foot,   and  which  is  so 
flexible  that  it  possesses  in  a  very  consider- 
able#&egree  the  advantageous  properties 
of  rope.     It   can  be  bent  round  the  in- 
equalities of  a  building  with  the  utmost 
facility,  can  be  manufactured  in  continu- 
ous lengths  to  any  extent,  and  can  even 
be  coiled  for  convenience  of  transport. 
This  copper  tape  is  three-quarters  of  an 
inch  wide,  and  an  eighth  of  an  inch  thick, 
and  therefore  contains  a  sectional  area 
of  a  little  more  than  a  tenth  of  a  square 
inch    of    solid    metal.     This   will   most 
probably   be   found  to  be  ample  for  all 
ordinary  purposes,  and  it  can,  of  course, 
be  readily  doubled  in  any  case  where 
lofty  buildings  have  to  be  protected. 

The  French  electricians,  who  are  un- 
questionably very  high  authorities  in 
matters  of  this  class,  commonly  employ 
metallic  ropes,  in  preference  to  bars,  for 
the  main  stretch  of  the  conductor,  be- 
cause they  possess  a  larger  sectional  area 
than  solid  rods  of  the  same  diameter,  are 
more  easily  placed,  and  adapt  themselves 
to  irregularities  of  structure  without  the 
trouble  of  forging,  because  they,  can  be 
readily  made  of  any  continuous  lengths 
that  can  be  required,  and,  in  the  case  of 
iron,  can  be  easily  galvanized,  and  bo- 


46 


VAN  NOSTRAND'S   ENGINEERING  MAGAZINE. 


cause  they  are  so  supple  and  more  man- 
ageable. They  consider  that  an  iron 
cable  should  have  a  diameter  rather  more 
than  twice  and  a  half  that  of  copper' 
cable  (27.3  millimetres  against  1  centi- 
metre) to  have  the  same  efficiency.  M. 
Callaud,  an  eminent  French  electrical 
engineer,  who  has  very  recently  printed 
an  excellent  book  on  the  "Paratonnerre," 
records  that  a  rope  of  copper,  four-tenths 
of  an  inch  (one  centimetre)  in  diameter, 
employed  as  a  lightning  conductor  at 
the  church  of  Sainte  Croix,  at  Nantes, 
and  which  was  made  of  seven  strands, 
having  each  seven  threads  of  wire  of  a 
gauge  of  0.039  of  an  inch  (one  millime- 
tre) in  diameter,  had  certainly  trans- 
mitted several  very  heavy  electrical 
discharges  without  suffering  any  injury 
in  its  own  substance,  and  that  a  similar 
rope  of  one-fifth  smaller  diameter  (eight 
millimetres)  previously  employed  had 
been  injured  by  lightning  discharges. 
Copper  bars  a  fifth  of  an  inch  (exactly 
five  millimetres)  have  been  known  to  be 
as  much  injured  by  a  single  storm  as  by 
ten  years  of  exposure  and  rust.  M. 
Viollet  Leduc,  on  the  other  hand,  states 
that  copper  ropes  seven  -  tenths  of 
an  inch  (eighteen  millimetres)  in  thick- 
ness were  burned  at  Carcassone.  Fi%m  a 
consideration  of  these  facts  and  some 
others  of  a  similar  character,  the  French 
electricians  of  the  present  day  employ 
ropes  of  copper  from  four-tenths  to 
eight-tenths  of  an  inch  (one  to  two  cen- 
timetres) for  each  82  feet  of  height. 
Mons.  R.  Francisque  Michel,  who  has 
printed  an  interesting  notice  of  the 
faulty  state  of  the  lightning  defence  of 
the  public  monuments  of  Paris,  with 
some  allusion  to  the  views  of  M.  Cal- 
laud, in  Les  Mondes  of  October,  1874, 
considers  that  a  rope  of  galvanized  iron 
wire  should  have  a  diameter  of  eight- 
tenths  of  an  inch,  to  afford  efficient  pro- 
tection under  ordinary  circumstances. 
M.  Callaud  prefers  that  metallic  ropes 
should  be  constructed  upon  hempen 
cores,  on  account  of  the  greater  pliability 
which  this  contrivance  gives.  It  has 
been  already  observed  that  lightning- 
conductors  require  to  be  of  larger  size  in 
proportion  to  their  length.  The  law 
which  rules  this  proportion  is  simply 
that  the  facility  of  electrical  transmis- 
sion in  any  conductor  is  in  the  exact 
ratio  of  the  co-efficient  of  the  conducti- 


bility  of  the  metal  of  which  it  is  composed,, 
multiplied  by  the  number  representing 
the  section  of  the  rod,  and  then  divided 
by  the  number  representing  its  length. 
The  durability  of  any  rod  is,  in  general 
terms,  in  proportion  to  the  square  of  its 
diameter.  M.  Melsens,  a  high  French 
authority,  prefers  that  there  should  be 
several  conductors  of  small  size  rather 
than  one  large  one;  and  it  is  at  any  rate 
generally  agreed  that  a  large  building 
should  be  furnished  with  several  con- 
ductors, and  that  when  several  con- 
ductors are  combined  into  one  stem,  that 
stem  must  be  of  a  size  sufficient  for  the 
safe  transmission  of  all  the  electrical 
force  that  can  be  furnished  to  it  by  the 
contributory  branches. 

If  it  so  happens  that  metallic  cables 
have  to  be  joined,  the  individual  wires 
of  the  connected  ends  must  be  untwisted, 
and  spliced  or  mingled  together,  and 
then  be  bound  tightly  round  with  wire 
in  such  a  way  that  the  whole  can  be 
dipped  into  melted  solder,  or  solder  be 
carefully  run  in  over  a  fire.  Cables  may 
be  satisfactorily  connected  with  rods  by 
turning  a  spliced  loop  upon  their  ends 
in  this  way,  and  by  then  binding  this 
loop  in  upon  the  rod  by  means  of  strong 
,screw  nuts.  Monsieur  Michel,  in  speak- 
ing of  the  need  of  renewing  the  efficiency 
of  the  public  lightning  conductors  of 
Paris,  makes  the  excellent  practical  sug- 
gestion, that  the  ends  of  rods  requiring 
to  be  spliced  in  continuous  electrical 
communication  should  have  plates  of 
soft  lead  firmly  nipped  in  by  screw 
power  between  the  ends  that  are  to 
make  contact,  the  entire  joint  being 
afterwards  enclosed  in  a  sufficient  invest- 
ment of  solder. 

The  disintegrating  energy  of  an  elec- 
trical discharge  is  mainly  expended  upon 
the  extremities  of  a  conductor.  It.  ef- 
fects the  most  marked  molecular  disturb- 
ance on  the  part  where  it  first  falls, 
where  most  probably  the  first  meeting 
of  the  two  antagonistic  forces  occurs, 
and  where  the  terms  of  the  new  alliance 
have  to  be  arranged,  and  also  on  the 
part  by  which  it  has  to  issue  from  the 
conductor  to  the  ground — the  great  nat- 
ural reservoir  of  the  reserve  of  the  en- 
ergy. On  this  account  lightning  con- 
ductors require  to  be  expanded  and  am- 
plified both  at  their  summits  and  at  their 
roots  or  base.     The  French  Academie 


THE   PROTECTION   OF   BUILDINGS   FROM    LIGHTNING. 


47 


des  Sciences  directed  that  the  top  of  the 
conductor  should  be  a  bar  of  iron  two 
and  a  quarter  inches  in  diameter,  whether 
square  or  round,  tapering  up  to  a  blunt 
conical  copper  point,  shaped  to  an  angle 
of  thirty  degrees.  The  pointed  termin- 
ation of  the  conductor  is  a  matter  of 
some  practical  consequence,  because  it 
establishes  a  slow  and  gentle  discharge 
of  an  accumulation  of  electrical  force  at 
high  tension,  as  is  illustrated  in  the  ordi- 
nary experiment  where  the  charged  con- 
ductor of  an  electrical  machine  is  quietly 
discharged  by  the  presentation  of  a 
sharp  needle  to  it.  De  la  Rive  held  that 
a  metallic  ball  was  quite  as  efficient  for 
an  upper  terminal  as  a  point.  But  when 
a  great  number  of  lightning-conductors 
are  brought  near  together,  as  in  protect- 
ing the  buildings  of  an  extended  town, 
there  is  no  doubt  that  if  they  are  pointed 
at  the  top  they  serve  to  saturate  an  ap- 
proaching cloud,  and  to  deprive  it  of  its 
sting  before  it  comes  within  striking  dis- 
tance. After  the  city  of  Pietermaritz- 
burg,  in  Natal,  had  been  largely  supplied 
with  pointed  lightning-conductors,  under 
the  author's  fostering  influence,  the  ac- 
tual discharge  of  violent  lightning  strokes 
within  the  area  of  the  town  became  al- 
most unknown.  During  several  years 
the  only  cases  that  came  under  the 
author's  notice  were  the  tops  of  two 
chimney-stacks  somewhat  damaged,  and 
a  few  lofty  blue  gum  trees  shattered. 

On  account  of  the  facility  with  which 
it  could  be  supplied  by  ordinary  work- 
men, the  author  adopted  a  terminal  for 
the  upper  end  of  the  conductor  in  the 
colony  of  Natal,  which  proved  very  ef- 
fective and  satisfactory.  In  this  arrange- 
ment the  top  of  a  galvanized  iron  rope 
was  inclosed  in  a  tube  of  stout  sheet  zinc, 
finished  at  the  summit,  for  the  sake  of 
ornament,  by  a  gilded  ball  of  turned 
wood,  above  which  the  strands  of  the 
wire  were  opened  into  the  form  of  a  sort 
of  brush.  Each  conductor,  in  this  way, 
had  42  points  of  its  own,  and  the  aug- 
mentation of  terminal  capacity  was  se- 
cured by  the  addition  of  the  external 
zinc  tube.  The  tube  also  supplied  a 
ready  and  convenient  means  of  attach- 
ing the  conductor  to  chimney  stacks,  or 
to  other  protruding  parts  of  the  build- 
ing. 

The  especial  function  and  power  of 
points  is  very  pleasingly  and  completely 


illustrated  by  a  series  of  three  experi- 
ments devised  by  M.  Gavarret,  Professor 
of  Natural  Philosophy  to  the  Faculty  of 
Medicine  at  Paris.  He  first  charges  the 
prime  conductor  of  an  electrical  macliine 
to  the  highest  point  of  tension  that  it 
can  contain  ;  he  then  places  near  to  it 
an  earth-connected  rod,  furnished  with  a 
point  directed  towards  the  conductor, 
and  he  shows  that  the  tension  which  can 
be  produced  in  the  conductor  diminishes 
constantly  as  the  angle  of  the  neighbor- 
ing point  is  made  less.  He  next 
provides  a  Leyden  jar  that  discharges 
itself  by  spark  through  a  given  neigh- 
boring point,  and  unscrewing  this  point, 
and  replacing  it  by  a  crown  of  points, 
he  shows  that  thenceforth  the  same  jar 
will  only  discharge  itself  silently,  and 
without  a  spark.  He  then  so  arranges 
the  jar  that  it  discharges  by  sparks  be- 
low the  plane  of  a  neighboring  terminal 
point,  and  on  fixing  lateral  points  below 
that  plane  the  spark-discharges  imme- 
diately cease. 

Perhaps,  however,  the  most  telling 
proof  of  the  beneficial  influence  of  points- 
in  relieving  the  tension  of  an  excited 
electric  is  that  which  is  given  by  a  very 
simple  and  pretty  experiment,  most  eas- 
ily performed.  If  a  living  man  stands 
upon  a  stool  with  glass  legs,  and  is 
placed  in  electrical  communication  with 
the  prime  conductor  of  an  electrifying 
machine  at  work,  with  a  gold-leaf  elec- 
trometer on  the  table  three  or  four  yards 
away  from  him,  and  holds  in  his  hand  a 
sewing  needle,  with  one  finger  pressed 
over  the  point,  the  gold-leaves  of  the 
electrometer  show  no  manifestation  of 
the  electricity  in  the  operator,  until  he 
unmasks  the  needle  by  withdrawing  the 
finger  from  its  point,  when  the  gold- 
leaves  immediately  start  asunder,  under 
the  influence  of  the  stream  of  electricity 
which  is  poured  out  upon  them  through 
the  point,  even  at  that  distance.  Or  yet, 
again,  if  a  large  tassel  of  strips  of  light 
tissue  paper  is  made  to  throw  its  several 
strips  out  into  a  divergent  brush,  by  elec- 
trifying the  tassel  from  a  machine,  the 
tassels  of  the  paper  collapse  together 
immediately  upon  unmasking  upon  them 
a  needle  point  held  in  the  operator's  hand 
at  the  distance  of  two  or  three  feet  away. 
There  is  one  very  important  result  of  the 
employment  of  terminal  points  to  light- 
ning rods  which  should   never  be  lost 


48 


VAN   NOSTRAND  S   ENGINEERING   MAGAZINE. 


sight  of.  A  lightning  rod  with  efficient 
points,  and  in  satisfactory  operation, 
might  be  grasped  by  the  hand  of  a  living 
man,  even  when  in  action,  with  entire 
impunity,  because,  on  account  of  the 
continued  drain  set  up  by  the  points,  the 
rod  can  never  assume  any  dangerously 
high  tension.  A  conductor  acting  with- 
out a  point,  on  the  other  hand,  is  in  a 
state  of  very  considerable  tension  when 
it  effects  its  first  discharge,  and  if  it 
were  grasped  in  the  same  way  by  a  hand, 
would,  in  all  probability,  strike  through 
that  hand  some  very  inconvenient  and 
possibly  painful  proportion  of  the  dis- 
charge. Conductors  that  have  been  act- 
ing silently  with  points  have  been  seen 
to  be  struck  by  sinuous  tracks  of  fire, 
indicating  dangerous  discharges  of  high 
tension,  when  they  have  been  disarmed 
of  their  points. 

Platinum  has  very  generally  been  re- 
commended for  the  construction  of  the 
terminal  points  of  lightning  rods,  because 
it  is  one  of  the  hardest  known  metals  to 
melt,  and  because  it  is  also  not  easily 
oxydized.  The  points  are  shaped  to  an 
angle  of  from  7  to  10  degrees  at  the  top, 
and  are  made  a  trifle  less  than  two  inches 
(5  centimetres  by  the  French)  long.  In 
this  form  they  are  screwed  firmly  into 
the  top  of  a  rod  of  copper,  which  is 
then  in  its  turn  connected  with  a  cable 
or  metallic  bar  below.  The  terminal  rod 
is  usually  made  of  augmenting  size  as  it 
descends,  and  is  generally  projected  from 
12  to  20  or  30  feet  above  the  building 
that  is  to  be  protected.  Platinum  points 
are  specially  made  for  lightning  conduc- 
tors in  Paris.  They  are  supplied  by 
Collins,  of  118,  Rue  Montmartre  ;  Beig- 
net,  of  96,  Rue  Montmartre  ;  and  De- 
touche,  of  222,  Rue  St.  Martin.  The 
cost  of  a  platinum  point  at  these  houses, 
grafted  on  brass,  and  from  50  to  70 
centimetres  (1.9  to  2.7  inches)  long,  is 
from  16  to  22  francs.  For  better  finish- 
ed work,  with  larger  needles  of  platinum, 
grafted  upon  copper,  the  cost  is  from  60 
to  200  francs. 

M.  Francisque  Michel  considers  that 
the  points  may  be  quite  as  advantageous- 
ly made  of  silver  alloyed  with  copper, 
in  the  same  way  that  it  is  when  used  for 
coining  silver  money,  that  is,  containing 
165  parts  of  copper  to  835  parts  of  sil- 
ver. Such  points  have  the  unquestion- 
able recommendation  that  this  alloy  pos- 


sesses a  very  much  higher  conducting 
power  than  platinum,  which  has  12  times 
less  conducting  power  than  silver  and  1 1 
times  less  than  copper.  Messrs.  Sander- 
son &  Proctor  construct  their  points 
very  neatly,  by  simply  twisting  the  cop- 
per tape  spirally  at  the  end,  after  the 
fashion  of  an  auger,  and  then  filing  away 
the  termination  of  the  flat  metal  into 
the  shape  of  a  sharp  angle.  The  entire 
terminal  is  also  glided  over  the  copper 
to  the  extent  of  eight  inches.  "  This  kind 
of  point  has  the  very  obvious  recommen- 
dation that  it  forms  a  continuous  portion 
of  the  actual  rod,  and  needs  no  joining 
or  attachment. 

The  French  electricians  strongly  re- 
commend, upon  the  ground  of  the  ex- 
periments of  Professor  Gavarret,  that 
the  lio-htnino-rod  should  be  terminated 
by  a  cluster  or  a  crown  of  points,  instead 
of  by  one  alone,  and  M.  Callaud  has 
given  two  sketches,  in  his  treatise,  of 
forms  of  terminal  points  that  have  been 
adopted  in  France,  in  one  of  which  a 
circle  of  ten  points  radiates  at  an  angle 
of  45  degrees  round  the  base  of  the 
principal  terminal,  which  rises  some 
inches  above  them;  whilst  in  the  other  a 
kind  of  plume  of  points  feathers  out 
from  the  base.  M.  Beignet,  of  the  Rue 
Montmartre,  exhibits  a  model  of  the 
multiple  point  which  the  French  electri- 
cians most  affect.  Mr.  Francis,  of  South- 
ampton Street,  Strand,  constructs  a  very 
simple  and  efficient  multiple  point  of 
copper.  The  Hotel  de  Ville  at  Brussels, 
which  is  a  very  large  building,  and  which 
has  been  furnished  with  lightning  rods 
upon  a  very  complete  scale,  by  M.  Mel- 
sens,  a  distinguished  Belgian  electrician, 
is  literally  bristling  with  points.  It  has 
228  points  of  copper,  and  36  points  of 
iron,  in  its  system. 

The  lower  termination  of  a  lightning 
conductor  requires  the  exercise  of  even 
more  care  than  its  upper  end,  because  it 
is  less  constantly  and  less  generally  under 
observation,  and  any  shortcoming  or  mis- 
take in  reference  to  it  is  fatal  to  the  effi- 
ciency of  the  rest  of  the  arrangements, 
however  judiciously  they  may  have  been 
carried  out.  A  faulty  termination  of 
the  earth  connection  is,  of  all  else,  the 
most  common  and  frequent  blunder,  in 
relation  to  lightning  conductors,  that  is 
made.  As  that  is  one  of  the  termina- 
tions of  the  artificially  provided  conduct- 


THE   PROTECTION   OF   BUILDINGS   FROM    LIGHTNING. 


49 


Ing  track,  it  must  be  of  enlarged  dimen- 
sions, as  has  been  already  explained.  It 
must  be  in  very  intimate  communication, 
not  merely  with  the  ground,  but  with  the 
freely  conducting  portion  of  it.  If  a 
moist  contact  can  be  secured  by  inser- 
tion of  the  rope  or  rod  into  constantly 
damp  soil,  the  contact  need  only  be  large 
enough  to  diffuse  what  is  known  as  the 
electrolytic  action — that  is  the  chemical 
disintegration  of  corrosive  metals  at 
moist  contact  when  electric  currents  are 
operative — over  a  fairly  extended  space. 
If  the  contact  is  made  with  dry  earth, 
the  surfaces  must  be  very  large  indeed. 
The  drier  the  material  that  is  involved — 
unless  it  be  an  extended  system  of  con- 
tinuous metallic  substance,  such  as  the 
underground  iron  tubes  of  water  and 
gas  supplies  in  towns,  which  are  among 
the  most  efficient  ground  terminals  that 
can  be  adopted — the  more  expanded 
must  be  the  surfaces  of  communication 
and  contact. 

It  is  worth  while  here  to  make  a  pass- 
ing allusion  to  a  few  flagrant  instances 
of  faulty  construction  in  the  establish- 
ment of  earth  contacts  of  lightning,  con- 
oiuctors  on  account  of  the  sti'ength  of  the 
illustration  that  dwells  in  such  failures. 
In  a  well  known  case  of  a  lighthouse  at 
Genoa,  which  was  injured  by  lightning, 
and  which  was  presumed  to  have  been 
furnished  with  seemingly  efficient  protec- 
tion, it  was  found  that  the  bottom  of  the 
conductor  had  been  plunged  into  the  in- 
terior of  a  stone  rain-water  cistern,  prim- 
arily constructed  especially  to  keep  out 
the  infiltration  of  the  sea,  and  therefore 
well  adapted  to  prevent  that  moist  con- 
tact with  the  mass  of  the  earth  which  is 
essential  to  the  object  in  view.  Mr. 
Preece  has  drawn  attention  to  a  very 
similar  case  at  Lydney,  in  North  Mon- 
mouthshire, where  the  hollow  of  an  iron 
gas  tube,  intended  to  protect  the  church, 
was  inserted  into  the  substance  of  a  loose 
stone  that  was  itself  imbedded  on  dry 
pavement.  One  of  the  most  sublime  in- 
stances of  this  form,  not  merely  of  super- 
fluous but  of  actually  dangerous  care, 
came  under  the  author's  own  observa- 
tion a  few  years  ago,  when  he  found  in 
the  case  of  a  church  in  Norfolk,  which 
was  injured  by  lightning,  although  the 
tower  was  furnished  with  an  apparently 
sufficient  conductor,  that  the  metallic 
xod  was  carried  through  the  necks  of 
Vol.  XIII.— No.  1—4 


glass  bottles  wherever  it  was  attached  to 
the  masonry,  and  that  the  system  of  pre- 
caution was  finally  consummated  at  the 
base  by  putting  the  bottom  of  the  rod 
into  a  glass  bottle  buried  in  the  dry 
earth.  But  a  few  months  since,  the 
author  undertook  to  see  the  protection 
of  the  residence  of  a  friend  in  the  neigh- 
borhood of  Kensington  Gardens,  in 
which  an  exceptionally  lofty  house,  even 
for  that  aspiring  neighborhood,  had  to 
be  defended.  A  sufficient  copper  rope 
was  brought  down  from  an  iron  balus- 
trade that  surrounded  the  summit  of  the 
roof,  but  it  so  chanced  that  this  was  left 
lying  at  the  lower  end  on  the  stone  pave- 
ment of  a  sunk  basement  floor,  before 
the  permanent  earth  contacts  had  been 
established,  and  that  a  thunderstorm 
suddenly  burst  over  the  neighborhood 
while  the  system  of  protection  was  left 
in  that  unfinished  state.  The  head  of 
the  household,  in  the  absence  of  his 
scientific  adviser,  was,  however,  equal  to 
the  emergency.  He  had  the  bottom  of 
the  rope  carefully  coiled  away  into  the 
interior  of  a  wooden  pail,  determined, 
most  probably,  that  if  the  lightning  did 
come  down  the  rope,  it  should  at  any  rate 
be  kept  in  the  pail  until  it  could  be  car- 
ried away  by  some  competent  hand.  In 
one  very  instructive  instance,  a  house  in 
Natal,  which  had  been  furnished  with 
one  of  the  author's  galvanized  wire  ropes 
for  a  conductor,  but  not  under  his  per- 
sonal superintendence,  was  injured  by 
lightning.  The  house  was  a  low-hipped 
structure,  of  one  story.  The  rope  had 
been  brought  from  the  top  roof  ridge, 
which  was  of  metal,  along  one  of  the 
hip  angles,  then  down  a  corner  post,  and 
buried  in  the  ground.  The  lightning, 
however,  had  perversely  preferred  to  go 
down  an  opposite  hip,  where  there  was, 
so  far,  a  metal  road,  and  had  then  leaped 
through  the  wall,  taking  some  iron  sash 
weights  of  a  window  by  the  way,  and 
shattering  the  brick  work  and  doing 
other  damage  in  its  course.  The  author 
went  down,  as  soon  as  he  had  heard  of 
this  accident,  to  investigate  its  cause; 
and  the  cause  was  simply  this:  The 
lightning  conductor  had  been  plunged 
into  a  tract  of  dry  sand  at  the  corner  of 
the  house.  But  at  the  other  corner,  by 
which  the  lightning  had  effected  its  own 
escape  to  the  ground,  was  an  old  pool  of 
water  that  had  been  filled  up  with  earth, 


50 


VAN   NOSTRAND  S   ENGINEERING   MAGAZINE. 


but  was  still  saturated  with  moisture, 
and  still  connected  with  ramifications  of 
infiltrated  soil.  In  this  case  the  light- 
ning, when  it  struck  the  roof  of  the 
house,  had  divided  itself  between  the 
two  routes  which  were  offered  to  it,  the 
conductor  and  the  dry  sand  contact  of 
insufficient  area,  and  the  wall,  with  its 
stepping  stones  of  sash  weights,  and  its 
abundant  wet  contact  beneath.  The 
proportion  of  the  discharge  which  had 
taken  these  different  routes  was  deter- 
mined by  the  specific  resistance  of  each 
way,  and  in  the  course  that  involved  the 
leap  through  the  non-conducting  wall, 
the  amount  which  passed  was  sufficient 
to  produce  the  destructive  disruption 
which  occurred.  All  competent  electri- 
cal engineers  are  now  keenly  alive  to  the 
automatic  electrolytic  action  that  is  apt 
to  take  place  in  the  earth  contacts  of  a 
•lightning  conductor,  and  urge  that  it  is 
not  enough  merely  to  construct  an  effi- 
cient lightning  conductor  in  all  its  essen- 
tial particulars,  but  that  the  arrange- 
ments must  be  examined  from  time  to  ' 
time,  to  make  sure  that  no  derangement 
has  taken  place.  Such  examination  may 
readily  be  effected  by  making  short  cir- 
cuits through  the  conductor  with  the 
wire  of  a  galvanometer,  so  as  to  prove 
by  the  movements  of  the  needle  that  the 
electric  path  is  efficiently  clear. 

From  the  instant  that  an  earth  contact 
is  established  for  a  lightning  conductor, 
destructive  change  of  the  surfaces  of 
contact  begins,  and,  sooner  or  later,  the 
power  of  the  conductor  is  materially  im- 
paired from  this  cause.  This  action, 
known  as  the  electrolytic  disintegration, 
requires  to  be  constantly  watched,  be- 
yond all  else,  and  all  the  more  because 
it  proceeds  in  a  region  where  the  con- 
ductor is  removed  from  observation  by 
the  eye,  and  it  is  most  fortunate  that 
such  watching  may  be  most  efficiently 
and  satisfactorily  accomplished  by  so 
ready  and  convenient  a  means  as  the 
employment  of  the  galvanometer.  M. 
"Wilfred  de  Fonvielle  has  indeed  pro- 
posed that  every  lightning  conductor 
should  have  an  arrangement  of  a  short 
circuit  wire  with  the  galvanometer  at- 
tached permanently  to  it,  in  a  form 
which  he  terms  Le  Controleur  des  Para- 
tonnerres,  and  which  is  so  designed  as  to 
be  always  ready  for  the  eye  of  the  ob- 
server.    The  author  was  once  very  near 


indeed  so  furnishing,  at  his  own  cost,  a 
proof  of  the  material  need  of  some  test 
and  evidence  of  this  character.  He  had 
supplied  his  own  residence  in  the  capital 
of  Natal  with  one  of  his  galvanized  iron 
ropes,  with  the  zinc  tube  and  brush  so 
demonstratively  displayed  above  as  to 
be  a  constant  object  of  observation  and 
remark  to  his  compatriots  and  neighbors. 
The  finial  was  placed  so  as  to  be  a  sort 
of  advertisement  of  the  enlightened 
practice  of  the  owner  of  the  house,  and 
a  standing  reproof  to  the  negligence  of 
those  who  would  not  follow  so  excellent 
an  example.  The  earth  contact  was  very 
efficiently  made,  by.  carrying  the  rope 
along  the  muddy  bottom  of  one  of  the 
streams  of  constantly  running  water 
that,  in  the  old  Dutch  settlements  of 
South  Africa,  are  always  found  fringing 
the  streets;  and  during  many  very  severe 
thunderstorms  the  author  sat  in  his  easy 
chair,  priding  himself  on  the  complete- 
ness of  his  arrangements.  He  subse- 
quently, however,  by  mere  accident,, 
made  the  astounding  discovery  that  for 
a  considerable  length  of  time  the  tail  of 
his  lightning  rope  had  not  been  trailed 
in  the  wet  mud,  but  was  carefully 
packed  away  along  a  stretch  of  dry 
ground,  under  the  shelter  of  a  thick-set 
hedge,  that  served  effectually  to  conceal 
its  presence  there.  On  some  unhappy 
occasion,  when  the  author  was  away,  the 
water  -  courses  had  been  undergoing 
cleansing  and  repair  by  the  civic  author- 
ities, and  the  workmen,  finding  the  metal 
rope  in  the  mud,  had  taken  considerable 
pains  to  pack  it  away  in  the  drier  and 
cleaner  place  in  which  it  was  ultimately 
discovered.  If  any  accident  from  light- 
ning had  in  the  meantime  occurred  to 
the  house,  this  case  would  certainly  have 
lived  in  the  annals  of  Natal,  for  a  couple 
of  centuries  at  least,  as  a  remarkable 
proof  of  the  inefficacy  of  lightning-rods,, 
and  the  great  lightning  doctor  himself 
would  have  been  held  to  have  brought 
down  the  vengeance  of  the  clouds  upon 
his  own  ignorance  and  presumption. 

The  French  electricians  have  contrived 
a  very  excellent  expedient  for  making 
an  efficient  earth  contact.  They  con- 
struct a  stout  harrow  of  galvanized  iron, 
with  recurved  teeth,  connect  this  care- 
fully with  the  end  of  the  cable  or  rod,, 
and  then  bury  it,  imbedded  in  a  mass  of 
coke,  in  moist  earth.     The  cable  or  rod. 


THE   PROTECTION   OF  BUILDINGS   FROM    LIGHTNING. 


51 


is  conducted  to  a  suitable  site  for  this 
terminal  in  channels  of  curved  tiles,  well 
filled  with  broken  coke,  or  even  sealed 
up  in  leaden  tubes,  if  there  are  ammoni- 
acal  vapors  to  be  encountered  by  the 
way.  M.  Callaud  has  a  still  more  in- 
genious and  admirable  plan  of  effecting 
this  purpose.  He  hangs  at  the  bottom 
of  the  cable  a  galvanized  iron  grapnel, 
with  four  upturned  and  four  down-curved 
teeth,  and  entangles  these  within  a 
basket  of  netted  wire,  and  then  packs  in 
this  basket  with  fragments  of  coke;  and 
the  basket,  coke,  and  grapnel  are  after- 
wards sunk  into  a  pit  or  well,  or  buried 
deep  in  moist  earth.  M.  Callaud  pre- 
fers^ coke  to  charcoal,  on  account  of  its 
greater  porosity  and  accessibility  to 
moisture;  and  he  has  made  some  careful 
experiments  to  satisfy  himself  of  the 
size  which  this  earth  terminal  should 
have.  According  to  the  experiments  of 
M.  Pouillet  and  M.  Ed.  Becquerel,  pure 
water  conducts  the  electrical  force  6,754 
million  times  less  freely  than  copper, 
and  therefore,  for  free  transmission,  the 
earth  contact,  if  effected  by  pure  water, 
should  have  6,754  million  times  the  area 
of  the  main  conducting  cable  or  rod. 
This  theoretical  argument  is,  however, 
very  materially  affected  by  the  fact  that 
the  water  in  the  earth  contains  conduct- 
ing principles  of  considerable  power,  and 
,by  other  analogous  considerations;  and 
an  earth  contact  of  1,000  square  metres 
(1,196  square  yards)  has  been  fixed  by  the 
best  French  authorities  as  sufficient  for 
all  practical  purposes  for  a  conductor  of 
copper,  that  is,  one  centimetre  (four- 
tenths  of  an  inch)  square.  M.  Callaud 
calculates  that  in  order  to  accomplish 
this  purpose  his  earth-basket  must  con- 
tain one  hectolitre  (two  bushels  and 
eight-tenths)  of  broken  coke.  In  order 
that  a  lightning  rod  may  perform  its 
work  perfectly,  it  is  obvious  that  there 
must  not  be  any  greater  resistance  to 
the  passage  of  the  electrical  discharge  at 
its  earth-outlet  than  there  is  in  the  rod, 
or  main  channel  of  the  discharge.  Very 
commonly  in  badly-arranged  lightning- 
rods,  it  is  found  that  there  is  ten  thou- 
sand times  more  resistance  at  the  outlet 
into  the  earth  than  there  is  in  the  main 
rod  of  the  conductor.  When  this  alto- 
gether excellent  expedient  of  M.  Cal- 
laud's  cannot  be  adopted,  a  bore,  four  or 
five  inches  in  diameter,  should  be  sunk 


sixteen  or  twenty  feet  into  damp  soil, 
into  which  the  cable  should  be  inserted, 
and  then  the  bore  should  be  filled  round 
the  cable  with  broken  coke,  and  the 
whole  be  firmly  rammed  down;  or  radi- 
ating trenches  should  be  cut  as  deep  as 
possible  in  the  ground,  and  correspond- 
ing branches  from  the  cable  be  then 
packed  into  these  with  an  investment  of 
broken  coke.  M.  Francisque  Michel 
gives  an  unqualified  approval  to  the 
attachments  of  the  lower  terminal  of 
the  cable  to  iron-service-pipes,  whether 
of  water  or  gas,  in  towns. 

In  Gay-Lussac's  report  to  the  French 
Academy  of  Sciences,  in  1823,  it  was 
held  that  all  large  metallic  masses  con- 
tained in  any  building  should  be  brought, 
into  metallic  communication  with  the 
main  system  of  conductors,  and  that 
there  was  no  need  whatever  for  the  em- 
ployment of  insulating  supports  in  at- 
taching the  lightning  rod  to  the  struc- 
tures that  it  is  intended  to  defend. 
These  conclusions  of  Gay-Lussac's  have 
been  generally  acted  upon  since  his  time, 
and  no  very  marked  case  has  ever  oc- 
curred to  stamp  the  practice  that  has 
been  adopted  in  these  particulars  as  radi- 
cally wrong.  In  my  own  practice,  in  the 
colony  of  Natal,  I  have  almost  invariably 
acted  upon  them,  and  no  single  instance 
of  insufficiency  of  protection  has  ever 
come  under  my  notice  in  consequence  of 
the  arrangement. .  The  point  is,  how- 
ever, one  upon  which  there  is  now  some 
difference  of  opinion  in  high  quarters. 
M.  Callaud,  for  instance,  in  his  recently- 
printed  treatise  on  the  Paratonnerre,  in- 
sists upon  the  adoption  of  insulating 
supports  for  the  rod,  and  unconditionally 
condemns  the  electrical  communication 
of  the  rod  with  the  metallic  masses  con- 
tained within  the  building;  and  he  states 
in  one  part  of  that  work  that  M.  Pouillet 
has  to  some  extent  given  in  his  adhesion 
to  these  revolutionary  views.  M.  Fran- 
cisque Michel,  on  the  other  hand,  upon  a . 
full  review  of  all  M.  Callaud's  argu- 
ments, maintains  the  old  doctrine  that 
the  conductor  may  safely  be  attached  to 
the  masonry  of  the  building  by  ordinary 
staples  or  holdfasts,  or  any  convenient 
way,  and  that  insulating  supports  are  of 
no  use  whatever,  and  that  all  masses  of 
metal  contained  in  a  building  should,  as 
a  general  rule,  be  metallically  connected 
with   the   main   line  of    the  conductor. 


52 


VAN   NOSTRAND'S   ENGINEERING   MAGAZINE. 


Professor  Melsens,  of  the  Royal  Acad- 
emy of  Belgium,  one  of  the  highest 
Belgian  authorities,  contends,  upon  ex- 
perimental grounds,  that  the  well-known 
laws  of  derived  electrical  currents  apply 
with  equal  force  to  the  transmissions  of 
electrical  force  of  high  tension,  and  that 
scattered  masses  of  metal  in  any  build- 
ing should  be  metallically  connected  with 
the  conductor  by  closed  circuits  consti- 
tuted by  contacts  with  two  distinct 
points  of  the  rod.  This  divergence  of 
view  among  high  authorities  is  of  not- 
able import,  because  it  is  virtually  the 
only  material  difference  of  practice  that 
is  encountered  in  the  treatment  of  this 
subject  by  well  qualified  scientific  men, 
and  it  may  therefore  be  very  readily  ad- 
mitted to  be  an  affair  that  yet  requires  a 
more  searching  investigation,  and  fur- 
ther severe  question  by  observation  and 
experiment.  In  the  meantime  it  is  of 
some  importance  that  the  exact  bearing 
of  the  doctrine  advocated  by  M.  Callaud 
should  be  understood. 

In  illustration  of  his  argument  M. 
Callaud  takes  the  case  of  an  iron  balcony 
supported  in  front  of  the  window  of  a 
house  at  some  elevation  from  the  ground, 
and  considers  the  possible  result  to  liv- 
ing men  and  women  contained  in  this 
balcony  at  the  time  of  a  severe  thunder- 
storm, accordingly  as  the  balcony  is,  or 
is  not,  electrically  connected  with  an  effi- 
cient lightning  rod.  He  argues,  if  the 
balcony  is  connected  with  a  lightning 
rod,  a  living  person  standing  upon  it,,  or 
leaning  against  its  rail,  is  very  much 
more  likely  to  be  struck  by  a  dischai'ge 
of  lightning,  than  if  the  balcony  had  no 
such  connection.  In  the  former  case,  the 
living  body  is  likely  to  be  made  a  step- 
ping-stone for  the  lightning  on  its  way 
to  the  rod.  He  holds  that  in  the  case  of 
a  lightning  stroke  the  chances  are  a  hun- 
dred to  one  that  a  lightning  rod  is  struck 
in  preference  to  any  part  of  a  building, 
that  if  the  conductor  is  faulty  in  any 
particular,  and  scattered  metallic  masses 
are  connected  to  it,  this  is  tantamount  to 
attaching  the  hundred  chances  of  danger 
to  the  metallic  masses  and  to  living 
people  placed  near  them.  He  says,  in 
effect,  a  satisfactory  and  perfect  light- 
ning rod  should  be  so  placed  that  it  effi- 
ciently protects  every  part  of  the  struc- 
ture it  is  attached  to,  and  that  if  it  does 
this  no  scattered  mass  of  metal  within 


the  building  can  possibly  be  struck  by  a 
discharge.  Therefore,  connection  of  the 
rod  with  scattered  masses  of  metal  is 
superfluous  and  useless  where  the  rod  is 
efficient  and  perfect  in  itself,  and  objec- 
tionable and  dangerous  when  the  rod 
is  not  in  an  efficiently  acting  condi- 
tion. And  perhaps  the  greatest  force  of 
this  argument  falls  upon  a  fact  which  is 
veiy  earnestly  pressed  by  M.  Callaud, 
that  a  lightning  rod  is  a  merely  passive 
piece  of  mechanism,  which  does  not  give 
visible  or  palpable  signs  of  its  own  de- 
rangement, like  a  clock,  but  which  may 
furnish  fatal  proof  of  its  imperfection 
too  late,  by  killing  the  person  who  places 
unmerited  and  undue  trust  in  its  effi- 
ciency and  excellence.  M.  Callaud  re- 
marks with  some  force:  "Lightning  can- 
not strike  a  structure  that  is  well  pro- 
tected. If  the  lightning  finds  at  the  side 
of  the  Paratonnerre  an  electrical  con- 
ductor that  is  superior  to  itself,  the 
structure  is  then  inefficiently  defended. 
A  Paratonnerre  ought  to  dominate,  to 
cover,  to  protect,  a  building,  in  all  its 
parts,  and  in  all  its  details,  or  it  is  better 
away."  The  gist  of  the  whole  matter, 
therefore,  is,  take  care  that  your  conduc- 
tor is  perfect  and  efficient  in  all  its  parts, 
and  that  it  is  in  every  sense  adequate  to 
the  work  that  it  is  required  to  do,  what- 
ever may  be  the  size  of  the  building, 
and  then  it  becomes  a  matter  of  small 
moment  whether  scattered  masses  of 
metal  comprised  in  the  building  are  con- 
nected with  the  rod  or  are  not  connected, 
and  whether  the  rod  is  connected  to  the 
building  by  insulating  or  by  non-insulat- 
ing supports.  M.  Callaud's  conclusion, 
however,  (and  it  is  the  one  upon  which 
he  states  that  M.  Pouillet  has  given  in 
his  adhesion),  is  substantially,  "  Connect 
any  masses  of  metal  with  the  Paraton- 
nerre that  are  of  necessity  removed  from 
the  occasional  close  presence  of  living 
people,  but  on  no  account  ever  connect 
such  masses  with  the  Paratonnerre  when 
they  may  at  any  time  have  living  people 
in  their  close  neighborhood."  Pending 
further  investigation  of  this  very  inter- 
esting point,  there  can  be  no  doubt  that 
this  distinction  is  a  prudent  and  a  safe 
one  to  be  adopted  in  practice,  and  that 
it  is  more  prudent  and  more  required  ia 
proportion  to  the  insufficiency  of  the 
arrangements  of  the  conductor.  Con- 
ducting   masses    which    are    connected 


THE   PROTECTION   OF   BUILDINGS   FROM   LIGHTNING. 


53 


with  the  earth  by  less  readily  conducting 
substances  occasionally  give  rise  to  a 
curious  effect,  which  is  techinally  known 
as  the  return-shock,  and  which  is  alto- 
gether a  result  of  inductive  action. 
When  a  powerfully  charged  electric 
comes  within  a  moderate  distance  of 
them,  an  electrical  charge  of  an  opposite 
character  is  drawn  into  them  by  induc- 
tion, but  this  secondary  charge  escapes 
back  towards  the  earth  the  instant  the 
inducing  tension  is  removed.  The 
production  and  character  of  this  return 
shock,  caused  by  inductive  action, 
admits  of  very  complete  illustration  by 
electrical  apparatus.  An  insulated  con- 
ductor of  long  cylindrical  form,  but 
with  its  glass  supports  only  half  the 
length  of  the  glass  pillar  of  a  prime  con- 
ductor of  an  electrical  machine,  may  be 
placed  parallel  with  the  prime  conductor, 
but  about  an  inch  away.  The  secondary 
conductor  is  then  to  be  raised  to  the 
same  height  as  the  prime  conductor,  by 
fixing  its  glass  pillar  itpon  the  top  of  a 
pillar  of  wood,  a  fine  wire  being  carried 
from  the  metal  cylinder  to  the  wood.  A 
wire  is  then  also  to  be  carried  from  the 
secondary  conductor  to  the  earth,  but  is 
to  be  so  arranged  that  a  small  gap  may 
be  left  in  some  convenient  part  of  its 
course.  When  the  prime  conductor  is 
charged  positively  by  the  machine,  the 
positive  electricity  of  the  secondary  con- 
ductor is  inductively  driven  out  through 
the  wire  and  the  wooden  pillar  to  the 
earth,  and  the  conductor  itself  remains 
negatively  charged.  But  when  the  work- 
ing of  the  machine  is  stopped,  and  the 
prime  conductor  is  deprived  of  its  posi- 
tive charge  by  a  touch  of  the  finger,  the 
negative  charge  in  the  secondary  con- 
ductor is  also  set  free  from  its  condition 
of  inductively  maintained  constraint, 
and  positive  electricity  leaps  back  from 
the  earth  to  restore  its  proper  balance 
and  saturation,  and  as  it  does  so  is  seen 
passing  as  a  spark  through  the  gap  in 
the  earth-wire,  because  that  gap  affords 
less  resistance  to  the  passage  of  electric- 
ity of  tension  than  the  supporting  pillar 
of  wood.^  If  a  little  gun-cotton,  or  some 
other  suitable  inflammable  substance  is 
placed  in  the  gap,  it  is  fired  by  the 
spark  at  the  instant  of  the  discharge. 
Professor  Tyndall,  in  his  lectures  at  the 
Royal  Institution,  shows  the  production 
of  this  sympathetic  inductive  discharge 


in  a  very  magnificent  form.  He  has  a 
flat  coil  of  copper  wire  imbedded  in  a 
mass  of  insulating  resin,  through  which 
he  can  pass  the  discharge  of  the  power- 
ful battery  of  the  institution,  consisting 
of  fifteen  Ley  den  jars;  and  he  has  also  a 
second  flat  coil  similar  to  the  first,  which 
he  can  place  parallel  to  it  and  about  an 
eighth  of  an  inch  away,  the  two  ends  of 
the  second  coil  being  connected  with  a 
wire  presenting  a  small  gap  of  continui- 
ty. When  the  discharge  of  the  battery 
is  passed  through  the  first  coil  a  power- 
ful sympathetic  discharge  rushes  at  the 
same  instant  through  the  secondary  coil, 
and  makes  itself  manifest  by  a  bright 
flash  and  a  loud  snap  in  the  gap  of  the 
connecting  wire.  The  discharge  of  an 
electric  cloud  in  this  way  not  uncom- 
monly produces  a  number  of  sympathet- 
ic minor  discharges  from  neighboring 
bodies.  The  induced  discharge  is  some- 
times quite  strong  enough  to  produce 
mechanical  mischief  in  resisting  bodies 
that  lie  in  its  path.  The  shocks  experi- 
enced by  living  people  on  the  instant  of 
a  discharge  of  lightning,  without  fatal 
results,  are  generally  of  this  character. 
It  was  to  meet  the  case  of  these  inciden- 
tal induced  charges,  and  the  consequent 
"  return  shocks,"  that  the  expedient  of 
connecting  scattered  masses  of  metal 
with  the  conductor  was  originally  de- 
vised. The  return  shock  resulting  from 
a  limited  inductive  disturbance  may  be 
strong:  enousrh  in  some  circumstances  to 
cause  death  by  the  mere  arrest  ot  the 
vital  action  of  the  nerve  structures 
through  which  it  passes,  without  leaving 
behind  it  any  trace  of  mechanical  vio- 
lence, such  as  is  generally  produced  by 
the  true  lightning  stroke. 

The  old  practice  of  protecting  build- 
ings from  lightning  consisted  in  erecting 
rods  of  metal  upon  wooden  frames,  near 
to,  but  not  in  actual  contact  with,  the 
walls  of  the  house.  When  the  author 
of  this  article  first  visited  Natal,  in  185  7, 
the  houses  in  the  two  principal  towns, 
that  were  defended  at  all,  had  independ- 
ent conductors  of  this  class,  of  the  rud- 
est possible  kind,  erected  by  the  side  of 
the  one-storied  houses  upon  ungainly 
wooden  frames.  The  conductor  was 
composed  of  an  iron  rod,  joined  in 
three  lengths,  and  rudely  pointed  above, 
and  it  was  made  of  three  different  pieces 
— a  comparatively  thick  one  below,  and 


54 


VAN   NOSTEAND'S   ENGINEERING   MAGAZINE. 


a  comparatively  thin  one  at  the  top. 
This  practice  was  primarily  based  upon 
an  investigation  which  was  conceived  to 
demonstrate  that  all  structures  lying 
within  a  conical  space,  which  had  the 
conductor  itself  for  its  height  and  a 
breadth  for  its  base  equal  to  four  times 
the  height  of  the  conductor,  were  safe. 
This  estimate  gives  a  fair  approximation 
to  a  truth,  but  it  is  by  no  means  abso- 
lute, and  must  not  be  empirically  relied 
upon.  It,  however,  furnishes  a  very 
good  indication  of  the  way  in  which  the 
upper  termination,  or  terminations,  of 
the  rod  must  be  arranged.  The  termi- 
nal point  should  go  some  considerable 
distance  above  the  housetops,  and  then 
if  any  projecting  parts  of  the  house 
extend  beyond  the  surface  of  a  line  hav- 
ing, perhaps,  a  somewhat  more  acute 
figure  than  the  one  which  has  been 
named,  other  subsidiary  points  must  be 
reared  up  from  the  line  of  the  conductor 
above  such  conical  slopes.  Mr.  Preece, 
in  his  paper,  considers  that  the  lightning 
conductor  should  only  be  held  to  afford 
absolute  protection  within  a  conical 
space  in  which  the  base  is  as  large  again 
as  the  height  of  the  line.  When,  how- 
ever, the  general  idea  of  the  limits  of 
this  lateral  protection  is  once  clearly 
conceived,  it  becomes  very  easy,  indeed, 
to  render  the  arrangements  of  the  upper 
terminals  perfect  for  any  individual  case. 
It  is  only  necessary  that  all  prominent 
masses  of  metal  shall  be  connected  with 
the  system  of  metallic  communication, 
and  that  an  addition  branch  of  the  sys- 
tem of  defence  shall  be  carried  out 
"whenever  outlying  parts  of  the  structure 
get  near  to  the  conical  limit  of  protec- 
tion. This  is  virtually  what  has  been 
done  in  the  case  of  the  Hotel  de  Ville, 
at  Brussels,  with  its  terminal  of  264 
points. 

When  Sir  William  Snow  Harris,  now 
some  years  ago,  turned  his  attention  to 
the  protection  of  ships  from  lightning, 
lie  devised  a  plan  of  making  the  light- 
ning conductor  a  part  of  the  original  de- 
sign and  essential  construction  of  the 
ship.  Now  all  large  and  well-contrived 
"vessels  are  always  built  with  the  light- 
ning rod  included  in  their  structure.  It 
Is  almost  incredible  that  up  to  this  time 
the  same  course  has  not  been  taken  with 
liouses.  It  is  hard  to  understand  why 
lightning  conductors  should  be  objects 


of  exceptional  luxury,  and  rain  pipes 
objects  of  daily  need,  and  the  more  so 
when  rain  pipes  themselves  can  be  so 
easily  turned  by  a  little  forethought  and 
mechanical  ingenuity  into  lightning  con- 
ductors of  the  most  efficient  character  ; 
they  only  need  that  their  joints  shall  be 
made  mechanically  continuous,  that  their 
earth  contacts  shall  be  perfected,  that 
all  masses  of  metal,  with  perhaps  the 
limitation  that  is  contended  for  by  M. 
Callaud,  shall  be  brought  into  metallic 
communication  with  them,  and  that 
metal  terminals  shall  be  distributed  from 
them  to  the  roofs  above  upon  the  prin- 
ciple that  has  been  explained.  Mr. 
Preece  has  thrown  out  one  very  excel- 
lent suggestion  which  well  deserves  fur- 
ther thought  ;  it  is  to  the  effect  that 
metal  ventilating  pipes  carried  up  from 
the  sewers  over  the  roof  of  the  house 
may  advantageously  be  made  part  of 
the  arrangements  for  protection  against 
lightning.  The  familiar  case  of  the 
Monument  of  London  is  continually  ad- 
duced as  a  proof  of  the  readiness  with 
which  the  accidental  features  of  a  build- 
ing may  be  turned  to  account  for  this 
purpose.  The  metallic  emblems  of  flame 
at  the  top  of  the  column  are  continuous- 
ly connected  with  the  ground  by  means 
of  a  very  thick  balustrade  of  iron  that 
runs  as  a  hand-rail  down  the  stairs  ;  the 
structure  is  200  feet  high,  and  towers 
above  all  neighboring  buildings,  and  yet 
it  has  now  stood  within  three_  years  of 
two  centuries  without  ever  having  been 
injuriously  touched  by  the  lightning. 

It  was  conceived,  until  recently,  that 
St.  Paul's  Cathedral  had  been  efficiently 
protected  in  some  similar  way  by  the  ar- 
rangement of  water-pipes,  and  some  sup- 
plementing of  them  by  metallic  rods, 
added  by  a  Committee  of  the  Royal  So- 
ciety some  120  years  ago.  Mr.  Faulk- 
ner, of  Manchester,  however,  found,  in  a 
careful  examination  made  subsequently 
to  1872,  that  the  system  had  become  en- 
tirely inefficient  for  the  purpose  for 
which  it  was  intended,  by  the  formation 
of  thick  incrustation  of  rust  on  the  con- 
tact surface  of  the  rods,  and  by  the  inter- 
polation of  blocks  of  dry  granite,  some 
nine  inches  thick,  in  places,  into  the  ac- 
tual line  of  electrical  conduction.  The 
entire  building  has  now  been  most  effi- 
ciently protected,  under  the  skilful  direc- 
tion of  Mr.  Faulkner,  by  carrying  eight 


THE  PROTECTION   OF   BUILDINGS   FROM    LIGHTNING. 


55 


octagonal  half-inch  ropes  of  common 
wire  from  the  Cross,  Ball  and  Golden- 
Gallery  through  the  metal- work  of  the  roof 
of  the  dome,  and  through  the  metal  work 
and  rainfalls  of  the  lower  parts  of  the 
building  to  the  sewers,  where  the  con- 
ducting strands  terminate  in  copper 
plates  pegged  into  the  moist  earth.  In 
carrying  out  this  work  every  important 
metallic  portion  of  the  building  was 
separately  tested  by  the  galvanometer, 
to  make  sure  that  the  electrical  commu- 
nication with  the  earth  was  virtually  and 
substantially  clear.  The  galvanometer 
was  first  made  into  a  circuit  with  a 
metallic  gas-pipe  ;  and  then  the  circuit 
was  opened  out,  so  that  earth  was  made 
in  one  direction  through  the  gas-pipe, 
and  in  the  other  through  the  metallic 
portion  of  the  building  for  the  time 
under  examniation  ;  and  the  test  was 
not  considered  satisfactory  until  the  de- 
flections of  the  galvanometer  were  the 
same  under  both  alternatives.  In  ar- 
ranging methodical  architectural  plans 
of  this  kind  it  must  always  be  carefully 
borne  in  mind  that  small  gas-pipes  of 
easily  fusible  metal  must  on  no  account 
form  part  of  the  connecting  lines  of  con- 
ducting circuit.  Gas-pipes  are  most  eas- 
ily fused  by  a  stroke  of  lightning,  and 
when  they  are  so  fused  the  gas  which 
escapes  from  the  extemporized  orifice  is 
invariably  set  light  to. 

One  point  which  was  expressly  urged 
by  Mr.  Preece  and  by  Captain  Douglas 
Galton  in  the  discussion  of  Mr.  Preece's 
paper  at  the  Society  of  Telegraph  Engi- 
neers, should  be  most  carefully  kept  in 
view  in  any  structural  plan  matured  for 
the  protection  of  buildings,  namely,  the 
including  of  all  fireplaces  or  stoves,  and 
soot  -  blackened  chimneys  in  the  sys- 
tem of  connected  construction.  To 
adopt  Mr.  Preece's  own  statement  of 
this  need:  "It  must  not  be  forgotten 
that  a  chimney  lined  with  a  thick  layer 
of  soot,  up  which  a  current  of  heated  air 
and  volumes  of  smoke  are  ascending, 
and  terminated  by  a  mass  of  metal  (the 
grate),  is  an  excellent  but  dangerous 
conductor,  for  it  ends  in  the  room,  and 
not  in  the  earth." 

Since  the  first  preparation  of  this 
paper,  two  pamphlets  by  Messrs.  Gray 
&  Son,  of  Limehouse,  have  come  into  the 
hands  of  the  author,  which  are  valuable 
and  interesting  on  account  of  the  details 


which  they  contain  of  a  considerable 
series  of  instances  of  damage  from 
lightning.  Mr.  W.  J.  Gray,  of  this 
firm,  was  originally  concerned  with  Sir 
Wm.  Snow  Harris  in  perfecting  his  plan 
for  protecting  ships,  and  obviously  pos- 
sesses a  large  amount  of  practical  infor- 
mation in  regard  to  accidents  that  have 
occurred.  Space  now  only  serves  to 
say  that  the  Messrs.  Gray  endorse  the 
practice  of  connecting  all  metallic  mass- 
es in  a  structure  with  the  main  line  of 
conduction,  and  especially  urge  the  sur- 
rounding of  all  prominent  objects,  such 
as  the  tops  of  tall  chimneys  and  church 
towers,  with  continuous  bands  of  copper 
brought  down  into  direct  connection 
with  the  discharging  rod. 

The  great  length  to  which  this  paper 
has  already  extended  itself  alone  pre- 
vents some  allusion  being  here  made  to 
the  views  of  Professor  Zenger,  of  Prague, 
who  advocates  the  use  of  circular  zone- 
like or  ring-shaped  conductors,  embrac- 
ing within  their  span  the  objects  which 
are  to  be  defended  from  injury. 

There  is  no  sufficient  ground  for  the 
popular  idea  that  accidents  from  light- 
ning are  of  such  rare  occurrence  that  it 
is  scarcely  worth  while  to  incur  the 
trouble  and  cost  which  artificial  protec- 
tion involves.  The  figures  of  the  statis- 
tician prove  that  accidents  are  very  fre- 
quent indeed.  The  Escurial  in  Spain 
has  been  set  fire  to  four  times  by  light- 
ning in  less  than  three  centuries.  As 
many  as  1,308  persons  were  ascertained 
to  be  killed  by  lightning  in  France 
between  1835  and  1852.  Some  time 
ago  the  mean  number  of  deaths  from 
lightning  in  each  year  was  marked 
at  3  in  Belgium;  9  in  Sweden;  22 
in  England ;  50  in  the  United  States 
of  America  ;  and  95  in  France.  M. 
D'Abbadie  records  the  destruction  of 
two  thousand  sheep  by  a  single  discharge 
of  lightning.  Mr.  Preece  tells  of  897 
telegraph  instruments  injured  by  light- 
ning in  the  first  six  months  of  IS 72  in  a 
staff  of  9,475  instruments.  Mi".  G.  J. 
Symons,  one  of  the  secretaries  of  the 
Meteorological  Society,  has  given,  as  the 
list  of  accidents  that  he  had  ascertained 
to  have  happened  during  two  severe 
storms  in  June,  1872  ;  10  deaths  and  15 
cases  of  injury  to  human  beings  ;  60 
houses  struck  and  15  burned  down  ;  and 
23  horses  or  cattle,  and  99  sheep  killed. 


56 


VAN  NOSTRAND'S   ENGINEERING   MAGAZINE. 


It  need  scarcely  be  said  that  many  acci- 
dents also  occur  every  year  from  light- 
ning, over  and  above  those  which  get 
publicly  spoken  of  or  placed  on  record. 
In  large  towns  damage  to  property  is 
more  frequent  than  destruction  of  human 
life,  but  in  the  open  country  destruction 
of  life  is  the  more  frequent  oc- 
currence. In  the  face  of  figures  like 
these,  and  of  the  fact  of  the  slowness  of 
man  to  avail  himself  of  the  ready  de- 
fence which  science  places  at  his  com- 
mand, unfortunate  humanity  certainly 
stands  very  much  in  need  of  the  consola- 
tion which  the  physiologist  affords  when 
he  tells  us  that  all  danger  from  lightning 
is  past  when  the  flash  of  the  electrical 
discharge  is  seen,  and  when  he  further 
states  that  when  men  are  killed  by  light- 
ning  they  are   dead  before   they  have 


time  to  know  anything  about  the  fact,  or 
indeed  to  be  conscious  of  the  fatal  blow; 
a  conclusion  by  the  way  that  is  striking- 
ly corroborated  by  an  unintentional  ex- 
perience of  Professor  Tyndall's,  who 
upon  one  occasion  passed  the  full  charge 
of  the  Leyden  jar  battery  of  the  Royal 
Institution,  by  accident,  through  him, 
and  was  perfectly  unconscious  of  any 
shock.  It  is  something,  at  any  rate,  to 
have  this  comfortable  assurance  when 
the  sense  of  neglected  opportunity  comes 
over  the  mind  in  an  exposed  situation 
and  in  an  unprotected  house  during  a 
severe  thunderstorm.  But  it  is  humbly 
submitted,  as  an  appropriate  last  word 
of  this  paper,  that  to  men  of  well-regu- 
lated minds  a  good  lightning  conductor 
may,  in  such  emergency,  be  found  to  be 
an  even  greater  satisfaction  and  comfort,. 


THE  IKON  AND  STEEL  INSTITUTE. 

Address  of  the  President,  Mb.  W.  MBNELAUl.. 
Abstract  from  "  The  Engineer." 


My  first  duty  is  to  thank  you  for  the 
very  high  honor  which  you  have  con- 
ferred upon  me  in  electing  me  to  fill  the 
office  of  President  of  the  Iron  and  Steel 
Institute.  As  an  iron  maker  my  mission 
has  been  to  bring  into  profitable  use  the 
valuable  inventions  of  Bessemer,  Siemens, 
and  others,  and  to  apply  the  scientific 
research  of  men  like  Mr.  Bell  to  the  im- 
provement of  old  and  new  processes. 

So  much  has  been  said,  and  well  said, 
by  my  predecessors  about  the  history, 
the  position  and  the  prospects  of  Eng- 
lish iron  making,  that  I  propose  on  this 
occasion  to  confine  my  remarks  mostly 
to  the  manufacture  of  wrought  iron  and 
steel,  and  the  application  of  the  latter 
to  constructive  purposes.  For  the  con- 
version of  pig  into  wrought  iron,  the 
rotary  puddling  machine,  in  one  or  other 
of  its  forms,  has  occupied  the  attention 
of  iron  makers  for  many  years,  and 
various  attempts  have  been  made  from 
time  to  time  to  perfect  the  machine. 
When,  under  the  auspices  of  this  Insti- 
tute, the  Danks  machine  was  introduced 
into  this  country,  success  seemed  cer- 
tain :    several    machines   were   erected, 


mostly  at  and  near  Middlesborough,  but 
they  seemed  to  have  failed,  chiefly  from 
defects  in  mechanical  construction. 
These  defects  have,  I  am  told,  been 
rectified,  and  several  important  improve- 
ments have  been  made  in  the  construc- 
tion and  mode  of  working  the  machines. 
To  Messrs.  Hopkins,  Gilkes  &  Co.,  is 
due  the  credit  of  having  first  introduced 
and  practically  tested  these  machines  in 
England.  The  Erimus  Company  fol- 
lowed, and  erected  extensive  works,  in 
which  the  Danks  machines  alone  are 
us^I.  Certain  difficulties  were  met  with,, 
and  no  doubt,  for  a  time,  some  disap- 
pointment was  felt;  how  these  difficul- 
ties were  met  and  overcome  is  fully 
explained  in  an  interesting  communica- 
tion from  Mr.  John  A.  Jones,  which  I 
will  read: 

A  year  ago  the  writer  stated  in 
London,  what  were  at  that  time  consid- 
ered to  be  the  chief  drawbacks  to  the 
success  of  rotary  puddling.  They  were 
stated  to  be  the  education  of  the  men 
and  the  removal  of  prejudice  from, 
amongst  them;  the  difficulty  with  the 
fettling  of  the  furnace,  and  the  mechan.- 


THE   IRON   AND   STEEL  INSTITUTE. 


67 


ical  weakness  of  the  Danks  machine.  It 
was  quite  evident  that  unless  the  com- 
pany could  procure  a  certain  quantity  of 
iron  from  each  machine  in  a  given  time 
and  in  a  regular  manner,  rotary  puddling 
could  not  favorably  compete  with  hand 
puddling,  so  far  as  the  cost  of  puddled 
iron  was  concerned.  The  obstacles  were 
in  chief  as  stated  above,  and  to  the  re- 
moval of  these  the  company  devoted 
their  attention.  The  education  of  men, 
which  includes  the  change  from  a  posi- 
tive state  of  indifference  to  that  of  active 
assistance,  has  given  more  trouble  and 
anxiety  than  was  anticipated;  and  to 
this  day  we  have  not  received  that 
active  co-operation  from  the  men  which 
is  necessary  to  the  complete  success  of 
rotary  puddling.  At  the  same  time 
much  progress  has  been  made  in  that 
direction,  and  it  is  earnestly  hoped  that 
in  a  short  period  we  shall  receive  that 
assistance  which  will  enable  us  to  do 
better  than  has  hitherto  been  done.  The 
fettling  of  the  furnace,  and  the  materials 
used  for  the  same,  are  no  longer  ques- 
tions of  difficulty,  and  in  this  respect  we 
have  no  drawback.  We  line  the  furnace 
after  each  heat  with  best  tap,  pottery 
mine,  purple  ore,  and  Spanish  ore;  suit- 
able proportions  are  mixed  in  a  grinding 
mill,  and  then  used  in  the  furnaces. 
Fettling  can  be  procured  suitable  to  any 
district  where  the  difference  in  the  qual- 
ity of  the  pig  iron  mostly  necessitates  a 
variation  in  the  fettling  ingredients. 
With  regard  to  the  mechanical  imper- 
fections of  the  Danks  machines,  they 
have  been  of  a  serious  character.  The 
repairs  have  been  very  costly,  and  the 
loss  of  output,  by  reason  of  frequent 
stoppage,  has  affected  the  cost  of  pro- 
duction most  unfavorably.  It  became 
apparent  that  unless  the  mechanical 
construction  of  the  furnace  was  such  as 
to  insure  regularity  of  work,  it  was 
hopeless  to  expect  satisfactory  results; 
and  the  attention  of  the  directors  was 
devoted  to  this  necessity.  It  was  at  last 
agreed  that  new  furnaces  of  a  different 
construction  should  be  adopted,  and  to 
that  end  one  was  erected  as  an  experi- 
mental furnace.  This  furnace  has  been 
at  work  for  nearly  two  months.  It  is  a 
double  -  case  wrought  iron  furnace, 
hooped  with  steel,  and  is  water-jacketed. 
There  is  a  constant  flow  of  water  to  and 
from  the  water  space,  and  the  water  at 


the  outlet  pipe  is  kept  at  from  80  deg. 
to  100  deg.  Fah.  —  in  fact,  perfectly 
cool.  This  double-cased  furnace  has 
maintained  its  mechanical  accuracy, 
which  it  is  almost  impossible  that 
a  single-cased  furnace  can  do,  owing  to 
the  effects  of  expansion  and  contraction. 
The  firing  of  the  new  furnace  is  done  in 
the  usual  manner.  It  will  not  be  neces- 
sary for  me  to  describe  in  detail  the 
improvements  of  this  machine;  let  it 
suffice  that  it  has  been  designed  and 
constructed,  after  all  the  weak  points  of 
its  fore-runner  have  been  carefully  con- 
sidered. The  directors  are  so  satisfied 
with  the  work  done  by  this  machine 
that  they  have  ordered  five  more,  and 
six  sets  of  new  engines  to  drive  them. 
In  designing  the  engines  the  same 
amount  of  care  has  been  taken.  They 
are  over-head  double-cylindered  engines; 
the  wearing  parts  have  been  carefully 
designed,  and  nothing  in  strength  or  in 
the  detail  is  left  unprovided  for,  so  as 
to  insure  continuous  and  satisfactory 
working. 

In  manufacturing  puddled  bars  at 
the  Erimus  Ironworks,  the  pig  iron  is 
first  melted  and  refined  in  one  of  Thom- 
as' cupolas.  The  refining  is  done  during 
the  smelting  process,  and  is  accom- 
plished by  simply  mixing  scrap  iron  and 
ore  in  the  charges.  The  perceptible  effect 
it  has  upon  the  iron  is  that  where  the 
charge  is  exclusively  of  No.  4  forge 
grey  pig,  the  fracture  becomes  that  of 
white  or  refined  iron.  The  chemical 
effect  is  that  a  portion  of  the  silicon  and 
phosphorus  is  removed,  and  it  is  to  this 
end  that  the  refining  is  done,  so  t hat- 
there  will  be  as  little  action  as  possible 
upon  the  lining  of  the  furnace.  The 
effect  of  using  refined  iron  is  very 
marked.  We  do  not  perceive  any  melt- 
ing out  of  fettling  per  se;  but  what  is 
used  is  reduced,  and  thus  adds  to  the 
yield.  Again,  the  refining  of  the  iron 
does  not  necessitate  the  fettling  of  the 
furnace  so  often,  whereby  much  economy 
is  effected  in  the  fettling  used,  and  in 
the  time  which  is  devoted  to  puddling. 
We  charge  entirely  with  melted  and  re- 
fined iron,  and  the  weight  of  our  present 
charge  is  14  cwt.,  which,  when  the  new 
furnaces  are  erected,  will  be  increased 
to  a  ton.  The  Cleveland  forge  iron. 
which  is  almost  exclusively  made  from 
a  foundry  burden,  is  very  silicious.     It 


58 


VAN   NOSTRAND  S   ENGINEERING   MAGAZINE. 


holds  from  2  to  3  per  cent,  of  silicon.  It 
is  obvious,  therefore,  what  an  evil  effect 
this  pig  iron  has  upon  the  fettling;  and 
a  portion  of  this  is  removed,  as  is  stated, 
by  refining.  In  Cleveland  scarcely  any 
grey  forge  is  made  from  a  forge  burden, 
but  it  is  derived  from  an  attempt  at 
foundry  iron,  and  the  finished  iron- 
making  suffers  severely  from  this.  No 
heat  takes  more  than  thirty-five  minutes 
to  puddle.  The  heat  is  removed  in  a 
single  ball,  and  squeezed  or  shaped  into 
a  piece  about  14  ft.  long  by  15  in.  diam- 
eter. It  is  then  cut  up  at  the  same  heat, 
and  taken  to  reheating  furnaces,  where 
it  is  reheated,  hammered,  and  rolled  into 
bars.  The  Erimus  Company  are  now 
making  angles,  bulbs,  bars,  and  tees, 
with  no  other  iron  than  Cleveland. 
Three  relays  of  men  are  employed  at  the 
machines,  and  work  eight  hour  shifts. 
It  is  expected  that  each  furnace  will 
work  six  heats  in  the  eight  hours,  and 
this  is  regularly  done  unless  some  break- 
down or  accident  interferes;  and  with 
the  old  machines  those  breakdowns  are 
unfortunately  only  too  frequent.  At 
the  present  time  the  company  are  work- 
ing six  furnaces,  and  they  average  nearly 
300  tons  per  week  of  puddled  bar,  thus 
giving  an  output  of  50  tons  per  furnace 
per  week.  The  present  consumption  of 
coal  is  for  actual  puddling  9|  cwt.  to 
the  ton  of  bars.  Of  fettling  (half  bought 
and  half  from  first  heating  or  mill  fur- 
naces) 9  cwt.  to  the  ton  of  bars.  The 
yield  of  bar  from  pig  is  20  cwt.  of  pig 
to  20  cwt.  of  bars.  The  whole  quantity 
of  coal  used  to  the  ton  of  bars,  including 
reheating,  is  under  20  cwt.  The  price 
we  pay  the  puddlers  is  at  present  3s. 
2itod.  per  ton  long  weight,  they  paying 
their  own  under-hands.  The  whole 
wages  of  every  kind,  including  cupola- 
refining  and  re-heating,  is  under  20s. 
per  ton  of  bars.  The  question  now 
arises — Are  we  satisfied  with  a  produc- 


tion of  300  tons  per  week  from  six  fur- 
naces; and  is  there  any  prospect  of 
increasing  that  quantity  ?  The  answer 
is — We  are  not  satisfied;  and  there  is 
every  prospect  of  the  quantity  being 
increased  to  500  tons  per  week  from  six 
furnaces.  To  this  end  new  machines 
and  engines  are  ordered,  capable  of  tak- 
ing one  ton  charges;  and  the  tools  are 
being  remodeled  to  handle  the  heavier 
charges.  The  experiment  of  working  a 
ton  charge  has  frequently  been  made, 
and  the  time  required  for  puddling 
never  exceeds  forty  minutes.  The  num- 
ber of  heats  will  be  the  same  as  at 
present — viz.,  six  in  eight  hours;  and  it 
is  simply  by  the  increase  of  the  weight 
of  the  charge  that  the  quantity  will  be 
raised  from  300  to  500  tons.  The  actual 
puddling  of  the  six  heats  will  take  up  four 
hours,  leaving  the  other  four  hours  for 
fettling,  repairing,  cleaning  grate-bars, 
etc.  We  find  that  it  takes  the  same 
coal  to  puddle  a  ton  as  to  puddle  14 
cwt.,  and  as  the  time  consumed  in  charg- 
ing, drawing,  fettling,  and  squeezing, 
will  be  the  same  as  at  present,  it  is  obvi- 
ous that  the  increase  of  the  charge  to  a 
ton  is  the  proper  course.  We  have  no 
doubt  that  we  shall  be  able  to  bring  the 
consumption  of  coal  for  puddling  down 
to  7  cwt.  to  the  ton  of  bars;  and  the 
whole  of  the  coal  consumed  in  the  pud- 
dling department  to  15  cwt.,  and  we 
anticipate  that  the  wages  will  not  ex- 
ceed 15s.  on  the  ton  of  bars,  which  will 
include  all  labor  charges  in  the  puddling 
department.  The  new  furnace  at  the 
Erimus  Works,  when  worked  experi- 
mentally, gives  results  much  better  than 
are  stated  here.  The  foregoing  figures 
give  the  average  results  of  our  working 
in  a  regular  manner. 

(Signed)  J.  A.  Jones, 

Managing  Director. 
The  Erimus  Company  Limited. 


*       The  Erimus  Ironworks. 

Make  at  Forge,  four  weeks  ending  March  27th,  1875, 

Tons. 

"Week  ending  6th  of  March;  number  of  furnaces,  5 193 

Week  ending  13th  of  March;  number  of  furnaces,  6 282 

Week  ending  20th  of  March;  number  of  furnaces,  6 298 

Week  ending  27th  of  March;  number  of  furnaces,  6 275 


In  thirty-six  working  days  of  twelve  hours. 


cwt.  qr.  ••lb. 

2  1      15 

7  15 

0  3        0 

5  2      10 


1048      16        0 


0 


THE   IRON   AND    STEEL   INSTITUTE. 


59 


Coals  consumed  for  Puddling  alone,  four  weeks  ending  March  27th. 

Tons.    cwt.  qr.  lb. 

Week  ending  6th  March 02        5  0  0 

13th      "      116      10  0  0 

20th      "      141        1  2  0 

"          27th      "      124        8  0  0 

474        4  2  0 

cwt.  qr.  lb. 

Coal  to  a  ton  of  bars  on  puddling  alone 9  0  6 

Certified  to  be  correct,  and  taken  from  our  pay  books.         John  A.  Tood,  Pay  Clerk. 

J.  A.  Jones. 


■  The  members  of  this  Institute  have 
taken  such  a  deep  interest  in  the  Danks 
method  of  puddling,  that  I  believe  you 
will  all  be  pleased  to  know  the  precise 
position  in  which  it  now  stands,  and  we 
ought  to  be  very  much  obliged  to  Mr. 
Jones  for  the  very  explicit  statements 
which  you  have  just  heard.  Mr.  Heath, 
with  his  usual  enterprise,  was  one  of  the 
first  to  take  up  in  earnest  the  Danks 
system  of  puddling.  Mr.  Heath  informs 
me  that  he  has  had  six  Danks  furnaces 
at  work  for  some  time,  and  has  four 
additional  furnaces  ready  for  work.  He 
is  rolling  from  Danks  blooms,  in  the 
ordinary  forge  rolls,  16  in.  bars,  24  ft. 
long.  Mr.  Heath  states  that  he  is  mak- 
ing these  bars  more  cheaply  than  by  the 
old  puddling  process,  to  say  nothing  of 
the  saving  in  waste  in  cutting  up  long 
bars  as  compared  with  bars  one-fourth 
the  length.  Mr.  Orampton,  who  has 
made  a  long  series  of  experiments  on 
mechanical  puddling,  having  been  at 
work  on  the  subject  over  five  years,  has 
produced  some  very  excellent  results  as 
to  quality  of  metal;  and  he  assures  me 
that  his  experimental  machine  at  Wool- 
wich is  workiug  very  economically,  and 
that  it  will  bear  the  test  of  continuous 
work;  to  use  his  own  language,  "The 
furnace  is  fitted  to  stand  the  rough 
usage  to  which  such  a  machine  must  be 
subjected  in  ordinary  iron  works,  and  it 
involves  a  minimum  expense  for  wear 
and  tear,  and  for  general  repairs." 

Sir  John  Alleyne  has  also  worked  at 
this  problem  of  mechanical  puddling. 
He  is  experimenting  with  the  Siemens 
rotator  and  also  with  a  modification  of 
Maudslay's  machine.  Mr.  Reynold  Al- 
leyne thus  describes  the  latter  machine 
as  modified  by  his  father:  "  We  are  now 
working  my  father's  machine  with  Sie- 
mens' gas  furnace,  and  also  heated  by 
direct  combustion  in  the  ordinary  way. 


The  machine  consists  of  a  pan,  which 
rotates  on  a  vertical  axis,  and  the  pud- 
dler,  which  is  fixed  overhead,  and  which 
works  the  rabble  to  and  fro  at  right 
angles  to  the  front  of  the  furnace.  When 
the  heat  is  ready  to  ball  up,  the  puddler 
is  stopped,  but  the  pan  continues  to  re- 
volve. The  work  of  balling  is  done  at 
the  door,  and  it  is  never  necessary  to 
reach  across  the  furnace.  In  the  gas 
furnace  we  charge  five  heats  of  6  cwt. 
per  shift.  The  waste  is  2j  to  3  per 
cent.  The  waste  in  the  direct  combus- 
tion furnace,  with  the  same  charges,  is 
10  per  cent.;  showing  the  advantage  of 
using  gas  in  place  of  solid  fuel.  The 
two  furnaces  are  worked  by  one  puddler 
each,  and  a  boy  to  look  after  the  ma- 
chinery of  both  furnaces."  Sir  John 
himself  expresses  an  opinion  in  favor  of 
the  pan,  or  "  soup  plate,"  as  he  calls  it, 
heated  by  Siemens'  gas  furnace."  At 
our  annual  general  meeting  in  May  of 
last  year,  the  Pernot  furnace  was  de- 
scribed. The  furnace  is  the  revolving- 
pan  with  the  axis  inclined,  as  invented 
by  Maudslay;  but  M.  Pernot  has  made 
an  important  improvement  on  Mauds- 
lay's  furnace.  He  has  mounted  the 
revolving  pan  on  a  carriage  on  wheels, 
and  it  can  be  withdrawn  from  the  pud- 
dling chamber  for  repairs.  Mr.  Snelus, 
who  has  just  returned  from  a  tour 
through  the  French  works,  informed 
me  that  he  saw  three  Pernot's  puddling 
furnaces  at  work  at  Messrs.  Petin  Gau- 
det's  works.  "*  They  were  working  one 
ton  charges  of  iron,  mostly  white,  and 
each  charge  produced  18  cwt.  of  puddled 
bars.  The  fuel  was  slack  coal,  of  which 
they  use  14  cwt.  to  the  ton  of  puddled 
bars.  The  fans  are  fettled  with  Motka 
iron  ore,  about  2-£  cwt.  being  used  to 
the  ton  of  iron  made.  Each  furnace 
produces  about  4  tons  of  puddled  bars 
in  twelve  hours.     Two  puddlers  at  each 


60 


VAN    NOSTRAND  S   ENGINEERING  MAGAZINE. 


furnace  ball  up  the  iron.  Mr.  Snelus 
adds  that  the  furnaces  have  been  at 
work  some  time,  and  that  they  seemed 
in  fair  working  condition.  In  the  manu- 
facture of  steel,  we  are  making  in  Eng- 
land, by  the  Bessemer  process  alone,  ten 
thousand  tons  per  week,  and  the  produc- 
tion is  rapidly  increasing.  Various  me- 
chanical improvements  have  been  made, 
which  enable  us  to  turn  out  larger  quan- 
tities. In  some  cases  as  much  as  one 
thousand  tons  per  week  has  been  made 
from  a  pair  of  converters.  When  Mr. 
Bessemer  first  designed  his  steel-making 
plant,  his  idea  was  to  run  the  iron  direct 
from  the  blast  furnace  into  the  convert- 
ers. His  first  apparatus,  on  a  large 
scale,  was  erected  at  Dowlais,  where  it 
was  put  down  in  front  of  a  blast  furnace, 
and  the  iron  was  run  direct  from  the 
furnace.  The  experiment,  for  reasons 
quite  independent  of  the  mode  of  charg- 
ing the  converter,  was  not  successful; 
nevertheless,  we  in  England  have  ever 
since  been  content,  for  no  sound  reasons, 
I  think,  to  melt  down  the  pig  iron  at 
considerable  cost,  instead  of  running  it 
straight  from  the  furnace.  In  most 
cases  in  France,  and  in  some  other  coun- 
tries, the  iron  is  run  direct  from  the 
furnaces;  and  I  see  no  reason  why  in 
England  we  should  not  revert  to  Mr. 
Bessemer's  original  plan,  and  so  save  all 
the  cost  and  waste  of  melting.  Of 
course,  it  will  require  careful  manage- 
ment at  the  blast  furnaces;  but  with 
our  pure  fuel,  excellent  ores,  and  with  a 
plentiful  supply  of  pure  foreign  ores  as 
a  mixture,  I  see  no  difficulty  in  carrying 
out  this  economy  in  the  production  of 
Bessemer  metal.  Mr.  Bessemer  informs 
me  that,  under  his  advice,  in  one  of  our 
leading  steel  works  they  are  about  to 
run  the  iron  direct  from  the  furnace;  to 
use  his  own  language,  "They  will  use 
my  process  of  further  carburising  20 
tons  of  metal  at  a  time  in  a  hot  vessel, 
mounted  on  wheels  and  running  on  rails 
to  the  converters;  the  metal  will  keep 
hot  for  several  hours  in  this  vessel.  Less 
carburetted  metal  may  be  made  in  the 
blast  furnace,  and  the  necessary  quantity 
of  carbon  added  at  almost  no  cost." 
Another  member  of  our  Institute,  Dr. 
Siemens,  has  worked  out,  in  a  different 
way,  the  same  problem,  with  much  suc- 
cess. The  idea  of  producing  steel  by 
melting  together  cast  and  wrought  iron, 


or  cast  iron  and  ores,  in  suitable  propor- 
tions, is,  of  course,  old,  but  it  was  not 
until  Mr.  Siemens  brought  his  scientific 
and  practical  knowledge — and  a  no  less 
wonderful  amount  of  perseverance — to 
bear  on  the  subject,  that  the  mode  of  mak- 
ing steel,  known  as  the  "  Siemens-Martin 
process,"  was  perfected.  The  most  im- 
portant element  in  the  successful  accom- 
plishment of  the  Siemens-Martin  process 
is  unquestionably  the  "Siemens,  or  re- 
generative, gas  furnace."  By  its  means, 
any  degree  of  heat,  even  to  the  fusing 
point  of  the  most  refractory  materials, 
can  be  obtained  economically  and  with- 
out resorting  to  air-blast  or  cutting 
draughts,  and  these  conditions  are  indis- 
pensable where  we  have  to  deal  with  a 
bath  of  mild  steel,  exposed  to  the  sur- 
face action  of  the  flame.  An  adequate 
idea  of  the  elevated  temperature  obtain- 
able in  these  furnaces  may  be  formed  by 
considering  that  near  the  end  of  each 
operation  the  furnace  contains  from  five 
to  six  tons  of  almost  chemically  pure 
iron  in  a  state  of  perfect  fluidity,  beneath 
a  covering  of  slag,  several  inches  thick. 
Mr.  Siemens  estimates  this  temperature 
at  2200  Cent.  Mr.  Siemens  states  that 
he  is  now  erecting  furnaces  of  10  tons 
capacity,  which  will  be  capable  of  pro- 
ducing 20  tons  of  steel  in  twenty-four 
hours  if  pig  and  ore  be  used,  and  30  tons 
if  pig  and  scrap  be  employed.  The  steel 
made  by  the  Siemens-Martin  process  is 
used  for  all  the  purposes  to  which  soft 
steel  is  commonly  applied.  It  is  used  in 
England  for  casting  screw  propellers, 
and  for  various  other  high-class  steel 
castings.  At  Creusot  a  mild  steel  is 
produced  by  this  process  containing  only 
10  per  cent,  of  carbon,  which  is  used  for 
piston  rods,  and  other  parts  of  engines, 
for  boiler-plates,  and,  more  recently,  for 
shipbuilding.  As  we  know,  Mr.  Sie- 
mens has  for  some  years  been  engaged 
on  a  method  for  producing  malleable 
metal  direct  from  the  ore.  The  process 
consists  in  treating  ore  with  reducing 
materials  in  a  rotary  furnace,  under  the 
influence  of  a  reducing  atmosphere,  ac- 
companied by  the  intense  heat  produced 
by  his  regenerative  gas  furnace.  His 
object  is  to  produce  either  bar  iron  or 
metal  from  the  bath  furnace  direct  from 
the  ore  in  one  operation,  and  at  a  greatly 
reduced  expenditure  of  fuel;  but,  al- 
though  this   method  has,   as   I    under- 


THE   IRON   AND   STEEL   INSTITUTE. 


61 


.stand,  succeeded   experimentally,  proof 
is  as  yet  wanting  of  its  practical  success 
on  a  large  scale.    M.  Pernot  has  applied 
Maudslay's  revolving  pan,  not  only  for 
puddling,  but  also  for  making  Siemens- 
Martin    steel.      The    furnaces    produce 
over  ten  tons  of  steel  per  shift  of  twelve 
hours.     The  waste  is  said  to  be  7  per 
cent.,   and   the   consumption   of   fuel   7 
cwt.   to  the  ton  of  ingots  made.     The 
cost  of  labor  is  stated  to  be  4f.  per  ton. 
This  furnace  is  worthy  of  the  attention  of 
English   steel-makers,    and  is,    I   think, 
destined  to  play  an  important  part  in  the 
manufacture  of  Siemens-Martin  steel.     I 
have  said  that  Mr.  Bessemer  has  given 
us   what   may   be   fairly   called   a   new 
metal,  and  a  wonderful  metal  it  is;  and 
that,   by   an   entirely  different    process, 
Mr.  Siemens  has  enabled  us  to  produce 
the  same  metal  also  at  a  moderate  cost, 
and  with  all  the  excellent  qualities  of 
Bessemer    metal.     For    a    considerable 
period  I  have  been  engaged  in  making 
Bessemer  and  Siemens-Martin  soft  steel, 
and  I  claim  to  know  something  of  the 
excellences  of  both.   Speaking  as  a  man- 
ufacturer, I  am  of  opinion  that,  with  our 
present   knowledge,    in   no    other   form 
can   iron   or   steel   be   produced   at  the 
same  cost,  and  of  a   quality   equal   to 
that  of  the  steel  made  by  the  Bessemer 
and  Siemens  processes.     Having  a  high 
opinion  of  the  value  of  the  material  for 
constructive  purposes,  and  seeing  with 
how  much  success  it  has  been  applied  on 
our   leading  railways,  and   how   it   has 
almost   completely   superseded   the   old 
forms  of  wrought  iron,  where  it  has  been 
introduced  with  skill  and  a  full  knowl- 
edge  of  its   properties,  I  wonder,  and 
wonder  much,  that  many  of  our  leading 
engineers  and  shipbuilders  have  ignored 
this  material  as  if  it  did  not  exist;  and 
this  in  the  face  of  the  fact  that  for  years 
this  metal  has  been  used  for  purposes 
where  only  material  of  the  highest  qual- 
ity is  admissible,  and  that  it  has  given, 
and  is  giving.,  so  much  satisfaction  that 
those  men  speak  of  it  the  most  favorably 
who  have  used  it  the  most  largely.     So 
many    distinguished     mechanical    engi- 
neers have  used  Bessemer  steel,  that  in 
speaking  of  their  varied   experience,  I 
hardly  know  where  to  begin.  Sir  Joseph 
Whitworth  is  making  from  the  Besse- 
mer converter  some  of  the  finest  material 
known.     By  his  process  of  compressing 


the  steel  while  it  is  in  a  liquid  condition, 
he  produces  a   quality  far   superior   to 
anything   which    can   be   made   by   the 
ordinary    methods    of    treatment.      Sir 
Joseph  writes,  "  During  the  last  twelve 
months   we   have   been    working   night 
and  day,  principally  on  guns,  cylinders 
for  hydraulic  purposes,  cylinder  linings, 
torpedoes,  etc. ;  the  melting  has  been  by 
the   Bessemer    and    crucible    processes, 
and  we  are  just  about  to  use  the  Siemens- 
Martin  process  also.     The  state  of  my 
health  has  prevented  us  from  commenc- 
ing new  works,  but  we  hope  to  do  so 
before  long."  This  material  is  as  yet  too 
expensive  for  use  in  ordinary  work,  but 
Sir  Joseph  has  shown  that  out  of  the 
Bessemer  converter  can  be  produced,  as 
I  have  said,  some  of  the  finest  material 
known.       Mr.    Ramsbottom,    when    at 
Crewe,  began  to  use  Bessemer  steel  in 
the  construction  of  locomotives,  and  for 
other  purposes,  and  his  able  successor, 
Mr.    Webb,    has    greatly    distinguished 
himself  by  his  care  in  the  manufacture 
of  Bessemer  and  Siemens  steel,  and  by 
his   skillful  and  spirited   application  of 
the  metal  to  almost  every  purpose,  and 
particularly  in  cases  where  material  of 
the  very  highest  quality  is  indispensable. 
No  man,  I  think,   has  done  more  than 
Mr.   Webb   to   improve   the    quality  of 
mild  steel,  or  so  much  to  extend  its  gen- 
eral use.     Mr.  Sharp,  of  Bolton,  was  one 
of  the  first  to  produce  excellent  boiler 
and  ship   plates  of   steel,  and  to  make 
boilers  of  steel  plates.     Mr.  Sharp  tells 
me  that  they  have  made  between  nine 
and  ten  thousand  tons  of  steel  plates  at 
Bolton,  three-fourths  of  which  have  been 
used  in  the  construction  of  boilers.     He 
says   that   steel   plates,    with   a    tensile 
strength  of  from  30  to  34  tons,  are  easily 
and  safely  worked  by  experienced  men. 
They  have  had  steel  boilers  at  work  for 
nine  years,  and  they  have  given  perfect 
satisfaction,    and    the   repairs  are   light 
to   those  compared   with    iron    boilers. 
Mr.  Adamson,  whose  talent  as  a  mechan- 
ical  engineer   is  well  known  to  us  all, 
informs  me  that  in  his  steam  engines, 
when  the  choice  of  materials  is  left  with 
him,  all  the  principal  parts  are  made  of 
Bessemer  steel,  and  that  the  results  have 
been   most   satisfactory.     Mr.  Adamson 
states  that  he  has  used  various  kinds  of 
steel  in  boiler  work,  but  since  the  intro- 
duction of  Bessemer  steel  plates  he  has 


62 


VAN   NOSTRAND  S   ENGINEERING   MAGAZINE. 


used  no  other;  of  this  material  he  has 
made  between  six  and  seven  hundred 
boilers,  mostly  for  high  pressures.  He 
is  now  making  a  number  of  steel  shell 
and  lire-box  boilers,  of  7  ft.  diameter,  to 
work  80  lb.  and  100  lb.  pressure  per 
square  inch.  Mr.  Adamson  has  used 
mostly  steel  plates  of  Barrow  make. 
He  says  that  they  are  very  uniform  in 
quality,  and  from  all  causes  he  has  not 
had  to  return  or  set  aside  more  than  one 
plate  in  a  thousand.  He  describes  his 
method  of  working  steel  plates  as  fol- 
lows: "A  piece  is  cut  off  every  plate 
and  tested  before  the  plates  are  accepted; 
the  edges  of  the  plates,  when  used  for 
boilers,  are  all  planed,  the  rivet  holes 
are  drilled  through  both  plates  together, 
after  the  plates  are  bent  and  in  place;  in 
every  case  double  or  chain-riveting  is 
adopted."  He  goes  on  to  say:  "In  the 
application  of  steel  plates  for  fire-boxes, 
I  have  experienced  the  most  satisfactory 
results;  there  is  no  blistering,  and  the 
plates  show  great  endurance.  When 
boilers  have  been  allowed  to  run  short 
of  water,  the  plates  have  bulged  or  col- 
lapsed, but  they  were  never  fractured." 
In  this  respect,  he  thinks  that  steel 
plates  are  superior  to  any  iron  ever 
made.  Mr.  Adamson,  like  Mr.  Sharp, 
advocates  the  use  of  steel  of  compara- 
tively low  tensile  strength,  from  30  to  32 
tons  per  square  inch.  Steel  of  38  to  40 
tons  to  the  inch  was  found  quite  unsuit- 
able for  boiler  work;  it  was  wanting  in 
ductility,  and  the  use  of  such  a  material 
was  quickly  abandoned.  A  great  deal 
has  been  said  and  written  about  the 
want  of  uniformity  in  Bessemer  steel, 
but  what  could  be  more  satisfactory 
than  Mr.  Adamson's  experience  on  this 
head  ?  Messrs.  Galloway,  of  Manchester, 
who  have  a  large  experience  in  boiler 
making,  and  who  are  noted  for  the  excel- 
lence of  their  work,  inform  me  that  when 
they  commenced  using  Bessemer  steel 
plates,  about  1861,  the  results  were  not 
satisfactory,  the  plates  being  too  hard, 
but  that  of  late  they  have  used  steel 
plates  extensively,  and  that  the  conclu- 
sion they  have  come  to  is  that  when  the 
annealing  is  carefully  performed  the 
plates  are  perfectly  trustworthy;  in 
fact,  in  the  testing  of  boilers  they  now 
find  quite  as  little  trouble  with  steel 
plates  as  with  iron  ones,  if  not  less. 
They  state  further  that  careful  annealing 


has  a  most  beneficial  effect;  and  they 
refer  to  some  experiments  made  for  the 
Manchester  Boiler  Insurance  Company 
by  Mr.  Kircaldy  on  the  strength  of 
riveted  joints,  which  conclusively  proved 
that  even  in  the  case  of  wrought  iron 
plates,  which  are  punched,  it  is  advisable 
to  anneal  them.  With  respect  to  the 
employment  of  steel  for  bridge  work, 
Mr.  Maynard,  of  the  Crumlin  Viaduct 
Works,  writes:  "With  regard  to  the 
question  of  employing  steel  for  railway 
bridges  in  this  country,  I  may  at  once 
say  that,  practically  speaking,  steel  is 
excluded  from  use  by  the  somewhat  arbi- 
trary limitation  laid  down  by  the  Board 
of  Trade — to  5  tons  strain  per  square 
inch  when  used  in  tension,  and  4  tons 
per  square  inch  in  compression  —  no 
higher  strain  being  allowed  whatever 
may  be  the  quality  of  the  material,  and 
even  if  steel  is  used  in  place  of  iron. 
When  a  girder  bridge  is  required  of  a 
trifle  over  400  ft.  span  for  a  railway  it  is 
found  that  the  weight  of  the  iron,etc.,nec- 
essary  for  its  construction  is  alone  suffi- 
cient, without  the  rolling  load  of  a  train, 
to  strain  the  iron  in  the  most  important 
parts  of  the  structure  to  very  nearly,  if 
not  fully,  the  limit  laid  down  by  the 
Board  of  Trade — therefore,  we  make 
but  little  progress  in  large  span  bridges 
in  this  country.  Steel  has  been  employed 
very  successfully  in  some  bridges  of  large 
span  which  I  have  seen  in  Holland,  and 
elsewhere,  whilst  in  England  we  adhere 
to  the  old  rule-of-thumb  practice  with- 
out much  chance  of  improvement.  It  is 
obvious  that  if  a  material  is  used  that 
will  bear  a  high  strain,  it  results  in  a 
lighter  and  stronger  structure,  and  I 
should  be  glad  to  employ  steel  even  in 
small  girders,  but  for  the  difficulty  of 
getting  the  Board  of  Trade  to  acknowl- 
edge its  superiority  over  iron,  and  to 
allow  a  higher  strain  to  be  imposed  than 
is  adopted  for  iron."  Having  given  you 
the  results  of  -the  experience  of  some  of 
our  leading  mechanical  engineers  as  to 
the  value  of  mild  steel  for  constructive 
purposes,  I  have  now  the  pleasure  of 
laying  before  you  the  opinion  of  a  man 
who  has  earned  a  world-wide  reputation 
as  a  shipbuilder,  and  whose  professional 
advice  is  sought  by  the  most  powerful 
Governments  in  Europe;  Mr.  Reed,  the 
late  Chief  Constructor  of  our  navy, 
writes  to  me  as  follows :    "  In  reply  to 


THE  IKON   AND   STEEL   INSTITUTE. 


63 


your  favor  of  the  20th,  allow  me  to  say 
that   for   more   than  two  years  past  I 
have  been  thoroughly  satisfied  that  the 
production    and    methods    of     working 
steel   had  reached   a    point   when   that 
material  might  he  extensively  and  very 
advantageously   used    for    shipbuilding 
purposes.     I,  therefore,   designed   some 
very  fast  war  vessels  in  steel,  and  ob- 
tained some  provisional  orders  for  them, 
but  when  I  came,  two  years  ago,  to  the 
question  of  building,  I  could  not  satisfy 
myself  that  the  proper  supplies  could  be 
secured  under  the  same  conditions  and 
facilities  as  iron.    This  was  due,  however, 
entirely  to  the  fact  that  my  orders  would 
not  have  been  sufficient  alone  to  justify 
any  large  firm  in  entering  systematically 
upon  the  production  of  steel  plates  and 
angles  for  ship  purposes.  Great  progress 
has  been  made  in  this  respect  since  then, 
and    I    am    now   receiving    orders    for 
despatch  war  vessels  to  be  built  of  steel 
— boilers  and  engines  as  well  as  vessels — 
and  I  am  about  to  build  two  at  Pembroke, 
and  probably  to  place  others  for   con- 
struction  in   other   establishments.      It 
will,  therefore,  be  a  very  great  advantage 
if  in  your  address  you  can  stimulate  the 
attention  or  the  profession  and  the  trade 
to  the  subject,  because  I  am  satisfied, 
that  when  once  a  systematic  commence- 
ment is  made  there  will,  henceforth,  be 
no  obstruction  to  the  large  development 
of  steel  for  shipbuilding.     I  say  nothing 
here  about  the  special  arrangements  which 
the  use  of  steel  for  shipbuilding  purposes 
renders  necessary,  because,  although  they 
are   unusual   and    additional,   they    are 
such  as  present  no  real  difficulties   to  a 
careful  builder."  I  would  also  call  atten- 
tion to  the  somewhat  extensive  use  of 
steel  in  the  French  navy;    and,  above 
all,  I  would  point  to  what  the  Germans 
are  doing.    In  Germany  there  is  no  want 
of  confidence  in  the  character  of  steel. 
Mr.    Krupp,  who    may    be    called    the 
father  of  the  steel   trade,  has  evinced  a 
wonderful  amount  of  skill  in  the  produc- 
tion of  large  masses  of  steel,  and  in  its 
application  to  purposes  where  its  strength 
and  ductility  are  submitted  to  the  most 
severe  tests.     Mr.  Longsden  informs  me 
that  they  are  making  at  Essen  at  the 
present  time  14  inch  guns  of  steel,  which 
weigh,  when  finished,  57^  tons,  carrying 
a  shot  9  cwt.  9^  English  miles,  using  a 
charge  of  210  lb.  of  gunpowder.     They 


are  about  to  make  steel  guns  of  the  fol- 
lowing capacities  and  weights — 15f   in. 
bore,  30  ft.  long,  weighing  82  tons,  using 
300  lb.  of  powder,  with  a  shell  of  1,500 
lb.  weight;  guns  of  18  in.  bore,  32.  ft.  6 
in.  long,  weighing  124  tons,  using  440 
lb.  of  powder,  with  a  shell  of  2,270  lb. 
weight.     Mr.  Longston   demurely  adds, 
"It  is  calculated,  for  the  present,  that 
these   guns   will    be   heavy    enough    to 
destroy  any   armor  a   ship    can  carry." 
In  gloating  over  the  destructive  proper- 
ties of  these  weapons,  he  is  leaving  out 
of  his  calculation,  perhaps,  the  flash-of- 
lightning  ships  which  Mr.  Reed  is  about 
to  build,   and  which  may,  under  smart 
management,  be  able  to  get  out  of  the 
way  of  such  a  conspicuous  object  as  a 
shell  weighing  over  a  ton,   even  when 
fired  with   about  a  quarter  of  a  ton  of 
gunpowder.     In  alluding  •  to  the  use  of 
high- class  steel  for  guns,  I  wish  it  to  be 
understood  that  I  am  not  seeking  to  give 
any  opinion  as  to  the  superiority  of  steel 
over  wrought  iron  for  this  special  pur- 
pose.    I  merely  wish  to  call  attention  to 
the  fact  that  in  Germany  and,  I  believe, 
in  most  continental  countries,  as  also,  I 
may  add,  by  one  at  least  of  our  most 
celebrated  gunmakers  in  England,  steel 
is  being  used  for  making  guns  of  the 
heaviest  description ;  and  it  is  well  known 
that  these  steel  guns  have  stood  the  most 
severe  tests  at  proof,  and  also  when  put 
to  their  more  legitimate  use.  Speaking  of 
guns  gives  me  the  opportunity  of  calling 
special  attention  to  the  wonderful  struct- 
ures in  wrought  iron  now  being  built  urp 
at   Woolwich    and   Elswick.     Foro-ino-s 
are  made  there  which  for  weight  and 
quality  of  material  were  never  equalled; 
and. the   guns,   when   finished,    even   if 
looked  at  simply  as  engineering  works, 
reflect  credit  not  only  upon  the  men  who 
produced  them,  but  upon  England  as  a 
nation.     As   we   are   about   to  have  an 
inquiry  as  to  the  merits  of  these  guns, 
I  sincerely  hope  that  it  may  turn  out,  as 
I  daresay  it  will,  that  those  wonderful 
weapons  have  not  been  constructed  to 
load  at  the  wrong  end.     You  will  have 
observed  that  in  speaking  of  the  present 
position  of  mechanical  piiddling,  and  of 
the   improvements   now   in   progress,    I 
have  preferred,  for  the  most  part,  to  use 
the  language  in  which  the  information 
reached  me.     It  was  my  intention,  for 
the  purpose  of  this  address,  to  make  a 


64 


van  nostrand's  engineering  magazine. 


tour  through  all  the  works  of  England 
and  France  where  puddling  machinery 
is  in  operation.  But  when  I  considered 
that  some  machines  of  great  promise  are 
still,  strictly  speaking,  in  their  experi- 
mental phase,  I  felt  that,  in  the  circum- 
stances, even  a  very  careful  inspection 
would  not  enable  me,  from  my  own  ob- 
servation, to  arrive  at  perfectly  sound 
conclusions.  I  therefore  thought  it  bet- 
ter to  invite  the  gentlemen  who  are  so 
ably,  and  I  think,  successfully,  working 
out  the  problem  of  mechanical  puddling, 
to  give  me  information  as  to  the  results 
of  their  experience,  and  as  to  the  pros- 
pects of  their  various  plans.  These  gen- 
tlemen have  with  the  greatest  courtesy, 
furnished  all  the  information  that  I 
sought — information  which  I  am  sure  will 
be  of  the  greatest  interest  to  the  members 
of  this  Institute.  I  have,  like  many  of 
you,  watched  with  great  interest  the  ad- 
vance of  mechanical  puddling;  and  from 
the  day,long  ago,on  which  I  saw  Mr. Tooth 
at  work  at  Stepney  until  now,  I  have  never 
for  a  moment  doubted  that  mechanical 
puddling  would  sooner  or  later  be  per- 
fected. I  think  that  there  is  now 
almost  a  certainty  that  this  problem, 
upon  which  has  been  expended  so  much 
labor  and  thought,  and  which  has 
brought  to  many  so  much  disappoint- 
ment, will  within  a  short  period  be  fairly 
solved.  I  have  told  you,  with  the 
authority  of  Mr.  Bessemer  and  Mr.  Sie- 
mens, what  improvements  they  are  con- 
templating in  the  way  of  cheapening  the 
production  and  increasing  the  make  of 
steel,  and  I  believe  that  every  leading 
steel  maker  in  England  is  engaged  in 
devising  new  modes,  or  introducing  new 
methods  already  tried,  for  increasing 
and  cheapening  production  and  no  less 
for  insuring  excellence  and  uniformity 
of  quality.  On  the  question  of  the  ap- 
plicability of  steel  to  various  purposes 
where  it  is  now  used  but  sparingly  or 
not  at  all,  I  have  sought  the  opinions  of 
men  whom  we  all  know,  most  of  them 
being  members  of  this  Institute,  and 
all  of  them  holding  high  rank  in  their 
profession;  and  here  again  I  have  pre- 
ferred, where  it  was  practicable,  to  give 
the  opinions  of  the  various  gentlemen  in 
their  own  language.  Although  I  have 
expressed  my  surprise  that  steel  has  not 
been  more  largely  employed  in  great 
engineering  works  and   shipbuilding,  I 


am  well  aware  that  there  is  much  to  be 
said  in  defence  of  the  cautious  policy 
which  has  guided  our  engineers  and 
shipbuilders;  and  I  have  no  desire  to 
cast  the  slightest  reflection  on  members 
of  either  profession  for  the  exercise  of  a 
caution  which,  in  all  the  circumstances, 
was  perhaps  natural.  If  blame  there  be, 
manufacturers  must  take  to  themselves 
a  fair  share  of  it,  as  at  first,  steel  was 
made  of  unsuitable  quality;  and  when 
this  difficulty  was  got  over,  they  were 
somewhat  slow  to  put  themselves  in  a 
position  to  supply  the  trade  with  steel 
of  suitable  sections  at  a  moderate  cost. 
For  a  long  jDeriod,  as  I  have  said,  steel 
was  expensive,  and  this  stood  in  the 
way  of  its  general  introduction.  Makers 
have  ascertained  that  it  possessed  great 
tensile  strength  as  compared  with 
wrought  iron,  were  anxious  that  it 
should  be  used  if  possible  with  a  com- 
paratively high  percentage  of  carbon,  so 
as  to  retain  this  excellent  quality;  and 
at  first  steel  with  a  tensile  strength  of 
forty  tons  per  square  inch  and  upwards 
was  made  into  plates  and  used  for  other 
purposes,  for  which,  as  experience  has 
since  proved,  it  was  unfitted.  There  is 
now,however,amongst  the  manuf ucturers 
a  perfect  knowledge  of  what  is  wanted 
for  various  engineering  purposes.  There 
is  also  the  power  to  produce  steel  of 
almost  any  shape  or  quality  at  a  moder- 
ate cost,  and  it  only  requires  the  hearty 
co-operation  of  the  engineering  profes- 
sion to  induce  manufacturers  everywhere 
to  erect  suitable  machinery  for  convert- 
ing steel  into  the  necessary  forms  for 
constructive  purposes;  and  if  reasonable 
encouragement  is  given  in  this  direction, 
I  have  no  doubt  that  healthy  competition 
will  soon  bring  the  cost  of  steel  to  a 
point  where  it  will,  as  a  matter  of  econ- 
omy, beat  certain  classes  of  iron,  out  of 
the  field.  I  assume,  of  course,  that  upon 
proper  proof  being  given  of  the  superi- 
ority of  steel,  the  Board  of  Trade  will 
modify  their  rules  as  to  its  use.  Al- 
though the  proper  business  of  this  Insti- 
tute is  to  discuss  technical  subjects,  I 
will  venture  to  follow  the  example  of 
my  predecessor,  and  say  something  of 
the  present  position  and  prospects  of 
our  trade.  At  our  last  annual  meeting, 
Mr.  Bell  concluded  his  excellent  address 
with  the  following  hopeful  and  spirited 
remarks:  "Whatever  difficulty  maybe- 


STRAINS   IN   CONTINUOUS   GIRDERS. 


65 


set  us  at  the  present  moment,  it  can 
only  be  of  a  temporary  character.  Of 
raw  materials  we  have  an  abundance;  of 
our  skill  as  manufacturers,  whatever 
may  be  said  to  the  contrary,  we  have  no 
reason  to  be  ashamed,  and  it  will  be  a 
strange  thing  if,  with  these  advantages, 
British  energy  is  unable  to  hold  its  own 
against  any  people  in  the  world."  If 
England  had  a  fair  field  she  would, 
beyond  doubt,  hold  her  own;  and  fur- 
ther would  continue  to  be  for  a  long 
period,  as  far  as  iron  is  concerned,  the 
workshop  of  the  world.  But  from  many 
important  markets  in  Europe,  and  from 
the  United  States  of  America,  English 
iron  and  steel  are  practically  excluded. 
Heavy  import  duties  are  imposed  with  the 
avowed  purpose  of  encouraging  native 
manufacture,  which  means  excluding  the 
manufactures  of  England.  The  effect 
of  this  policy  is  being  severely  felt  at 
the  present  moment,  for  we  have  but 
little  demand  from  Europe,  and  we  seem 
to  have  lost  our  American  market  en- 
tirely. 

With  our  free  trade  notions  we  all 
believe  that  our  neighbors  in  Europe 
and  our  friends  in  the  United  States  are 
pursuing  a  mistaken  policy,  that  they 
had  better  confine  themselves  to  the 
charming  Arcadian  occupations  of  grow- 
ing fine  "  corn  and  wine,"  and  let  Eng- 
land continue  to  drudge  in  the  grimy 
business  of  iron  and  steel  making.   Some 


sanguine  persons  believe  that  some  day 
they  will  see  the  error  of  their  ways,  and 
that  they  will  adopt  the  course  above 
indicated.  I  confess  that  on  this  point  I 
am  far  from  hopeful.  If  it  were  merely 
a  trade  question  we  might  expect  that 
by  and  by  the  example  of  England 
would  be  followed  as  a  matter  of  self 
interest,  but  it  is  needless  to  say  that  in 
powerful  countries  the  home  production 
of  iron  and  steel  means  more  than  giving 
employment  to  a  portion  of  the  popula- 
tion. In  certain  contingencies  it  renders 
a  nation  independent  of  foreign  supplies 
at  times  when  such  dependence  would 
cripple  the  most  powerful  nation  in  the 
world.  There  is,  moreover,  another 
reason  why  we  can  hardly  expect  to  see, 
within  a  reasonable  time,  the  principles 
of  free  trade  introduced.  Governments 
have  encouraged  the  growth  of  gigantic 
industries  devoted  to  the  manufacture 
of  iron  and  steel ;  and  any  one  who  has 
had  the  privilege  of  seeing  the  vast 
works  of  Creusot  and  Essen,  would,  I 
think,  admit  that  no  Government,  how- 
ever wise  or  strong,  would  lightly  ven- 
ture on  a  policy  which  would  interfere 
with  the  prosperity  of  such  establish- 
ments. We  must,  I  think,  frankly  accept 
the  position  in  which  we  are  placed,  and 
prepare  to  seek  new  markets  for  our 
produce  in  countries  which,  even  if  they 
have  the  will,  have  not  yet  the  power  to 
impose  restrictions  on  our  trade. 


STRAINS  IN  CONTINUOUS  GIRDERS. 

By  MANSFIELD  MERRIMAN,  C.  E.,  New  Haren,  Conn. 
Written  for  Van  Nostrand's  Magazine. 


In  designing  a  bridge  truss  continuous 
over  many  supports  the  engineer  is  often 
at  a  loss  for  want  of  English  treatises  on 
that  subject.  Such  as  he  is  able  to  con- 
sult, he  is  generally  apt  to  find  unsatis- 
factory on  account  of  their  incomplete- 
ness, or  the  tediousness  of  the  approxi- 
mate methods  used.  Although  the  later 
works  of  German  and  French  writers 
contain  the  complete  and  satisfactory 
theory  of  the  continuous  girder  under 
every  variety  of  loading,  the  results  have 
not  yet  been  made  available  to  the  prac- 
tical engineer.  In  fact  the  formulae  for 
the  maximum  bending  moments  in  every 
Vol.  X1LL— No.  1—5 


section  due  to  a  combination  of  the  dead 
and  live  loads  are  complex,  and  not  easy 
of  application.  Such  formula  are,  how- 
ever, entirely  unnecessary  for  the  calcu- 
lation of  strains  in  any  truss.  They  do 
not  shorten  the  work,  but  rather  impede 
it,  particularly  in  the  hands  of  those  to 
whom  algebraic  expressions  are  not 
thoroughly  familiar. 

The  maximum  stresses  in  a  continuous 
truss  may  be  easily  and  completely  de- 
termined, when  the  moments  and  vertical 
forces  at  every  support  due  to  any  posi- 
tion of  a  concentrated  load  can  be  found. 
In  a  simple  girder,  we  know  at  once  from 


66 


VAN  NOSTRAND'S   ENGINEERING  MAGAZINE. 


the  law  of  the  lever,  the  reactions  at  the 
abutments  ;  hut  in  a  continuous  girder 
they  are  not  so  easily  obtained.  In  fact 
it  is  not  generally  known  among  Amer- 
ican engineers  that  the  shearing  forces, 
due  to  a  single  concentrated  weight  on  a 
girder  continuous  over  any  number  of 
supports,  can  be  computed.  Although 
the  extension  of  Clapeyron's  theorem  to 
concentrated  loads  was  published  ten 
years  ago,  and  has  since  been  prominent 
in  German  and  French  engineering 
works,  it  has  not  yet  gained  the  atten- 
tion of  the  English  and  American  public. 
For  example,  in  a  recent  work  on  the 
Analysis  of  Bridge  Trusses,  by  the 
graphical  method  it  is  stated  that  "a 
complete  solution  for  the  bending  mo- 
ment and  shearing  force  at  every  section, 
under  moving  partial  and  irregular  loads, 
is  well  nigh  impossible,  on  account  of 
the  complexity  of  the  formula,  so  far  as 
any  practical  application  of  them  by  the 
engineer  is  concerned,"  and  the  same 
author*  frequently  asserts  that  Clapey- 
ron's theorem  can  only  be  used  for  uni- 
formly distributed  loads. 

I  propose  to  give  in  this  article  a  de- 
monstration of  the  Theorem  of  Three 
Moments  for  the  case  of  girders  of  con- 
stant cross  section,  subject  to  loads 
either  regular  or  irregular,  uniform  or 
concentrated,  and  to  show  how  the  re- 
actions due  to  such  loads  can  be  found. 
Then  by  practical  examples  I  shall  show 
how  the  maximum  moments  and  shear- 
ing forces  at  every  section  can  be  com- 
puted, without  the  aid  of  any  formulae, 
except  those  for  finding  the  moments  and. 
vertical  forces  at  the  supports,  by  a 
method  as  simple  and  as  easily  applied 
by  the  engineer  as  those  in  common  use 
for  the  case  of  a  truss  of  one  span. 

Let  Z,  and  £2  be  two  spans  of  a  girder- 
continuous  over  any  number  of  supports, 
the  supports  being  either  on  the  same  or 
different  levels,  and  the  two  ends  either- 
fastened  or  lying  free  upon  abutments. 


responding  to  that  of  the  support,  thus 
M2  and  M,  are  the  moments  at  the  sup- 
ports 2  and  3.     The  reaction  will  be  rep- 
j  resented  by  R  in  the  same  way.     In  the 
span  ?j  let  there  be  a  single  concentrated 
i  load,  Pj  at  a  distance  k^  from  the   left 
hand  support,  also  in  the  span  Z2,  a  load 
P2  at  a  distance  kl^  from  2  ;  k  being  any 
fraction  and  not  necessarily  the  same  in 
|  the  two  cases.     Let  us  take  the  support 
!  2  as  an  origin  ;  and  designate  by  m  the 
moment  at  any  juoint  in  the  span  /2.  Now 
I  if  we  consider  any  section   between  the 
•  load  P2  and  the  support  3,  we  know  the 
sum  of  the  moments  of  all  the  exterior 
j  forces  acting  upon  the  beam  upon  the 
left  of  this  point  must  be  equal  and  op- 
j  posed  to  the  moment  of  the  molecular 
i  forces  in  the  section.     Now  all  the  ex- 
I  terior  forces  to  the  left  of  the  point  2 
may  be  conceived  as  acting  at  2  in  the 
unknown  moment  M„  and  an  unknown 
J  vertical  shearing  force  S2.    Denoting  the 
distance  of  the  section  from  the  origin  by 
x;  we  have  the  equation  of  moments  with 
reference  to  this  section  : 

(1)     M2-S2a;  +  P2  (x-kQ-m=o 

Making  in  this  x=li,m.  becomes  M3,  and 
we  have 

(2)   s  =  ^y^+p2(i-&) 

Considering  now  a  section  in  the  span  Z3 
between  ~P1  and  the  support  1,  we  have 
all  the  exterior  forces  to  the  right  of  2 
represented  by  the  moment  M2  and  an 
unknown  vertical  force  S'2,  and  the  equa- 
tion of  moments  for  that  section  is  an- 
alogous to  (1)  ;  making  x=lv  we  deduce 
the  value 


The  moment  at  a  support  will  be  desig- 
nated by  the  letter  M  with  an  index  cor- 

*  C.  E.  Greene,  Graphical  Method  for  the  Analysis  of 
Bridge  Trusses.    D.  \an  NoEtrsnd,  New  "Xork.   1875. 


(3)      S', 


M-M 


/, 


i  +  P^ 


Now  the  reaction  at  the  point  2  is  the 
sum  of  these  two  partial  reactions,  hence 
adding  (2)  and  (3)  we  have 


(4)R, 


M„ 


M+M, 


M„ 


+  P^  +  P2(1-^) 


Hence  the  shearing  force  and  the  reac- 
tion at  any  support  may  be  obtained 
when  the  moments  at  that  support  and 
at  the  preceding  and  following  supports 
are  known. 

These    are   found    by  the   wonderful 


STRAINS   IN   CONTINUOUS   GIRDERS. 


67 


Theorem  of  Three  Moments,  of  which  an 
abridged  demonstration  will  now  he 
given.  Through  the  origin  pass  a  hori- 
zontal line  pq,  and  let  the  height  of  any 
support  above  that  line  be  denoted  by  h. 
Let  the  tangent  of  the  angle  which  the 
elastic  curve  at  any  point  makes  with 
this  horizontal  be  denoted  by  t.  The 
well  known  equation  of  the  elastic  line  is 


(5) 


m 


dUj__ 
dx3     EI 


Where  E  is  the  modulus  of  elasticity,  I 
the  moment  of  inertia  of  the  girder,  and 
m  the  moment  at  the  point  whose  coor- 
dinates are  x  and  y.  Inserting  for  m 
its  value  from  (1)  we  have 


(6) 


d*y_M-S2x  +  F2(x-kl2) 


d  x2 


EI 


Integrating  this  once,  the  constant  of  in- 
tegration is  t2  the  tangent  at  2,  and 


Integrating  again  the  constant  is  zero, 
and 


(8)  y=t2x+ 


3M2x2-S2x3  +  F2(x-kl2y 


6EI 


Making  in  (8)  «=£2  we  have  y=h3,  and 
substituting  for  S2  its  value  from  (2)  we 
have  for  t2  the  expression 


^  t^-Aii 


2M2Z2  +  M3Z2-P2V 
[2&-3/fc2  +  /<;! 

dy 


If  now  we  make  in  (7)  x=l2,  -~  becomes 

a  x 

£3,  and  by  substituting  in  (7)  the  value  of 
t2  from  (9),  we  get 


w^hM 


Considering  now  the  origin  at  the  sup- 
port 1,  we  may  derive  a  value  for  t2  by 
simply  diminishing  each  of  the  indices 
in  (10)  by  unity,  therefore 

an  ^-^+_I_/MA  +  2M2z-P^\ 

(11)  ^-^+6Ei\  [*-*!; 

Comparing  (9)  and  (11)  the  tangents 
will  eliminate,  and  we  have 


(12)  M^,  +  2M,ft  +IJ  +M,l2  = 

6  E  I  (j  +  j)  +PA'  (&-&)+?,  I.;  (2  h 

Stf+tf) 

Which  is  the  most  general  form  of  the 
theorem  of  three  moments  for  a  girder 
of  constant  cross  section.  When  the 
origin  is  at  1  as  in  (11)  the  line  p  q  is 
supposed  to  pass  through  that  support, 
and  since  (12)  refers  to  the  support  2,  h2 
should  be  replaced  by  —  hx,  as  is  there 
done.  If  the  supports  are  all  upon  the 
same  level  A=o,  and  the  .second  member 
of  the  equation  contains  only  loads  in- 
volving P.  If  there  be  several  loads,  it 
is  only  necessary  to  prefix  the  sign  of 
summation  2  to  the  two  terms  involving 
P.  For  the  case  of  a  uniform  load  io1 
and  w2  per  unit  of  length,  we  have  only 
to  put  2  F1=w1  d  (k  IJ  and  2  P2=w2  d 
(k  l2),  and  to  integrate  between  the  re- 
quired limits  ;  thus,  if  the  load  cover 
both  spans  entirely,  the  integral  is  taken 
between  the  limits  o  and  I,  and  we  have 
(if  the  supports  are  on  the  same  level) 

(12)*  Mt  l1  +  2Mi  ft  +  O+M,  K=\v>X 

And  the  reaction  for  the  corresponding 
support  becomes,  from  (4) 

.     x  „      M -M,  ,  M.-M,     ,       , 

(13)  R2=-^— -1+-a-r- 1  +  iwJ1-{- 

When  the  supports  are  on  the  same 
level,  and  the  ends  of  the  girders  he  up- 
on abutments,  formula  (4)  and  (12)  are 
of  easy  application.  The  moments  at 
the  ends  are  then  zero,  and  for  each  in- 
termediate support  may  be  written  an 
equation  of  the  form  of  (12)  by  which 
the  moments  can  be  found,  since  the 
number  of  equations  is  the  same  as  that 
of  the  unknown  qualities.  Then  by  sub- 
stitution in  expressions  of  the  form  of 
(4)  the  reactions  become  known. 

If  we  have  two  spans  a  b=l,  b  e=n  I, 
there  is  only  one  equation  of  moments. 
Let  us  apply  this  to  a  single  concentrated 
weight  on  the  span  a  b.  Kef  erring  to 
(12),  we  have  then 


*  This  is  the  form  as  first  deduced  by  Clapeyron,  Comptes 
Re7idus,  1S5T.  The  form  as  given  in  (18)  is  due  to  Bresse, 
La  Mecanique  Appliquee,  1S65.  A  more  general  extension 
to  the  case  of  variable  moment  of  inertia  is  given  by 
Weyrauch,  Thcorie  der  Conlinuirlichen  Trdger,  1S73. 


-68 


van  nostrand's  engineering  magazine. 


I      JCl 


F^p— r 


(14)  2Ma  (l+nl)=YP  (k-k3)  or 

M  =     F/     (k-k>) 

2     2  +  2  w  v  ' 

Then  from  (4)  we  Lave 

R=-^  +  P(l-*)  = 

l2  +  2w+  (3  +  2  w)  &  +  &3) 


2  +  2» 


<18>  R«=T+§+p* 


2« 


V[2  »+!]*-#) 


n  I 


2  71  +  2  7V 


lk-k*\ 


Now  for  our  practical  illustration,  let 
a  5=  80  ft.  and  b  c=  100  ft,  hence  we  have 
^=1.25,  and  the  formula  become 

Ex=     P  (l  — 1.222  &+ 0.222  &') 

(16)  R2=     P  (lAk-OAk3) 

R3=-P  (0.177  &-0.177&3) 

For  a  load  P'  on  the  span  b  c,  we  may 
call  &c=7  and  ab=nl}  and  estimate  the 
abscissa  of  the  load  by  kl  measured 
from  the  support  c.  Then  we  have 
#2=0.8,  and  from  (15)  we  have 

(17)  Rx=-P'  (0.3742  £-0.3742  k3) 

etc. 

Suppose  now  the  span  a  b  to  be  divid- 
ed into  eight  and  be  into  ten  panels. 
Let  the  dead  load  of  the  truss  be  2.5 
tons  per  panel,  and  the  live  load  5  tons. 
To  find  all  the  strains  in  the  span  b  c  it 
is  only  necessary  to  compute  the  reactions 
at  &  due  to  a  load  P=P'  =  5  tons  for 
every  panel  point.  Putting  then,  in  the 
first  of  formula  (16),  k  equal  successively 
to  £,  |,  f,  etc.,  we  find  the  values  for  all 
loads  on  the  span  a  b  ;  then  in  (17)  mak- 
ing &=tV,  r%,  etc.,  we  get  the  values  for 
loads  on  b  c.  There  are  given  in  the  an- 
nexed table,  Pj  to  P7  inclusive,  being  the 
loads  on  the  span  ab,  as  shown  in  the 
diagram  given  below,  while  Pa  to  P16  are 


Reactions  at  a,  P=4  tons. 


Load. 

R. 

Load. 

R, 

Pi 

+4.24 
+3.49 

Ps 

—0.29 

P2 

P9 

—0.54 

P3 

+2.77 

P10 

—0.65 

P4 

+2.08 

Pxi 

—0.66 

P5 

+1.45 

p12 

—0.65 

Ps 

+0  88 

Pl3 

—0.58 

P7 

+0.39 

Pl4 

—0.47 

Pis 

—0.33 

Pi  6 

—0.17 

Pi-Pt 

+15.30 

P8-P16 

—4.34 

the  loads  on  the  span  b  c,  P8  being  the 
one  nearest  to  the  pier  b,  and  the  others 
following  in  the  order  of  their  indices. 
The  computation  of  reactions  is  always 
very  simple  when  the  formula  are  once 
put  into  the  shape  of  (16)  and  (17),  and 
may  be  done  by  an  office-boy  acquainted 
with  only  the  first  elements  of  algebra. 
However  great  the  number  of  spans, 
there  will  never  be  more  than  three  terms 
involving  k,  the  numerical  coefficients  of 
which  may  be  deduced  for  every  case  by 
a  process  similar  to  that  illusti'ated 
above. 

Let  us  take  the  Murphy- Whipple  pat- 
tern as  the  style  of  our  practical  example; 
the  vertical  posts  are  to  be  struts,  and 
the  diagonals  ties.  The  load  is  to  be  ap- 
plied to  the  lower  chord.  We  then  know 
that  the  ties  near  the  end  a,  must  slope 
upward  toward  the  abutment,  and  that 
those  near  b  must  slope  upward  toward 
the  pier.  These  two  systems  of  ties 
must  meet  at  the  panel  point  where  the 
shearing  force  due  to  a  uniform  load 
changes  from  positive  to  negative.  In  a 
simple  girder  this  point  is  at  the  middle 
of  the  truss.  From  our  table  of  reac- 
tions, we  see  that  a  reaction  at  a  for  a 
uniform  load  of  5  tons  per  panel  is 
15.30—4.34=10.96  tons,  and  this  is  the 
positive  shearing  force  in  the  panel  A, 
for  the  panel  B  we  have  10.96  —  5  =  5.96 
tons,  for  C  5.96—5  =  0.96,  and  for  D 
0.96  — 5  =  — 4.04  tons.  Hence  the  two 
systems  of  ties  meet  at  the  panel  point 
between  C  and  D.  From  the  table  of 
reactions  we  may  now  tabulate  the  shear- 
ing forces  due  to  each  weight.  Taking 
for  instance  the  load  P2,  its  reaction  is 
+  3.49  tons  ;  this  acts  as  a  positive  shear 
in  the  panels  A  and  B  ;  for  all  the  other 


STRAINS    IN    CONTINUOUS    dTTJDERS. 


W 


Shearing  Forces. 


A 

B 

C 

D 

E 

F 

G             H 

1 

Pi 
P2 
P3 
P* 
P5 
P6 
P7 

P8-P,6 

-• 

-4.24 
-3  49 

-2.77 
-2.08 
-1.45 
-0.88 
-0.39 
-4.34 

—0.76 
+3.49 
+2.77 
+2.08 
+1.45 
+0.88 
+0.39 
—4.34 

—0.76 
—1.51 

+2.77 
+2.08 
+1.45 
+0.88 
+0.39 
—4.34 

—0.76 
—1.51 
—2.23 

+2.08 
+1.45 
+0.88 
+0.39 
—4.34 

—0.76 
—1.51 
—2.23 

—2.92 
+1.45 
+0.88 
+0.39 
—4.34 

—0.76 
—1.51 
—2.23 
—2.92 
—3.55 
+0.88 
+0.39 
—4.34 

—0.76 
—1.51 
—2.23 
—2.92 
—3.55 
—4.12 
+0.39 
—4.34 

—0.76 
—1.51 

0 .  23 

2.92 

—3^55 
—4.12 
—4.61 
—4.34 

2 

Live 
Load 

+ 

+15.30 

+11.06  !  +7.57 

+4.80 

+2.72 

+1.27 

+0.39 

3 

— 

—4.34 

—5  10  |  —6.61 

—8.84 

—11.76 

—15.31 

—19.43 

—24.04 

4 

Sums 

+10.96 

+5.96     +0.96 

—4.04 

—9.04 
—4  52 

—14.04 

—19.04 

—24.04 

5 

Dead  Load 

+5.48 

+2.98  |  +0.48 

—2.02 

—7.02 

—9.52 

—12.02 

6 

+  Maxima 

+20.78 

+14.04  |  +8.05 
—2.12     —6.13 

+2.78 

7 

— 

Maxima 

—10.86 

—16.28 

—22.33 

—28.95 

—36.06 

panels  we  have  +3.49  — 5.  =  — 1.51  tons. 
In  this  way  all  the  shearing  forces  are 
readily  tabulated,  and  the  position  of 
the  load  required  to  produce  the  maxima 
is  seen  by  inspection.  For  the  panel  D 
we  see  that  P4  to  P,  inclusive  give  posi- 
tive shears  while  all  the  other  loads  pro- 
duce negative.  The  maximum  positive 
shear  will  then  obtain  when  the  rolling 
load  extends  from  D  to  the  pier  b,  and 
the  greatest  negative  shear  when  the 
span  b  c  and  the  segment  a  D  is  covered. 
Adding  then  the  positive  values  in  the 
vertical  columns  we  get  the  horizontal 
column  2,  which  gives  the  maximum 
positive  shearing  forces  due  to  the  roll- 
ing load  of  5  tons  per  panel.  Adding 
the  negative  values  we  get  in  3,  the  nega- 
tive maxima.  Taking  the  sums  of  the 
quantities  in  2  and  3,  we  have  in  4  the 
shearing  forces  due  to  a  dead  load  of  5 
tons  per  panel.  Since  the  dead  load  is 
2.5  tons  per  panel,  we  take  one-half  of 
these  quantities,  which  giVes  us  in  5  the 
shears  due  to  the  actual  dead  load.  Then 
the  positive  maxima  are  the  sums  of  the 


values  due  to  the  dead  load  and  the 
maximum  values  for  the  live,  that  is  the 
sums  of  the  numbers  in  2  and  5  give  the 
positive  maximum  shears  which  are 
placed  in  column  6.  Similarly  the  nega- 
tive maxima  in  7  are  obtained  by  the  ad- 
dition of  the  values  in  3  and  5.  For  the 
panels  B,  C  and  D,  we  notice  that  either 
a  plus  or  minus  shear  may  occur,  which 
necessitates  the  introduction  of  counter 
ties  in  those  panels,  and  which  are  showu 
on  the  diagram  by  dotted  lines.  The 
shearing  forces  are  the  strains  upon  the 
posts,  and  multiplied  by  the  secant  of 
the  angle  which  the  diagonals  make  with 
a  vertical,  they  give  the  strains  upon  the 
ties. 

We  may  now  pass  to  the  calculation 
of  the  moments.  Let  those  be  taken  as 
positive  which  tend  to  produce  tension 
in  the  upper  chord,  while  those  causing 
compression  will  be  negative.  Suppose 
only  one  load  upon  the  truss,  say  P.,.  and 
consider  its  action  upon  the  upper  chord 
in  the  panel  G.  If  the  chord  be  cut  at 
this  panel,  revolution  will  begin  at  the 


70 


VAN   NOSIBANDS   ENGINEERING   MAGAZINE. 


intersection  of  the  diagonal  and  lower 
chord,  the  point  marked  by  Pt.  in  the 
figure.  This  then  is  the  centre  of  mo- 
ments. The  reaction  of  P2  is  3.49,  and 
its  lever  arm  with  reference  to  the  centre 
of  moments  is  the  length  of  six  panels 
or  60  feet.  The  moment  of  the  reaction 
is  then  —3.49X60,  the  negative  sign  be- 
ing used  because  it  tends  to  turn  the  sys- 
tem in  a  right-handed  direction  about  the 
centre  of  moments,  and  hence  to  cause 
compression  in  the  upper  chord.  The 
lever  arm  of  P„,  with  reference  to  the 
same  point,  is  the  length  of  four  panels 
or  40  feet,  hence  its  moment  is  5  X  40, 
with  a  positive  sign  since  it  acts  down- 
ward. Then  the  total  moment  for  the 
upper  chord  in  the  panel  G  is 

5X40  —  3.49X60=  —9.4  ft.  tons. 

In  this  way  the  moments  due  to  every 
concentrated  load  are  readily  obtained 


and  tabulated.  Since  all  of  the  loads  in 
the  span  b  c  produce  a  negative  reaction 
at  a,  the  moments  due  to  their  action  is 
simply  obtained  by  the  product  of  the 
reaction  —4.34  into  the  various  lever 
arms,  10,  20,  etc. 

An  inspection  of  this  table  shows  that 
the  maximum  negative  moment  for  all 
the  upper  chords,  except  that  of  the 
panel  H,  is  produced  when  the  span  a  b 
is  fully  loaded  and  b  c  unloaded.  For  H 
the  negative  maximum  occurs  when  only 
the  loads  P5,  P6  and  P7  are  present,  and 
the  positive  maximum  when  these  three 
are  absent  and  the  remainder  of  the 
girder  loaded.  Adding  the  positive  and 
negative  values  we  get  in  the  horizontal 
columns  2  and  3,  the  maxima  due  to  the 
live  load.  Taking  one-half  of  the  al- 
gebraic sum  of  the  numbers  in  2  and 
3,  we  get  in  4  the  moments  due  to  the 
dead  load  of  2.5  tons  per  panel.     Then 


Moments  fob  Upper  Chord. 


A 

B 

C 

D 

E 

F 

G 

H 

1 

Pi 
P2 
P3 
P4 
P5 

?: 

P8 Pi  6 

—42.4 
—34.9 
—27.7 
—20.8 
—14.5 
—8.8 
—3.9 
+43.4 

—34.8 
—69.8 
—55.4 
—41.6 
—29.0 
—17.6 
—7.8 
+86.8 

—27.2 
—54.7 
—83.1 
—62.4 
—43.5 
—26.4 
—11.7 
+130.2 

—27.2 
—54.7 
—83.1 
—62.4 
—43.5 
—26.4 
—11.7 
+130.2 

—19.6 
—39.5 
—60.8 
—83.2 
-58.0 
—35.2 
—15.6 
+173.6 

—12.0 
—24.5 
-38.5 
—54.0 
—72.5 
—44.0 
—19.5 
+217.0 

—4.4 
—9.4 
—16.2 
—24.8 
—37.0 
—52.8 
—23.4 
+260.4 

+3.2 

+5.7 

+6.1 

+4.4 

—1.5 

—11.6 

—27.3 

+303.8 

2 

Live 

— 

—153.0 

—256.0 

—309.0 

—309.0 

—312.0 

—265  0 

—168.0 

-40.4 

3 



4 

Load 

+ 

+43  4 

+86.8 

+130.2 

+130.2 

+173.6 

+217.0 

+260.4 

+323.2 

Sums 

—109.6 

—169.2 

—178.8 

—178.8 

—138.4 

—48.0 

+92.4 

+282.8 

5            Dead  Load 

—54.8 

—84.6 

—89.4 

—89.4 

—69.2 

—24.0 

+46.2 

+141.4 

6 

—  Maxima 

—207.8 

—340.6 

—398.4 

—398  4 

—381.2 

—289.0 

—121.8 

7 

+ 

Maxima 

+2.2 

+40.8 

+40.8 

+104.4 

+193.0 

+306.6 

+464.6 

combining  5  with  2  and  3  we  get  in  6 
and  7,  the  negative  and  positive  maxi- 
mum moments  due  to  the  combination  of 
the  dead  and  live  loads. 

For  the  lower  chord  the  centres  of 
moments  will  be  at  the  intersection  of 
the  ties  with  the  upper  flange.  Hence 
we  have  the  moment  for  A  equal  to  zero, 
and  the  moments  for  B,  C,  D,  E,  F,  etc., 
will  be  the  same  with  a  reversed  sign  as 


those  for  the  upper  chord  in  A,  B,  E,  F, 
G,  etc.  Only  the  moment  for  the  lower 
chord  in  H  remains  to  be  found.  This 
may  be  computed  in  the  same  way  as 
those  above.  Its  value  is  523.2  ft. 
tons. 

Let  the  height  of  the  truss  be  10  feet. 
Then  from  the  table  of  shears  the  maxi- 
mum stresses  for  the  diagonals  are  found 
by  multiplying  by  the  secant  of  45°orA/2. 


STRAINS  IN   CONTINUOUS   GIRDERS. 


71 


From  the  table  of  moments  the  chord 
strains  result  by  dividing  by  the  depth 

of  the  truss.     Hence  the  following  table 
of 

Maximum  Strains. 

A 

B 

C 

D 

E 

F 

G             H 

Left  Hand  Post 

—20.8 

—14.0 

—8.1 

—8.9 

—10.9 

—16.3 

—22.3 

—29.0 

Tie 

+29.7 

+19.6 

+11.3 

+15.3 

+22.8 

+31.3 

+40.6 

+50.5 

Counter  tie 

+3.0 

+8.6 

+3.9 

—20.8 

—34.1 

+0.2 

—39.8 
+4.1 

—39.8 
+4.1 

—38.1 
+10.4 

—28.9 
+19.3 

—12.2 
+30.7 

+46.5 

Lower  chord 

0.0 

+20.8 

+34.1 

+38.1 
—10.4 

+28.9 
—19.3 

+12.2 
—30.7 

—46.5 

—0. 

— 52.3 

Where  +  denotes  tension  and  —  com- 
pression. To  complete  the  calculation 
for  the  span  be  it  is  only  necessary  to 
find  the  strain  in  the  post  over  b.  This 
Is  evidently  a  maximum  when  the  whole 
girder  is  covered  with  both  dead  and 
live  loads,  and  is  equal  to  the  reaction  of 
the  pier,  or  to  the  sum  of  the  shearing 
forces  in  the  two  adjacent  panels.  From 
(16)  and  (17)  we  find  the  reaction  at  b 
for  that  case  to  be  77.5  tons,  which  is 
the  value  of  the  maximum  compression 
in  the  post. 

To  recapitulate  then  the  processes  for 
finding  the  maximum  strains  in  the  end 
spans  of  any  continuous  truss  ;  compute 
the  reactions  at  the  free  end  by  the 
foi-mula  (4)  and  (12)  for  a  single  load  at 
each  panel  point.  Then  tabulate  the 
shearing  forces  in  every  panel  due  to 
each  weight  and  deduce  the  maximum 
shears  by  a  combination  of  the  dead  and 
live  load,  as  fully  explained  above.  Then 
from  the  reactions  compute  the  moments 
due  to  single  loads.  From  the  shears 
the  strains  in  web  are  found,  while  the 
moments  give  the  stresses  for  the  chords. 


The  truss  which  has  been  computed 
above  is  the  simplest  form  of  a  continu- 
ous girder.  There  being  no  moment  at 
the  abutments  the  computations  of  the 
ends  reactions  is  alone  sufficient  to  de- 
termine the  strains  ;  but  as  we  see  from 
(1)  the  moment  at  any  section  depends 
upon  the  moment  at  the  support,  and 
when  these  exist  they  must  be  taken 
into  account.     If  it  be  required  to  com- 


pute a  truss  of  six  spans,  we  need  then 
to  find  the  moment  and  shear  at  each 
support  for  every  position  of  a  single 
weight.  These  can  be  determined  by 
the  Theorem  of  Three  Moments  for 
every  case,  but  when  the  number  of 
spans  becomes  great  the  preliminary  cal- 
culation of  these  quantities  is  tedious. 
A  general  solution  of  the  equations  of 
moments  can,  however,  be  made,  and 
put  into  shape  for  direct  use. 

I  propose  now  to  present  without  de- 
monstration a  few  simple  expressions 
that  contain  the  whole  theory  of  con- 
tinuous girders  over  level  supports.  A 
proof  for  analogous  expressions  as  ap- 
plied to  girders  of  equal  span  may  be 
seen  by  the  reader  in  the  "  Journal  of  the 
Franklin  Institute,"  for  April,  1875. 
These  formula  will  give  the  moments  at 
every  section  due  to  a  single  load  P,  and 
the  shearing  force  at  the  right  hand  side 
of  every  support.  They  will  be  found 
by  the  engineer  to  be  easy  of  application, 
and  in  connection  with  the  method  of 
tabulation  given  above  will  completely 
solve  every  girder. 

Let  Vs=  number  of  spans,  h  =  length 
of  the  span  containing  the  load  P,  lx  l^  ls, 
etc.,  the  length  of  the  spans  counting 
from  the  left  hand  end,  and  ls,  ^-i,  etc., 
beginning  at  the  right  hand  end.  In  the 
same  wray  let  the  supports  be  numbered 
1,  2,  3,  etc.,  then  r  will  denote  the 
support  at  the  left  of  the  loaded  span. 
A  single  load  will  be  called  P,  and  its 
distance  from  the  rth.  support  will  be  a, 
or  klr  where   Jc   denotes   anv   fraction. 


72 


VAN   NOSTRAND'S   ENGINEERING   MAGAZINE. 


The  moment  at  any  support  will  be 
called  Mn,  and  the  shearing  force  at  a 
point  infinitely  near  to  the  support  will 
be  designated  by  Sn. 

Then  the  moments  and  shears  due  to  a 
single  load  P  will  be  given  by  the  follow- 
ing formulae  : 

(I.)  The  moments  at  the  supports 
when  7i<r+l, 


Mr 


and  when  »>r, 

Mn  =    (4-n+2 


A  dS-r-{-2   +   B  f7g-r+l 

A  cT  +  B  cr+i 


4-i^s-i  +  2  (k-i  +  lB)ca 

(II.)  The  shears  at  the  supports 

Mr+i 


at  the  rth 


Sr  = 


Mr 


'+P(l-&) 


,        _,        Mn— Mn+1 
at  any  other   bn  = - — — ,  ' 

(III.)  The  moments  at  any  section, 
whose  distance  from  the  left  hand  sup- 
port is  x. 

Between  P  and  the  right  hand  support 
m=  Mr— Sr  x  +  F  (x—a) 

At  any  other  section     m=  Mn— Sn  x 

The  constants  c1  c2  cn,  etc.,  and  dx  d2  ds, 
etc.,  depend  only  on  the  lengths  of  the 
various  spans  ;  A  and  B  depend  only  on 
the  load  P  and  its  position  in  the  r*  span; 
the  values  of  these  constants  are  : 


C,=  0 

c  =  1 


etc. 

d1  =  0 
d2=  1 

d,  =  —  2 


2   l*  +  l* 

4  K     \ 

etc. 


4  +  4- 
4-1 


d. 


>  (4+4-i)  (k-i  +  k-2)-iVi 

4-1  4-2 


7  r»  J  4-2  +  4-3  -j  4-2 

c?5  =  -  2  di — dsJ— 

fs-3  ^6-3 


etc. 


etc. 


A=P42  (2&-3F  +  F)      B=FPr  (k-k3) 


a 


To  apply  these  to  any  case  we  first  in- 
sert the  lengths  of  the  spans  in  the  series 
c  and  d.  For  six  spans  we  need  only  to 
use  them  as  far  as  c6  and  d0  Then  take 
a  load  on  the  first  span,  or  r=l,  and  mak- 
ing n  equal  to  2,  3,  4,  etc.,  find  from  (I.) 
the  moments  at  every  support.  For  ex- 
ample, let  us  take  a  girder  of  six  spans, 
one-half  of  which  is  represented  in  the 
sketch,  and  the  other  half  of  which  is 
symmetrical  to  this 


l 

t     P4     A 

or  ^=^=80'  l2 

=  1  =40'  I  =1  =100'. 

Inserting  these  values  in  the  series  c  and 

d  we  get 

C!    = 

d1  =     0 

C2    = 

d2=     1 

C3    = 

d3=-6 

c*  = 

dt  =      16.4 

c5  = 

d^  =  —  59.6 

cc  = 

dR  =     222. 

Now  to  compute  the  span  3  — .4,  we 
need  to  find  the  moments  at  3  and  4  for  a 


load  at  every  panel  point.  This  is  easily 
done  from  formula  (I).  For  example, 
take  the  load  P4  in  the  second  span,  here 
r=2,  and  w=2,  hence  we  get 

M3=  1.873  P4  (4&  +  3  Is*— Ik*),  or  since 


h: 


M„ 


3.513  P„ 


and  M4= -0.525  P4  (4&  +  3F-7  F)  or 

M4=  — 0.985  P4 

Then  the  shearing  force  due  to  P4  is  by  (II) 


S, 


I 


0.045  P 


BUILDING   MATERIALS   AS   REPRESENTED   AT   VIENNA. 


73 


From  the  moment  M3  and  the  shearing 
force  S3  the  moment  for  any  section  can 
be  found.  Then  by  a  tabulation  of  the 
moment  due  to  every  load  the  maxima 
are  easily  obtained  as  shown  above. 


If  the  dead  load  be  10  tons  per  panel 
and  the  live  20  tons  ;  the  height  of  the 
truss  10  feet,  the  maximum  strains  in  the 
upper  chord  are  : 


A 

B 

C 

D 

E 

F 

+184.  tons. 

+52.4 

+16.9 
—26.4 

+31.1 
—29.0 

+96.3 

+220.6 

By  comparing  these  with  the  strains  in  a 
simple  girder  of  the  same  span,  height 
and  load,  the  reader  will  observe  that 


the  continuous  girder  effects  a  saving  of 
over  twenty  per  cent,  in  material. 


BUILDING  MATERIALS  AS  REPRESENTED  AT  VIENNA. 


From  "The  Builder." 


Few  things  are  likely  to  prove  more 
instructive  to  the  architect,  or  to  the 
builder,  than  a  comparative  view  of  the 
character  of  building  materials,  as  now 
employed,  not  only  in  this  country,  but 
on  the  Continent.  For  such  a  glance 
the  reports  and  technical  papers  relating 
to  the  Vienna  Exhibition  furnish  valu- 
able information.  The  collections  of 
building  materials  there  exhibited  were 
of  sufficient  importance  to  prove  of  great 
interest  to  the  engineer,  the  architect, 
and  the  builder,  although  it  was  difficult 
to  obtain  a  clear  and  satisfactory  view 
of  the  whole  of  them  ;  as  they  were  di- 
vided into  two  groups,  and  scattered 
through  the  various  galleries,  the  pavil- 
ions, and  the  grounds. 

The  United  States  sent  specimens  of  a 
fine  red  sandstone,  known  as  Connecticut 
freestone.  This  stone  is  much  employed 
in  New  York;  as  its  appearance  is  much 
in  its  favor,  and  it  is  easily  worked.  The 
price  is  about  half  that  of  granite.  A 
yellow  sandstone,  easy  to  cut  and  to 
carve,  was  exhibited  from  Cleveland, 
Ohio  ;  and  specimens  of  granite  from 
Vermont  ;  and  of  red,  white,  black,  and 
red-grained  marble  ;  completed  the  list 
of  the  American  exhibits  of  this  class. 

From  England,  the  specimens  forward- 
ed were  principally  those  of  artificial, 
rather  than  of  natural,  building  mate- 
rials. Of  the  latter,  the  samples  of  slate 
were  most  worthy  of  notice,  and  far  ex- 


celled any  from  other  countries.  A  slab 
from  the  Welsh  Slate  Company  was  9 
feet  10  inches  long,  and  6  feet  3  inches 
wide,  weighing  32  cwt.  At  the  other 
extremity  of  the  scale  of  size,  plates  of 
only  four  hundredths  of  an  inch  in  thick- 
ness, were  also  shown.  Fine  building 
materials,  including  sandstones,  lime- 
stones and  clay,  were  contributed  from 
Canterbury,  in  New  Zealand  ;  and 
Queensland  sent  specimens  of  marble  and 
of  clay. 

Amongst  artificial  building  materials, 
the  first  place  seems  to  have  been  ac- 
corded to  the  Portland  cement,  which  is 
manufactured  on  the  banks  of  the 
Thames  and  of  the  Medway.  The  ma- 
terials employed  are  chalk  and  clay,  and 
the  works  are,  for  the  most  part,  situat- 
ed on  the  chalk,  the  clay  being  brought 
to  the  manufactory  from  a  distance.  In 
the  cement  works  on  the  banks  of  the 
Thames,  the  white,  or  upper  chalk,  in  a 
portion  of  which  flint  bands  and  modules 
occur,  is  used.  On  the  Medway,  the 
gray,  or  lower  chalk,  in  which  much 
siliceous  matter  is  distributed  through 
the  mass,  so  that  it  serves  for  a  very  line 
material  for  interior  work,  is  employed. 
The  clay  is  the  common  dark  blue  clay, 
which  is  obtained  in  any  requisite  quan- 
tity along  the  shores  of  the  confluent 
rivers.  It  consists  of  68  per  cent,  of 
silica,  12  per  cent,  of  alumina,  15  per 
cent,  oxide  of  iron,  with  a  small  quan- 


74 


VAN  nostrand's  engineering  magazine. 


tity  of  alkaline  matter,  and  a  trace  of 
lime. 

Cement  is  manufactured  either  by  a 
wet  or  a  dry  process.  In  the  former, 
some  four  parts  of  gray  chalk,  or  three 
of  white,  mixed  with  one  of  clay,  are 
ground  with  water  in  a  mill,  until  they 
attain  the  consistency  of  cream.  This 
is  allowed  to  flow  from  the  mill  into 
settling-tanks  ;  whence  it  is  removed, 
when  dry,  to  hot  plates.  It  is  then  burnt 
in  a  kiln,  and  finally  reduced  to  powder 
in  a  grin  ding-mill. 

The  dry  process  is  much  used  on  the 
the  Continent.  The  chalk  and  clay  are 
first  dried,  then  broken  up,  and  then 
ground  between  vertical  stones,  The 
powder  is  placed  in  a  pug-mill,  and 
mixed  with  water  containing  freshly- 
bmrned  chalk,  with  the  addition  of  a 
little  calcined  soda,  in  the  proportion  of 
three  measures  of  powder  to  one  of 
water.  The  semi-fluid  thus  produced  is 
cut  into  bricks  as  it  issues  from  the  pug- 
mill,  in  a  continuous  stream  10  inches 
wide  and  5  inches  deep.  These  blocks 
are  removed  on  boards,  dried,  baked  in  a 
kiln,  and  finally  ground  to  powder.  It 
will  be  seen  that  although  the  latter  is 
called  a  dry,  and  the  former  a  wet,  pro- 
cess, the  chief  difference  lies  in  the 
amount  of  water  which,  in  one  or  the 
other  series  of  operations,  is  first  mixed 
with  calcareous,  agrillaceous,  and  silice- 
ous matter,  and  afterwards  driven  off  by 
heat. 

The  selenitic  mortar  invented  by  Lieu- 
tenant-General  Scott,  R.E.,  is  another 
artificial  building  material,  described  in 
the  same  reports.  The  process  of  pro- 
duction consists  in  mixing,  with  the 
water  used  in  the  preparation  of  the 
mortar,  a  small  quantity  of  sulphate 
of  lime,  in  the  form  of  either  plaster 
of  Paris,"  gypsum,  or  green  vitriol. 
The  water  and  sulphate  are  first 
mixed  in  a  pan,  the  lime  is  then  added, 
and  the  mixture  is  worked  into  a  creamy 
paste.  After  grinding  for  three  or  four 
minutes,  the  sand,  burnt  clay,  or  other 
ingredient  used  in  the  composition  is 
added,  and  the  whole  is  ground  for  ten 
minutes  more.  It  is  claimed  that  by  this 
invention  ordinary  lime  can  be  at  once 
converted  into  an  excellent  cement-like 
mortar,  which  sets  rapidly  and  well,  and 
«an  be  used  for  masonry,  concrete,  or 
plasterers'  work. 


General  Scott  applies  a  modification  of 
the  same  process  to  the  manufacture  of 
bricks.  He  mixes  one  part  with  lime, 
eight  or  ten  parts  sand  or  burnt  clay, 
and  produces  bricks  which  are  said  to 
be  ready  for  use  in  about  ten  days  after 
pressing,  without  being  burned.  The 
addition  of  sulphur  to  the  lime  used  is 
also  said  to  have  the  effect  of  preventing 
the  swelling  of  the  brick,  from  the  water 
absorbed  by  the  lime  in  process  of  stack - 

An  invention  of  posterior  date  to  that 
of  the  selenitic  mortar,  is  General  Scott's 
sewage  cement.  The  principle  of  this 
manufacture  is  the  precipitation  of  the 
solid  ingredients  of  sewage,  and  the  re- 
moval of  their  organic  constituents  by 
burning.  In  the  mineral  deposit  which 
is  left,  substances  are  present  which  are 
analogous  to  the  components  of  the 
limestones  that  are  used  in  the  manufac- 
ture of  hydraulic  cement.  The  residue 
after  calcination  bears  the  nearest  affinity 
to  Portland  cement,  which  is  produced 
by  calcining  three  parts  of  chalk  with 
one  of  clay.  But  the  state  of  comminu- 
tion in  which  the  material  existed  in  the 
sewage  is  such  as  to  make  the  mixture 
more  homogeneous  than  in  the  case  of 
the  Portland  process.  It  should  be  re- 
marked that  the  calcined  residuum  is 
said  to  be  valuable  as  manure,  not  only 
from  the  lime  which  it  contains,  which 
would  be  of  service  on  arenaceous  or 
agrillaceous  soils,  but  also  from  the  pres- 
ence of  from  1  to  2  per  cent,  of  phos- 
phoric acid.  It  is  on  this  element  that 
the  utility  of  sewege  as  manure  princi- 
pally depends.  The  organic  matter  con- 
tained in  sewage  is  not  a  material  which 
the  roots  of  plants  can  assimilate.  It  is 
the  chief  source  of  danger  in  case  of 
neglect. 

In  pottery,  the  exhibits  do  not  appear 
to  have  come  up  to  the  number  or  qual- 
ity of  those  which  we  have  hitherto  des- 
cribed as  displayed  at  South  .Kensington. 
The  encaustic  tiles  of  Messrs.  Minton, 
made  from  Kaolin  and  various  colored 
clays,  dried  and  pressed,  the  glaze  being 
obtained  from  felspar,  are  well  known. 
Mr.  Robert  Minton  Taylor  exhibited  a 
novelty,  under  the  name  of  mosaic  tiles. 
They  consist  of  small  cubes  of  about  § 
inch  on  the  side,  closely  compressed  in  a 
powerful  press,  and  afterwards  burnt. 
A  third  specialty  consisted  in  the  majoli- 


BUILDING   MATERIALS   AS    REPRESENTED   AT   VIENNA. 


75 


ca  tiles,  made  of  white  clay,  with  draw- 
ings either  painted  or  printed,  partly 
under  and  partly  on  the  glazing.  While 
small  in  number,  these  exhibits  were  ex- 
quisite in  quality. 

The  natural  building  materials  sup- 
plied from  France  contained  a  large  col- 
lection of  slates  from  the  Ardennes. 
Roofing  slates,  in  thickness  of  from  £ 
inch  to  j\  inch,  ranged  in  color  from  a 
pale  red  to  a  clear  pale  blue.  Other 
specimens  exhibited  enamelled  paintings 
on  a  highly  polished  dark  ground,  of 
the  natural  color.  A  beautiful  fine- 
grained white  sandstone  is  supplied  from 
the  Dr6n.  French  marbles  are  numer- 
ous and  excellent.  The  fine  Griotte 
d'  Italie  and  Griotte  Compan  marbles  are 
dark  red,  with  spots  of  a  dark  color,  and 
white  veins.  They  come  from  the  quar- 
ries of  Felines-Hautpoul  (Herault).  The 
Languedoc  is  another  marble  from  the 
same  quarries,  with  white  spots,  and 
dark  in  veins.  A  light  red  marble,  with 
spots  of  a  darker  red,  comes  from  the 
Hautes  Pyrenees.  The  Breche  Imperiale 
is  a  light-colored  marble,  clouded  with 
red  and  grey,  spotted  with  red  and  yel- 
low, and  darkly  veined.  It  is  quarried 
near  the  mouth  of  the  Rhone.  The 
Grand  Antique,  from  La  Rochelle,  has 
an  almost  uniform  red  hue.  A  dark 
green  marble,  veined  here  and  there  by 
both  lighter  and  darker  streaks,  which 
takes  a  beautiful  polish,  comes  from  the 
Basses  Alpes.  A  fine  white  statuary 
marble,  not  unfit  to  compete  with  those 
of  Italy,  is  quarried  in  the  Haute-Gar- 
onne,  and  known  as  the  Blanc  de  Beat. 
The  transparent  onyx  marbles,  with 
which  we  have  had  the  opportunity  of 
making  ourselves  acquainted  at  South 
Kensington,  are  not  found  in  France, 
but  are  imported  from  Mexico.  A  simi- 
lar, but  somewhat  inferior  quality,  is 
found  in  Algiers. 

The  art  tiles  manufactured  by  M. 
Deck,  and  those  of  M.  Collinet,  both  of 
Paris,  are  excellent  in  design  and  in 
execution,  although  their  price  is  too 
high  to  allow  of  a  very  general  introduc- 
tion of  this  decorative  material.  The 
bright  colors  employed  by  M.  Deck  are 
heightened  by  a  peculiar  glaze  ;  most  of 
the  designs  are  Persian.  M.  Collinet  has 
succeeded-  in  the  production  of  large 
tiles — some  as  much  as  a  metre  square. 
A  special  process,  called  email-cloisonne, 


is  applied  to  these  large  panneaux.  A 
white  glaze  is  first  placed  on  the  tile. 
On  this  the  design  is  painted  in  black. 
During  burning,  the  enamel  contracts, 
which  gives  a  relief  to  the  drawing,  the 
colors  of  which  are  heightened.  A  panel 
of  3  feet  3  inches  square,  thus  finished, 
costs  from  £14  to  ,£18. 

In  coarser  pottery,  and  the  manufac- 
ture of  bricks,  France  was  not  a  formid- 
able competitor  with  ourselves.  Some 
curved,  wedge-shaped,  and  dove-tailed 
bricks,  constructed  for  different  special 
purposes,  were  sent  from  Mezieres. 

The  Boulogne  cement  is  a  remarkable 
manufacture,  well  known  in  France.  Its 
ordinary  color  is  yellow,  but  it  is  made 
into  blocks  of  a  pale  blue  tint.  Plates 
of  two  metres  long  by  one  wide,  and  not 
more  than  \  inch  in  thickness,  were  ex- 
hibited with  perfect  surfaces.  Thirty 
bricks,  placed  one  on  another  in  a  pile, 
united  by  this  cement,  were  suspended 
from  a  beam.  The  hydraulic  lime  of 
Lapage-du-Thiel  is  produced  in  large 
quantities  in  the  Ardeches.  As  much  as 
18,000  cubic  per  diem  is  turned  out  from 
thirty-four  furnaces,  which  use  from  80 
to  100  tons  of  coal.  The  slacking  of  the 
burnt  limestone,  which  is  carried  on  in 
sheds,  is  aided  by  jets  of  steam.  Ten 
days  are  required  to  pulverize  the  mass, 
which  is  then  passed  through  bolting- 
machines.  The  residuum  is  ground  and 
made  into  cement.  This  lime  is  used  to 
a  large  extent  for  harbor  work,  in  the 
form  of  beton,  or  concrete  ;  blocks  of 
which  were  exhibited  that  had  been 
under  water  for  twenty-five  years,  with- 
out showing  any  signs  of  change.  The 
cement  made  from  the  refuse  of  the  bolt- 
ing-machines, mixed  in  equal  proportions 
with  sand,  make  good  water-pipes,  with 
smooth  and  even  surfaces.  A  proportion 
of  three-parts  sharp  new  sand  to  one  of 
the  cement  makes  a  serviceable  brick. 
Colored  tiles  of  various  hues,  paving, 
pedestals,  and  other  architectural  requi- 
sites, are  made  from  the  same  material. 

The  "carton  pierre  "  of  MM.  Hardouin 
and  Lefevre,  of  Paris,  is  largely  em- 
ployed for  architectural  decoration  in 
that  city.  Its  superiority  to  plaster  is 
so  great  that  it  would  be  interesting  to 
know  why  the  attempt  made,  some 
time  since,  to  introduce  this  material 
into  London  has  not  been  attended  by 
more  si<nial  success. 


76 


YAN   NOSTRAND  S   ENGINEERING   MAGAZINE. 


The  native  marbles  of  Belgium  may 
compete  with  those  of  France.  Some 
very  beautiful  kinds  are  found  in 
the  province  of  Namur.  The  Grive 
Gerard  is  of  a  light  grey  color, 
with  small  black  spots  distributed  regu- 
larly over  the  whole  surface.  The  Lilas 
is  of  a  brighter  grey,  with  white  and 
also  very  dark  spots.  The  Florence  is  of 
a  reddish  grey  color,  with  brown  spots; 
the  Coquille  is  bluish  black,  with  light 
spots,  in  the  form  of  mussel-shells;  the 
Marbre  Bois  shows  a  fibrous  pattern  on 
a  back  ground.  A  pure  black  marble, 
from  Mazy-Galzines,  is  remarkable  for 
the  facility  with  which  it  can  be  worked, 
a  quality  very  rare  in  black  marbles.  It 
is  worth  as  much  as  15s.  per  cubic  foot. 
Inferior  marble  suitable  for  pavements, 
can  be  obtained  for  a  part  of  this  price. 

Roofing  slates  from  Luxembourg  are 
divided  into  fifteen  different  classes, 
varying  in  thickness,  as  in  the  case  of 
the  French  slates,  from  £  in   to  -h  in. 

Fire-clays  are  wrought  in  the  province 
of  Namiir,  varying  in  color,  from  an 
almost  perfect  white,  to  dark  bluish 
grey,  and  reddish  brown.  Fire -proof 
bricks,  of  a  superior  quality,  are  priced 
at  from  32s.  to  40s.  per  ton.  Hearth 
blocks  for  welding  furnaces  fetch  as 
much  as  64s.  per  ton.  Fire-bricks,  from 
the  province  of  Liege,  are  compressed 
by  hydraulic  pressure,  and  afford  a 
dense,  compact  material  at  a  reasonable 
price. 

The  bricks  of  Holland  are  described 
as  sound  and  durable,  though  not,  as  a 
rule,  well  finished.  The  corners  are 
rounded,  and  the  surface  coated  with 
sand.  They  appear  to  be  well  burnt 
through,  without  vitrification  on  the 
outside,  and  are  dense  and  very  hard. 
The  largest  size  is  8f  inch  by  4^  inch  by 
2  inch  ;  and  the  price  varies  from  20s. 
to  40s.  per  1,000.  The  second  size  is  6£ 
inch  by  6^  inch,  by  \~h  inch  ;  for  which 
the  price  is  from  8s.  to  10s.  per  mille. 
Clinker  bricks  are  supplied  for  paving. 
It  is  worthy  of  remark  that  the  prices  of 
machine-made  bricks  are  2  or  3  per  cent, 
higher  than  of  those  which  are  made  by 
hand. 

Wall-tiles  of  white,  pale  blue,  and 
lavender,  of  the  well-known  old  Dutch 
patterns,  vary  in  price  between  60s.  and 
80s.  per  thousand.  The  usual  size  is  9  inch 
by  6   inch.     Millions  of   these   tiles  are 


made  annually  at  Utrecht,  a  little  under 
5  inch  square,  and  costing  from  8  to  10 
centimes  each,  or  about  64s.  per  thou- 
sand. They  are  also  produced  in  finer 
qualities,  at  prices  from  60s.  to  68s.  per 
thousand. 

Denmark  has  shown  but  little  of  its 
building  products,  Messrs.  Erichsen's 
roofing  tiles  being  almost  the  sole  ex- 
hibit. These  are  solid,  flexible,  and  per- 
fectly adapted  to  the  requirements  of 
the  builder.  Sweden  only  exhibited 
small  specimens  of  her  rich  and  varied 
stores  of  building-stones,  granite,  por- 
phyry, marbles  and  limestones. 

The  varied  and  inexhaustible  wealth 
of  the  Italian  peninsula,  in  all  that  forms 
the  material  of  the  builder,  the  sculptor 
and  the  decorator,  was  well  and  com- 
pletely represented  at  Vienna.  The 
Italian  Minister  of  Agriculture,  Industry 
and  Trade,  exhibited  a  fine  collection  of 
stones  for  building,  quarried  and  worked 
in  Italy. 

The  physical  conformation  of  the  Span- 
ish peninsula  is  such  as  to  leave  little 
room  to  doubt  that  the  mineral  products 
of  that  country  are  in  no  way  inferior  to 
those  of  Italy.  Indeed,  in  the  neighbor- 
hood of  Logrono,  there  is  said  to  occur 
excellent  coal,  while  bituminous  shale  is 
the  only  combustible  mineral  with  which 
we  are  acquainted  as  native  in  Italy. 
Many  specimens  of  building-stone  were 
sent  from  Spain,  chief  among  which 
may  be  noted  magnificent  specimens  of 
pure  alabaster  from  Guadalajaro.  Fine 
dark-colored  slate  is  found  in  the  same 
province.  Marbles  of  various  kinds  are 
quarried  in  the  Balearic  Islands;  and  hy- 
draulic limes  and  cements  are  also  pro- 
duced in  Spain.  Encaustic  tiles,  manu- 
factured by  Signor  Nollo,  of  Valencia, 
are  exported  in  large  numbers  to  Italy 
and  to  South  America.  Messrs.  Soto  y 
Tello,  of  Seville,  manufacture  tiles  col- 
ored with  white,  green,  blue  and  black, 
made  after  designs  taken  from  the  works 
of  the  Alhambra,  in  the  repairs  of  which 
building  they  are  employed.  Nothing,, 
however,  of  merit  approaching  that  of 
the  famous  Buen  Retiro  faience  was 
forthcoming  from  Spain  in  1873.  In 
Portugal,  mining  industry  has  of  late 
taken  a  fresh  start,  under  the  impulse 
given  by  a  modification  of  the  laws  regu- 
lating mines  and  quarries.  Marbles  were 
exhibited_  from  Estremas,  and  very  fine- 


BUILDING   MATERIALS   AS   REPRESENTED   AT   VIENNA. 


77 


dark  slates,  some  of  which  were  almost 
black,  are  found  in  the  district  of  Oporto. 

The  most  numerous  and  most  complete 
series  of  exhibits  of  building  materials 
to  be  seen  at  Vienna  came,  as  was  natu- 
rally to  be  expected,  either  from  the  Do- 
minions of  the  Austrian  Emperor,  or 
from  those  of  his  German  brothers. 
Under  the  latter  head,  the  Mining  Com- 
mission of  Alsace  and  Lorraine  contri- 
buted a  fine  collection  of  some  180  speci- 
mens from  the  quarries  of  these  provinces. 
These  comprehend  granite,  gneiss,  por- 
phyry, various  sandstones,  limestones 
and  marble.  The  dark  yellow  sandstone 
found  in  the  vicinity  of  Halle  was  repre- 
sented by  a  large  lion,  sculptured  from 
the  material.  A  grey  sandstone  from 
the  same  exhibitors  was  formed  into  a 
pedestal  supporting  a  bust  of  the  Crown 
Prince. 

The  granite  from  Silesia  is  remarkable 
for  its  excellence.  A  carefully-wrought 
slab;  16  feet  long,  12  feet  4  inches  wide, 
and  1  inches  thick,  was  sent  from  Saarau, 
in  this  district.  The  slate  quarries  of 
Lehesten  have  been  carried  on  since  the 
tenth  century.  The  color  of  the  slate  is 
dark  blue,  and  its  imperishable  character 
is  explained  by  the  chemical  analysis, 
which  shows  64  per  cent,  of  silicic  acid, 
17  per  cent,  of  alumina,  and  13  per  cent. 
of  various  oxydes,  combined  with  4  per 
cent,  of  water,  and  but  little  more  than 
1  per  cent,  of  carbon  and  carbonate  of 
lime  ;  the  slate  is  fine  in  grain  and  regu- 
lar in  cleavage,  producing  plates  as  thin 
as  .04  inch.  The  price  also  is  low,  and 
the  consumption  very  large. 

The  Saxon  serpentine,  from  the  stone 
works  of  Zoblitz,  appears  to  be  free  from 
the  usual  defect  of  this  very  beautiful 
material ;  a  defect  to  which  the  serpen- 
tine of  our  own  south-western  district  is 
liable,  namely,  the  numerous  cracks  that 
divide  the  mass,  rendering  it  impossible 
for  the  quarrymen  to  extract  large  and 
sound  blocks.  In  the  Norman,  and  also 
in  the  Florentine  work,  in  which  this  ma- 
terial is  used,  the  pieces  are  very  small. 
The  Zoblitz  Company,  however,  produce 
not  only  large  blocks,  but  veneers  for 
covering  surfaces  of  stone,  and  their 
work  has  attained  a  high  degree  of  ex- 
cellence. The  usual  color  of  this  serpen- 
tine is  a  dark  green  ;  but  black,  red  and 
yellow  varieties  also  occur,  and  are  used 
with  good  effect  in  mosaic. 


The  "cajalith"  of  M.  Schmidt,  of 
Dresden,  is  a  beautiful  artificial  building 
material,  the  composition  of  which  Is 
kept  secret  by  the  inventor.  It  is  near- 
ly white,  fine  in  grain,  and  closely  re- 
sembles marble  in  appearance.  When 
first  made  it  is  plastic,  and  may  be 
moulded  into  any  required  form.  It  sub- 
sequently sets,  and  becomes  extremely 
hard.  It  can  also  be  made  of  any  de- 
sired color,  but  the  specimens  of  mosaic 
formed  from  cajalith,  made  in  imitation 
of  various  natural  stones,  had  suffered 
from  exposure  to  the  weather..  As  much 
as  50  tons  of  this  material  is  now  pro- 
duced per  month. 

A  tufa,  found  in  the  vicinity  of  the 
Laacher  Sea,  near  Andernach,  is  interest- 
ing as  showing  the  appearance,  in  this 
region,  of  this  light,  durable,  volcanic 
material,  which  cuts  with  almost  the  fa- 
cility of  chalk  ;  and  tp  the  abundance  of 
which,  in  Italy,  the  introduction  of  the 
vault,  as  an  architectural  feature,  may 
with  great  justice  be  attributed.  The 
Andernach  tufa,  however,  is  blue  ;  that 
of  the  South  of  Italy  is  of  a  pale  yel- 
lowish brown.  The  analysis  of  the 
former  shows  it  to  contain  52  per  cent, 
of  silicic  acid,  15  per  cent,  of  alumina, 
and  11  per  cent,  of  sesquioxyde  of  iron. 
It  has  been  used  since  the  time  of  the 
Normans,  for  the  manufacture  of  hy- 
draulic cement.  As  many  as  twenty-five 
cement-makers  competed  at  Vienna  from 
Germany.  The  tertiary  clay,  and  the 
chalk,  of  Riigen  and  Stettin,  and  the  de- 
posits near  the  mouth  of  the  larger 
rivers,  as  for  instance  near  Emden,  which 
are  analogous  to  those  of  the  Med  way, 
are  used  for  this  manufacture.  Light 
yellow  bricks,  inlaid  tiles,  glazed  deco- 
rative plates,  terra-cotta  columns  and 
capitals,  a  terra-cotta  statue  of  Germania, 
mosaic  tiles  for  pavements,  fire-bricks 
and  blocks  for  blast-furnaces,  large  clay 
retorts,  up  to  the  weight  of  1£  ton,  glazed 
tiles,  and  white  Dutch  tiles,  gilded  and 
brightly  enamelled,  are  exhibits  which 
say  much  for  the  industry  of  the  clay- 
workers  of  Germany. 

Artificial  -  roofing  materials  are  also 
much  in  use  in  Austria.  There  were 
twenty-three  exhibitors  of  felt,  paper, 
wood  and  various  cements,  for  this  pur- 
pose. Herr  Irmes,  of  Berlin,  works  up 
1,500  tons  of  raw  material  into  roofing 
material  per  annum.     Zinc  plates,  color- 


78 


VAX  NOSTRAND  S   ENGINEERING-    MAGAZINE. 


ed  red,  black  and  white,  in  imitation  of 
tiles,  were  taken  from  a  roof  in  Munich, 
where  in  twenty-seven  years  they  had 
suffered  but  little  loss  of  weight.  Con- 
sidering, however,  the  conducting  power 
of  metal,  the  instances  can  be  but  few 
in  which  a  wise  architect  would  substi- 
tute a  thin  zinc  plate  for  a  sound  and 
impervious  tile. 

The  building-stones  of  Austria  are 
numerous  and  excellent.  White,  light 
grey,  blue  and  yellow  varieties  of  lime- 
stone are  quarried  in  the  Vienna  basin. 
The  Wollersdorf  stone  is  distinguished 
for  great  hardness  and  purity  of  color. 
The  Mukden  dorf  limestone  is  of  a  simi- 
lar quality,  although  in  places  it  contains 
crystals  of  dolomite.  A  blue  and  yellow 
stone,  from  Sonimerin,  extremely  hard  in 
its  lower  bed,  is  known  as  Imperial  stone. 
A  fine  white  statuary  limestone  is  found 
in  the  neighborhood  of  Neusiedeler.  A 
fine  sandstone,  which  has  been  used  in 
the  restoration  of  the  Cathedral  of  St. 
Stephen,  at  Vienna,  is  from  St.  Margar- 
ethen.  A  fine  red  sandstone,  variable  as 
to  quality,  is  quarried  at  Brun  am  Stein- 
feldt,  and  also  at  Baden.  The  Vienna 
or  Karpathen  sandstone  is  of  a  bluish- 
grey  color,  with  a  fine  quartz  base,  ce- 
mented by  lime  and  clay.  It  disinteg- 
rates by  exposure  to  the  atmosphere. 

Marbles  are  found  in  Carinthia.  Quar- 
ries of  a  dark  red  marble  have  recently 
been  opened  at  Arnoldstein.      A  light- 


blue  marble-like  stone,  with  dark  veins, 
which  takes  a  high  polish,  and  a  fine- 
grained white  and  reddish  limestone,  with 
green  veins,  are  largely  used.  Tuface- 
ous  limestone  is  also  frequent  in  Carin- 
thia. It  is  light,  and  easily  quarried. 
Most  of  the  slate  used  in  Austria  comes 
from  the  Silesian  and  Moravian  pro- 
vinces, which  possess  good  qualities  of 
green  and  of  dark  blue  slates. 

In  the  Lengau  Valley  about  30,000 
tons  of  materials  are  annually  worked  up 
into  hydraulic  lime  and  cement.  In 
Vienna,  50,000  tons  of  cement  and  hy- 
draulic lime,  and  12,500  tons  of  gypsum, 
are  annually  made  and  sold.  Near  Stein- 
briick,  in  Styria,  an  argillaceous  marl 
slate  and  a  dark  blue  limestone  have 
been  quarried  for  the  same  purpose  for 
fourteen  years.  Building  blocks,  com- 
posed of  broken  stone  and  cement,  are 
manufactured  at  Vienna. 

The  brick  industry  of  Austria  is  also 
very  active,  a  thousand  million  of  bricks 
having  been  turned  out  from  the  various 
factories  in  1870.  The  Wienenberger 
bricks,  from  their  acknowledged  excel- 
lence, are  chiefly  used  for  public  build- 
ings. The  Wienenberger  Company  pro- 
duce also  tiles  and  objects  in  terra-cotta, 
and  it  is  said  to  be  owing  to  the  magni- 
tude of  these  works  that  the  building 
for  the  Exhibition  of  1873  was  com- 
pleted in  time. 


THE  "BESSEMER." 


From  "  Engineering." 


The  steamship  "  Bessemer  "  made  her 
first  public  trip  across  the  Channel, 
May  8th,  carrying  as  passengers  a  large 
party  who  had  accepted  the  invitations 
to  a  trip  to  Paris  issued  conjointly  by 
the  London,  Chatham,  and  Dover  Kail- 
way  Company,  the  Bessemer  Steamship 
Company,  and  the  Northern  Railway 
Company  of  France.  A  special  train 
from  the  Victoria  station  conveyed  the 
passengers  to  Dover,  and  shortly  after 
eleven  o'clock  the  "Bessemer"  steamed 
out  of  Dover  Harbor  on  her  way  for 
Calais.  Of  course,  one  of  the  chief 
attractions  which  had  drawn  the  compa- 
ny together  was  the   swinging   saloon, 


and  hence  much  disappointment  was 
naturally  expressed  when  it  was  learned 
that  the  saloon  was  to  remain  fixed  and 
was  not  to  be  worked  at  all  during  the, 
trip,  the  reasons  assigned  being  first  that 
the  gear  for  controlling  the  saloon  was. 
not  completely  adjusted,  and  second 
that  no  opportunity  had  yet  offered  for 
the  man  controlling  the  hydraulic  gear 
to  obtain  that  practice  in  working  the 
machinery  which  is  naturally  essential 
to  a  satisfactory  result.  These  are,  of 
course,  good  reasons  for  leaving  the  sa- 
loon fixed,  and  we  think  that  the  company 
acted  wisely  in  not  working  the  saloon 
at   all  rather  than   run  the   chance  of 


THE    "BESSEMER. 


79 


working  it  unsatisfactorily.  Trials  of 
such  a  nature  are  far  better  made  in 
private,  as  first  experiments  of  this 
nature  cannot  be  expected  to  be  all  suc- 
cesses, and  the  impressions  of  public 
failures  are  not  easy  to  remove.  Wheth- 
er or  not  it  would  not  have  been  more 
judicious  to  have  postponed  the  public 
trial  until  the  swinging  saloon  was  ready 
to  be  shown  in  action  is,  however,  anoth- 
er question,  which  it  is  scarcely  necessary 
to  discuss  here. 

Luckily  there  was  really  no  want  of  a 
swinging  saloon.  With  the  exception  of 
a  slight  fog  at  starting  the  weather  was 
all  that  could  be  desired  by  a  landsman 
making  the  Channel  passage,  while  the 
sea  was  so  calm  and  the  "  Bessemer  "  so 
steady  that  none  but  the  most  exceed- 
ingly qualmish  were  likely  to  suffer 
inconvenience.  Under  these  circum- 
stances the  passengers,  if  they  were  dis- 
appointed in  not  witnessing  the  working 
of  the  swinging  saloon,  had  at  least  the 
satisfaction  of  being  able  to  appreciate 
the  numerous  comforts  with  which  the 
"  Bessemer  "  abounds — comforts  which 
appear  all  the  greater  to  those  familiar 
with  the  accommodation  existing  on 
board  the  ordinary  Channel  steamers. 

We  have  so  recently  published  descrip- 
tions of  the  chief  features  of  the  "  Bes- 
semer "  that  it  will  be  quite  unnecessary 
for  us  to  enter  into  any  detailed  account 
of  the  vessel  here.  We  may  mention, 
however,  for  convenience  of  reference 
that  she  is  350  ft.  long  over  all,  and  40 
ft.  actual  beam,  there  being,  however,  a 
row  of  overhanging  private  cabins  down 
each  side  between  the  paddle-wheels, 
which  increase  the  apparent  beam  to  54 
ft.  On  deck  the  length  is  270  ft,  the 
low  pointed  ends  which  form  such  a 
prominent  feature  in  the  design  making 
up  the  remainder  of  the  length.  The 
"  Bessemer "  is  propelled  by  two  pairs 
of  oscillating  engines  driving  feathering 
paddles  30  ft.  in  diameter,  the  two  pairs 
of  wheels  being  situated  at  a  distance  of 
106  ft.  apart  from  centre  to  centre,  with 
the  swinging  saloon  between  them.  The 
after  wheels  have,  of  course,  to  act  upon 
water  which  has  been  previously  put 
in  motion  sternward  by  the  forward 
wheels,  and  hence  the  former  wheels  run 
slightly  quicker  than  the  latter.  On 
May  8th  the  difference  in  speed  of  the 
two  pairs  of  wheels  was  almost  exactly 


two  revolutions  per  minute,  the  former 
wheels  making  25£,  and  the  aft  wheels 
2*7  £  revolutions  per  minute  for  the  great- 
er part  of  the  trip.  The  difference  in 
speed  of  the  two  pairs  of  wheels  was  thus 
about  8  per  cent. 

The  engines  of  the  "  Bessemer  "  were 
put  on  board  before  the  vessel  wae 
launched,  and  to  this  probably  is,  to 
some  extent,  to  be  attributed  their  pres- 
ent state.  At  all  events  they  are  at 
present,  to  use  a  workshop  term,  consid- 
erable "  out  of  truth,"  this  being  particu- 
larly the  case  with  the  pair  which  were 
aft  during  the  run  from  Dover  to  Calais, 
and  the  result  naturally  being  hot  bear- 
ings. Apart  from  the  defect  just  men- 
tioned the  engines  are  of  plain  substan- 
tial design,  and  we  trust  that  they  will 
eventually  be  put  in  proper  condition. 
As  regards  the  pressure  of  steam  main- 
tained, state  of  the  vacuum,  and  indi- 
cated power  developed  during  the  trip 
we  have  no  data,  and  we  believe  in  fact 
that  the  engines  have  not  yet  been  sub- 
jected to  any  regular  trial  to  pr'ove  their 
capabilities. 

On  May  8th  the  run  from  Dover  to 
Calais  was  made  in  an  hour  and  thirty- 
three  minutes,  and  it  unluckily  termi- 
nated by  the  vessel  destroying  a  portion 
of  the  western  pier  of  Calais.  As  those 
familiar  with  Calais  harbor  well  know, 
the  chief  pier  is  situated  on  the  eastern 
side,  the  western  pier  being  a  much  lighter 
structure.  There  was  a  strong  tide  set- 
ting eastward  across  the  mouth  of  the 
harbor;  and  the  "Bessemer"  was  ac- 
cordingly made  to  approach  the  mouth 
slightly  from  the  westward,  port  helm 
being  given  to  cause  her  to  enter  the 
harbor.  As  she  came  between  the  piers 
the  helm  was,  we  believe,  steadied  and 
then  placed  to  starboard,  but  as  the  ves- 
sel lost  way  the  effect  of  the  starboard 
helm  was  unnoticeable,  and  under  the 
influence  of  the  transverse  current  the 
stern  still  paid  off  to  the  eastward  and 
the  bow  to  the  westward,  the  result 
being  that  the  vessel  ran  into  the  west- 
ern pier,  completely  clearing  it  away  for 
some  100  ft.  or  so.  The  shattering  of 
the  pier  timbers  was  a  mere  trifle  to  the 
"  Bessemer,"  the  shocks  experienced  on 
board  being  scarcely  perceptible,  while 
the  only  damage  the  vessel  sustained 
consisted  in  the  removal  of  a  few  splin- 
ters from  the  sponsons  at  the  bow  and 


80 


van  nostrand's  engineering  magazine. 


the  carrying  away  of  the  foremast  in  con- 
sequence of  the  pier  coming  in  contact 
with  the  wire  rope  stay.  A  few  minutes 
after  the  disaster  the  "  Bessemer  "  was 
laid  alongside  the  eastern  pier  without 
difficult)',  and  after  partaking  of  a 
luncheon  provided  at  Calais  station,  her 
passengers  proceeded  on  then-  way  to 
Paris  by  special  train. 

The  behavior  of  the  "  Bessemer "  in 
entering  Calais  Harbor  has  naturally 
given  rise  to  grave  doubts  as  to  whether 
or  not  the  vessel  will  be  ever  placed 
regularly  on  the  Dover  and  Calais  service. 
She  has  now  paid  three  trips  to  Calais, 
and  on  two  occasions  out  of  the  three 
she  has  come  into  contact  with  the  piers, 
the  entrance  on  the  second  occasion 
being  made  without  difficulty.  So  far, 
too,  she  has  had  the  benefit  of  fine 
weather,  and  how  she  can  be  got  into 
Calais  with  a  high  sea  running  has  yet 
to  be  proved.  Her  commander,  Captain 
Pittock — well  known  for  his  experience 
in  the  Channel  service — is,  we  are  cer- 
tain, able  to  do  all  that  can  be  done  in 
the  matter,  but  whether  further  experi- 
ence will  enable  the  vessel  to  be  success- 
fully handled  in  such  a  harbor  as  that  of 
Calais  has  yet  to  be  proved.  A  report 
has  been  circulated  in  some  quarters 
that  on  May  8th  the  hydraulic  steering 
gear  (Brown's  patent)  did  not  act  prop- 
erly at  the  critical  moment ;  but  for  this 
report  there  was,  we  have  every  reason 
to  believe,  not  the  slightest  foundation. 
The  gear,  in  fact,  appears  to  be  all  that 
can  be  desired.  It  is  to  be  remembered, 
however,  that  with  this,  as  with  other 
mechanical  steering  gears,  the  motion 
of  the  rudder  is  not  absolutely  synchron- 
ous with  the  motion  of  the  steering 
wheel.  The  former  follows  the  latter 
faithfully,  but  it  follows  it  at  a  very 
brief  interval  of  time — an  interval  not 
noticeable  in  fact  under  ordinary  circum- 
stances, but  of  importance  perhaps  under 
certain  conditions.  This  being  so,  it 
would,  we  think,  be  an  advantage  if 
there  was  provided  a  tell-tale  worked 
from  the  rudder  and  showing  the  actual 
position  of  the  latter,  this  tell-tale  being 
situated  so  that  it  could  be  readily  seen 
by  the  captain  or  officer  conning  the 
vessel,  who  would  thus  have  positive 
information  afforded  him  as  to  the  helm 
which  was  being  given.  With  a  long, 
shallow  vessel  such  as  the  "  Bessemer," 


the  helm  necessary  to  effect  any  desired 
movement  has,  of  course,  to  be  given 
earlier  than  it  would  be  with  a  shorter 
vessel,  and  how  much  earlier  is  a  mattter 
which  only  experience  can  determine,  so 
that  it  is  quite  possible  that  further 
practice  may  materially  improve  the 
control  obtained  of  her  movements  in  a 
narrow  entrance  and  under  the  action  of 
cross  currents. 

Another  point  yet  to  be  determined  is 
the  effect  of  the  bow  rudder.  Up  to  the 
present  time  no  experiments  have  been 
made  on  the  effect  of  employing  the 
rudder  situated  in  what  is  for  the  time 
being  the  bow,  to  assist  that  astern;  but 
we  think  that  some  trials  of  this  kind 
should  be  made,  and  are  inclined  to  be- 
lieve that  under  the  influence  of  cross 
currents  the  action  of  the  bow  rudder 
would  be  especially  beneficial.  This,  how- 
ever, is — like  the  other  points  to  which 
we  have  referred — one  on  which  it  is 
useless  to  theorize,  as  it  is  one  regarding 
which  experience  alone  can  give  infor- 
mation of  value.  In  leaving  this  subject 
for  the  present  we  may  remark  that 
when  fairly  under  way,  the  "  Bessemer  " 
answers  her  helm  well,  and  there  appears 
no  reason  whatever  to  grumble  regard- 
ing her  steering  qualities  so  long  as  she 
is  moving  through  the  water  at  a  fair 
speed. 

The  return  trip  was  made  on  May 
10th,  a  special  train  conveying  the  pas- 
sengers from  Paris  to  Calais,  and  a  start 
being  made  from  the  latter  place  to 
Dover,  at  3  p.  m.  The  run  from  the 
actual  start  at  Calais  to  the  vessel  being 
laid  alongside  at  Dover  was  made  in  1 
hour  and  46  minutes,  and  the  run  from 
pier  head  to  pier  head  in  1  hour  and  44 
minutes.  The  "Bessemer"  was  not 
turned  for  the  return  trip,  and  the  end 
which  on  May  8th  was  the  bow  was  thus 
on  May  10th  the  stern,  and  vice  versa. 
The  difference  between  the  speeds  of  the 
two  engines  was  the  same  as  during  the 
outward  passage,  the  actual  speeds  dur- 
ing the  trip  being  26  per  minute  for  the 
pair  which  were  for  the  time  being 
the  forward  engines,  and  28  per  minute 
for  those  aft.  The  bearings  proved  to 
be  in  better  condition  on  her  return  trip, 
and  although  they  still  heated,  the  heat- 
ing was  very  much  less  than  during  the 
outward  trip,  and  it  was  necessary  to 
run  water  on  them.     On  her  arrival  at 


A1ST   ANALYSIS    OF   THE   PEAUCELLIER   COMPOUND   COMPASS. 


81 


Dover  the  vessel  was  brought  alongside 
the  Admiralty  Pier  in  a  manner  which 
elicited  from  the  passengers  three  hearty 
and  well-deserved  cheers  for  Captain 
Pittock,  and  shortly  afterwards  a  special 
train  conveyed  the  passengers  to  Lon- 
don. 

Thus  ended  the  first  public  trial  of  the 
'"  Bessemer  " — a  trial  which  was  certainly 
not  without  interest,  although  the  great 
feature  of  the  vessel,  namely,  the  swing- 
ing saloon,  remained  untested.  The 
weather,  too,  was  so  fine  that  the  sea- 
going qualities  of  the  vessel  were  but 
very  little  tried;  but  there  is,  neverthe- 
less, every  reason  to  believe — judging 
from  such  experience  as  has  been  already 
gained — that  they  will  be  satisfactory. 
As  regards  speed  the  prospect  is  not  so 
promising,  the  times  occupied  in  the 
runs  on  both  trips  showing  that  the 
"  Bessemer "  is  at  present  certainly  not 
.a  fast  vessel. 


To  what  extent  this  result  is  to  be 
attributed  to  the  excess  of  draught  above 
that  originally  intended,  or  how  much 
may  be  due  to  the  non-development  by 
the  engines  of  the  proposed  power,  it  is 
at  present  impossible  to  say;  but  it  is 
much  to  be  hoped  that  such  experiments 
may  be  carried  out  as  may  afford  some 
information  on  this  head,  as  any  data  of 
this  kind  referring  to  a  vessel  of  the 
peculiar  build  of  the  "Bessemer"  have  a 
special  interest.  We  shall,  no  doubt, 
before  long  have  more  to  say  regarding 
the  "Bessemer"  and  her  capabilities; 
but  in  taking  leave  of  her  for  the  present 
it  is  only  just  to  add  that  whatever 
speed  she  may  ultimately  attain  and 
whatever  may  be  the  results  of  the  trials 
of  the  swinging  saloon,  the  vessel  offers 
admirable  accommodation  for  passen- 
gers, and  the  comforts  which  she  affords 
can  scarcely  fail  to  be  appreciated  by 
the  traveling  public. 


AN  ANALYSIS  OF  THE  PEAUCELLIER  COMPOUND  COMPASS. 

By  WALTER  SCOTT. 
Written  for  Van  Nostband's  Engineering  Magazine. 


Having  constructed  a  Peaucellier  Com- 
pound Compass,  and  being  compelled  to 
work  out  for  myself  the  formula  for 
using  it,  I  submit  the  result  for  the  bene- 
fit of  others. 


Let  PBCDA,  Fig.  1,  represent  the 
outline  of  a  "Positive  Cell"  instru- 
ment, consisting  of  the  equilateral  cell 
A  B  C  D  A,  and  the  connectors  B  F,  D  F, 
of  equal  length.     From  the  construction 


of  the  figure,  the  points  F,  C,  A,  are  in 
the  same  right  line.  Let  PA=V,  FC 
=V,  FD=FB=L,  and  a  side  of  the 
inner  cell  =  I.  With  D  as  centre  and 
radius  =  D  C=D  A,  describe  the  semi- 
circle EC  AG,  and  produce  FD  to  G. 
Vol.  XIII.— No.  1—6 


Draw  CG,  AE.  The  angle  FAE, 
F  G  C,  being  measured  by  the  same  arc, 
are  equal,  and  since  the  <AFE  is  com- 
mon the  triangles  F  G  C,  A  F  E,  are  equi- 
angular and  similar,  hence  the  propor- 
tion 


82 


VAN"  nostrand's  engineering  magazine. 


FC  :FG::FE  :  FA:-FC,  FA=FG, 
FE. 

But   FC=V,    FA=V,F   G  =  Lx/, 
PE=L-?j  hence 

V.Y'=(L  +  l)  (L-l)='Lt-r,  that  is, 

the  product  of  the  arms  FA,  FC,  is 
constant,  and  equal  to  the  difference  of 
the  squares  of  a  side  of  the  greater  and 
lesser  cell. 


If  the  point  F  be  fixed  as  a  fulcrum, 
and  the  point  C  he  compelled  to  follow 
any  curve  given  by  its  equation  and  rela- 
tive to  the  point  F,  the  curve  described 
by  the  point  A  may  be  determined. 

Let  X  Y  represent  the  co-ordinate  axis, 
and  the  point  P  the  origin  of  the  curve 
H  C  J  in  which  C  is  constrained  to  move. 
Let  the  curve  GAL,  described  by  the 
point  A,  be  referred  to  the  fulcrum  F 
as  origin. 


X  K 


Let  the  radius-rector        FA=V, 
FC=v} 
"    variable  angle  A  F  G=d, 
"    distance  FP  =a, 


Then  F  C= 


u—r 


(i) 


v 

CE=FC,  Sin.  d=^?-  Sin.  d 


p^vrc^-f^-^sin.^ 


FE=FP  +  PE=a  +  yV-l^3Sin.'rf 


FC-?w7z_a+r  «-S 


V3 


Sin.'tf 


Cos.  d 


(2) 


From  eqs.  (1)  and  (2)     v„  — 


Cos.  d 

Reducing  and  arranging  this  equation 
we  have 


TT3     n  TTa(Ls— I1)    _        _    (U—VY     (3) 

V3  +  2  V-^-j /.  Cos.  d=y— i-     v  ' 

v — a  v — a 

which  is  the  general  polar  equations  of 
the  resulting  curve  GAL.  From  this 
general  equation  maybe  found  the  equa- 
tions corresponding  to  any  given  gener- 
ating curve. 

If  the  generating  curve  is  a  circle  with 

centre  P  and  radius  P  H r.  the  radius 

vector  P  C  becomes  constant  and  equal 
to  r,  and  equation  (3)  becomes 

TTJ     nTra(Ls— r)   _        ,     (V—l°y      (4) 

V  +  2V  -\ ~  Cos.  d=^ f-     v  f 

r — a  r — a 

The  polar  eq.  of  circle  of  radius  R, 
passing  through  G,  and  referred  to  F  as 
origin,  is 


V  +  2V (R— L'     -\    Cos.  d=2 
\  r  +  a  / 


{r  +  ay 


La— P 

r  +  a 

(5) 


Comparing  eqs.  (4)  and  (5)  it  appears 

that  eq.  (4)  is  the  eq.  of  a  circle  whose 
jj p 

radius  ==r.— -3,  hence   if   the  point  C 

r  — a 

moves  in  a  circle  whose  radius  =r,  the 


GEOLOGICAL  RELATIONS  OF  IRON  ORES. 


83 


point   A   will    describe   a   circle   whose 
radius 

La— I'  (6) 


R= 


r — a 


In  eq.  (6)  if  r=a,  the  value  of  R 
becomes  infinite,  showing  that  the  re- 
sulting curve  GAL  becomes  a  straight 
line.  Hence  by  causing  the  generating 
circle  to  pass  through  the  fulcrum  the 
famous  problem  of  parallel  motion  is 
solved. 

When  r  is  greater  than  a,  R  is  posi- 
tive, and  the  resulting  circle  will  be 
concave  toward  F  and  enclose  it. 

When  r  is  less  than  a,  R  is  negative, 
and  the  resulting  circles  will  be  convex 
toward  F,  and  fall  outside. 

If  in  eq.  (4)  we  make  d=0,  we  have 

Tl p 

V= =FG,  the  distance  from  the 

r  +  a 

fulcrum  at  which  the  curve  cuts  the  axis. 
If  the  length  of  the  radius  bar  P  C  be 
fixed  the  required  length  of  FP  can  be 
found  necessaiy  to  give  the  resulting 
curve  any  given  radius,  or,  conversely  if 


the  distance  F  P  is  fixed  the  required 
length  of  radius  bar  can  be  found. 
From  eq.  16 

jj p 

R  =  r.  — -,  from  which  we  find 


(L2— I1)  T  a/(L3— I')1  +  4  R'  «2 

2  It 


^l/RrW<RL'~f)=^-R  <L,-''> 

If  the  sides  L,  Z,  are  respectively  15 
and  5  inches,  and  the  radius  bar  r=  10 

inches,  then  0=4/100—^-°  inches.     If 

R 

R=200  inches,  a=9j  inches,  nearly. 

If  the  generating  curve  HJ  is  an  El- 
lipse, Parabola,  or  any  other  plane  curve 
given  by  its  equation  referred  to  P„  the 
resulting  curve  GL  can  be  determined 
in  the  same  way,  and,  conversely,  if  any 
given  curve  G  L  is  required  to  be  traced 
by  A,  the  generating  curve  necessrry  to 
develop  that  curve  can  be  found. 


THE  ORES  OF  IRON  CONSIDERED   IN   THEIR   GEOLOGICAL 

RELATIONS.* 

From  the  "London  Mining  Journal." 


In  addressing  an  audience  like  this 
Institute,  composed  of  men  to  whom  the 
subject  matter  is  familiar,  the  lecturer 
has  the  advantage  of  being  able  to  dis- 
pense with  most  of  the  usual  intro- 
ductory explanations.  I  will,  therefore, 
with  the  concurrence  of  my  hearers, 
assume  that  it  is  unnecessary  to  dwell 
upon  the  special  characters  of  the  differ- 
ent ores  of  iron,  further  than  to  accentu- 
ate those  in  particular  upon  which  my 
later  statements  and  arguments  in  to- 
night's discourse  will  mainly  depend, 
omitting  the  discussion  of  certain  sili- 
cates, rarely  employed  for  smelting,  and 
of  iron  pyrites,  the  recent  technical  his- 
tory of  which  has  introduced  to  us  a 
new  purple  ore  on  a  large  scale.  The 
ores  of  iron  to  which  I  would  invite 
your  present   attention   are  simply  the 

*  Read  before  the  Iron  and  Steel  Institute,  by  Prof. 
Warington  W.  Smyth,  F.  R.  S. 


oxides,  as  met  with  per  se,  or  combined 
with  water,  or  with  carbonic  acid — the 
substances,  in  fact,  which  form  the  great 
bulk  of  the  material  employed  for  the 
production  of  the  metal. 

When  we  observe  the  various  results 
of  analysis,  or  even  carefully  look  into 
the  actual  samples  of  ore,  there  are  often 
anomalies  noticeable  where  not  expected, 
often  two  or  more  kinds  mingled  togeth- 
er, and  giving  intermediate  results;  but 
I  hold  it  not  the  less  desirable  that,  as 
far  as  possible,  we  should  fix  the  charac- 
ters of  certain  species,  hold  fast  to  them 
through  their  sundry  minor  variations, 
and  learn  how  to  follow  the  clue  when 
these  substances  are  found  to  pass  dis- 
tinctly from  one  specific  condition  to 
another.  I  would,  therefore,  pass  under 
review  these  important  ores,  to  impress 
their  individuality  on  the  memory,  and 
would  then  consider  some  of  the  changes 


81 


VAN   NOSTRAND  S   ENGINEERING   MAGAZINE. 


which  nature  in  many  cases  has  wrought 
in  them,  and  which  sometimes  may  even 
need  to  be  noticed  in  the  smelting  pro- 
cess, but  which  very  generally  will  have 
to  engage  the  attention  of  the  explorer 
and  the  miner. 

Magnetite. — First  in  order,  if  we  omit 
from  the  elementary  metal,  which,  as 
such,  is  a  rare  and  often  disputed  con- 
stituent of  the  earth's  crust,  we  recog- 
nize magnetite,  or  magnetic  iron  ore,  by 
its  octahedral  crystallization,  often  taken 
partially  or  entirely  the  form  of  the 
rhombic  dodecahedron,  but  even  when 
almost  compact  betraying  its  crystalline 
form  by  the  brightness  of  the  triangular 
faces;  further,  by  its  black  color,  and 
black  streak,  and  its  magnetic  property 
after  showing  polarity. 

This  mineral,  Fe  O  +  Fe2  03,  with  72.41 
per  cent.,  when  pure,  is  the  fine  rich  ore 
which  Dannemora  in  Sweden,  Arendal  in 
Norway,  and  several  other  mines  in 
Scandinavia,  have  worked  with  great 
success  for  centuries  from  elongated  de- 
posits which  are  neither  lodes  nor  true 
strata.  It  is  mainly  this  ore  which  forms 
the  vast  mass  at  Gellivara,  in  Lapland, 
apparently  on  a  larger  scale  than  any 
other  known  agglomeration  of  iron  ore; 
this  it  is  also  which  is  the  chief  constitu- 
ent of  the  remarkable  protrusions  boast- 
ed of  by  the  Uralian  metallurgists,  the 
Katschkanar,  the  Blagodat,  near  Kusch- 
winsk,  and  the  Vissokaya  Gora.  In 
Italy,  fine  examples  of  magnetite  are 
those  of  Traversella,  in  the  Piedmontese 
Alps,  and  that  of  Cape  Calamita,  in  the 
Isle  of  Elba.  In  North  America,  the 
older  stratified  rocks,  both  Lawrentian 
and  Huronian,  in  Canada,  as  well  as  in 
New  York  and  New  Jersey,  abound  in 
strips,  beds,  and  masses  of  magnetite, 
which  are  concordant  with  the  stratifica- 
tion, and,  though  by  no  means  uniformly 
rich,  are  sometimes  wondrously  massive. 
These  have  been  opened  out  in  hundreds 
of  mines,  and  are,  doubtless,  destined  to 
play  a  great  part  in  the  iron  trade  of 
the  United  States. 

In  Great  Britain,  a  few  localities  can 
only  be  quoted  as  offering  magnetite  in 
workable  quantities.  A  small  vein  near 
Penryn,  in  Cornwall,  and  another  or  two 
near  Roche,  and,  perhaps,  that  of  Bally- 
coog,  near  Arklow,  ought  to  be  available 
in  favorable  times;  while  a  singular 
series  of  several  successive  beds  exist  at 


Key  Tor,  near  Bovey,  in  Devon,  which 
has  only  now  in  these  last  few  weeks 
been  placed  in  working  position.  (Mr. 
Smyth  here  submitted  a  section  of  these 
remarkable  crystalline  deposits,  as  show- 
ing on  the  line  of  cross-cut  level  a  thick- 
ness worthy  of  attention,  and  a  mode  of 
occurrence  bearing  strong  analogy  to 
some  of  the  Scandinavian  mines.) 

The  minutely  crystalline  magnetite, 
which  occurs  in  the  north  flanks  of  Aran 
Mowddy  and  of  Cader  Idris,  in  North 
Wales,  has  never  yet  been  opened  out 
with  perseverance,  and  the  objection  to 
some  of  it,  that  it  is  pyritous,  is  to  be 
met  by  more  careful  selection. 

Hematite. — The  second  species  is  the 
well-known  hematite,  termed  specular 
ore,  or  oligist  when  crystallized,  red  or 
kidney  ore  when  in  a  compact  or  fibrous 
condition.  This  substance  Fe2  0s,  with 
70  per  cent,  of  iron  in  its  state  of  high- 
est purity,  too  well  known  to  need  de- 
scription, and  an  important  ingredient 
in  the  trade  of  most  of  the  ironmaking 
countries,  is  distinguishable  in  most  cases 
instantly  if  not  by  its  external  aspect, 
by  the  blood-red  streak,  which  is  some- 
times difficult  to  produce  on  surfaces  as 
hard  and  as  smooth  as  polished  steel,  will 
appear  even  though  the  color  of  the  out- 
side be  purple  or  black.  The  value  of 
this  ore,  so  little  recognized  thirty  years 
ago,  is  now  too  well  known  for  me  to 
enlarge  upon.  Its  strange  occurrence  in 
Furness  and  near  Whitehaven  has  been 
well  described  in  the  pages  of  your  jour- 
nal,, and  a  very  curious  parallel  to  the 
northern  mines  may  be  found  on  a 
smaller  scale  in  the  numerous  deposits, 
partly  of  red  and  partly  of  brown  hema- 
tite, which  have  for  years  been  worked 
in  the  Mendip  Hills. 

I  have  to  thank  the  proprietors  and 
agents  of  two  of  the  most  remarkable  of 
these  mines  for  enabling  me  to  place 
before  you  to-night  the  plan  and  section 
of  the  Roanhead  and  Park  doposit,  and 
those  of  the  ITodbarrow  mine.  There 
could  not  be  better  examples  of  the  en- 
tire irregularity  of  form  assumed  by 
these  vast  masses,  of  their  great  produc- 
tive capability,  and  of  the  well-merited 
success  due  to  the  unsparing  use  of  the 
boring  rods. 

In  our  western  districts,  as  near  St. 
Austell  and  at  Exinoor,  hematite  occurs  in 
veins,  not  generally  large,  but  exhibiting 


GEOLOGICAL  RELATIONS  OF  IRON  ORES. 


85 


some  splendid  ores,  and  showing,  where 
they  intersect  the  clay-slates,  an  analogy 
with  the  rich  district  of  Siegen  in  Prus- 
sia, also  situated  on  the  rocks  of  the 
Devonian  system. 

There  are  cases  in  which  these  ores 
are  certainly  of  a  bedded  character,  as 
in  Canada,  and  at  La  Marquette  in 
Michigan,  where  very  extensive  workings 
have  proved  certain  strata,  mostly  made 
up  of  this  ore,  to  be  from  50  ft.  to  near 
100  ft.  in  thickness.  Probably  those  of 
Bilboa  may  be  thus  stratified.  The 
Americans  seem  mostly  to  ascribe  an 
intrusive  origin  to  their  great  masses  of 
red  ore  in  Missouri,  the  well  -  known 
Pilot  Knob,  aud  Iron  Mountain ;  and  the 
magnificent  displays  of  ore  in  Elba,  some 
seven  in  number,  occurring  in  a  straight 
line,  are  regarded  by  numerous  authors 
as  of  volcanic  origin. 

In  fact,  when  observers  have  been 
familiar  with  the  marvelous  production 
of  crystallized  specular  iron  by  sublima- 
tion from  the  neighboring  volcanic 
yents,  it  is  easy  to  lean  to  the  belief  of 
its  being  connected  with  the  volcanic 
influences  in  Elba. 

Bauxite  and  Wo-ehnite. — The  curious 
ores  to  which  the  names  of  Bauxite  and 
Wo-ehnite  have  been  given,  in  which 
alumina,  Al20',  take  the  place  of  much 
of  the  sesquioxide  of  iron,  deserve  special 
mention,  from  the  fact  of  the  Irish  vari- 
ety being  so  largely  employed  in  the 
smelting  of  hematites.  Mr.  Snelus  has 
kindly  supplied  me  with  analyses  of 
some  of  these  ores  in  practical  use, 
which,  with  the  percentage  of  58,  34.37, 
and  28.93,  of  peroxide  of  iron,  contain 
respectively  17.89,  39.20,  and  45.75  of 
alumina. 

Turgite. — Next,  we  have  an  ore  called 
Turgite,  after  the  mine  of  Turginsk,  in 
the  Ural  Mountains,  2  Fe  0!  +  H20,  an 
oxide  of  iron,  with  5.3  percent,  of  water, 
of  brownish  color,  but  with  bright  red 
streak;  otherwise  with  fibrous  structure 
and  mammilated  surface,  looking  much 
like  the  botryoidal  hematites.  We  know 
but  little  about  this  species,  yet  it  doubt- 
less occurs  largely  among  the  brown 
ores  which  come  to  the  furnace.  It  is 
quoted  as  found  at  divers  European 
localities,  especially  Horhausen  in  Nas- 
sau; and  it  has  been  met  with  at  the 
Restormal  Mine,  in  Cornwall.  A  com- 
pact black  ore  now  being  raised  at  that 


mine,  gave  to  Mr.  Ward,  of  Dr.  Percy's 
laboratory,  only  3.25  per  cent,  of  water. 

Go-thite  is  the  name  generally  given 
to  the  definite  compound  Fe2. 0s  +  IPO, 
in  which  10  per  cent,  of  water  is  added  to 
the  ferric  oxide.  One  of  the  varieties, 
Lespidverokite,  is  translucent  and  red 
by  transmitted  light;  another  "needle 
iron  ore,"  brilliant,  but  only  slightly 
translucent;  a  third,  wood  iron,  opaque 
and  fibrous;  a  fourth,  brown  or  black 
ore,  opaque  and  with  no  regular  struct- 
ure; but,  from  the  splendid  prismatic 
crystals  of  Lostwthiel  downwards,  all 
these  varieties  have  a  brown  streak. 
The  most  notable  examples  of  these  ores 
in  our  own  country  are  at  the  Restormel 
Mine,  in  Cornwall,  on  Exmoor,  on  the 
Brenden  Hill,  in  the  Mendip,  near  Bris- 
tol, and  in  the  Forest  of  Dean;  but 
there  are  very  numerous  places,  at  home 
as  well  as  abroad,  where,  amidst  the  ores 
called  in  the  large  scale  brown  iron,  or 
brown  hematite,  a  portion  will  prove  to 
be  this  monohydrate,  whilst  other  parts 
of  the  same  deposit  may,  very  likely, 
belong  to  the  next  following  species. 
The  name  of  stilpnosiderite  has  been 
given  to  a  mineral  with  a  lustrous  pitchy 
fracture,  but  it  is  somewhat  uncertain  as 
to  whether  it  belongs  to  the  above-named 
division. 

Zimonite,  2  Fe2  0s  +  3H  20,  with  iron 
59.9,  and  water  14.4  per  cent.  A  large 
proportion  of  the  "  brown  iron  ore,"  or 
that  which  gives  a  brown  streak,  be- 
longs to  this  series,  but  both  the  external 
contour  and  the  structure  are  very  vari- 
able. The  fact  of  the  brown  ores  being 
often  met  with  in  the  shallower  parts  of 
repositories,  which  may  contain  other 
substances  in  depth,  is  an  explanation  of 
their  having  been  largely  explored  and 
worked  from  a  very  early  period.  Thus, 
as  a  stratified  rock  limonite  it  may  some- 
times in  great  thickness  be  followed 
downward  a  long  way  without  change, 
as  in  the  mines  near  Elbingerode,  in  the 
Hartz,  or  it  may  change  downward  into 
the  impure  carbonate,  as  in  the  Lias  and 
Oolitic  strata.  When,  in  veins,  it  will 
commonly  be  found  to  constitute  a  sort 
of  gassan  or  iron-hat,  fated  to  yield  to 
other  minerals  in  depth. 

In  the  Alston  Moor  district,  hitherto 
but  little  worked,  it  is  observable  that 
the  "  rider "  of  the  lead  lodes  often 
shows  itself  at  surface  in  a  o-reat  mass 


86 


TAN   NOSTRAND  S   ENGINEERING   MAGAZINE. 


of  brown  ores;  and  similarly,  in  the  cen- 
tral part  of  Cornwall,  between  Par  Sta- 
tion and  Ladoek,  a  number  of  lodes, 
apparently  continuous  in  their  course, 
with  veins  bearing  elsewhere  copper  and 
tin  ores,  carry,  as  they  approach,  and, 
in  some  cases,  enter  the  granite  rock, 
brown  ores  in  considerable  abundance. 

To  illustrate  the  different  conditions 
of  hydration  and  admixture  in  brown 
ores  from  the  same  locality,  I  am  enabled, 
by  Messrs.  Snelus  and  E.  Jackson,  to 
compare  two  examples  of  the  ore  so 
largely  imported  from  Porman,  near 
Carthagena: 

No.  1.     No.  2. 

Peroxide  of  iron 83.80        74.85 

Alumina 50  3.00 

Oxide  of  manganese  ....     Trace         0. 83 

Lime 1.69 

Magnesia 0.55 

Silica 1.50         8.60 

Sulphur 20  0.21 

Phosphoric  acid -.07  0.14 

Combined  water 14.00        10.17 

100.07     100.04 

Metallic  iron 58.6        52.40 

No.  1,  a  particularly  lustrous,  stripy 
ore,  would  thus  approach  limonite;  No. 
2,  Gothite  in  its  composition. 

Xanihoriderite,  or  yellow  iron  ore, 
Fe2Os  +  IFO,  with  18.4  per  cent,  of 
water.  This  ore  is  of  a  yellowish  color, 
sometimes  in  silky  fibres  and  needles,  in 
other  cases  more  like  an  ochre;  but  it  is 
cited  definitely  from  only  a  few  locali- 
ties; and  from  the  character  of  the 
occurrence,  so  commonly  in  successive 
incrustation,  it  is  difficult  with  many  of 
the  substances  called  "  morass,"  or  "  bog 
iron  ore,"  etc.,  to  feel  assured  where  the 
line  should  be  drawn. 

Chalybite,  Siderite,  White  Iron  Ore, 
Carbonate,  Spathic,  Spathose,  or  Sparry 
Iron.  FeO,  CO2,  with  62.1  of  protoxide 
of  iron.  Such  a  percentage  would  give 
48.22  of  metallic  iron ;  but  this  is  an  ore 
which  almost  invariably  contains,  in  lieu 
of  some  of  the  iron,  a  notable  amount  of 
manganese,  calcium,  or  magnesium.  The 
rhombohedral  crystallization  and  the 
crystalline  structure  are  sometimes  mi- 
nutely, but  often  largely  lamellar,  both 
outer  and  inner  planes  often  curvilinear, 
with  its  light  shades  of  color  so  readily 
heightened  by  exposure,  these  are  toler- 
ably distinct  external  characters.     It  is 


only,  however,  within  the  last  twenty -five 
years  that  inquiries  after  steel  irons,  and 
more  recently  after  the  means  of  making 
spiegeleisen,  have  attracted  attention  to 
it  in  this  country,  and  have  led  to  ex- 
tended observations  like  those  read  by 
Mr.  Smith  to  your  Institute  a  year  ago. 
The  late  Mr.  Charles  Attwood  was  the 
first  to  utilize  the  considerable  quantities 
of  this  mineral  present  as  "  rider  "  in  the 
ironstones  of  many  of  the  lead  mines  in 
Weardale  and  other  parts  of  the  North. 
In  the  granite  of  Foxdale,  in  the  Isle  of 
Man,  in  the  great  cross-course  lead  lode 
of  Frank  Mills  in  Devon,  and  in  many  of 
the  Cornish  mines,  the  admixture  of 
chalybite  with  other  ores  is  often  on  a 
large  scale,  but  its  value  is  commonly 
marred  by  difficulties  of  carriage.  More 
important  is  the  range  of  veins  occupy- 
ing a  length  of  some  30  miles  in  Somer- 
set and  North  Devon,  from  the  Ebbw 
Vale  mine  of  Raleigh's  Cross  westward, 
to  near  Ilfracombe.  Nor  can  I  omit  to 
mention  the  fine  lode  of  Perran,  some- 
times 100  ft.  across,  if  taken  horizontally 
from  wall  to  wall,  where  workings,  com- 
menced in  brown  ore,  have  opened 
downwards,  at  depths  of  from  30  ft.  to 
120  ft.,  into  large  masses  of  chalybite. 

The  varieties  of  ironstone  in  which  the 
carbonate  is  mingled  with  a  very  va- 
riable amount  of  clay,  of  lime  carbonate, 
or  of  carbonaceous  matter,  are  thorough- 
ly well-known  to  my  hearers  from  their 
wide  diffusion  over  this  country,  and  their 
commercial  importance.  They  are,  in 
fact,  objects  of  more  interest  to  the 
smelter  than  to  the  mineralogist.  Cer- 
tain of  these,  as  the  celebrated  Cleveland 
ore,  date  their  employment  from  a  very 
few  years  ago;  others,  like  the  dark 
pisolitic  masses  of  the  pulverzoic  schists 
of  Anglesey  and  North  Wales,  have 
hitherto  met  with  but  little  attention. 

Let  us  now,  in  order  to  see  more  clear- 
ly the  relationship  between  these  several 
oxides,  examine  a  few  typical  specimens, 
taken  from  localities  where  the  develop- 
ment maybe  studied  on  a  large  scale.  I 
place  on  the  table  a  piece  of  what  looks 
like  chalybite  or  spathic  ore,  from  Hiit- 
tenberg,  in  Carinthia  ;  it  is  covered  with 
large  rhombohedral  crystals  character- 
istic of  that  ore,  and  through  the  mass 
may  be  traced  lines  showing  the  tend- 
ency to  rhombohedral  cleavage.  But  it 
is  chalybite  no  longer;  the  brown  streak, 


GEOLOGICAL   RELATIONS    OF   IRON   ORES. 


87 


the  presence  of  water,  and  the  percent- 
age of  iron,  prove  it  to  have  been  changed 
into  brown  ore.  Here  is  a  fragment  from 
the  lodes  of  the  Deer  Park  in  Exmoor  ; 
the  cellular  mass  is  pervaded  by  lines 
still  exhibiting  distinctly  the  rhombohed- 
ral  structure,  but  the  rich  brown  color, 
and  the  innumerable  array  of  brilliant 
needles  of  Grdthite,  show  that  this,  too, 
has  lost  its  carbonic  acid,  has  acquired 
oxygen  and  water,  and  actually  become 
a  different  substance.  The  first  stage  of 
the  change  may  be  observed  in  heaps 
exposed  in  the  shaft  tips  even  for  a  few 
months  ;  a  brown  tint,  heightening  with 
time,  takes  the  place  of  the  yellowish 
grey,  and  shows  that  a  chemical  action 
attacks  the  exterior  and  proceeds  towards 
the  interior.  Similarly,  at  Raleigh's 
Cross,  that  well  defined  lode,  in  places 
over  20  feet  in  thickness  was  found  at 
from  25  to  30  fathoms  deep  (vertically) 
to  yield  lumps  of  cellular  ore,  with  ker- 
nels of  undecomposed  spatic,  and  thence 
down  to  the  bottom  of  the  mine,  this 
latter  ore  in  greatly  increased  propor- 
tion. In  the  great  Perran  lode,  near 
Truro,  the  entire  mass,  sometimes  for  a 
few  feet  in  depth,  in  other  places  down 
to  10  or  20  fathoms,  is  proved  to  consist 
of  brown  ores,  which  then  begin  to  show 
nuclei  of  undecomposed  chalybite  ;  and 
lastly,  solid  masses  of  that  mineral. 

It  has  been  argued  by  some  that  the 
change  commences  with  the  formation  of 
the  more  hydrated  species,  and  passes 
through  successive  stages  to  those  with 
the  least  amount  of  water  ;  but  on  this 
point  the  evidence  is  as  yet  defective. 

The  brown  ores  are  undoubtedly  (for 
one  may  watch  the  process  in  old  work- 
ings) formed  by  another  series  of  changes, 
from  pyrites  through  the  sulphate  of 
iron.  The  crystals  of  brown  ore,  in  the 
form  of  pyrites,  are  among  the  best 
known  pseudomorphs,  and  there  are  lo- 
calities which  invite  the  inference  that 
this  action  has  taken  place  on  an  import- 
ant scale. 

Let  us  now  proceed  a  step  further. 
It  was  long  since  argued  by  Haidinger, 
that  red  ore  is  a  pseudomorph  after 
brown  ore,  and  many  instances  were 
cited  to  prove  that  this  change  may  gen- 
erally be  proved  to  have  taken  place. 
Unfortunately,  the  most  notable  example 
described,  was  that  of  specimens  from 
Restormel.       The     highest     authorities 


were  called  in  to  aid  in  the  decision. 
Gustav  Rose  crystallographically  showed 
that  the  forms  of  the  crystals  were  those 
of  G-othite  ;  Rammelsberg  proved  that 
the  substance  was  pure  anhydrous  oxide. 
I  fear,  however,  that  the  whole  phenome- 
non arose  from  the  ingenuity  of  a  rogu- 
ish mineral  dealer,  who,  by  exposing 
the  Gothite  to  a  suitable  heat,  expelled 
the  water,  and  thus  manufactured  de- 
ceptive specimens.  But  the  fact  is  better 
borne  out  in  other  cases,  and  though 
difficult  to  prove  in  hard  fragments,  it 
has  been  shown  by  Morgans  that  a  good 
deal  of  red  ore  was  found  in  shallow 
levels  of  the  Raleigh's  Cross  vein,  which 
may  probably  have  passed  through  the 
intermediate  hydrated  stage. 

If  we  now  examine  a  specimen  from 
Bearland  Wood,  on  Brendon  Hill,  an- 
other from  Roger's  lode,  Exmoor,  a 
third  from  the  Eiserne  Haardt,  by 
Siegen,  and  a  fourth  from  Somorrostro, 
at  Bilbao,  all  analogous,  we  shall  notice: 
first,  that  the  large  crystals  are  the  rhom- 
bohedrons  of  chalybite  ;  secondly,  that 
the  distinct  cleavage  of  that  miner- 
al permeates  the  entire  mass  ;  thirdly, 
that  the  substance  is  pure  red  ore  ;  and, 
fourthly,  that  this  last  crystallizes  out 
boldly  as  specular.  In  all  these  cases, 
therefore,  and  innumerable  others,  even 
to  a  batch  of  ore  brought  by  the  inde- 
fatigable Livingstone  from  Central  Afri- 
ca,  the  hematite  has  indisputably  been 
originally  deposited  as  chalybite. 

I  dare  not  venture,  in  the  present 
brief  sketch,  upon  the  vexed  question  of 
the  original  deposition  of  our  great  nor- 
thern masses  of  hematite,  although 
strong  arguments  for  their  having  once 
been  chalybite  may  be  deduced  from  the 
occurrence  of  mountain  limestone  fossils 
turned  into  red  ore.  The  half-way  stage 
may  be  seen  on  the  north  side  of  Cross 
Fell,  where,  at  Fox-fold,  I  have  obtained 
fossils,  now  brown  ore,  which  must  in  all 
probability  have  been  changed  in  situ, 
through  the  intermediate  stage  of  the 
carbonate. 

There  is  still  a  last  change  of  condition 
among  the  oxides  of  iron  to  be  noticed. 
Is  it  not  a  significant  fact,  that  magne- 
tite is  characteristic  of  the  older  forma- 
tions of  those  bodies  of  rock  which  have, 
during  the  longest  period  of  time,  been 
exposed  to  the  influences  which  bring 
about    metamorphism     and    change    of 


88 


van  nostrand's  engineering  magazine. 


substance  ?  In  the  Perran  lode  small 
portions  of  magnetite  have  been  found 
among  the  brown  ores  near  the  surface. 
In  some  of  the  Cornish  copper  lodes, 
notably  in  the  Fowey  Consols,  specimens 
of  magnetic  ore  have  occurred,  which 
look  very  much  as  if  they  had  been  car- 
bonates. Among  the  beautiful  red  ores 
of  Siegen,  small  grains  of  magnetite  ap- 
pear to  testify  to  a  partial  change;  and 
in  the  classical  case  of  the  mine,  Alte 
Birke  in  Siegen,  a  singular  black  rather 
powdery  substance,  "eisenmulm,"  of 
which  an  example  is  placed  before  you, 
shows  how  the  ore  of  the  mine,  in  some 
places  chalybite,  in  others  red  ore,  is 
changed  into  an  earthy  magnetite.  This, 
it  is  true,  has  been  by  some  explained  by 
the  contiguity  of  a  dyke  ;  but  without 
dwelling  on  the  opposing  arguments  of 
Birchof,  there  appear  to  be  sufficient 
grounds  for  believing  that,  in  many  cases 
at  least,  this  last  change  in  the  degree 
of  oxidation  may  be  produced  by  the 
ordinary  action  of  natural  causes. 


REPORTS  OF  ENGINEERING  SOCIETIES. 

Society  of  Engineers.— At  a  recent  meeting 
of  the  Society  of  Engineers,  a  paper  by- 
Mr.  Ernest  Spon  on  "The  Use  of  Paint  as  an 
Engineering  Material"  was  read.  The  author, 
in  the  first  place,  considered  the  necessity  for 
the  use  of  paint,  and  then  noticed  the  composi- 
tion and  characteristics  of  the  pigments  usually 
employed  by  engineers.  White  lead,  he  ob- 
served, should  be  of  good  quality  and  unmixed 
with  substances  which  may  impair  its  bright- 
ness. It  is  usually  adulterated  with  chalk, 
sulphate  of  lead,  and  sulphate  of  baryta,  the 
latter  being  the  least  objectionable.  Zinc  white 
is  not  so  objectionable  as  white  lead,  but  is  dry 
under  the  brush  and  takes  longer  in  complete- 
ly drying .  Red  lead  is  durable  and  dries  well, 
but  should  chemical  action  commence,  it  blis- 
ters and  is  reduced  to  the  metallic  condition. 
Antimony  vermilion  was  suggested  by  the 
author  as  a  substitute  for  red  lead,  and  its  qual- 
ities enlarged  upon.  Black  paints  from  the 
residual  products  of  coal  and  shale  oil  manu- 
facture, and  oxide  of  iron  paints  are  generally 
used  for  ironwork,  for  which  purpose  they  are 
peculiarly  suited.  Allusion  was  also  made  to 
anti-corrosive  paints,  and  to  those  containing 
silica.  Referring  to  the  oils  used  in  painting, 
the  author  stated  that  linseed  oil  was  by  far 
the  most  important,  and  that  its  characteristics 
deserved  careful  study.  It  improves  greatly 
by  age,  and  ought  to  be  kept  at  least  six 
months  after  it  has  been  expressed  before  being 
used.  It  may  be  made  a  drier  by  simply  boil- 
ing, or  by  the  addition  of  certain  foreign  sub- 
stances. Nut  oil  and  poppy  oil  are  far  inferior 
in  strength,  tenacity,  and  drving  qualities  to 
linseed  oil,  and  are  used  to  adulterate  the  lat- 


ter. The  author  noticed  the  driers  employed, 
and  alluded  to  the  properties  and  means  of 
testing  the  purity  of  spirits  of  turpentine. 
He  then  dwelt  at  length  upon  the  mixing  and 
practical  application  of  paint  to  new  and  old 
woodwork,  the  preservation  of  cast-iron  by 
means  of  Dr.  Smith's  pitch  bath,  and  the 
cleansing,  painting,  and  care  of  wrought-iron 
structures.  He  stated  that  when  used  under 
proper  supervision  no  better  protection  could 
be  found  for  iron  structures  than  oxide  of  iron 
paints.  He  concluded  by  observing  that  the 
real  value  of  any  paint  depended  entirely  upon 
the  quality  of  the  oil,  the  quality  and  composi- 
tion of  the  pigment,  and  the  care  bestowed  on 
the  manufacture  ;  and  that  the  superiority  of 
most  esteemed  paints  was  due  to  these  causes 
rather  than  to  any  unknown  process  or  mate- 
rial employed  in  their  preparation. 

At  a  meeting  of  the  Edinburgh  and  Leith  En- 
gineers' Society,  held  at  Edinburgh,  a  pa- 
per was  read  by  Mr.  Duncan  Menzies,  C.E.  ,_on 
the  disposal  of  sewage.  After  briefly  alluding 
to  the  methods  of  irrigation  in  use  among  the 
ancients,  both  as  described  by  the  sacred  and 
profane  writers,  he  proceeded  to  state  the  va- 
rious modes  of  treatment  at  present  in  opera- 
tion in  different  parts  of  England  and  Scot- 
land. The  result  of  careful  observation  proved 
that  the  application  of  sewage  to  land  increas- 
ed the  value  of  the  crops  to  a  very  consider- 
able extent — land  which  was  let  originally  at 
£1  per  acre  now  yielding  grass  and  other  crops 
of  the  annual  value  of  £30,  and  even  more. 
Mr.  Menzies  then  proceeded  to  describe  some 
irrigation  works  near  Craigmillar,  which  were 
laid  out  under  his  superintendence.  The  water 
of  the  Pow  burn,  which  drains  the  south  of 
Edinburgh,  was  led  by  main  drains  and  cross- 
feeders  on  to  fields,  the  soil  of  which  was  clay 
loam,  well  drained,  and  the  result  of  three 
years'  experience  was  that  crops  of  from  £17 
to  £21  per  acre  had  been  taken  off,  the  annual 
value  increasing  with  the  longer  application  of 
the  sewage.  This  sewage  was  necessarily  very 
much  diluted,  as  the  natural  flow  in  the  Pow 
burn  was  great  in  proportion  to  the  number  of 
houses  draining  into  it ;  but  in  spite  of  the 
weakness  of  the  irrigation  water,  the  result 
was  highly  satisfactory. 

At  the  ordinary  meeting  of  the  sanitary  and 
social  economy  section  of  the  Philosophical  So- 
ciety of  Glasgow,  Mr.  James  MTntyre,  Port  Glas- 
gow, read  a  paper  on  "A  Scheme  for  Inter- 
cepting and  Utilising  the  Sewage  of  Towns, 
and  Preventing  the  Pollution  of  Rivers."  His 
scheme  included  a  sewer  led  along  the  banks 
of  the  river,  having  double  tanks  at  intervals 
between  the  towns  from  which  the  sewage  was. 
drained.  In  these  tanks  the  solid  matter  "would 
be  intercepted,  and  from  them  it  could  be  lift- 
ed at  intervals  of  several  days,  and  distributed 
by  means  of  branch  lines  to  the  railways,  and 
so  to  the  districts  where  it  was  required. 
Mr.  MTntyre  described  an  application  of  this 
scheme  to  the  Clyde,  which  would  serve  Glas- 
gow and  the  towns  above  it. 

Mr.  Murray  exhibited  to  the  section  a  model 
of  a  self-acting  machine  for  separating  and 
utilising  the  sewage  of  Glasgow,  in  -which  he 


REPORTS   OF   ENGINEERING   SOCIETIES. 


89 


proposed  to  spread  out  the  stream  of  sewage 
going  into  the  machine,  so  that  its  course 
would  not  be  too  rapid,  and  to  strain  off  the 
solid  matter  on  the  way.  He  proposed  also  to 
purify  the  water  by  means  of  niters  of  char- 
coal, or  some  other  deodoriser. 

In  the  course  of  a  discussion  on  the  papers, 
Mr.  Deas,  C.  E. ,  remarked  that  the  fall  along 
the  banks  of  the  Clyde  was  not  sufficient  for 
working  Mr.  M'Intyre's  scheme.  If  he  could 
overcome  this  and  deodorise  the  water,  the 
plan  would  be  a  capital  one.  Mr.  M'Adam 
said  that  all  attempts  to  make  the  solid  matter 
got  from  sewage  of  commercial  value  had  fail- 
ed .  Mr .  James  Brown  observed  that  Mr.  M'In- 
tyre's scheme  was  substantially  the  same  as  one 
which  he  himself  proposed  twenty  years  ago. 
Mr.  Gavin  Campbell  contended  that  sifting  the 
solid  matter  from  the  liquid  in  sewage  was 
simply  nonsense.  The  best  way  to  separate 
the  two  was  by  means  of  lime.  Mr.  M'Intyre 
having  replied. 

Mr.  W.  P.  Buchan  described  a  self-acting 
sewage  gas-trap,  a  specimen  of  which  he  ex- 
hibited. The  ordinary  trap  put  into  water- 
closet  cisterns  he  showed  to  be  defective,  from 
the  fact  that  the  egg-shaped  receptacle  which 
was  usually  filled  with  water  to  trap  the  gas 
often  dried  up,  and  the  gas  had  then  free  ac- 
cess to  the  cistern.  Mr.  Buchan's  trap  is  so 
constructed  that  every  time  the  water  rises  in 
the  cistern  a  new  supply  of  water  rises  in- 
to the  trap,  and  it  is  thus  kept  constantly  closed 
against  the  ingress  of  sewer  gas  by  about  an 
inch  of  water. — Iron. 

The  American  Society  of  Civil  Engineers. 
—This  Society  convened  at  Pittsburg,  ac- 
cording to  the  programme  announced  last 
month.  We  extract  from  the  Tribune  the  fol- 
lowing discussions  of  the  meeting  of  the  10th 
of  June : 

With  the  greatest  unanimity  of  feeling, 
there  is  a  wide  ground  for  difference  of  opin- 
ion among  civil  engineers  on  what  is  known  as 
the  Bridge  Question.  It  is  an  outgrowth  of 
the  bridge  accidents  of  last  year,  which  a  com- 
mittee of  bridge  builders  belonging  to  the  So- 
ciety of  Civil  Engineers  took  into  considera- 
tion. They  brought  in  a  majority  and  three 
minority  reports,  and  ever  since  the  bridge 
business  has  been  a  vexed  question.  The  dis- 
agreement is  as  to  the  means  of  preventing 
such  accidents.  The  majority  of  the  Commit- 
tee favor  the  adoption  of  a  standard— that  all 
bridges  should  be  built  to  carry  not  less  than  a 
certain  number  of  pounds  per  square  foot;  the 
number  being  fixed  in  tables,  with  reference  to 
span  and  the  uses  to  which  different  classes  of 
bridges  are  subjected.  These  tables  would  re- 
quire bridges  which  are  unquestionably  within 
the  limits  of  safety.  But  the  opponents  of 
this  proposition  say  that  no  account  is  made 
by  it  of  the  difference  in  iron  or  other  mate- 
rials. If  the  best  iron,  for  instance,  is  by  this 
restriction  to  be  used  in  the  same  abundance 
with  the  worst,  there  is  no  object  to  be  gained 
by  using  the  best,  and  the  result  would  be 
either  that  the  rule  would  be  ignored  or  infe- 
rior materials  would  be  everywhere  used. 
Gen.  Ellis,  discussing  the  subject  said  that  the 


Committee  seemed  to  be  unanimous  as  to  the 
load  which  ought  to  be  used  to  test  a  railroad 
bridge  :  two  heavy  locomotives  and  a  train  of 
cars  loaded  to  the  maximum. 

Mr.  Herschel  advocated  the  plan  of  subject- 
ing the  iron  used  for  bridges  to  specific  tests. 
The  fact  that  such  tests  would  be  applied 
would  cause  contractors  to  furnish  good  iron. 
Mr.  Clarke,  engineer  of  the  Phenixville  Bridge, 
said  that  Western  people  were  urgent  that  a 
standard  of  strength  for  bridges  should  be 
fixed.  But  if  the  State  was  to  select  experts 
to  decide  upon  bridges  the  whole  business 
would  become,  too  soon,  a  mere  political 
placer.  There  was  discussion  over  the  mathe- 
matics of  one  of  the  reports,  and  they  were 
explained  by  Mr.  Macdonald.  But  he  thought 
that  if  the  strength  of  the  iron  used  was  to  be 
taken  into  account,  the  limit  of  its  elasticity 
was  a  far  more  important  factor  than  its  break- 
ing strength  ;  he  named  an  instance  where  the 
former  was  only  one-half  the  latter. 

Mr.  Macdonald  urged  the  adoption  of  the 
majority  report  on  preventing  bridge  acci- 
dents. He  would  somewhat  modify  it,  and  he 
proposed  that  a  Committee  of  three  be  appoint- 
ed to  report  whether  legislation  on  the  subject 
should  be  recommended. 

Mr.  Ellis  spoke  of  the  difference  of  iron, 
used  in  various  localities.  The  English  factor 
of  safety  in  bridges  was  one-third  ;  ours  only 
one-fifth.  Mr.  Herschel  said  that  France, 
Prussia,  England,  and  some  minor  European 
States  had  adopted  laws  respecting  bridges  de- 
fining the  strain  they  must  bear  to  the  square 
inch  ;  since  those  laws  went  into  force  no 
bridge  accidents  had  happened  in  those  States, 
The  public  demand  of  the  engineers  of  this 
country  a  similar  protection . 

Mr.  Richard  H.  Buel,  of  New  York,  not  be- 
ing able  to  meet  with  the  Convention,  sent  to 
the  Secretary  a  paper  which  was  read,  contain- 
ing a  severe  criticism  upon  the  report  of  the 
Committee  on  Rapid  Transit.  To  this  Mr. 
Collingwood  replied  that  the  Committee  had 
not  found  any  practical  scheme  of  rapid 
transit  on  a  paying  basis,  but  they  did  not 
propose  to  select  any  one  scheme  as  the  best, 
since  some  of  the  plans  came  from  members 
of  the  Society.  This  morning  Mr.  Wm.  H. 
Searles,  of  New  York,  resuming  the  debate 
upon  this  subject,  said  that  an  ordinary  rail- 
road is  built  only  to  accomplish  a  long  journey 
in  a  short  time;  rapid  transit  requires  high 
speed  with  stops  at  frequent  intervals.  Great 
loss  of  power  is  incident  to  frequent  stops,  and 
where  the  frequency  increases  the  loss  of  power 
is  even  disproportionately  augmented.  In  the 
case  supposed,  the  maximum  velocity  between 
the  stops  must  be  2£  times  the  average  veloci- 
ty of  the  train  when  niovins;. 

Mr.  J.  Dutton  Steele  discussed  the  inevitable 
features  of  rapid  transit,  which  he  regarded  as 
necessarily  implying  an  elevated  railway  and  a 
narrow  gauge.  Mr.  Charles  E.  Emery  thought 
that  even  if  an  endless  railroad  were  not  desir- 
able, the  system  of  landing  passengers  on  a 
moving  train  by  a  subsidiary  railroad  was 
worth  considering.  If  the  friction  system  was 
unadvisable,  the  supplementary  road  at  the 
side  misrht  have  its  cars  drawn  by  light  engines 


90 


VAN   NOSTRAND'S   ENGINEERING   MAGAZINE. 


till  their  speed  equaled  that  of  the  rapid  train, 
and  then  the  two  trains  he  coupled  at  the 
sides  till  the  passengers  to  be  added  or  left 
were  transferred. 

There  was  a  discussion  on  the  shape  of  rails, 
in  which  Mr.  Holley,  who  knows  more  about 
Bessemer  steel  than  any  other  member  of  the 
Convention,  gave  a  lucid  explanation  of  the 
laws  which  regulate  the  composition  of  rails, 
depending  on  the  different  kinds  of  strains  to 
-which  the  parts  of  the  rail  are  subjected. 


IRON  AND  STEEL  NOTES. 

Tests  of  the  Strength  of  Iron  and  Steel. 
— The  importance  of  the  Commission  late- 
ly authorized  by  Congress  to  determine  the 
strength  of  iron,  steel,  and  other  metals,  will 
appear  from  the  following  considerations:  So 
undetermined  is  the  safe  working  load  of  dif- 
ferent metals  and  of  different  structural  forms 
that  the  professional  rule  is  to  subject  bridges, 
roofs,  and  general  machinery,  to  but  one-sixth 
of  the  loads  that  are  supposed  to  be  great 
enough  to  break  them.  Although  this  rule  is 
wasteful  of  material  in  most  cases,  it  does  not 
insure  safety  in  all.  In  the  fear  that  structures 
may  be  too  weak,  they  are  overloaded  with 
costly  materials;  yet,  despite  this  precaution, 
bridges,  roofs,  and  floors  give  way,  and  ma- 
chinery is  perpetually  breaking  down. 

The  problem  is  by  no  means  a  simple  one. 
Because  an  inch  square  bar  will  stand  a  certain 
load,  it  does  not  follow  that  each  square  inch 
section  of  every  bar  will  sustain  the  same 
load.  The  resistance  of  a  simple  structure 
formed  of  bars — for  instance  the  end-post  of 
an  iron  bridge — is  notably  changed  by  no  less 
than  seven  conditions,  namely,  the  chemical 
constitution  of  the  material,  its  temper  and 
initial  strains,  due  to  manufacture,  the  length 
of  the  members  of  the  structure,  their  thick- 
ness, their  shape,  the  dimensions  of  the  struct- 
ure as  a  whole,  and  the  arrangement  of  its 
parts  with  reference  to  the  number  and  direc- 
tion of  strains.  In  other  cases,  the  character 
of  the  stress  —  impact,  vibration,  or  statical 
load — also  changes  the  conditions  of  strength. 
Nor  is  the  ultimate  resistance  of  the  material 
the  criterion  of  safety;  it  is  the  resistance 
within  the  limit  of  elasticity.  The  former  is 
comparatively  easy — the  latter  difficult  to  de- 
termine. Then  there  is  the  apparatus  for 
accurately  weighing  strains  reaching  to  a 
thousand  tons,  and  for  measuring  changes  of 
figure  under  stress  to  less  than  the  thousandth 
of  an  inch.  The  useful  formulation  of  results, 
and  the  deduction  of  general  laws  from  the 
numerous  phenomena  developed,  is  the  crown- 
ing feature  of  the  undertaking.  These  consid- 
erations give  some  idea  of  the  magnitude  and 
importance  of  the  work  before  the  Commis- 
sion. 

Judging  from  the  character  of  the  experts 
appointed  by  the  President  to  do  this  work, 
we  may  reasonably  expect  results  of  great  and 
far-reaching  usefulness.  Colonel  Laidley,  of 
the  Ordnance,  Colonel  Gillmore,  of  the  En- 
gineers, Commander  Beardslee,  and  Chief- 
Engineer  David  Smith,  of  the  Navy,  and  Prof. 


Thurston,  are  not  only  competent  mathema- 
ticians and  professional  observers  of  the  uses 
and  tests  of  materials,  but  they  are  trained  ex- 
perimenters in  this  very  direction.  For  in- 
stance, Colonel  Gillmore  is  the  foremost 
authority,  abroad  as  well  as  at  home,  on  limes, 
cements,  and  artificial  stone.  General  Sooy 
Smith  is  an  experienced  bridge  builder  and 
civil  engineer,  and  Mr.  A.  L.  Holley  is  a  me- 
chanical engineer  and  a  practical  metallurgist 
and  steel  maker. 

The  work  the  Commission  has  laid  out  is  not 
narrow  and  incomplete.  It  involves  not  mere- 
ly testing  and  branding  specimens  sent  in  by 
different  makers,  (which  is  very  important  as 
far  as  it  goes,)  but  in  several  respects  it  em- 
braces features  never  before  undertaken  by 
Government  Boards,  or  on  a  comprehensive 
basis.  Two  of  these  features  deserve  special 
mention  : 

First — The  combination  of  chemical  and  me- 
chanical tests.  It  is  now  well  settled  that  the 
effects  of  carbon  and  of  the  metalloids  upon 
iron,  and  upon  each  other  in  combination 
with  iron,  produce  as  many  physical  characters 
as  there  are  uses  for  iron  and  steel.  Determin- 
ing the  behavior  of  materials  under  stress 
merely  proves  that  substances  adapted  to  vari- 
ous uses  are  in  existence;  what  these  sub- 
stances are,  and  how  they  may  be  reproduced, 
is  taught  only  by  chemical  analysis.  Perhaps 
the  highest  usefulness  of  these  combined  tests 
will  be  the  development  of  greater  strength, 
toughness,  hardness,  and  various  other  resist- 
ances to  innumerable  varieties  of  stress — the 
establishment  of  scientific  synthesis  in  the 
manufacture  of  materials,  by  means  of  which 
they  may  be  perfectly  adapted  to  their  uses, 
thus  largely  economizing  cost  and  promoting 
safety. 

Second. — The  testing  of  structures  and  parts 
of  structures  of  the  sizes  actually  employed, 
and  under  the  conditions  of  actual  service. 
Few  bridges  fail  because  the  ultimate  resistance 
of  a  bar  of  the  iron  composing  them  is  un- 
known to  their  builders.  Many  bridges  break 
down  because  no  builder  has  yet  determined 
by  anything  short  of  the  breaking  down  itself, 
the  exact  effect  of  compound  strains  on  com- 
pound structures  ;  and  even  this  does  not  give 
the  laws  of  resistance.  "When  a  bridge-post, 
for  instance,  carries  but  a  sixth  of  the  weight 
that  a  specimen  of  its  material  will  bear,  it  may 
fail.  The  Commission  purposes  subjecting,  in 
each  of  their  standard  forms,  whole  bridge- 
posts,  and  whole  sections  of  bridge  chords  and 
whole  floors  of  girders  and  whole  large  struc- 
tures, just  as  they  are  used,  to  destructive 
stress  ;  to  measure  the  stress  and  its  effects  at 
each  stage,  and  to  deduce  laws  of  resistance 
which  will  enable  engineers  to  develop  better 
forms,  thus  dispensing  with  an  unnecessary 
margin  of  safety,  and  promoting  actual  safety 
and  economy.  In  short,  it  proposes  to  grapple 
with  these  great  practical  problems  just  as  they 
are  presented,  and  not  to  skirmish  around  them 
by  breaking  little  iron  rods,  and  then  figuring 
out  conclusions  in  which  a  small  error  is  mag- 
nified at  every  step. 

Sucb  experiments  will  occupy  years  of  care- 
ful work  and  many  thousands  of  dollars  in 


RAILWAY   NOTES. 


91 


money  ;  but  what  an  insignificant  percentage 
this  cost  will  be  upon  the  millions  now  wasted 
in  overloading  on  the  one  hand  and  in  failure 
on  the  other.  Whatever  degree  of  improve- 
ment later  years  have  witnessed  in  the  con- 
structive arts  is  due  to  such  researches  as  these, 
limited  and  imperfect  though  they  may  have 
been.  It  is  the  duty  of  this  commission,  and 
we  believe  that  it  will  be  its  privilege,  to  de- 
termine the  laws  by  which  the  safety  and  econ- 
omy of  engineering  structures  are  to  be  largely 
increased. — iV.  T.  limes. 


Organization  of  the  U.  8.  Board  appointed  to 
test  Iron,  Steel,  etc. 

President,  Lt.  Col.  T.  T.  S.  Laidley,  U.  S.  A., 
Commander  L.  A.  Beardslee,  U.  S.  N.,  Lt.-Col. 
Q.  A.  Gillmore,  U.  S.  A.,  Chief  Eng'r  David 
Smith,  U.  S.  N.,  W.  Sooy  Smith,  C.  E.,  A.L. 
Holley,  C.  E.,  R.  H.  Thurston,  C.  E.,  Secre- 
tary. 

Standing  Committee  of  ihe  Board. 

(A)  On  Abrasion  and  Wear— R.  H.  Thurs- 
ton, C.  E.,  Chairman,  A.  L.  Holley,  C.  E., 
Chief  Eng'r  D.  Smith,  U.  S.  N. 

Instructions : — To  examine  and  report  upon 
the  abrasion  and  wear  of  railway  wheels,  axles, 
rails  and  other  materials,  under  the  conditions 
of  actual  use. 

(B)  On  Armor  Plate.— Lt.  Col.  Q.  A.  Gill- 
more,  IT.  S.  A.,  Chairman,  A.  L.  Holley,  C.  E., 
R.  H.  Thurston,  C.  E. 

Instructions  .-—To  make  tests  of  Armor  Plate, 
and  to  collect  data  derived  from  experiments 
already  made  to  determine  the  characteristics 
of  metal  suitable  for  such  use. 

(C)  On  Chemical  Research.— A.  L.  Holley, 

C.  E.,  Chairman,  R.  H.  Thurston,  C.  E. 
Instructions  .-—To  plan  and  conduct  investi- 
gations of  the  mutual  relations  of  the  chemical 
and  mechanical  properties  of  metals. 

(D)  On  Chains  and  Wire  Ropes.— Com- 
mander L.  A.  Beardslee,  U.  S.  N.,  Chairman, 
Lt.  Col.  Q.  A.  Gillmore,  U.  S.  A.,  Chief  Eng'r 

D.  Smith,  U.  S.  N. 

Instructions : — To  determine  the  character  of 
iron  best  adapted  for  chain  cables,  the  best 
form  and  proportions  of  link,  and  the  qualities 
of  metal  used  in  the  manufacture  of  iron  and 
steel  wire  rope. 

(E)  On  Corrosion  of  Metals.— W.  Sooy  Smith, 
C.  E.,  Chairman,  Lt.  Col.  Q.  A.  Gillmore, 
U.  S.  A.,  CammanderL.  A.  Beardslee,  U.  S.  A. 

Instructions  .-—To  investigate  the  subject  of 
the  corrosion  of  metals  under  the  conditions  of 
actual  use. 

(F)  On  the  Effects  of  Temperature .— R.  H. 
Thurston,  C.  E.,  Chairman,  Lt.  Col.  Q.  A. 
Gillmore,  U.  S.  A.,  Commander  L.  A.  Beards- 
lee, U.  S.  N. 

Instructions :— -To  investigate  the  effects  of 
variations  of.  temperature  upon  the  strength 
and  other  qualities  of  iron,  steel  and  other 
metals. 

(G)  On  Girders  and  Columns. — W.  Sooy 
Smith,  C.  E.,  Chairman,  Lt.  Col.  Q.  A.  Gill- 
more, U.  S.  A.,  Chief  Eng'r  D.  Smith.  U.  S.  N. 

Instructions: — To  arrange  and  conduct  ex- 
periments to  determine  the  laws  of  resistance 


of  beams,  girders  and  columns  to  change  of 
form  and  to  fracture. 

(H)  On  Iron,  Malleable. — Commander  L.  A. 
Beardslee,  U.  S.  K,  Chairman,  W.  Sooy 
Smith,  C.  E.,  A.  L.  Holley,  C.  E. 

Instructions : — To  examine  and  report  upon 
the  mechanical  and  physical  proportions  of 
wrought  Iron. 

(I)  On  Iron,  Cast.— Lt.  Col.  Q.  A.  Gillmore, 
U.  S.  A.,  Chairman,  R.  H.  Thurston,  C.  E., 
Chief  Eng'r  D.  Smith,  U.  S.  N.' 

Instructions  : — To  consider  and  report  upon 
the  mechanical  and  physical  properties  of  cast 
iron. 

(J)  On  Metallic  Alloys.— R.  H.  Thurston, 
C.  E.,  Chairman,  Commander  L.  A.  Beardslee, 
U.  S.  N.,  Chief  Eng'r  D.  Smith,  U.  S.  N. 

Instructions : — To  assume  charge  of  a  series 
of  experiments  on  the  characteristics  of  alloys, 
and  an  investigation  of  the  laws  of  combina- 
tion. 

(K)  On  Orthogonal  Simultaneous  Strains. — 
W.  Sooy  Smith,  C.  E.,  Chairman,  Commander 
L.  A.  Beardslee,  U.  S.  N.,  R.  H.  Thurston, 
C.  E. 

Instruetions : — To  plan  and  conduct  a  series 
of  experiments  on  simultaneous  orthogonal 
strains,  with  a  view  to  the  determination  of 
laws. 

(L)  On  Physical  Phenomena. — W.  Sooy 
Smith,  C.  E.,  Chairman,  A.  L.  Holley,  C.  E., 
R.  H.  Thurston,  C.  E. 

Instructions : — To  make  a  special  investiga- 
tion of  the  physical  phenomena  accompanying 
the  distortion  and  rupture  of  materials. 

(M)  On  Re-heating  and  Re-rolling. — Com- 
mander L.  A.  Beardslee,  U.  S.  N.,  Chairman, 
Chief  Eng'r  D.  Smith,  U.  S.  K,  W.  Sooy 
Smith,  C.  E. 

Instructions : — To  observe  and  to  experiment 
upon  the  effects  of  re-heating,  re-rolling,  or 
otherwise  re-working  ;  of  hammering,  as  com- 
pared with  rolling  and  of  annealing  the  metals. 

(N)  On  Steels  produced  by  Modern  Pro- 
cesses.— A.  L.  Holley,  C.E.,  Chairman,  Chief 
Eng'r  D.  Smith,  U.  S.  N.,  W.  Sooy  Smith,C.  E. 

Instructions : — To  investigate  the  constitution 
and  characteristics  of  steels  made  by  the  Bes- 
semer, open  hearth,  and  other  modern  methods. 

(O)  On  Steels  for  Tools.— Chief  Eng'r  D. 
Smith,  U.  S.  N. ,  Chairman,  Commander  L.  A. 
Beardslee,  U.  S.  N.,  W.  Sooy  Smith,  C.  E. 

Instructions  : — To  determine  the  constitution 
and  characteristics,  and  the  special  adaptations 
of  steels  used  for  tools. 


RAILWAY  NOTES, 

Steel  Rails  for  California. — It  is  gratify- 
ing to  know  that  the  Pacific  Coast,  which 
has  never  felt  the  effects  of  our  great  panic, 
is  coming,  to  the  rescue  of  the  Eastern  iron 
trade.  Recently  the  Southern  Pacific  Railroad 
Company  of  California  contracted  with  the 
Pennsylvania  Steel  Company  and  the  Bethle- 
hem Iron  Company  for  10,000  tons  of  steel 
rails — 5,000  from  each  company — to  be  used 
in  continuing  the  line  of  the  road  south  of  Los 
Angeles  in  the  direction  of  Fort  Yuma,  the 
southern  terminus  of  the  road,  at  the  junction 


92 


VAN   NOSTEAND  S   ENGINEEEING   MAGAZINE. 


of  the  Colorado  and  Gila  Rivers.  The  distance 
by  rail  from  San  Francisco  to  Fort  Yuma  is 
722  miles.  At  Fort  Yuma  the  Southern  Pacific 
will  connect  with  the  Texas  Pacific  (Col. 
Scott's  road),  and  farther  north,  at  Fort  Mo- 
have, on  the  Colorado  River,  another  eastern 
connection  is  expected  to  be  made  in  time. 
The  steel  rails  ordered  are  to  weigh  50  pound 
to  the  yard,  and  the  quantity  ordered  will  lay 
100  miles  of  single  track,  including  sidings. 

The  rails  will  be  shipped  to  Jersey  City  by 
rail,  and  thence  by  sailing  vessels  around  Cape 
Horn  to  San  Francisco .  The  freight  from  San 
Francisco  will  not  exceed  $10  a  ton,  and  is  ex- 
pected to  be  a  dollar  or  two  less.  The  rails 
will  serve  admirably  as  ballast  for  light  car- 
goes. 

We  hope  that  this  transaction  may  be  but 
the  beginning  of  a  large  trade  in  steel  rails  and 
iron  and  steel  products  generally  between  the 
east  and  the  Pacific  coast.  The  states  and 
territories  of  the  Pacific  slope  consume  annual- 
ly about  300,000  tons  of  iron  in  all  forms,  and 
until  they  are  ready  to  make  their  own  iron 
and  steel  it  would  certainly  be  wise  for  them 
to  buy  their  supplies  from  sister  states  rather 
than  from  foreigners.  They  will  thus  save 
money  and  be  better  served.  Heretofore  Cali- 
fornia has  been  a  large  importer  of  iron  and 
steel  products.  In  the  fiscal  year  ended  June 
30,  1874,  her  imports  of  these  articles  aggre- 
gated $1,555,000. — Bulletin  Iron  and  Steel  Asso- 
ciation, 

Brake  Trials. — The  Royal  Commission  on 
Railway  Accidents,  which  has  lately  been 
taking  evidence  in  different  towns  in  the  coun- 
try upon  means  for  diminishing  the  frequency 
of  disasters  on  the  iron  highways  of  the  coun- 
try, have  asked  the  Railway  Companies'  Asso- 
ciation to  make  experiments  with  continuous 
brakes.  The  Railway  Companies'  Association 
has  consented,  and  a  piece  of  level  line  on  the 
Nottingham  and  Lincoln  branch  of  the  Mid- 
land Railway  has  been  selected.  Several  con- 
tinuous Drakes  will  be  brought  forward  for 
trial — amongst  them  the  Westinghouse,  the 
Barker  brake,  Clark's  chain  brake  as  improved 
by  Webb,  vacuum  brakes,  and  others.  Mr. 
Edward  Woods,  C.  E.,  of  Westminster,  has 
been  appointed  to  conduct  the  trials,  and  Col- 
onel Inglis,  R.  E.,  is  associated  with  him. 
The  experiments  commence  on  the  9th  proxi- 
mo, and  we  believe  every  care  will  be  taken  to 
render  the  tests  exhaustive,  both  for  the  infor- 
mation of  the  Royal  Commission  and  for  the 
guidance  of  railway  managers  and  engineers. 
To  carry  out  such  a  series  of  tests  as  will  settle 
the  question  as  to  which  is  the  best  continuous 
brake,  can  be  no  easy  matter,  but  due  precau- 
tions will,  we  hope,  tie  taken  to  secure  a  good 
result. 

.  .       ENGINEERING  STRUCTURES. 

ENGINEERING  PROJECTS  IN  EGYPT.  —  An 
Egyptian  correspondent,  writing  recently, 
says  :  "  The  Soudan  Railway  is  being  rapidly 
pushed  forward.  Various  schemes  are  also 
under  consideration  for  the  better  irrigation  of 
Lower  Egypt.     One  proposal  is  for  the  con- 


struction of  a  series  of  locks  and  weirs  on  the 
existing  canals,  which  during  high  Nile  are  so 
many  deep  and  rapid  rivers.  Another  is  for 
the  construction  of  canals  taken  from  a  high 
level  on  the  river,  in  upper  Egypt,  and  distri- 
buting the  water  thus  obtained  over  the  sur- 
face of  the  Delta.  But  it  must  be  remembered 
that,  great  as  is  the  volume  of  water  in  the 
stream,  it  is  precisely  when  the  river  is  at  its 
lowest  that  the  cotton  crop  requires  most  irri- 
gation. Perhaps,  after  all,  the  moderns  could 
not  do  better  than  follow  the  example  of  the 
old  Egyptians  and  construct  another  Lake 
Mceris  as  a  vast  reservoir  for  the  surplus 
waters;  at  all  events,  his  Highness  has  at  his 
command  engineering  skill  second  to  none  in 
the  world." 

The  New  Clyde  Graving  Dock.— A  new 
graving  dock  is  being  constructed  at  Salt- 
erscroft,  on  south  side  of  the  Clyde.  The  con- 
tract for  the  dock  was  let  so  far  back  as  1860 
to  Mr.  William  Scott,  who  constructed  the  Al- 
bert Dock,  at  Leith,  but  a  variety  of  causes 
have  prevented  the  execution  of  the  work. 
The  new  dock  is  560ft.  in  length  on  the  floor, 
with  a  depth  of  22ft.  on  the  sill  at  high  water 
of  spring  tides,  and  20ft.  at  neaps.  It  faces  up 
the  river,  and  will  be  closed  by  a  caisson,  con- 
structed by  Messrs.  Hannah,  Donald  &  Wilson, 
engineers,  Paisley.  The  bottom  of  the  dock 
is  of  ashlar,  slightly  convex  in  cross  section, 
with  a  gentle  fall  towards  the  entrance.  The 
coping  and  the  caisson  check  of  the  dock  are 
of  granite,  and  the  remainder  of  the  masonry 
freestone.  The  pumping  station  is  at  the 
north-west  portion  of  the  dock,  the  contractors 
for  this  work  being  Messrs.  Eastons  and  Ander- 
son, of  London.  The  second  dock  is  intended 
to  be  15  ft.  longer  than  the  one  which  has 
been  finished,  its  total  length  being  575  ft. 
The  Parliamentary  engineer  for  the  dock  was 
the  late  Mr.  Duncan,  whose  death  soon  after 
the  act  was  passed  led  the  trustees,  pending 
the  appointment  of  a  successor,  to  entrust  the 
preparation  of  the  contract  plans  and  specifi- 
cations, to  Messrs.  Bell  and  Miller,  civil  en- 
gineers, of  Glasgow,  under  whose  supervision 
the  works  have  been  carrid  out.— The  Builder* 


ORDNANCE  AND  NAVAL. 

AN  interesting  series  of  torpedo  experiments 
against  the  old  Oberon  hulk  has  been  held 
in  Portsmouth  Harbor,  under  the  direction  of 
Captain  Singer,  of  the  Vesuvius.  The  object 
was  to  ascertain  the  respective  explosive  forces 
of  various  preparations  of  gun-cotton.  The 
weights  and  distances  were  in  every  instance 
identical.  The  mine  consisted  of  an  outriggar 
charged  with  100  lb.  of  gun-cotton  discs  firmly 
packed.  This  was  submerged  to  a  depth 
of  10  ft.  at  a  perpendicular  distance  of 
20  ft.  or  something  like  28  'ft.  from  the 
Oberon's  side,  the  intention  of  Captain 
Singer  being  to  make  an  indentation  in  the 
hulk  sufficient  for  the  purpose  without 
destroying  or  sinking  the  target.  The 
bursting  charge  consisted  of  the  same  weight 
of  solid  slabs  of  gun-cotton  fired  by  electricity. 


BOOK   NOTICES. 


93 


So  far  as  could  be  judged  from  the  force  of 
the  detonation,  and  the  volume  of  water  up- 
heaved, the  superiority  would  seem  to  rest 
with  the  compressed  slabs,  but  the  precise 
comparative  result  cannot  be  ascertained  until 
the  Oberon  has  been  examined  in  detail. — En- 
gineer . 


BOOK  NOTICES, 

Useful  Tables  compiled  by  W.  H.  Noble, 
M.  A.,  Captain  Royal  Artillery.  Lon- 
don :  24  mo,  paper.  For  sale  by  D.  Van  Nos- 
trand.     Price  25  cents. 

A  very  excellent  little  set  of  "Useful  Tables" 
containing  "Metric  Measures  of  Weight,"  "  of 
Length,"  and  "  of  Capacity,"  with  the  corres- 
ponding British  Measures  converted  into  metric 
system.  Also,  Tables  of  Comparisons  of  Ther- 
mometer Scales,  Tables  of  Natural  Sines,  Tan- 
gents, Secants,  &c.,  and  Five  Figure  Loga- 
rithms. 

catalogue  of  the  officers  and  students 
of  Columbia  College  for  the  Year 
1874-1875,  being  the  121st  since  its  foundation. 
New  York  :  D.  Van  Nostrand.  1875.  Price 
50  cents,  or  if  sent  by  mail,  67  cents. 

This  the  last  Annual  Catalogue  or  Register 
of  Columbia  College  has  just  been  published. 
It  forms  a  thick  octavo  volume  of  265  pages. 
It  contains  a  list  of  all  the  officers  and  students 
in  the  different  Schools  of  "Letters  and  Sci- 
ence," "Mines,"  "Law,"  and  of  "Medicine," 
with  general  information  as  to  each,  a  detailed 
description  of  each  Department  of  Instruction, 
with  plan  of  the  new  Building  for  the  School 
of  Mines,  the  Course  of  Study,  Rules  of  Or- 
der, Prizes,  Scholarships,  Officers  of  the  differ- 
ent Alumni  Associations,  Honor  Men,  Gradu- 
ates, Degrees,  Scheme  of  Attendance,  Lecture 
■Courses,  Text  Books,  Examination  Papers, 
etc.,  etc. 

A  Course  in  Description  Geometry  for  the 
use  Colleges  and  Scientific  Schools, 
by  Wm.  Watson,  Ph.  D.  4to.  portefolio  cloth. 
London  :  Longman,  Green  &  Co.  1875.  For 
sale  by  D.  Van  Nostrand.     Price  $7.00 

The  contents  of  this  work  comprise  Prob- 
lems of  Position  relating  to  the  Point,  the 
Right  Line,  and  Plane,  the  General  Method  of 
Rotations  ;  the  Method  of  Changing  the  Co- 
ordinate Planes  ;  Plane  Curves  and  their  Tan- 
gents; Curves  of  Error;  Cylinders;  Cones;  and 
Surfaces  of  Revolution;  Tangent  Planes;  Sec- 
tion Planes;  Intersection  of  Surfaces;  Spheri- 
cal Projections;  Developable  Surfaces;  Warp- 
ed or  Skew  Surfaces.  The  text  is  accompan- 
ied by  32  elegant  quarto  plates  engraved  by 
distinguished  European  artists.  The  appendix 
contains  36  stereoscopic  views,  engraved  on 
steel,  by  Rigel,  of  Nuremberg.  The  latter, 
many  of  which  are  elaborately  colored,  are 
designed  to  supersede  for  the  student  the  use 
of  the  eostly  models  generally  employed  to  illus- 
trate this  subject.  It  is  believed  and  hoped  by 
the 'author  that  the  work  will  be  found  the 
most  completely  illustrated  practical  treatise 
on  descriptive  geometry  in  the  English  lan- 
guage. 


Storms  :  Their  Nature,  Classification 
and  Laws.  By  Wm.  Blasius.  Philadel- 
phia :  Porter  &  Coates.  For  sale  by  D.  Van 
Nostrand.     Price  $2.50. 

This  work  will  prove  an  interesting  addition 
to  the  literature  of  Meteorolgy,  whether  it  af- 
fords sound  instruction  or  not.  The  author's 
explanation  of  his  method  in  beginning  his  re- 
searches cannot  be  read  without  feeling  respect 
for  the  opinions  founded  on  such  systematic 
methods.  We  remember  perfectly  the  storm 
in  Middlesex  County,  Massachusetts,  whose 
track  the  author  studied  and  mapped,  and  we 
remember  to  have  adopted  opinions  at  the 
time,  which  the  author  gives  sufficient  reasons 
for  abandoning.  The  chart  of  this  storm, 
which  he  calls  the  West  Cambridge  Tornado, 
forms  a  fitting  frontispiece  to  the  work,  while 
the  description  of  the  debris  along  its  track, 
and  the  author's  analysis  of  it,  forms  the  intro- 
ductory chapter, 

The  theories  of  Redfield,  Espy  &  Dove  are 
all  discussed  and  rejected.  The  views  offered 
as  substitutes  are  urged  in  a  fair  spirit  and  with 
an  abundant  knowledge  of  the   physical  facts. 

The  book  appears  at  a  good  time,  the  wide- 
spread and  growing  interest  in  the  subject  will 
doubtless  insure  a  wide  circle  of  readers.  It 
possesses  one  merit  wanting  in  the  standard 
works  on  Meteorology,  and  that  is  convenient 
size.  There  is  nothing  in  its  dimensions  to 
discourage  the  general  reader  from  attempting 
to  read  this  author  through  ;  at  the  same  time 
the  maps  and  other  illustrations,  without  being 
marvels  of  art,  suggest  a  clear  elucidation  of 
the  subject. 

Plattner's  Manual  of  Qualitative  and 
Quantitative  Analysis  with  the  Blow- 
pipe. From  the  last  German  Edition.  Re- 
vised and  enlarged  by  Prof.  Th.  Richter. 
Edited  by  T.  Hugo  Cookesley.  London  : 
Chatto  &  Winders. 

We  fear  there  is  a  growing  disregard  of  the 
eighth  commandment;  at  least  there  is  a  strong 
bit  of  testimony  to  this  effect  in  this  very  re- 
spectable looking  English  book.  The  title  page 
justifies  the  expectation  of  a  new  translation  of 
the  celebrated  German  work,  but  examination 
proves  it  to  be  an  accurate  copy,  so  far  as  it 
goes,  of  the  excellent  translation  by  Prof.  Corn- 
wall.    (New  York  :  D.  Van  Nostrand,  1872), 

The  preface  is  as  misleading  as  the  title  page. 
We  give  it  entire. 

"A  work  like  the  present  needs  but  a  short 
preface.  A  good  book  on  the  Blowpipe  has 
long  been  wanted  in  England,  and  it  is  because 
of  the  increasing  importance  of  Analysis  by 
means  of  this  instrument  that  I  have  edited 
the  great  work  of  Plattner. 

While  staying,  last  year,  at  the  Freiburg 
Mining  Academy,  Saxony,  I  was  so  impress- 
ed with  the  perfection  to  which  the  use  of  the 
Blowpipe  has  been  brought  by  the  German 
teachers  who  use  Plattner's  work  as  a  text- 
book, that  I  resolved  to  give  English  students 
the  benefit  of  Plattner's  researches. 

The  first  English  translation  of  this  work 
was  issued  in  New  York,  and  I  have  followed 
generally  the  translation  of  the  American  edi- 
tion, omitting,   however,   some  few  portions 


94 


VAN   NOSTRAND  S   ENGINEERING   MAGAZINE. 


which  I  have  thought  superfluous.  I  have  also 
omitted  the  long  list  of  minerals  given  under 
each  heading,  as  iron,  lead,  &c. ,  amounting  to 
several  hundreds  in  the  German  edition.  How- 
ever useful  such  lists  may  be  as  a  mineralogi- 
cal  reference,  still  they  hardly  belong  to  the 
province  of  the  Blowpipe,  The  headings  of 
the  different  combinations,  and  all  the  princi- 
pal minerals,  however  have  been  retained,  and 
their  characteristics  fully  described  as  in  the 
German  original.  I  have  added  a  new  draw- 
ing and  description  of  a  mechanical  blowpipe, 
which  is  the  only  one  which  is  at  once  portable 
and  thoroughly  simple  and  effective.  It  would 
not  have  been  a  very  laborious  or  difficult  task 
for  me  to  have  greatly  reduced  the  size  of  the 
book,  but  I  have  thought  it  better,  as  Plattner 
may  be  justly  called  the  father  of  this  depart- 
ment of  analysis,  to  edit  the  work  in  its  en- 
tirety. 

In  commending  the  volume  to  the  English 
student,  I  need  only  add  that  it  is  by  far  the 
most  complete  work  extant  on  a  subject  both 
of  growing  practical  importance  and  of  ex- 
treme interest," 

Now  this  preface,  brief  as  it  is,  is  very  near- 
ly the  sum  total  of  Mr.  T.  Hugo  Cookesley's 
work  in  connection  with  this  volume,  all  the 
rest  is  Prof.  Cornwall's  translation  ;  abbrevia- 
ted somewhat  but  otherwise  unaltered.  There 
is  not  the  slightest  acknowledgment  of  this 
latter  gentleman's  work  that  we  can  find  in  the 
book,  nor  is  there  any  mention  of  his  name 
save  in  the  last  two  paragraphs  of  the  appen- 
dix where  "Mr.  Cornwall"  is  mentioned  as  a 
person  holding  some  opinions  on  the  subject 
of  qualitative  teste  for  potassa  and  bismuth. 

Even  the  few  definite  statements  of  the  pre- 
face are  affected  with  a  rather  large  personal 
equation.  "A  new  drawing  and  description 
of  a  mechanical  blowpipe"  is  referred  to  as 
though  it  were  an  important  alteration  of 
the  original  work.  The  fact  is,  it  is  only 
a  badly  modified  diagram  of  the  same  in- 
strument described  on  page  7  of  the  American 
edition. 

The  claim  that  the  book  "is  by  far  the  most 
complete  work  extant"  on  this  subject,  is  of 
course  simply  absurd,  in  view  of  the  fact  that 
the  valuable  lists  of  minerals  of  both  Ameri- 
can and  German  editions  are  omitted.  We  can 
see  substantial  reasons  for  suspecting  that  there 
is  no  real  person  claiming  the  name  of  editor, 
but  that  it  simply  is  a  device  of  the  publishers 
to  evade  the  responsibility  of  doing  what  is 
characterized  in  the  preface  as  following  gener- 
ally the  American  translation.  The  work  is 
just  such  as  could  be  done  at  the  printer's  from 
a  copy  of  Prof.  Cornwall's  translation,  with 
the  general  instruction  to  omit  the  lists  of  min- 
eralogical  names  and  symbols  where  the  liabil- 
ity to  error  in  following  copy  was  greater  than 
usual.  No  skilled  labor  in  editing  higher  than 
this,  is  anywhere  apparent  in  the  volume. 

If  there  is  a  T.  Hugo  Cookesley,  the  reputa- 
tion he  has  recently  earned  is  not  enviable. 

A  Grammar  op  Coloring.  By  G.  Field. 
New  edition,  revised.  London  :  Lock- 
wood  &  Co.  For  sale  by  D.  Van  Nostrand. 
Price  $1.00. 


This  is  one  of  the  re-issues  which  are  being 
made  of  a  good  many  of  the  original  treatises 
comprised  in  "Weale's  Series;  "  the  "Grammar 
of  Coloring"  being  that  of  Field,  re-edited, 
with  additions,  by  Mr.  Ellis  A.  Davidson. 
Field's  treatise  must  not  be  confounded  with 
his  wellknown  one  on  color  in  the  wider  sense; 
the  present  treatise  being  an  entirely  practical 
one,  on  tlie  varieties  and  qualities  of  the  pig- 
ments used  in  coloring,  and  the  media  and  (to 
some  extent)  the  processes  of  manipulation  em- 
ployed. A  good  deal  of  what  is  included  un- 
der this  latter  head  is  supplied  by  the  editor, 
who  gives  directions  for  the  preparation  of  pa- 
per, canvas,  and  other  materials  for  paintng  on, 
the  ehoice  and  use  of  brushes,  &c.  ;  and  also 
a  chapter  on  the  characteristic  features  of  the 
various  styles  of  ornament;  the  latter,  however, 
is  only  of  an  empirical  nature,  and  not  intend- 
ed, probably,  to  do  more  than  give  a  general 
notion  of  the  matter  to  decorative  painters. 
Otherwise  the  book  is  a  most  useful  resume  of 
the  properties  of  pigments,  one  for  reference 
rather  than  reading.  In  re-editing,  however, 
it  should  have  been  pointed  out  that  the  old 
division  of  primary  and  secondary  colors 
(which,  as  far  as  pigments  are  concerned,  is  the 
practically  correct  one)  can  hardly  be  alluded 
to  now  without  at  least  a  reference  to  the  new- 
er theory  on  the  subject  evolved  by  Professor 
Church  and  others,  from  the  study  of  the  com- 
binations of  colored  rays,  instead  of  pig- 
ments, and  in  which  green  usurps  the  former 
place  of  yellow  as  a  primary.  The  point  is  of 
more  theoretical  than  practical  importance,  cer- 
tainly ;  but  the  results  arrived  at  in  Professor 
Church's  experiments  are  too  striking  to  be 
passed  over  in  any  book  in  which  the  subject 
is  touched  upon. — Builder. 

ELEMENTS  OP  EUCLID  ADAPTED  TO  MODERN 
Methods  in  Geometry.  By  James  Bryce, 
M.  A.,  LL.  D.,  and  David  Munn,  F.  R.  S.  E. 
London  and  Glasgow  :  W.  Collins,  Sons  &  Co. 
1874. 

The  editors  of  this  improved  edition  of  the 
time-honored  Elements  of  Geometry,  which 
has  held  its  own  as  a  text-book  for  ages  and 
which  is  not  likely  to  be  superseded,  approach 
their  task  with  profound  respect  for  the  vener- 
able author  whose  work  they  aim  at  amending 
in  some  degree.  Any  attempt  to  supplant  it 
altogether  they  strenuously  deprecate.  Not 
only,  they  say,  has  Euclid's  great  work  receiv- 
ed the  approval  of  many  successive  ages,  and 
served  to  connect  the  science  of  the  present 
with  that  of  the  past,  but  even  now,  in  the  ad- 
vanced state  both  of  the  Pure  and  the  Applied 
Mathematics,  it  is  open  to  criticism  on  very 
few  points  ;  and  with  true  conservatism  they 
urge  the  paramount  importance  of  its  retention, 
not  only  as  a  common  standard  of  reference, 
but  also  as  one  by  which  the '  'purity  and  rigo- 
rous character  of  geometrical  demonstrations 
shall  be  maintained,  and  a  true  logical  sequence 
kept  up  in  the  order  in  which  these  are  pre- 
sented to  the  mind  of  the  student."  The  im- 
provements introduced  are  of  three  classes. 
An  attempt  has  been  made  to  incorporate  in 
the  work  certain  geometrical  methods  which 
have  an  important  relation  to  those  of  the 


BOOK  NOTICES. 


95 


modern  analysis,  where  that  could  be  done 
without  abandoning  the  strict  methods  of 
Euclid  ;  the  order  of  the  propositions  has  been 
altered  in  several  cases,  so  as  to  make  the  con- 
nection between  them  more  apparent ;  and  the 
proofs  have  been  shortened  where  that  could 
be  done  without  omitting  any  link  in  the  chain. 
Each  of  the  six  books  used  in  this  manual  is 
followed  by  an  appendix,  in  which  are  placed 
supplementary  propositions  and  a  series  of  the- 
orems and  problems  for  the  exercise  of  the 
student,  gradually  increasing  in  difficulty,  and 
related  as  far  as  possible  to  the  order  of  the 
propositions. 

Principles  op  Mechanics  and  their  Ap- 
plication to  Prime  Movers,  &c.  By 
W.  J.  Millar,  C.  E.  London:  E.  &  N.  Spon. 
1874.  For  sale  by  D.  Van  Nostrand.  Price  $2. 
Mr.  Millar,  who  ably  officiated  as  the  succes- 
sor of  Professor  Rankine  in  the  period  be- 
tween the  death  of  that  eminent  teacher  and 
the  filling  up  of  the  professorial  vacancy,  has 
here  published  a  carefully  revised  abstract  of 
the  lectures  then  delivered  by  him  to  Professor 
Rankine's  Class  of  Civil  Engineering  and  Me- 
chanics. The  area  occupied  by  these  lectures 
was  an  extensive  one,  including  over  fifty  im- 
portant branches  and  a  considerably  larger 
number  of  subsidiary  ones,  such  as  water  and 
steam  power  motors,  naval  and  architectural 
construction,  thermo-dynamics,  water  supply, 
&c.  To  compress  this  into  a  small  manual  re- 
quires very  considerable  power  of  concentra- 
tion, and  the  exercise  of  great  judgment  in  the 
elimination  of  all  matters  not  strictly  essential 
to  the  subject  in  hand.  In  both  respects  Mr. 
Millar's  book  deserves  praise;  and,  on  account 
of  the  qualities  of  this  kind  which  it  displays, 
the  conciseness  and  quantity  of  the  informa- 
tion it  supplies,  and  its  general  correctness,  it 
must  take  a  high  place  as  an  important  addition 
to  tiie  educational  literature  of  the  mechanical 
arts. 

Principles  op  Metal  Mining.  By  J.  H. 
Collins,  F.  G.  S.  Collins'  Elementary- 
Science  Series.  London  and  Glasgow :  W. 
Collins,  Sons  &  Co.  1875.  For  sale  by  D.  Van 
Nostrand.     Price  75  cents. 

This  is  an  excellent  compendium  of  the 
methods  employed  in  an  important  industry, 
and  it  is  the  more  reliable  from  being  the  work 
of  a  practical  miner.  In  his  introduction,  Mr. 
Collins,  although  advising  the  tyro  to  gather 
information  from  books  and  every  other  avail- 
able source,  wisely  insists  that  the  art  of  min- 
ing must,  to  a  great  extent,  be  learnt  at  the 
mine.  Still,  the  practical  miner  will  learn 
much  from  such  a  work  as  the  present,  and  a 
manual  so  complete  and  popular  will  be  espec- 
ially serviceable  at  the  present  time,  when  a 
strong  desire  is  shown  by  the  best  of  the  min- 
ing population  to  attain  a  scientific  know- 
ledge of  their  profession.  Mr.  Collins  com- 
mences with  a  plain  treatise  on  the  geology  of 
the  subject,  and  follows  with  an  exposition  of 
the  practical  department  of  his  art,  describing 
not  only  the  methods,  but  also  the  tools  em- 
ployed, and  noting  the  comparative  value  of 
each.  Apparatus  for  draining  and  ventilation 
also  occupy  one  or  two  chapters,  and  examina- 


tion questions,  a  full  glossary  of  terms,  and  a 
copious  index  are  appended. — Iron. 

An  Elementary  Exposition  of  the  Doc- 
trine of  Energy.  By  D.  D.  Heath, 
M.  A.  Longmans,  Green  &  Co.  For  sale  by 
D.  Van  Nostrand.     Price  $2.25. 

In  this  book  we  have  a  very  good  elemen- 
tary exposition  of  the  Doctrine  of  Energy  ; 
perhaps,  however,  better  adapted  for  the  use 
of  schools  than  for  the  general  public.  In- 
deed, we  are  told  in  the  preface  that  the  work 
was  developed  from  a  set  of  lectures  given  to 
the  senior  classes  of  Surrey  County  School. 

After  dismissing  the  subject  of  fundamen- 
tal units,  the  writer  goes  on  to  dynamical  en- 
ergy, a  subject  which  is  fully  and  fairly  dis- 
cussed. The  author  next  proceeds  to  thermal 
and  other  energies,  and  ends  by  a  brief  ac- 
count of  molecular  theories.  If  we  have  any 
fault  to  find,  it  is  that  undue  preference  seems 
to  be  given  to  the  British  system  of  units, 
while  the  decimal  system  is  overlooked. 

The  author,  as  he  tells  us  in  his  preface,  has 
endeavored  to  give  the  young  student  some 
conception  of  the  possibility  of  explaining  the 
conservation  of  energy  by  the  theory  that  all 
phenomenal  changes  are  really  in  themselves 
changes  of  motion  and  position  among  the 
molecules  or  ultimate  atoms  of  substances  ; 
and  he  adds  the  hope  that  he  has  succeeded  in 
presenting  this  as  exhibiting  a  probable  sur- 
mise, which  may  be  false  without  vitiating  the 
doctrine  previously  developed. 

This  strikes  us  as  being  very  well  put.  The 
conservation  of  energy  would  hold  if  we  im- 
agine the  universe  to  be  composed  of  ultimate 
atoms,  with  forces  acting  in  lines  between 
them  ;  but  should  it  be  found  that  this  last  con- 
ception is  inapplicable  to  portions  of  the  uni- 
verse, as,  for  instance,  the  medium  which  con- 
veys light,  nevertheless  it  does  not  follow  that 
the  conservation  of  energy  does  not  still  hold 
true. — Nature. 

The  Commercial  Handbook  of  Chemical 
Analysis.     By  A.  Normandy.     New  edi- 
tion, enlarged  by  Henry  M.  Noad,  Ph.  D., 
F.  R.S.    London:  Lockwood  &  Co.     1875. 
For  sale  by  D.  Van  Nostrand.     Price  $6.25. 

When  the  late  Dr .  Normandy  first  published 
his  work  on  Commercial  Analysis  the  Adul- 
teration Act  did  not  exist,  and  the  book  was 
chiefly  used  by  chemical  manufacturers  and  by 
the  small  class  of  practical  analysts.  Dr. 
Noad's  enlarged  edition  of  the  work  appears 
very  opportunely,  and  it  will  be  found  to  be 
essential  to  the  analysts  appointed  under  the 
new  Act.  It  contains,  in  alphabetical  order,  a 
concise  list  of  all  ordinary  substances  which 
can  require  to  be  analysed  in  connection  with 
food  and  drink,  and  in  addition  the  methods  of 
analysing  many  substances  which  can  only  be 
required  in  special  manufactures,  or  are  only 
used  as  drugs.  Each  article  commences  with 
an  account  of  the  substance  in  its  pure  state  ; 
this  is  followed  by  a  list  of  the  most  common 
impurities  or  adulterations,  and  then  by  the 
best  means  of  detecting  them.  The  adultera- 
tions of  some  common  commodities  are  some- 
what startling  ;  thus,  bread  may  contain  rye 
and  barley  flour,  oatmeal,  pea  and  bean  meal, 


96 


VAN  NOSTRAND'S  ENGINEERING   MAGAZINE. 


potato  starch  and  rice  flour,  while  of  mineral 
constituents  there  may  he  lime,  alum,  magne- 
sia, ground  soapstone  and  sulphate  of  copper. 
The  substances  sometimes  employed  to  color 
sweetmeats,  liqueurs,  jellies,  &c,  include 
some  of  the  most  fatal  poisons,  such  as  the 
acetate,  arsenite  and  carbonate  of  copper, 
chromate  and  iodide  of  lead,  and  the  sulphides 
of  arsenic  and  mercury.  Indeed,  we  well  re- 
membei  going  over  a  sweetmeat  manufactory, 
and  on  remarking  on  the  bright  yellow  color 
of  some  large  comfits  we  were  told  that  chrome 
yellow  was  employed  to  produce  it,  our  infor- 
mant evidently  having  no  idea  that  the  sub- 
stance is  a  most  virulent  poison.  A  long  arti- 
cle is  devoted  to  the  adulteration  and  fabrica- 
tion of  wines,  and  the  "plastering"  and  "  for- 
tifying" of  sherries  is  discussed  at  length.  In 
all  cases  the  most  recent  results  are  given,  and 
the  work  is  well  edited  and  carefully  written. 
A  glossary  at  the  end  of  the  book  will  be  found 
useful  both  to  the  analyst  and  the  student. — 
Nature. 


MISCELLANEOUS. 

The  exact  period  when  the  art  of  manu- 
facturing glass  was  first  introduced  into 
England  is  not  easily  determined.  It  is  said 
to  have  been  brought  into  the  country  in  1557; 
and  the  finer  sort  of  window  glass  was  then 
made  at  Crutched  Friars,  in  London.  The 
first  flint  glass  made  in  England  was  manu- 
factured at  Savoy  House  in  the  Strand,  and 
the  first  plate  glass  for  looking  glasses,  coach 
windows,  etc.,  was  made  at  Lambeth  in  1673, 
by  Venetian  workmen  brought  over  by  the 
Duke  of  Buckingham.  The  date  of  the  intro- 
duction of  the  art  of  glassmaking  into  Scot- 
land is  more  easily  determined,  because  of 
more  recent  occurrence.  It  took  place  in  the 
reign  of  James  VI.  An  exclusive  right  to 
manufacture  glass  within  the  kingdom  for  the 
space  of  thirty -one  years  was  granted  by  the 
monarch  to  Lord  George  Hay  in  the  year  1610. 
The  right  his  lordship  transferred  in  1627,  for 
a  considerable  sum,  to  Thomas  Robinson, 
merchant  tailor,  London,  who  again  disponded 
of  it  for  £250  to  Sir  Robert  Mansell,  Vice- 
Admiral  of  England.  The  first  manufactory 
of  glass  tt  Scot10 nd,  an  extremely  rude  one, 
was  established  at  Wemyr,s,  in  Fife.  Regular 
works  were  afterwards  established  at  Preston- 
pans  and  at  Leith.  A  bottle  was  blown  at  the 
Leith  glass  works,  January  7th,  1747,  of  the 
extraordinary  capacity  of  105  imperial  gal- 
lons. 

MViolle  considers  that  the  emissive  power 
.  of  the  sun  at  a  given  point  on  its  surface 
will  be  the  relatiou  between  the  intensity  of 
the  radiation  emitted  at  such  point  and  the 
intensity  of  radiation  which  a  body,  having  an 
emissive  power  equal  to  unity  and  carried  to 
the  temperature  of  the  sun  at  the  considered 
point,  would  possess.  So  that  he  defines  the 
true  temperature  of  the  sun  as  the  temperature 
which  a  body  of  the  same  apparent  diameter 
as  the  sun  should  possess  in  order  that  this 


body  having  an  emissive  power  equal  to  the 
average  of  the  solar  surface  may  emit,  in  the 
same  period,  the  same  quantity  of  heat  as  the 
sun.  From  experiments  made  at  different 
altitudes,  M.  Violle  determines  the  intensity  of 
the  solar  radiation,  as  weakened  by  passage 
through  the  atmosphere,  and  finds,  for  the 
effective  temperature  of  the  sun,  2,822  deg. 
Fah.  Investigations  conducted  with  an  acti- 
nometer  by  the  dynamic  method  lead  the  inves- 
tigator to  conclude  that  steel,  as  it  emerges 
from  a  Siemens-Martin  furnace,  has  a  temper- 
ature of  2,732  deg.  Fah.  If  it  be  admitted 
that  the  average  emissive  power  of  the  sun  is 
sensibly  equal  to  that  of  steel  in  a  state  of 
fusion,  determined  under  like  conditions,  it 
appears  that  the  mean  true  temperature  cf  the 
solar  surface  is  about  3,632  deg.  Fah. 

It  appears  from  the  following  that  iron  water 
pipes  have  a  distinct  chemical  value.  Pro- 
fessor Medlock  proved  by  analysis,  several 
years  ago,  that  iron  by  its  action  on  nitrogen- 
ous organic  matter  produces  nitrous  acid, 
which  Muspratt  called  ' '  Nature's  scavenger. " 
The  latter  chemist  found,  as  a  general  result, 
that,  by  allowing  water  to  be  in  contact  with, 
a  large  surface  of  iron,  in  about  forty-eight 
hours  every  trace  of  organic  matter  was  either 
destroyed  or  rendered  insoluble,  in  which  state 
it  could  be  purified  effectually  by  filtration. 
Medlock  found,  on  examining  the  water  at 
Amsterdam,  which  smelt  and  tasted  badly, 
that  the  sediment  charred  on  ignition,  and  was 
almost  consumed,  showing  that  it  consisted  of 
organic  matter.  He  also  found  that  water,  in- 
stead of  taking  iron  from  the  service  pipes, 
before  entering  them  contained  nearly  half  a 
grain  of  iron  to  the  gallon  ;  while  in  the  water 
issuing  from  the  pipes,  there  was  only  an  un- 
weighable  trace. 

Before  entering  the  reservoir,  the  water  hold- 
ing iron  in  solution  formed  no  deposits,  while 
the  water  coming  from  the  pipes,  and  freed 
from  iron,  gave  organic  sediment  above  men- 
tioned. He  then  made  analysis  of  water 
brought  in  contact  with  iron,  and  water  not 
in  contact,  with  the  result  that  the  water  which 
had  not  touched  iron  contained  2.10  grains  of 
organic  matter,  and  0.96  grain  iron;  the  other 
gave  only  a  slight  trace  of  both,  showing  plain- 
ly that  the  organic  matter  in  the  water  was 
either  decomposed  or  thrown  down  by  con- 
tact with  iron,  and  this  water,  when  filtered, 
was  found  to  be  clear,  of  good  taste,  with  no 
smell,  and  free  from  organic  matter.  It  is  not 
stated  in  what  shape  the  iron  was  held  in  sol- 
ution, but  it  was  probably  in  that  of  carbon- 
ate, the  usual  iron  salt  of  springs. 

Some  weeks  since  a  notice  appeared  in  our 
pages  of  the  use  of  a  plain  disc  for  cutting 
steel  rails  cold.  Mr.  T.  L.  Lewis,  of  Pitts- 
burgh, states  that  for  some  years  past  M. 
Carnegie,  Kloman  &  Co. ,  of  Pittsburgh,  have 
been  using  a  plain  disc  to  cut  large  iron  beams 
cold,  and  since  its  introdnction  there  that 
many  other  American  mills  have  been  using  it 
for  the  same  or  similar  purposes. — Tlie  En- 
gineer. 


VAN     NOSTRAND'S 

ECLECTIC 

EMINEERIM    MAGAZINE. 


NO.  LXXX.-AUGUST,  1875 -VOL.  XIII. 


ON"  RIVER  GAUGING  AND  THE  DOUBLE  FLOAT. 

By  S.  W.  ROBINSON,  Professor  of  MeGhanical  Engineering  in  the  Illinois  Industrial  University. 
Written  for  Van  Nostkand's  Magazine. 


The  double  float,  used  so  extensively 
by  Messrs.  Humphrey  and  Abbot,*  in 
their  investigations  made  between  the 
years  1850  and  1860  on  the  Mississippi 
River,  has  proved  in  their  hands  to  be  a 
valuable  means  of  finding  current  veloci- 
ties. In  the  best  form  used  by  them,  it 
consisted  of  a  hollow  cylinder  (paint  keg 
with  bottom  knocked  out),  ballasted  so 
as  to  have  a  slight  sinking  tendency,  for 
the  lower  part,  and  connected  by  a  cord, 
which  allowed  it  to  sink  to  a  certain 
depth,  to  a  surface  float  only  partly  sub- 
merged, formed  of  a  tin  ellipsoid  bearing 
upon  a  wire  a  small  flag  to  assist  in  ob- 
serving it.f  The  method  adopted  for 
using  these  floats  was  to  put  out  several, 
one  after  another,  from  a  boat  stationed 
in  the  river  and  considerably  above  the 
points  of  observation.  The  time  of  pas- 
sage of  the  floats  between  two  parallel 
cross  sections  of  the  river  was  taken  by 
the  aid  of  two  transit  instruments,  one 
stationed  in  each  section  ;  each  float  was 
observed  across  each  section  by  both 
transits,  so  as  to  be  able  to  locate  the 
points  of  passage  by  triangulation.  The 
sections  were  usually  about  200  feet 
apart.  These  Mississippi  gauging  oper- 
ations appear  to  be  the  first  of  import- 

*  Gen.  A.  A.  Humphrey's,  Chief  U.  S.  Engineers,  and 
Gen.  H.  L.  Abbot,  .Navy  U.  S.  Engineers. 

t  See  Report  on  the  Physics  and  Hydraulics  of  the 
Mississippi  River,  by  Humphrey  and  Abbot,  p.  224. 

Vol.  XIII.— No.  2—7 


ance  in  which  the  double  float  was  used 
as  the  prevailing  means  for  finding  the 
velocity ;  though  Mr.  Chas.  Ellet  had 
previously  used  them  to  some  extent  on 
the  same  river. 

Though  the  double  float  was  suggested 
some  300  years  ago,  and  employed  to  a 
limited  extent,  yet  till  quite  recently  it 
seems  to  have  been  used  only  for  obtain- 
ing surface  velocity,*  the  lower  float 
being  submerged  only  a  few  inches  or 
perhaps  feet.  They  were  made  of  two 
balls  of  wax  connected  by  a  thread,  and 
each  properly  ballasted ;  the  object  of 
their  use  having  been  explicitly  to  get 
surface  velocity,  but  used  in  lieu  of  single 
floats  at  the  surface  for  the  purpose  of 
reaching  such  a  depth  as  to  avoid  influ- 
ence of  air  currents  upon  the  surface, 
and  at  the  same  time  not  exceeding  that 
depth  which  would  give  the  true  surface 
velocity. 

Subsurface,  velocities,  as  such,  were 
first  observed  by  aid  of  Pitot's  tube 
about  in  the  year  1730.  These  experi- 
ments made  known  the  true  law  of  velo- 
cities, previously  supposed  to  increase 
with  depth.f  This  tube  was  also  used 
to  some  extent  and  improved  by  Dubuat  J 

*  Encylopedia  Britannica,  S  ed.  vol.  sii.  p.  142,  aad 
Morins  Bydraliqne,  p.  114. 

t  Memoirs  of  the  French  Academy  for  1732  and 
D'Aubuisson's  Hydraulique,  art.  151. 

iBossut's  Hydraulique,  §  672,  and  D'Aubuisson's  Hy- 
draulique, art.  14S. 


100 


VAN  NOSTKAND' S   ENGINEEKING   MAGAZINE. 


and  Mallet,  and  subsequently  extensively- 
used  and  greatly  improved  by  Darcy.* 
In  the  form  adopted  by  Darcy  it  is  a 
valuable  instrument,  though,  for  a  single 
observation,  it  only  gives  the  velocity  at 
the  moment  a  certain  stopcock  is  turned, 
which  fixes  the  height  of  the  water 
column  until  observed. 

The  early  experiments  with  Pitot's  tube 
on  the  Seine,  not  only  overturned  the  theo- 
ries previously  advanced  by  Guglielmini, 
and  supported  by  others,  but  made 
known  the  fact  that  the  true  mean  ve- 
locity of  a  stream  can  only  be  obtained 
by  measuring  the  velocity  at  various 
parts  of  the  cross  section. 

Various  instruments  were  subsequently 
devised  for  measuring  the  velocity  of 
river  currents. 

Bossutf  and  also  DubuatJ  used  a  pad- 
dle or  float  wheel  with  floats  parallel  to 
the  axis,  and  so  placed  when  in  action 
that  the  floats  dip  an  inch  or  two  into 
the  surface  of  the  stream.  This  was 
long  since  abandoned  as  the  floats  were 
too  much  influenced  by  the  air. 

Zendrini,  Ximenes,  Michelotti,  Gerst- 
ner  and  Eytelwein,§  used  the  Hydro- 
metric  Pendulum,  a  ball  suspended  by  a 
thread,  in  gauging  the  River  Po.  In 
use  the  ball  was  lowered  into  the  cur- 
rent and  the  inclination  of  the  thread 
noted. 

Briinnings  improved  the  Tachometer 
or  pressure  plate,  and  used  it  on  the 
Rhine  in  Holland,  and  Ximenes  on  the 
Arno.||  It  was  also  used  by  Lorgna, 
Michelotti  and  Palette.  Boileau  des- 
cribes a  tachometer  balanced  by  a  spring 
instead  of  weights. 

Racourtl"  used  an  instrument  resemb- 
ling a  ship's  log  in  important  gauging 
operations  on  the  Neva  at  St.  Peters- 
burg. 

Woltmann's  mill,  or  meter,  however, 
is  the  instrument  which  has  been  most 
generally  employed,  and  is  believed  by 
most  hydraulic  engineers  to  be  superior 
to  all  other  means  ever  used  for  deter- 
mining the  volocity  of  running  water.** 


*  Morin's  Hydraulique,  p.  131. 

t  Bossut's  Hydraulique,  §  665. 

i  Morin's  Hydraulique,  p.  98,  and  D'Aubuisson's  Hy- 
draulique, art.  146. 

§  Encylopedia  Britannica,  vol.  xii.,  p.  142,  and  Weis- 
bach  Mech.  and  Eng.,  p.  1,000. 

I!  Brewster,  D'Aubuisson,  arts.  152  and  153,  and  Weis- 
bach,  Mech.  and  Eng.,  p.  1,001. 

H  Encyclopedia  Britannica,  vol.  xii.,  p.  144. 

**  Enc.  Brit.,  vol.  xii.,  p.  144.  Morin's  Hydraul.,  p.  111. 
D'Aubuisson,  art.  150. 


M.  Lapointe*  adopted  a  Woltmann's 
meter  wheel  in  his  gauging  cylinder,  the 
registering  apparatus  being  detached 
and  carried  outside  by  aid  of  level  gear- 
ing. This  arrangement  was  used  in 
elaborate  gaugings  at  the  Powdermill  du 
Bouchet,  and  also  at  the  Bassins  de 
Chaellot.  This  instrument  is  described 
at  length  and  elaborately  illustrated  on 
plate  2,  by  Morin  in  his  Hydraulique, 
and  recommended  for  use.  Woltmann's 
mill  has  been  extensively  used  by  De- 
fountaine  on  the  Rhine,  including  many 
points  of  observation,  and  by  Baum- 
garten  and  Darcy.f  Baumgarten  recom- 
mends it  very  highly.  % 

Krayenhoff,  Buffon  and  Destrem  used 
floats  of  the  form  of  rods  or  poles  so 
loaded  that  they  rode  nearly  vertical  in 
the  stream,  extending  from  the  surface 
nearly  to  the  bottom,  aiming,   by  this 
means,  to  obtain  the  mean  velocity^  at 
once  of  the  longitudinal  vertical  section 
of  the  stream. §     This  plan  was  perfect- 
ed by  J.  B.  Francis,  of  Lowell,  Mass., 
who  used  loaded  tin  tubes  two  inches  in 
diameter  in  straight  and  uniform  flumes. || 
These  experiments  are  among  the  most 
elaborate  and  trustworthy  to  be  found 
recorded,  and  prove  beyond  a  doubt  the 
great  value  and  precision  of  such  floats 
in  cases  where  the  bed  of  the  stream  is 
sufficiently  uniform.     These  floats  give 
very  nearly  the   mean  velocity  for  the  • 
depth  of  the  tube,  without  regard  to  the 
form   of    vertical    curve    of    velocities. 
They  would  give  it  exactly  if  the  resist- 
ance of  a  medium  to  solid  bodies  passing 
through  it  varied  as  the  first  power  of 
the  velocity.     But  varying  as  the  second 
power,  the  true  mean  differs  from  the 
observed  velocity  of  tube  as  pointed  out 
by  Mr.  Francis.    When  the  tube  extends 
nearly  to  the  bottom,  calculation  shows 
that  for  that  depth  the  true  mean  is  less 
than   tube   velocity  by  about  five   per 
cent. 

Hirn  used  sheet  floats  in  small  canals 
which  nearly  filled  the  whole  transverse 
section,  and  thus  obtained,  at  once,  the 
approximate  mean  velocity  of  the  whole 
stream.^" 


*  Morin's  Hydraul. ,  pp.  99  and  100. 
+  Morin's  Hydraul.,  p.  11,  and  D'Aubuisson,  art.  152. 
i  Pants  et  Chaussees  for  1847. 

§  Humphrey's  and  Abbot's  report  on  the  Mississippi, 
p.  202. 
I  Lowell's  Hydraulic  Experiment,  p.  1T2. 
%  Humphrey's  and  Abbot's  Miss,  report,  p.  203. 


ON  RIVER  GAUGING  AND  THE  DOUBLE  FLOAT. 


101 


Those  gaugings  which  are  conceded  to 
be  the  most  important  of  Europe  were 
made  with  Woltmann's  mill,  the  tach- 
ometer, and  Racourt's  ship's  log.  Of 
these  instruments,  the  former  receives 
the  highest  favor,  and  has  been  the  most 
extensively  used. 

In  this  country,  the  double  float  and 
the  Krayenhoff  tube  float,  have  been 
most  used  in  gaugings  of  importance, 
though  various  current  meters  have  been 
employed  from  time  to  time,  and  recent- 
ly they  have  been  rapidly  gaining  favor. 
A  peculiar  telegraphic  meter  was  devised 
and  used  by  Asst.  D.  F.  Henry,*  under 
Gen.  W.  F.  Raynolds,  Supt.  U.  S.  Lake 
Survey,  in  extensive  gaugings  of  the 
rivers  of  the  Great  Lakes  undertaken  in 
1868-9.  This  meter  is  illustrated  and 
described  at  length  in  the  "  Journal  of 
the  Franklin  Institute,"  foi*  May,  1869, 
p.  305.  In  these  gaugings  the  double 
float,  modeled  after  that  used  on  the 
Mississippi,  was  first  adopted,  but  after- 
wards abandoned  as  far  inferior  to  the 
Henry  meter. 

This  sketch  of  the  various  means 
which  have  been  employed  for  measur- 
ing current  velocities  in  river  gaugings 
of  importance,  together  with  the  names 
of  those  hydraulic  engineers  who  adopt- 
ed them  in  individual  cases,  and  of  those 
authors  who  described  and  used  them, 
has  been  given  that  we  may  form  an 
opinion  of  the  relative  merits  of  the  dif- 
ferent instruments  based  on  the  estimate 
placed  upon  them  by  men  of  eminence* 
It  is  clearly  indicated  that  a  current 
meter  or  moulinet  of  some  form  stands 
in  most  universal  favor,  the  Woltmann's 
mill  being  one  of  the  best. 

It  is  evident  that  those  qualities  which 
should  be  possessed  by  a  current  measur- 
er are  :  1st,  accuracy  and  constancy  in 
indications ;  2d,  that  it  give  the  mean 
velocity  for  the  time  during  which  a 
single  observation  is  taken  ;  and  3d,  that 
it  be  convenient  and  reliable.  That 
these  qualities  are  found  possessed  in 
the  highest  degree  in  a  well  constructed 
current  meter  is  made  clearer  by  notic- 
ing a  few  points  of  peculiarity  in  the 
different  instruments,  and  of  difficulties 
in  the  way  of  their  use.  In  all  streams 
there  is  more  or  less  of  eddying,  and  of 
unaccountable  meandering  local  currents 


Now  Chief  Engineer  of  the  Detroit  Water  Works. 


continually  shifting  the  water  in  lateral 
directions.     These  are  liable  to  take  ef- 
fect upon  the  instrument  causing  it  to 
record  a  greater  velocity  than  that  which 
it  evidently  should,  viz. :  the  horizontal 
component.      Pitot's   tube    in    its    best 
form,  as  for  instance  it  was  left  by  Darcy 
gives,  for  one  observation,  the  compon- 
ent parallel  to  the  tube  at  its  open  end 
at  the  instant  the  column  is  fixed.     The 
fluctuations  of  the  column,  however,  are 
reduced   considerably  by  reducing    the 
bore  of  the  tube  at  some  part  to  a  small 
calibre,  by  which  means  the  height  of 
column  is  made   to   represent   approxi- 
mately the  mean  height  for  a  time  more 
or  less  extended,  though  at  best  the  in- 
terval will  be  short.     This  requires  num- 
erous raisings  and  lowerings  of  the  in- 
strument.    In  the  tachometer  we  have 
difficulty  with  the  variation  of  the  pres- 
sure against  the  plate.     The  ship's  log 
is  free  from  this,  but  it  is  liable  to  be  led 
about  in  various  directions  by  the  trans- 
verse currents,  giving  an  erroneous  re- 
sult.    The  double  floats  are  likely  to  be 
subject  each  to  such  lateral  currents  and 
one  float  never  found  above  the  other  ; 
this  inclines  the  connecting  cord  decreas- 
ing the  depth.     The  Woltmann's  mill,  if 
directed  by  a  vane,  will  head  in  various 
directions  and  not  give  the  up-and-down 
stream  component  of    velocity.     In  the 
illustrations,  however,  this  meter  is  rep- 
resented as  attached  rigidly  to  a  pole  or 
rod,  which,  when  rightly  directed,  will 
give  the  desired  component.     The  illus- 
tration of  Henry's  meter  represents  it  as 
directed  by  a  vane.     The  same  is  true  of 
Baumearten's  Velocimeter.   These  should 
be  rigidly  held  in  a  position  directed  up 
stream,  unless  it  can  be  shown  that  the 
lateral  movements  of  the  water  have  no 
appreciable  effect  to  turn  it  out  of  its 
true  course  when  directed  by  a  vane. 

The  objections  above  noticed  are  seen 
to  be  unavoidable  in  every  case,  except 
the  current  meter,  in  its  different  forms. 
As  the  current  meter  is  one  of  the  most 
convenient  instruments  for  use,  there 
seems  to  be  sufficient  cause  for  the  pre- 
vailing preference  for  its  use. 

In  selecting  a  current  meter,  the  best 
form,  of  course,  should  be  adopted.  It 
must  necessarily  have  some  form  of  reg- 
ister. This  is  usually  attached  to  the  in- 
strument and  submerged  with  it,  and 
generally,  in  fact,  regarded  as  part  of  the 


102 


VAN  NOSTEAND'S  ENGINEEEING   MAGAZINE. 


instrument.  But  we  find  an  exception 
to  this  in  the  Henry  meter.  The  meter 
wheel,  in  this,  has  simply  to  break  an 
electric  circuit  at  each  rerolution,  the 
same  being  recorded  by  an  electric  reg- 
ister at  the  surface.  This  separation  of 
the  wheel-work  and  relief  of  the  meter 
wheel  from  the  load  of  driving  them  is 
very  advantageous,  for  the  resistance  of 
the  wheel- work  in  water  of  variable  de- 
grees of  grittiness  must  be  different  at 
different  times,  causing  irregular  indica- 
tions. Also  the  register  being  at  the  sur- 
face, it  is  not  necessary  to  raise  the  meter 
at  each  observation.  From  these  facts 
it  appears  that  the  Henry  telegraphic 
meter  or  moulinet  possesses  advantages 
which  render  it  superior  to  all  other 
means  yet  tried  for  measuring  the  veloc- 
ity of  running  water  in  large  rivers. 

It  is  much  to  be  regretted  that  the 
gauging  operations  on  the  lake  rivers 
were  prematurely  stopped,  preventing 
the  more  thoroughly  testing  of  this  in- 
strument. Enough  was  done,  however, 
to  indicate  its  superiority  over  double 
floats,  with  which  it  was  put  in  experi- 
mental comparison,  and  which  finally  led 
to  the  abandonment  of  the  floats  and  the 
adoption  of  the  meter. 

Careful  comparative  observations  of 
the  floats  and  meter  indicated  almost 
perfect  agreement  at  the  surface,  but  be- 
low this  the  floats  gave  too  high  veloci- 
ties, increasing  with  depth.  These  dis- 
crepancies led  to  the  discovery  of  errors 
due  to  floats  which  Mr.  Henry  pointed 
out  in  substance  as  follows*  :  First,  the 
upper  float  drags  the  lower  increasing  its 
velocity.  Second,  the  pressure  of  cur- 
rent against  the  connecting  cord  increases 
the  velocity  of  the  lower  float  ;  and 
Third,  these  effects  incline  the  cord  down 
stream  and  raise  the  lower  float.  The 
comparisons  indicate  that  a  correction 
should  be  applied  to  gaugings  made  with 
double  floats  by  deducting  about  six  per 
cent. 

The  necessity  of  a  float  correction  be- 
coming evident,  the  writer  was  requested 
to  make  a  mathematical  investigation  of 
the  matter,  the  results  of  which  were 
forwarded  to  Mr.  Henry  some  time  after 
and  published  in  his  pamphlet  on  the 
flow  of  water.  Though  the  analysis  is 
somewhat  complex,  the  correction  found 


*  Pamphlet  on  the  Plow  of  Water,  by  D.  P.  Henry,  p, 
16,  and  Jour.  Tr,  Inst,  for  1871. 


confirms  the  result  obtained  by  experi- 
mental comparison  of  the  float  and 
meter. 

In  the  analytical  problem  a  vertical 
curve  of  velocities  was  required  in  order 
to  determine  the  pressure  of  current 
against  the  connecting  cord.  This  was 
assumed  elliptical  and  agreeing  with  the 
observed  float  velocities.  This  assump- 
tion was  perceived  to  be  illogical,  be- 
cause it  rendered  implicit  the  curve 
which  it  sought  to  correct.  But  this 
was  done  because  the  true  curve  was  un- 
known, the  first  result  being  regarded 
only  as  an  approximation,  giving  a  new 
curve  which  could  be  again  used  for  a 
second  approximation,  &c. 

The  table  below,  taken  from  Mr. 
Henry's  pamphlet,  contains  the  first  cor- 
rections, and  the  ordinates  of  the  result- 
ing curve,  f  q$md  by  aid  of  the  formulas, 
for  an  example  of  double  float  measure- 
ments taken  from  the  report  of  Humph- 
rey's and  Abbot,  p.  230.  The  observa- 
tions were  taken  on  the  Mississippi  River 
at  Carrollton,  La.,  in  1851. 

Computed  Corrections  for  Float  Obser- 
vations. 


Depth  of 

Observed 

Computed 

Difference 

float,  ft. 

velocity. 

velocity. 

0 

4.230 

4.230 

0.000 

18 

4.298 

4.298 

0.000 

36 

4.346 

4.346 

0.000 

54 

4.274 

4.250 

0.024 

72 

4.158 

4.015 

0.143 

90 

4.053 

3.785 

0.268 

102 

3.948 

3.275 

0.673 

110 

Bottom. 

2.670 

These  figures  show  quite  large  correc- 
tions for  the  greater  depths,  and  for  the 
mean  velocity  a  correction  of  about  3.8 
per  cent.  This  correction  falls  some- 
what short  of  that  obtained  by  Mr. 
Henry  in  his  direct  comparison  of  the 
float  and  meter,  a  result  which  may  be 
partly  attributed  to  the  fact  that  the 
second  or  third  corrections  were  not 
computed. 

Since  the  publication  of  Mr.  Henry's 
pamphlet,  the  problem  has  been  thor- 
oughly reviewed,  with  a  view  to  simpli- 
fying the  formulas,  and  of  obtaining 
more  complete  corrections.  Rigorous 
methods  led   to  complex  formulas,  for 


ON   RIVER   GAUGING  AND   THE   DOUBLE   FLOAT. 


103 


which  reason  approximate  methods  have, 
in  part,  been  adopted,  not,  however, 
without  comparing  in  each  case  with  the 
exact  formulas,  the  results  obtained  by- 
computation. 

As  these  formulas  are  of  great  value 
in  discussing  the  double  float  system,  and 
lead  to  a  knowledge  of  the  best  form  of 
double  float  for  practical  use,  they  will 
be  given  here,  together  with  an  example 
to  show  their  application  in  computing 
corrections. 

The  nature  of  the  problem  is  as  fol- 
lows :  The  float  combination,  consisting 
of  the  upper  and  lower  floats  and  con- 
necting cord,  is  supposed  to  be  observed 
when  moving  down  stream  with  a  com- 
mon velocity.  The  weight  of  the  floats 
and  cord  are  supposed  to  be  known,  and 
also  the  approximate  form  of  the  vertical 
curve  of  velocities.  Required  the  velo- 
city of  the  water  at  the  lower  float. 

Let  v0  =  velocity  of  water  at  surface  of 
stream. 
ve  =  velocity    of    current    at    any 
depth  y. 

i\  =  common  velocity  of  float  com- 
bination. 

v2  =  velocity  of  water  at  lower 
float. 

Vm  =  maximum  velocity  of  water  in 
the  vertical  section. 

W=  weight  o#  lower  float  when  im- 
mersed, and  also  assumed 
equal  to  the  tension  of  the 
connecting  cord  at  any  point. 

a1  =  area  of  upper  float  presented 
to  current. 

a2  =  area  of  lower  float  presented 
to  current. 

r    =  radius  of  connecting  cord. 

cx  =  coefficient  found  by  experiment 
giving  pressure  of  current 
upon  units  section  of  upper 
float  at  units  velocity. 

c,  =  similar  coefficient  for  lower 
float. 

c  =  similar  coefficient  for  connect- 
ing cord. 

x  and  y  =  coordinates  of  curve  of 
connecting  cord,  origin  at 
upper  float. 

d  —  depth  of  stream  in  the  longi- 
tudinal section  considered. 


For  a  cylinder*  c  =  .75,  and  resistance 

=  .75  av*. 
For  a  sphere  c  =  .50,  and  resistance 
=  .50  a  v\ 

The  velocity  of  the  water  past  the 
upper  float  is  v0—v1,  and  hence  the  pres" 
sure  of  the  water  upon  it  is 

P=A,  C,  (v-vf  lbs.  (1) 

For  the  lower  float  the  velocity  is 
v1—vi,  and  the  pressure  upon  it  is 


P=A,C,  («,-*,)' 'lbs. 


(2) 


Dividing  the  cord  into  elementary 
lengths  dy,  an  elementary  area  will  be 
2  r  dy,  and  hence  an  elementary  pressure 
against  it  is 


P=C  2r  dy  {v.-v^ 


(3) 


And  the  total  pressure  upon  the  cord 
from  the  surface  to  the  depth  y  is 


SY=2c 


ry 

rl  (ve—v 


Y  dy      (4) 


It  is  to  be  observed  that  the  difference 
vc—v1  changes  its  sign  between  the  sur- 
face and  lower  float,  while  the  square 
does  not ;  so  that  the  integral  between 
these  limits  would  express  the  sum  of 
the  upstream  and  downstream  pressures 
instead  of  difference,  which  is  required. 
This  expression  is  of  the  same  form  as 
that  for  the  moment  of  inertae,  for  which 
the  sum  is  reqired  instead  of  difference, 
and  hence  extreme  limits  admissible.  For 
the  present  case  our  limits  would  be  the 
surface  and  depth  where  vc=v1,  and  then 
the  latter  limit  and  depth  of  lower  float. 
The  difference  of  the  numerical  values 
of  these  two  quantities  is  then  to  be 
taken.  This  leads  to  such  complicated 
expressions  that  they  have  only  been 
used  to  check  the  approximate  formulas, 
and  insure  their  trustworthiness. 

The  velocity  (v0— vj  of  the  water  past 
the  cord  at  various  depths  y,  sometimes 
positive  and  sometimes  negative,  is  the 
distance  from  an  axis  A  B  to  the  true 
curve  of  velocities  DBE,  Fig.  1.  If 
now  the  mean  ordinate  to  this  curve  be 
found,  it  may  be  introduced  into  a  for- 
mula, to  give  an  approximate  value  of 
the  pressure  of  current  against  the  cord. 
Let    this    be    represented    by   (i'n — vj. 


*  Rankine's  Applied  Mechanics,  p.  599,  and  Bennett's 
Morin's  Mechanics,  p.  3T5. 


104 


VAN   NOSTRAND'S   ENGINEERING   MAGAZINE. 


Then 

2  P=2  cr  {v^—v^y  nearly.    (5) 

To  determine  this  mean  ordinate  we 
have 


v*-v,)y=J  {Vo-vjdy.      (6) 


To  find  an  expresssion  for  the  equation 
of  the  curve  of  cord,  we  may  take  mo- 
ments about  any  point  of  it,  of  the  forces 
acting  upon  the  combination  above  that 
point  :  thus 

Wx=(y-y)  2P+«A  (v-vj'y.  (7) 

In  which  y  is  the  depth  of  the  center  of 
pressure  upon  that  part  of  cord  consid- 
ered. To  get  a  simple  expression  for 
others,  it  is  assumed  to  be  at  the  center 
of  gravity  of  the  area  below  A  D  to  the 
depth  considered.     Hence 


Ji 


y^n-^ly^Jiv-v^ydy  (8) 

To  find  the  true  velocity  of  water  «2 
at  the  lower  float,  we  have  by  equating 
the  horizontal  forces  acting  upon  the 
float  combination, 

a*c*  iv-v^=a1o1  (v0-O2  +  2P.    (9) 

Assuming  that  the  vertical  curve  of 
velocities  is  a  parabola  with  its  axis  hori- 
zontal and  some  depth  below  the  surface 
of  stream,  as  done  by  Humphrey  and 
Abbot  and  others,  we  have 

(y-nciy=2F  (vm-ve)       (10) 

for  its  equation,  the  origin  being  taken 
at  the  surface  of  the  stream,  and  at  a 
distance  vm  from  the  vertex.  The  prin- 
cipal axis  of  the  parabola  is  at  a  depth 
nd,  and  2  P  is  the  parameter  of  the  para- 
bola. The  curve  might  be  assumed 
elliptical,  or  of  any  other  form. 

Combining  (10)  with  (5),  (6),  (8)  and 
(9),  we  get 

A 

(vu—v.)y=l    /  (y—ndY\  , 

I/y  J  o y^-v,)-^ 2Y} jay 

-J/  ^       {y—nd)3    n3d3) 

(ii) 

v  v>     o      i  /  \     {y—nciY    n3d3{* 

SP=2c,|K-Ul)-^p___^ 


(12) 


i 


fi  x      1/2/     2nd\      rfd'} 

<*-*.)- p(f— f)-18P 


{vm— vj 


{y-ndy         n3d3 
6Fy 


6T>y    J 


(  ct,ci  i  \        2P  )i   /10\ 


w 


w 


(v-vyy    (H) 


It  is  evident  that  in  all  these  formulas 
which  involve  the  action  of  the  current 
upon  the  cord  or  connecting  line,  such 
values  of  nd  and  2  P  should  be  used  as 
belong  to  the  true  curve  of  velocities  ; 
and  not  such  as  are  found  from  the 
curve  of  observed  float  velocities.  This 
effect  may  be  secured  in  two  ways;  first, 
by  a  series  of  approximating  curves  as 
above  mentioned  ;  or  second,  by  assum- 
ing a  guess  curve  or  parabola,  and  prov- 
ing it  by  a  computation,  using  nd  and 
2  P  as  belonging  to  it.  The  latter  is  in 
effect  the  same  as  the  former — we  guess 
at  the  first  approximation  instead  of  cal- 
culating it. 

In  proving  the  guess  curve  two  com- 
putations must  be  made,  one  to  deter- 
mine the  amount  the  lower  float  is  raised 
by  the  inclination  of  cord,  and  another 
for  the  difference  of  velocity  of  the 
lower  float  and  of  the  current  in  which 
that  float  is  dragged.  The  first  is  repre- 
sented in  Fig.  1  by'CF  and  the  second 
by  F  G.  When  these  are  obtained,  they 
are  to  be  plotted  as  shown  in  Fig.  1,  on 
the  same  diagram  with  the  parabolas. 
Starting  from  C,  if  G  pulls  on  the  guess 
curve,  that  curve  is  the  one  sought,  un- 
less its  figure  be  changed  by  similar  com- 
putations and  plottings  for  other  points. 

The  guess  curve  is  assumed,  for  con- 
venience sake,  to  be  a  parabola  obtained 
by  multiplying  all  the  vertical  ordinates, 
y,  of  the  primitive  parabola  by  a  certain 
constant  fraction  m.      If,  for  instance, 

50 
AC=70  and  AB=50,  m——.      By  so 

I  fO  3 

doing  it  is  to  be  observed  that  B  is  the 
point  where  the  velocity  of  the  stream 
is  the  same  as  the  observed  velocity  of 
the  floats  for  the  particular  cord  length, 
or  supposed  depth  A  C.  This  amounts 
to  estimating  the  position  of  B  and  find- 
ing m.  Then  our  guess  parabola  has 
the  equation 


ON   BIVER  GAUGING   AND   THE  DOUBLE   FLOAT. 


105 


{y—mnd)'t=W  2  P  (vm—ve) 

which  can  be  easily  shown.  If  this  is 
done,  then  these  values  of  mnd,  and 
m*  2  P  are  to  be  used  for  nd  and  2P  in 
equations  (11)  and  (12.) 

If  the  parabola  thus  found  is  believed 
to  represent,  with  sufficient  accuracy, 
the  real  curve  of  velocities,  its  mean 
ordinate,  for  a  depth  d,  is  to  be  com- 
pared with  the  mean  ordinate  of  the 
primitive  parabola  for  a  like  depth,  to 
obtain  the  correction,  per  centum,  for 
the  float  observations  in  the  vertical 
longitudinal  section  of  the  stream  consid- 
ered. It  will,  however,  be  better  to  com- 
pute several  corrections  for  different 
heights  in  the  vertical,  in  the  manner 
shown  in  Fig.  1,  after  which  a  curve, 
parabolic,  elliptical,  or  otherwise,  should 
be  found  which  best  agrees  with  the 
points,  and  it  adopted  for  the  true  curve 
of  velocities. 

The  problem  is  thus  solved  as  far  as 
proposed  in  this  article.  The  formulas 
are  approximate,  but  differ  so  very 
slightly  in  their  results  from  the  thor- 
oughly rigorous  formulas  first  worked 
out,  as  proved  by  very  laborious  compu- 
tions,  that  the  discussions  and  examples 
following  will  be  regarded  as  conse- 
quences of  the  rigorous  formulas  them- 
selves. 

The  formulas  furnish  the  following 
hints  which  should  be  observed  in  con- 
ducting float  observations: 

1ST — CONNECTING  COED. 

The  value  of  (11)  increases  directly  as 
r  or  radius  of  cord.  Hence  the  line  con- 
necting the  floats  should  be  reduced  to 
the  least  possible  value  to  make  the 
pressure  upon  the  cord  a  minimum.  For 
instance,  to  reduce  the  cord  from  0.2  of 
an  inch  to  a  wire  0.01  inch  in  diameter 
reduces  this  pressure  twentyf old.  As  2  P 
in  (13)  is  the  principal  part  of  that  equa- 
tion, we  have  the  velocity  correction 
varying  nearly  in  the  direct  ratio  of  the 
square  root  of  r.  And  similarly  x  varies 
nearly  as  the  first  power,  q  r.  Hence, 
in  every  sense  it  is  essential  to  reduce 
the  diameter  of  the  connecting  line  to 
the  veiy  minimum.  It  should,  therefore, 
be  a  wire,  which,  for  the  usual  dimen- 
sions of  the  floats,  may  safely  be  a  hun- 
dredth of  an  inch  or  less. 


2D — BALLASTING. 

In  (14),  W  is  the  weight  of  the  lower 
float  when  immersed,  or  tension  of  the 
cord,  which  shows  that  to  reduce  z,  the 
falling  back  of  the  lower  float,  W,  should 
be  considerable.  If  x  can  be  so  decreased 
as  to  make  the  rising  of  the  lower  float, 
depending  upon  the  inclination  of  the 
cord  or  line,  inconsiderable,  three-fourths 
of  the  labor  of  computing  corrections 
would  be  avoided.  This  indicates  that 
W  should  be  given  as  large  a  value  as 
practicable  without  unduly  increasing 
the  volume  of  the  upper  part  to  support 
it.  Though  the  latter  increases  the  ve- 
locity correction  as  indicated  by  (13), 
still  the  tenu  involving  a  is  usually  small 
compared  with  the  other;  and  the  value 
of  a,  whether  great  or  small,  makes  but 
little  difference  with  the  labor  of  com- 
puting corrections.  As  W  enters  no 
other  formula,  it  is  evidently  not  good 
policy  to  make  it  excessively  small.  The 
example  given  further  on  will  aid  in  de- 
ciding this  point. 

3D — FOEM  OP  UPPEE  FLOAT. 

It  is  evident  that  its  form  should  be 
that  of  least  resistance,  which  is  a  sphere 
or  ellipsoid. 

Suppose  W  to  be  wholly  resisted  by 
the  buoyancy  of  the  upper  float,  the  lat- 
ter without  weight,  and  a  spheroid  with 
shortest  axis  vertical.  Let  the  half 
depth  =  h,  and  the  horizontal  radius  =  b, 
then 


and 


a=%irbh=jj 


in  which  3  is  the  density  of  the  water, 
the  upper  float  always  being  supposed  to 
be  half  immersed. 

Now  regarding  W  as  constant,  we  see 
that  a  varies  inversely  as  b  the  diameter 
of  the  float.  Hence  the  upper  float 
should  be  a  large  and  flat  ellipsoid  lying 
on  the  surface  of  the  water,  that  a  may 
thereby  be  reduced  to  a  minimum. 

4TH — FOEM  OF  LOWEE  FLOAT. 

As  aa  and  c3  appear  only  in  the  de- 
nominator of  (13),  both  should  be  made 
as  large  as  practicable.  A  hollow  cylin- 
der, like  a  cask  with  both  top  and  bottom 


106 


VAN  NOSTRAND'S  engineering  magazine. 


knocked  out  and   held   upright,   would 
evidently  be  a  good  form. 

These  hints  all  agree  with  statements 
of  Gen.  H.  L.  Abbot,  in  an  article  in  the 
"  Journal  of  the  Franklin  Institute,"*  as 
far  as  made,  except  he  says  the  upper 
float  should  be  minute.  This  would  re- 
quire a  very  small  value  for  W,  and 
hence  give  great  danger  of  the  rising  of 
the  lower  float  to  an  unknown  depth, 
particularly  in  deep  rivers.  /Small  would 
be  sufficiently  superlative. 

AN  EXAMPLE. 

The  following  example  has  been  com- 
pletely worked  out  to  show  the  applica- 
tion of  the  f  ormulas  in  correcting  double 
float  velocity  measurements;  and  not 
only  this,  but  to  make  clear  the  necessity 
either  of  correcting  the  float  observations 
or  of  following  the  hints  brought  out  by 
the  discussion  of  the  above  formulas. 

The  example  selected  is  of  double 
float  observations  taken  at  Vicksburg, 
Miss.,  May  13th  and  Aug.  7th,  1858,  on 
the  Mississippi  River  in  a  depth  of  75 
ft.,  and  is  found  reported  in  the  second 
table  in  page  246  of  the  "  Report  on  the 
Physics  and  Hydraulics  of  the  Missis- 
sippi River,"  by  Humphrey  and  Abbot. 
This  example  is  chosen  because  the  ve- 
locity of  the  river  at  this  point  is  quite 
large,  for  which  it  is  supposed  the  floats 
would  be  most  disturbed,  and  not  be- 
'cause  the  number  observations  at  each 
depth  is  few.  The  sequel,  however, 
shows  that  the  disturbing  influence  of 
swift  currents  is  proportionally  about 
the  same  as  for  less  velocities.  The  data 
for  this  example  as  appearing  on  page 
246  are  given  in  the  following  table, 
together  with  the  ordinates  of  the  para- 
bola which  are  found  to  agree  best  with 
the  float  observations. 

"  sub-surface  velocity  observations  upon 
the  Mississippi  at  its  Highest  Stage, 
the  Depth  being  about  75  feet." 


Depth,  ft. 

Velocity- 
observed. 

Ordinates 
of  Parabola 

Difference. 

0 
40 
50 
60 
70 

7.50 
7.54 
7.29 
7.33 
6.82 

7.50 
7.533 
7.380 
7.162 
6.880 

.000 

+  .007 
-.110 
+  .168 
-.060 

Equation  (10)  gives  the  ordinates  in 
the  third  column  by  making 

nd=2l.2SS,  2P=3097.4,  <ym=7.646. 

A  guess  parabola  is  assumed  which 
starts  from  the  same  point  at  the  sur- 
face, has  the  same  maximum  ordinate 
vm,  and  for  which,  for  any  given  value 
of  vc,  the  value  of  y,  is  only  $  that  of  the 
above  primitive  parabola.  Hence,  for 
this  guess  parabola 

mnd=15.2,  m*  2P=1580.     vm=7.646, 

which  are  to  be  used  for  nd  and  2  P  in 
the  general  equations  (11)  to  (14)  in 
proving  the  guess  parabola.  The  verti- 
cal and  horizontal  corrections  OF  and 
and  F  G,  Fig.  1,  may  be  found  for  any 
point  of  supposed  depth,  say  70  ft.  By 
aid  of  (14)  the  values  of  x,  for  given 
depths  y,  are  computed  ;  which  are  the 
co-ordinates  of  the  curve  the  connecting 
cord  assumes  when  the  float  combination 
has  settled  into  equilibrium  in  the  stream. 
These  are  given  in  the  table  below. 

In  these  computations  definite  values 
for  W,  c,  r,  av  cl5  a2,  and  c2  are  required. 
On  page  224  of  the  Mississippi  Report 
2r=  somewhat  less  than  0.2  inch,  say 
=  .18  inch=.015  ft.  :  a,  =.022  ft.  by 
assuming  the  float  to  be  the  ellipsoid  5  J 
inches  in  diameter  by  1^  inches  deep 
half  immersed,  instead  of  the  half  inch 
pine  board  5j  inches  square,  both  of 
which  were  used  in  1858,  but  which,  in 
this  example,  is  not  stated  :  a2=§  ft.,  it 
being  a  keg  8X12  inches.  But  W  is 
not  given  in  the  report,  and  hence 
must  be  estimated.  The  weight  of  the 
tin  of  ordinary  thickness  ;  solder  ;  flag 
and  wire  for  supporting  it  ;  say  .25  lb. 
The  semi-ellipsoid  would  displace  .42  lb. 
of  water.  Difference  =  W=.11  lb.  The 
values  of  c  are  given  above.     Hence 


a,  c. 


a,  c. 


a.,  c„ 


.022,  2cr=.0112,      -^-  =  .0815. 


*"  Journal  Franklin  Institute  "  for  May,  1873,  p.  308. 


This  curve  is  plotted  to  scale  in  Fig.  2. 
It  is  observed  to  be  somewhat "  S-shaped," 
the  reversing  of  the  curvature  being  due 
to  the  fact  that  the  lower  portion  of  the 
cord  is  itself  dragged  along  more  rapidly 
than  the  water  moves.  The  lower  float 
is  observed  to  be  very  far  from  the  posi- 
tion supposed. 


ON  EIVER  GAUGING  AND  THE  DOUBLE  FLOAT. 


107 


Table  of  Co-ordinates  of  the  Curve  the 
Connecting  Cord  Assumes  in  the  Cur- 
rent. 


Depths  in.  ft. 

Values  of 

y 

aft. 

0 

0 

10 

1.55 

20 

6.90 

30 

14.72 

40 

26.26 

50 

31.92 

60 

34.03 

Now  laying  off  70  ft.  on  the  curve, 
we  find  the  float  to  be  situated  at  Fig.  1, 
and  at  an  actual  depth  of  almost  exactly 
60  feet  only,  including  an  excessive  lift- 
ing of  the  lower  float. 

This  depth,  60  feet,  is  now  to  be  used 
for  the  actual  depth  of  lower  float,  y,  in 
(11)  and  (13),  for  computing  the  velocity 
correction.     This  is  found  to  be 

V1—va  =0.516  ft. 

Laying  this  off  from  F,  Fig.  1,  brings 
us  exactly  to  the  guess  curve  ;  which 
shows  that  this  curve  was  correctly  as- 
sumed, and  hence  we  have  one  point  in 
the  real,  or  corrected  curve  of  velocities. 

The  correction  found  in  a  similar  man- 
ner for  a  cord  of  50  ft.  length  gives  the 
horizontal  displacement  of  float,  £,=2.51, 
which  is  too  small  to  decrease  the  depth 
appreciably.     Then 

v—  ?;2  =0.187  ft. 

Similarly  for  a  depth  of  30  ft. 

v1—va  =0.020. 

These  when  plotted  ought  to  give 
points  on  the  guess  parabola,  but  do  not 
exactly.  Plotting  them,  and  working 
out  a  parabola  which  best  fits  them  all, 
we  find 

nd=\1.32     2P=1500.     vm=7.7. 

Taking  this  and  proceeding  to  a  second 
approximation,  we  get  no  appreciable 
change  in  the  position  of  the  curve  of 
velocities.  The  parabola  is  the  curve 
which  fits  them  best,  confirming  in  this 
case  the  parabolic  law  of  Humphrey 
and  Abbot. 

The  equation  of  the  correct  velocity 


curve,  in  which  vc  represents  the  velocity 
of  current  for  the  depth  y,  is  therefore 

(2/-l7.32)8=1500  (7.7-0 

The  curve,  agreeing  best  with  the  float 
observations  from  which  Messrs.  Humph- 
rey and  Abbot  took  their  mean,  is 

(y-21.283)a  =3097.4  (7.646-<) 

Hent;e  the  actual  mean  velocity  of  the 
river  at  Vicksburg,  in  the  vertical  con- 
sidered, is  the  mean  ordinate  of  the 
above  corrected  parabola  for  a  depth 
t?=75  feet,  which,  found  by  an  equation 
like  that  just  preceding  (11),  is 

Correct  mean  7.148  ft.  per  sec. 

Mean  according  to  the  floats,  and  as  the 
Mississippi  Report  would  have  it,  for  the 
vertical  considered, 

Float  mean  7.458, 

greater  than  the  true  mean  by  over  4.3 
per  cent. 

This  correction  does  not  differ  very 
far,  per  centum,  from  that  found  from 
the  example  quoted  from  Mr.  Henry's 
pamphlet. 

I  wish  to  call  attention,  before  passing 
to  the  resemblance  between  the  above 
computed  corrections  for  the  Vicksburg 
observations,  and  those  obtained  by  Mr. 
Henry  in  his  experiments  on  the  St.  Clair 
River,  both  of  which  are  presented  in 
the  following  :  {See  table  next  page?) 

The  table  explains  itself.  Let  us  com- 
pare the  columns  of  differences.  These, 
we  observe,  are  negative  down  as  far  as 
to  point  of  maximum  velocity,  below 
which  they  are  positive  in  both  cases, 
and  increase  with  depth.  Though  the 
differences  found  by  meter  are  greater 
proportionally  at  mid-depths, — at  points 
near  the  bottom  they  are  nearly  alike. 
But  by  more  careful  inspection  it  is  seen 
that  the  apparent  dissimilarity  at  mid- 
depth  is  more  seeming  than  real.  The 
point  of  maximum  velocity  is  at  a  greater 
proportionate  depth  in  the  Mississippi 
velocities  than  in  the  St.  Clair.  At  propor- 
tionate depths  reckoned  from  this,  there 
is  an  almost  exact  similarity  in  the  pro 
rata  value  of  the  differences,  which  fully 
explains  the  apparent  anomaly,  and  re- 
ally exhibits  a  wonderful  conformity  of 
the  results.  This  would  indicate  that 
the   correction,  per    centum,  would   be 


108 


VAN   NOSTRANITS   ENGINEERING  MAGAZINE. 


Table  of 

Float  Velocities  Compared  with  Actual  Velocities. 

Observations  at  Vicksburg, 

Observations  in  St.  Clair  River, 

Corrects  by 

Calculation. 

Corrected  by  Telegraphic  Meter. 

Ordinates  of 

Ordinates  of 

Depth 

Parabola 
agreeing 

Parabola 
agreeing 

Differ- 

Depth 

Velocity 

by 
Floats. 

Velocity 

by 

Meter. 

Differ- 

feet. 

with 
Float 

with 
Computed 

ence. 

feet. 

ence. 

Observations 

Velocities. 

0 

7.500 

7.500 

.000 

0 

3.619 

3.655 

-.036 

10 

7.605 

7.664 

-.059 

5 

3.759 

3.782 

-.024 

20 

7.645 

7.695 

-.050 

10 

3.703 

3.674 

+  .029 

30 

7.621 

7.593 

+  .028 

15 

3.590 

3.516 

+  .074 

40 

7.533 

7.357 

+  .176 

20 

3.598 

3.405 

+  .193 

50 

7.380 

6.988 

+  .392 

25 

3.637 

3.441 

+  .196 

60 

7.162 

6.486 

+  .675 

35 

3.558 

3.166 

+  .390 

70 

6.880 

5.849 

+1.031 

45 

3.542 

2.985 

+  .577 

75 

Bottom. 

50 

Bottom. 

greatest  in  those  cases  where  the  maxi- 
mum velocity  of  stream  is  nearest  to  the 
surface.  In  the  corrections  to  the  Car- 
rollton  gauging,  given  above,  the  maxi- 
mum velocity  is  at  proportionally  the 
same  depth  as  in  those  of  Vicksburg, 
and  we  find  the  correction  about  the 
same,  per  centum,  regardless  of  the  great 
difference  in  velocity  of  stream. 

These  examples  indicate  that  in  streams 
where  the  maximum  velocity  is  at  about 
a  fourth  of  the  depth,  as  in  the  Missis- 
sippi observations,  the  correction  is  about 
4  per  cent.  ;  and  where  the  maximum 
velocity  is  at  a  seventh  of  the  depth,  as 
in  the  St.  Clair  experiments,  the  correc- 
tion is  about  6  per  cent.  ;  that  is  to  say, 
the  denominator  of  the  fraction  express- 
ing the  depth  of  maximum  velocity,  is 
very  nearly  the  per  centum  rate  of  cor- 
rection for  the  gauging. 

This  rule,  if  more  fully  verified  by 
more  numerous  examples,  would  only 
apply  in  cases  where  the  double  float 
used  is  patterned  after  those  used  on  the 
Mississippi  by  Humphrey  &  Abbot.  If 
the  conclusions  or  hints  above  pointed 
out  as  consequences  of  the  general  for- 
mulas be  carefully  observed  in  designing 
the  float,  the  corrections  may  be  reduced 
to  such  inconsiderable  quantities  as  to  be 
overlooked.  For  instance,  if  a  correction 
of  4  per  cent,  arises  principally  from  a 
cord  0,  2  inches  in  diameter,  a  cord  a 
twentieth  of  that  size  would  require  a 
correction  of  less  than  a  fourth  of  the 


former,  or  less  than  one  per  cent.  This 
is  a  consequence  of  (13)  and  (11),  which 
show  that  the  velocity  correction  varies 
nearly  as  the  square  root  of  the  diameter 
of  the  connecting  line. 

A  wire  filament  a  hundredth  of  an  inch 
in  diameter,  connecting  the  floats,  would 
present  to  the  current,  for  a  depth  of  90 
feet,  an  aggregate  area  of  three  times 
that  of  the  upper  float  of  the  size  and 
form  of  the  tin  ellipsoid  used  in  1858. 
This  shows  the  importance  of  giving  at- 
tention to  reducing  the  resistance  of  the 
connecting  line,  rather  than  that  of  the 
surface  float,  particularly  for  great 
depths,  and  also  the  hopelessness  of  en- 
deavor of  rendering  the  action  of  the 
current  upon  the  line  insignificant  as 
compared  with  the  upper  float  resistance. 

Though  the  dragging  action  of  the  up- 
per float  upon  the  lower  appears  to  have 
been  considered  while  the  Mississippi 
observations  were  going  on,  as  indicated 
by  the  fact  that  observations  were  made 
to  ascertain  the  effect  of  the  wind  upon 
the  upper  float  to  drive  the  combination 
about ;  and  as  also  evinced  by  the  reduc- 
tion of  the  area  presented  by  the  upper 
float  from  12  square  inches  to  3  square 
inches  between  the  observations  of  1851 
and  1858  ;  yet  the  effect  of  the  connect- 
ing cord,  nearly  a  quarter  of  an  inch  in 
diameter,  appears  to  have  been  entirely 
ignored. 

A  cord  0,  2  of  an  inch  in  diameter, 
stretched  through  a  depth  of   90   feet, 


AIR  AND   VENTILATION. 


109 


would  present  to  the  current  an  area  of 
216  square  inches.  The  largest  upper 
float  used  presented  only  12  square  in- 
ches, an  insignificant  quantity  compara- 
tively. The  largest  lower  float  used  was 
10  X 15  inches,  presenting  an  area  of  150 
square  inches,  giving  a  total  of  both 
floats  of  162  square  inches  ;  an  area  only 
three-fourths  of  that  of  the  connecting 
cord.  It  is  therefore  plain  that  for  these 
depths  the  cord,  itself,  must  have  be- 
come the  prevailing  float  instead  of  the 
float  proper,  the  observations  going  on 
more  after  the  manner  of  the  Krayen- 
hoff  pole  float  type,  than  according  to 
the  double  float  system,  giving,  in  reali- 
ty, no  idea  whatever  of  the  actual  veloc- 
ity, of  the  water  at  the  depth  where  the 
lower  float  was  supposed  to  be.  It  is 
difficult  to  discover  how  the  connecting 
cord  could  have  escaped  the  considera- 
tion of  the  Mississippi  observers,  when 
the  upper  float  received  so  much  atten- 


tion, a  matter  of  comparatively  no  con- 
sequence whatever. 

Since  the  appearance  of  the  float  and 
meter  comparisons,  it  has  been  suggested 
by  several  that  the  connecting  line  be 
reduced  to  a  fine  wire  ;  and  prominent 
among  them  is  Gen  H.  L.  Abbot*  him- 
self, who  is  supposed  to  be  in  a  measure 
responsible  for  the  dimensions  of  the 
float  combination  used  on  the  Mississip- 
pi River.  As  regards  the  suggestion  by 
Gen.  Abbot,  coming  from  a  man  of  his 
good  judgment  and  experience  in  the 
line  of  river  hydraulics,  it  may  be  con- 
sidered as  favorably  supporting  the 
points  made  above  ;  and  in  the  light  of 
the  above  showing,  as  equivalent  to  an 
admission  that  double  floats,  modeled 
after  those  used  on  the  Mississippi,  can-, 
not  give  the  exact  velocity. 

*  Jour.  Fr.  Inst,  for  May,  1873,  p.  308. 


AIR    AND    VENTILATION. 

By  W.  N.  HARTLEY,  Esq.,  F.  C.  S. 
From  the  "Journal  of  the  Society  of  Arts." 


In  the  treatment  of  this  subject,  I 
shall  be  compelled  to  omit  any  consider- 
ation of  the  first  half  of  the  title,  and 
confine  myself  to  ventilation  simply,  or 
I  would  rather  say,  to  the  pollution  of 
air,  and  rendering  of  air  fit  for  breath- 
ing. When  we  analyze  very  carefully 
the  atmosphere  we  find  it  consists  of  one 
volume  of  oxygen  diluted  with  four 
volumes  of  nitrogen,  the  oxygen  being 
an  active  gas,  diluted  with  an  inactive 
gas.  Therefore,  generally  speaking,  air 
has  the  properties  of  oxygen  somewhat 
enfeebled.  Besides  this,  we  have  in  air 
a  small  quantity  of  ammonia  and  a  small 
quantity  of  carbonic  acid  ;  that  is  the 
common  name,  but  the  scientific  name  is 
carbonic  anhydride,  and  it  is  also  called 
carbon  di-oxyde.  Now  the  quantity  of 
carbonic  acid,  as  I  shall  call  it,  is  only 
very  small,  but  nevertheless  it  varies 
very  widely  within  very  small  limits. 
The  properties  of  this  gas  form  the  first 
part  of  my  subject.  To  begin  then  with 
the  properties  of  carbonic  acid,  there 
are  two  which  are  especially  remarkable 


— one  is  the  very  great  weight  of  the 
gas,  and  the  other  is  the  property  it  has 
of  extinguishing  flame.  With  regard  to 
the  sources  of  the  gas.  Before  I  show 
its  properties,  I  will  show  the  sources  of 
this  gas.  First  of  all,  there  is  combus- 
tion ;  and  besides  the  sources  of  the  gas 
I  shall  have  to  refer  to  the  means  by 
which  we  detect  it  when  it  exists  in  any 
considerable  quantity  in  the  air,  for 
which  purpose  lime-water  is  a  very  con- 
venient test.  To  show  that  carbonic  acid 
is  produced  by  combustion,  I  place  some 
clear  lime-water  in  a  jar  in  which  a  gas 
jet  has  been  burnt,  and  you  see  the  lime- 
water  becomes  turbid  in  a  very  short 
space  of  time  from  the  separation  of  the 
insoluble  carbonate  of  lime.  The  next 
source  is  respiration.  This  may  be  easily 
shown  in  the  same  way  by  the  aid  of 
lime-water.  Here  is  an  apparatus  through 
which  I  can  draw  the  air  necessaiy  for 
my  respiration.  First  of  all,  the  air 
passes  through  lime-water,  and  by  so 
passing  through  lime-water  it  will  show 
you  if  there  is  any  considerable  amount 


iio 


VAN  nostrand's  engineering  magazine. 


of  carbonic  acid  in  the  air;  secondly,  the 
air  from  the  lungs  passes  thrqugh  lime- 
water  again,  and  that  will  show  whether 
there  is  any  excess  of  carbonic  acid  in 
the  air  of  the  lungs  over  that  in  the 
ordinary  air.  You  will  see  that  in  one 
of  these  bottles,  the  one  through  which 
the  air  passed,  the  lime-water  is  clear, 
while  that  through  which  my  breath 
passed  is  turbid,  showing  that  the  breath 
is  a  source  of  carbonic  acid.  Then  I 
have  again  to  show  you  the  properties 
of  this  gas  when  we  take  care  to  have  it 
undiluted  with  air,  and  in  order  to  get  it 
undiluted  with  air  as  much  as  possible 
we  prepare  it  from  marble,  and  any 
strong  acid,  such  as  hydro-chloric  acid 
or  sulphuric  acid.  This  apparatus  is 
now  making  carbonic  acid,  and  here  is  a 
vessel  into  which  this  carbonic  acid  is 
evolved.  The  gas  there  you  see  is  color- 
less at  any  rate.  Here  is  another  vessel 
which  also  supplies  me  with  a  certain 
amount  of  carbonic  acid,  and  with  this 
vessel  I  propose  to  show  you  the  power 
that  carbonic  acid  has  of  extinguishing 
flame.  Both  these  experiments  also  ex- 
,  plain  to  you  that  carbonic  acid  is  a  heavy 
gas  ;  in  other  words,  if  the  carbonic  acid 
were  lighter  than  air,  as  there  is  an  open- 
ing in  the  top  of  this  vessel,  it  would 
readily  escape  from  such  a  large  jar  as 
this,  but  as  it  is  a  heavy  gas,  you  may 
remove  the  top  of  the  vessel,  and  the 
carbonic  acid  will  remain  in  it  for  a  short 
time.  To  show  that  there  is  carbonic 
acid  in  this  jar,  I  will  put  a  lighted  taper 
in  it.  You  see  that  it  is  extinguished. 
But  to  show  it  on  a  large  scale,  I  will 
take  a  torch  of  tow  and  set  fire  to  it ; 
you  see  it  is  at  once  extinguished  in  this 
jar  of  gas.  To  show  you  that  it  is  a 
heavy  gas  I  will  inflate  this  small  balloon 
with  air,  and  put  it  into  this  glass,  and 
we  shall  see  whether  the  gas  is  sufficient- 
ly heavy  to  float  the  balloon.  You  see 
it  only  just  floats,  half  way  up  the  glass  ; 
but  if  I  blow  a  soap  bubble  it  will  float 
on  the  top  of  the  gas.  At  any  rate,  you 
see  these  two  effects  of  carbonic  acid — 
first,  that  it  extinguishes  flames  ;  and 
secondly,  that  it  is  a  very  heavy  gas.  I 
have  to  bring  before  your  notice  the  fact 
that  in  the  outside  air  the  carbonic  acid 
is  so  mixed  up  with  the  oxygen  and 
nitrogen  that  the  ah'  practically  over  all 
parts  of  the  world  has  the  same  composi- 
tion ;  and,  although  it  has  not  exactly 


the  same  composition,  yet  the  variations 
are  within  very  small  limits.     Neverthe- 
less, the  air  of  the  mountains  on  the  sea 
shore  of  Sootland  varies  from  the  air  in 
the  streets  of  London,  and  this  variation, 
which  is  occasionally  small,  you  will  see 
is   of    considerable   importance   by   the 
tables  on  the  wall.     These  tables,  which 
are  taken  from  the  analysis  of  Dr.  Angus 
Smith,  show  not  only  the  variation  in  the 
ah-  of  towns  from  the  air  of  the  country, 
but  also  show  the  variations  between  the 
air  of  one  street  and  that  of   another. 
Here  is  the  air  from  various  places  in 
Scotland  on  the  hills.     If  this  table  be 
read  with  the  first  number  as  a  whole 
number,  then  we  must  count  it  as  vo- 
lumes in  10,000  volumes  of  air;  and  that 
will  give  us  3.2  volumes  in  10,000  of  air. 
At  the  bottom  of  the  hills  it  is  3.41  in 
10,000.     Then  we  come  to  London ;  in 
the  parks  and  open  places  the  air  con- 
tains 3.01   volumes  of  carbonic  acid  in 
10,000  ;  on  the  Thames  3.43  in  10,000  ; 
in  the   streets   3.8 — that  was  in  April, 
1864.     Later  on,  in  April,  1869,  we  get 
the  carbonic  acid  in  the  streets  as  4.39. 
In  Manchester  during  fogs,  6. 79,  which 
is  a  considerable  variation  from  Scotland 
on  the  hills.     Then  I  come  to  some  large 
numbers,  which  I  will  not  allude  to  just 
now.     In  this  table  we  have  the  analysis 
of  air  in  duplicate,  so  as  to  ensure  the 
accuracy  of  the  analysis.     In  the  north, 
north-east   and   north-western    districts, 
Dalston,   Hoxton,  Hackney,   St.  John's 
Wood  and  Belsize  Park,  we  have  a  series 
of   analyses  made,   and   the  average  of 
these,  with  that  of  Belsize  Park  omitted, 
gives  us  4.445  in  10,000.     In  the  west 
and  west-central  districts  it  amounts  to 
4.115;  that  is,Woburn  Square,  Tavistock 
Square,   Regent   Street,    Oxford  Street, 
Hyde  Park  and  Sloane  Street.     In  the 
east  and  east-central  it  is  4. 745  in  10,000. 
In  looking  at  these  tables  it  must  strike 
anyone   that  in  the  part   of  the   town 
where   it   is  open,   consisting  of    wide 
streets  and  squares,  with  houses  thinly 
inhabited,  that  is  to  say,  large  houses 
and  no  factories,  the  air  is  considerably 
better  than  in  the  east  of  London,  where 
there  are  crowded  neighborhoods,  such 
as  Bethnal  Green,  and  where  there  are 
narrow  streets  and  manufactories  of  dif- 
ferent kinds.     This,  then,  shows  that  we 
have  considerable  variations   in  the  air 
even  in  one  town,  although  that  town  is 


AIR  AND   VENTILATION. 


Ill 


certainly  the  largest  we  can  take  for  the 
illustration. 

Now,  as  air  is  vitiated  by  carbonic 
acid  produced  by  combustion  and  by 
respiration,  when  a  number  of  people 
are  gathered  together  in  a  room,  what 
becomes  of  the  carbonic  acid  produced 
by  respiration  and  combustion  ?  Fortu- 
nately, the  heavy  gas  is  so  acted  upon 
that  it  ceases  to  be  heavy,  and  rises  to 
the  ceiling,  and  so  we  have  a  natural 
means  of  ventilation.  This  I  propose  to 
show  you  very  shortly.  I  have  here  ar- 
ranged two  little  jars,  which,  I  think, 
will  show  the  same  thing  on  a  somewhat 
smaller  scale.  They  both  contain  car- 
bonic acid.  That  I  will  see  first,  by 
putting  in  a  taper,  when  they  both  ex- 
tinguish it.  I  will  put  them  under  pre- 
cisely the  same  conditions,  except  that  I 
will  warm  the  gas  in  one  jar,  and  to  do 
that  I  will  put  in  a  little  flask  containing 
water,  the  water  in  one  being  hot  and 
in  the  other  cold.  After  a  few  minutes 
I  will  test  them  again  with  the  taper, 
and  see  whether  they  are  in  the  same 
state.  While  that  is  in  operation,  I  will 
show  you  what  becomes  of  the  gas  and 
the  vapor  produced  by  an  ordinary  fire 
or  burning  gas.  That  is  easily  done  by 
confining  the  gas  produced  by  the  com- 
bustion of  a  large  gas  burner  in  an  air 
balloon,  and  the  balloon  will  soon  be  in- 
flated and  rise  to  the  ceiling,  showing  the 
course  the  burnt  gas  would  take.  It  is 
evident  that  the  gas  rises  to  the  ceiling. 
We  have  there  one  natural  kind  of  ven- 
tilation. Now  I  will  show  you  with  the 
tapers  whether  these  two  jars  of  car- 
bonic acid  are  in  the  same  state  as  they 
were  at  first.  The  taper  is  put  out  in 
one,  but  in  the  other  it  still  burns  as 
brightly  as  it  would  in  the  open  air;  the 
carbonic  gas  warmed  by  the  flask  of  hot 
water  has  made  its  escape. 

The  next  fact  I  want  to  show  is  that 
if  air  has  once  been  drawn  into  the  lungs 
and  ejected,  it  is  useless  for  either  respi- 
ration or  combustion.  I  can  show  it  is 
useless  for  combustion,  and  you  must 
take  my  word  for  it  that  it  is  not  fit  to 
breathe.  If  I  extract  the  air  from  this 
jar  and  then  return  it  from  my  lungs 
into  the  jar  again  I  shall  be  able  to  test 
it  with  the  taper,  and  to  see  whether  it 
will  furnish  the  taper  with  sufficient  oxy- 
gen to  cause  it  to  burn.  You  see  the 
taper  is  extinguished,  all  the  oxygen  of 


the  air  has  not  been  taken  out,  as  I  will 
show  you  directly.  The  amount  of  car- 
bonic acid  in  the  expired  breath  is  about 
5  per  cent.  I  have  a  little  phosphorus 
here  in  a  spoon,  and  as  phosphorus  is 
much  more  combustible  than  gas  or  a 
taper  which  will  burn  with  less  oxygen, 
therefore,  if  there  is  still  any  oxygen 
here  I  shall  be  able  to  burn  it  in  the  jar 
— it  does  not  burn  quite  so  brightly  as 
it  did  in  the  open  air,  but  it  still  burns. 

The  next  experiment  is  to  show  the 
deterioration  of  the  air  by  means  of 
combustion ;  in  the  same  way  if  the 
taper  be  burnt  in  the  air,  and  be  allowed 
to  burn  so  as  to  consume  so  much  oxy- 
gen that  there  is  none  left,  it  goes  out. 
But  by  a  little  arrangement  I  can  show 
you  that  there  is  still  oxygen  in  the  air, 
that  it  does  not  consume  it  all.  There  is 
the  taper  burning  in  the  jar,  and  I  will 
close  the  bottom,  and  make  it  air-tight 
by  a  drop  of  water.  This  wire  passing 
into  the  jar  is  getting  hot,  so  that  I  may 
be  able  to  touch  a  piece  of  phosphorus 
in  the  centre.  As  soon  as  the  taper  goes 
out,  I  shall  by  that  means  be  able  to 
kindle  the  phosphorus,  and  show  that  all 
the  oxygen  in  the  jar  has  not  been  used 
up.  Now,  you  see,  the  taper  has  gone 
out,  but  still  that  there  is  oxygen  there 
is  shown  by  the  combustion  of  the 
phosphorus.  The  first  effect,  then,  of 
respiration  and  combustion  on  the  air  is 
to  render  it  unfit  for  respiration  again, 
and  unfit  for  combustion.  We  already 
see  that  the  carbonic  acid  produced  by 
combustion  and  also  by  respiration  to  a 
certain  extent  being  heated,  rises  to  the 
upper  part  of  a  building  ;  and  there  are 
other  means  yet,  besides  this  lightening 
of  the  heavy  carbonie  acid  gas  which 
causes  fresh  air  to  be  introduced  into  a 
house.  Some  experiments  made  by  Fed- 
derson,  of  Leipsic,  show  that  when  there 
are  two  atmospheres  in  two  different 
states,  one  hot  and  the  other  cold,  there 
is  between  these  a  porous  medium  for 
the  passage  of  the  gas  from  the  cold  to 
the  hot  side.  So  that  it  comes  to  this, 
if  we  take  a  tube  and  put  a  porous  plug 
in  the  centre,  and  make  one  side  hot, 
leaving  the  other  side  cold,  the  gas 
passes  from  the  cold  side  to  the  hot  side. 
This  is  found  to  take  place  in  houses, 
where  there  is  a  passage  of  gas  through 
the  walls  of  the  building.  Before  I  al- 
lude to  this  point  further,  I  will  just  give 


112 


VAN   NOSTRAND'S   ENGINEERING   MAGAZINE. 


you  an  illustration  or  two  of  ventilation 
caused  by  the  rising  of  the  heated  air. 
In  every  room  where  there  is  a  chimney 
there  is  a  source  of  fresh  air,  not  down 
the  chimney,  but  through  the  cracks  in 
the  windows  and  doors,  and  by  the  con- 
stant opening  of  doors,  and  thus  fresh 
air  thus  entering  drives  forward  the 
heated  air,  which  has  a  tendency  to  rise, 
and  drives  it  up  the  chimney.  If  we 
have  no  chimney  in  the  room  then  this 
source  of  fresh  air  is  practically  value- 
less, because  there  is  no  escape  for  the 
vitiated  air  ;  and  this  may  be  illustrated 
by  the  jar  which  I  have  here  with  two 
candles.  There  is  an  entrance  for  the 
air  below  by  cracks,  the  jar  being 
raised  1-1 6th  of  an  inch  above  the  glass 
plate.  The  opening  at  the  top  is  like 
the  chimney  in  a  room,  the  fire-place  is 
below,  the  opening  of  the  chimney  is 
below  here,  and  the  taper  bums  steadily 
below  the  chimney.  Here  is  a  faper 
burning  above  what  may  be  called  the 
fire-place  of  the  chimney,  and  as  the 
vitiated  air  rises  to  the  upper  part  in  the 
bell-jar,  it  will  in  course  of  time  vitiate 
the  upper  atmosphere,  and  so  cease  to 
support  combustion,  while  the  lower 
taper  continues  to  bum  as  brightly  as 
ever.  That  is  already  manifest  here  ; 
the  upper  taper  is  languishing,  while  the 
lower  one  is  burning  brightly.  Now  it 
is  out,  the  lower  one  burning  as  brilliant- 
ly as  at  first.  Supposing  we  have  a  con- 
dition of  things  where  we  have  no  chim- 
ney, where  the  source  of  contamination 
is  down  below,  such  as  we  have  in  a  coal 
mine,  we  must  have  fresh  air  entering 
somehow  or  other  ;  if  it  cannot  enter 
from  below,  it  must  enter  from  above. 
That  it  does  enter  from  above  is  shown 
here,  where  I  have  what  may  be  repre- 
sented as  a  cellar  or  coal  mine,  this  one 
tube  representing  the  chimney  of  the 
cellar,  and  the  other  tube  a  staircase 
into  it,  or  representing  the  up-cast  and 
down-cast  of  a  mine.  That  there  is  a 
draft  down  one  chimney  and  up  the 
other  may  be  shown  by  the  smoke  trav- 
eling down  the  left-hand  and  out  of  the 
chimney  where  the  light  is.  By  stop- 
ping the  down-shaft  we  may  extinguish 
the  light — the  light  is  extinguished  by 
reason  of  the  want  of  air.  That  illus- 
trates the  ventilation  of  mines;  and  here 
is  an  apparatus  which  illustrates  it  much 
better,  because  this  represents  more  near- 


ly what  is  the  actual  state  of  things,  A 
bell-jar  with  a  chimney  at  the  top,  in 
other  words  a  mine  with  a  short  shaft,  is 
closed  at  the  bottom  so  as  to  make  it 
air-tight,  with  a  little  water,  and  after  a 
time  you  will  see  the  taper  will  by  no 
means  burn  very  brilliantly.  It  is  not 
necessary  for  fresh  air  to  go  down  a 
separate  shaft  into  a  mine  or  cellar,  but 
it  may  go  down  the  same  shaft  by  which 
the  foul  air  escapes;  but,  in  order  to 
effect  that,  if  the  air  is  perfectly  still, 
the  shaft  must  be  divided,  and  that  I 
propose  to  do  as  soon  as  the  taper  begins 
to  languish.  I  will  then  introduce  a 
division,  which  will  cause  the  fresh  air 
to  enter  down  one  side  and  the  foul  air 
to  escape  by  the  other.  The  taper  is 
now  beginning  to  die  out;  by  interposing 
that  division  I  shall  cause  it  to  revive. 
It  takes  a  little  time  for  the  currents  to 
establish  themselves.  Now,  with  a  piece 
of  brown  paper,  which  gives  me  a  supply 
of  smoke,  I  will  now  find  out  which  is 
the  down-shaft  and  which  is  the  up — 
down  which  side  the  fresh  air  is  entering 
and  which  side  the  foul  air  is  escaping. 
We  have  here  very  plainly  shown  the 
action  of  currents  produced  by  the  heat- 
ing of  the  gases. 

Now,  the  next  part  of  the  subject,  the 
ventilation  of  a  house  by  means  of  the 
passage  of  air  through  the  walls,  can  be 
shown  in  an  exaggerated  form  by  the 
passage  of  hydrogen  through  a  porous 
material.  This  is  not  to  be  considered 
by  any  means  what  takes  place  in  a 
house,  that  is  to  say,  we  have  not  the 
passage  of  hydrogen,  but  we  have  a 
passage  of  cold  air  through  the  walls  of 
a  room  into  the  house,  and  this  experi- 
ment is  made  with  hydrogen  simply,  be- 
cause it  is  more  easily  shown  to  you 
than  by  any  other  means.  Here  is  a 
porous  vessel  which  may  be  taken 
roughly  to  represent  the  wall  of  a  house, 
and  if  I  bring  this  jar  of  hydrogen  gas 
over  the  porous  vessel,  you  will  notice 
the  passage  of  the  gas  through  the 
porous  vessel  causes  a  pressure  into  this 
vessel,  which  ejects  a  stream  of  liquid. 
It  has  been  proved,  by  experiment,  by 
Pettenkofer,  of  Munich,  that  the  passage 
of  air  through  the  wall  of  a  house  is 
very  considerable.  He  examined  the 
walls  of  an  ordinary  room  in  his  own 
house,  and  found  the  change  of  air 
through  the  brick  walls  in  a  room,  the 


AtE  AND  VENTILATION. 


113 


cubic  contents  of  which  were  2,650  feet, 
when  the  difference  between  outside  and 
inside  amounted  to  34°  F.,  amounted  to 
this: 

Cubic  feet. 


With  a  fire 

All  crevices  stopped 

With  a  difference  of  7°  Fah . . 
Window  open  8  feet  square . . 


2,650 
3,320 
1,060 
780 
1,060 


This  illustrates  what  takes  place  in  win- 
ter, when  one's  repugnance  to  cold  air 
causes  one  to  shut  the  doors  and  windows 
and  have  a  roaring  fire.  The  air  which 
cannot  get  in  by  crevices  or  by  doors 
makes  its  way  through  the  walls,  that  is 
to  say,  the  doors  and  windows  being 
shut,  a  certain  increased  amount  of  air 
passes  through  the  walls  into  the  room. 
What  is  the  advantage  of  this?  It  is 
this,  that  we  are  supplied  then  with 
fresh  air  free  from  draft.  Ventilation  is 
not  supplying  fresh  air,  but  supplying  it 
free  from  draft,  and  this  natural  source 
of  ventilation  gives  us  really  true  venti- 
lation. The  amount  of  carbonic  acid  in 
the  air  may  be  taken  on  an  average  as 
about  4  parts  in  10,000,  and  in  order  to 
keep  the  air  fresh  we  should  not  allow 
the  pollution  of  the  air  to  extend  to  a 
greater  quantity  than  2  parts  in  10,000 
over  this.  Therefore,  the  extreme  of 
carbonic  acid  in  the  air  is  6  parts  in 
10,060.  When  the  amount  is  more  than 
this,  the  air  begins  to  be  close,  that  is 
to  say,  we  begin  to  .feel  by  the  nose 
that  there  is  a  certain  pollution  in  the 
air  which  you  cannot  exactly  account 
for.  Six  volumes  in  10,000  is  the 
amount  of  carbonic  acid  which  is  allow- 
able, and  all  above  this  must  be  consid- 
ered unwholesome  vitiation  of  the  atmos- 
phere. Then,  in  close  places,  that  is  to 
say,  in  places  which  contain  more  than 
6  volumes  in  10,000,  of  which  there  are 
many — workshops,  offices,  public  build- 
ings, theatres,  all  contain,  generally 
speaking,  much  more  than  this — we  have 
an  atmosphere  which  can  be  known  as 
unwholesome  simply  by  the  nose.  The 
nose  tells  us  there  is  something  in  the 
air  which  ought  not  to  be  there.  What 
is  the  reason  of  this  ?  It  is  not  carbonic 
acid,  because  we  cannot  detect  carbonic 
acid  by  the  nose.  It  is  a  certain  amount 
of  organic  matter  thrown  off  from  the 
lungs,  and,  generally  speaking,  from  the 
body  in  some  form  or  other,  and  this 
Vol.  XIII.— No.  2—8 


organic  matter  rises  in  proportion  direct- 
ly with  the  carbonic  acid.  Therefore, 
if  we  measure  the  amount  of  carbonic 
acid  in  the  air  we  measure  the  amount 
of  pollution  by  organic  matter,  and  by 
determining  the  carbonic  acid  in  the  air, 
which  we  can  do  very  accurately  by 
chemical  analysis,  we  also  determine  the 
amount  of  organic  matter  which  vitiates 
the  air.  We  do  not  know  the  organic 
matter,  but  we  know  there  is  more  than 
there  should  be.  In  buildings  in  which 
the  natural  ventilation  is  not  allowed 
free  play,  and  in  which  no  extensive  me- 
chanical appliances  are  used  to  contrib- 
ute fresh  air,  this  vitiation  of  the  atmos- 
phere goes  on  to  a  very  great  extent. 
For  a  few  examples  of  this  we -have  the 
analyses  made  by  Dr.  Angus  Smith,  and 
we  find  by  this  table  that  in  workshops 
he  has  found  the  air  so  bad  that  it  rose 
as  high  as  30  parts  in  10,000;  that  is  to 
say,  the  carbonic  acid  was  very  nearly 
ten  times  as  much  as  it  should  have 
been.  In  theatres  he  found  it  rose  to  32 
volumes  in  10,000  of  air,  in  mines  78*5, 
an  enormous  quantity,  and  the  largest 
amount  he  ever  found  was  250  in  10,000. 
Here  is  a  table  giving  an  analyses  of  air 
in  different  places,  made  by  Dr.  Angus 
Smith.  In  a  Chancery  Court,  seven  feet 
from  the  ground,  with  the  doors  closed, 
he  found  the  proportion  was  19*35  car- 
bonic acid  to  10,000;  in  the  same  court, 
three  feet  from  the  floor,  20*3;  in  the 
same  building  with  the  doors  open,  that 
is  to  say,  when  the  fresh  air  had  entered, 
it  was  5 "07  and  4*5.  Then  in  the  Strand 
Theatre,  in  the  gallery  it  was  10*1,  in 
the  boxes  11*1;  in  the  Surrey  Theatre  at 
12  p.  m.,  21*8;  in  the  Olympic,  8*17;  in 
the  Olympic  in  the  boxes,  10*14;  in  the 
Haymarket,  7*5,  and  so  on.  In  hospitals, 
where  great  care  is  taken  to  have  large 
free  space  in  the  room  for  each  patient, 
and  a  supply  of  fresh  ah*  regularly  ad- 
mitted, the  amount  does  not  rise  above 
that  of  the  outside  air.  In  the  Queen's 
Ward  of  St.  Thomas'  Hospital  no  more 
than  in  the  outside  air;  in  Edward's 
Ward  of  the  same  hospital  it  was  5*2. 
These  tables  show  the  large  vitiation  of 
air  taken  in  crowded  buildings,  and  in 
the  case  of  the  low  courts  it  was  almost 
as  bad  as  any.  "  There  was  another  case, 
in  the  Queen's  Bench,  in  which  the  air  is 
described  by  Dr.  Angus  Smith  as  the  foul- 
est air  that  he  ever  found  above  ground. 


114 


VAN   NOSTRAND'S   ENGINEERING   MAGAZINE. 


It  seems  that  law  courts  were  always 
famous  for  being  filled,  with  foul  air.  In 
1796,  Brahman,  the  inventor  of  the 
patent  locks,  who  was  giving  evidence 
in  a  Chancery  suit  connected  with  one 
of  James  Watt's  patents,  complained 
that  he  could  not  give  his  evidence 
because  he  was  "  much  incapacitated  by 
those  alkalescent  and  morbific  exhala- 
tions ever  consequent  on  large  and  close 
assemblies,"  no  doubt  the  carbonic  acid 
and  the  organic  matter;  and  he  com- 
plained that  the  judge's  attention  had 
"  become  flaccid  through  fatigue."  This 
is  really  because  of  the  small  amount  of 
air  which  is  allowed  to  each  person  in 
the  building — that  is  to  say,  the  small 
cubic  space  which  is  available  for  each 
person's  use — and,  furthermore,  that  the 
amount  of  wall  space  is  very  small  com- 
pared with  the  production  of  carbonic 
acid  in  the  interior  of  the  building.  In 
summer,  when  the  difference  between 
the  temperature  of  the  inside  and  outside 
of  a  building  is  small,  it  is  quite  possible 
in  a  crowded  room  like  a  ball-room  for 
the  air  to  be  more  vitiated  than  in  win- 
ter. Therefore,  in  theatres  in  summer 
we  may  look  for  a  greater  vitiation  of 
the  atmosphere  than  in  winter,  when 
the  difference  between  outside  and  inside 
temperature  is  much  greater.  Acting 
upon  this,  last  year  I  made  some  experi- 
ments at  the  two  Italian  Operas,  Cov- 
ent  Garden  and  Drury  Lane,  and  from 
several  experiments  made  in  each  case,  I 
found  the  following  numbers:  April 
28th,  Covent  Garden  amphitheatre, 
amount,  22*5  in  10,000  of  air,  near  what 
is  called  a  ventilator,  although  the  air 
which  was  admitted  was  not  pure,  it 
was  17*6,  and  near  an  open  door  it  was 
14*8.  The  people  in  the  building  were 
listless  and  gaping,  and  evidently  want- 
ing in  attention  somewhat,  and  did  not 
seem  to  be  lively  and  animated,  and 
they  exclaimed  how  delightful  was  the 
fresh  air  coming  in  from  an  open  door, 
yet  this  fresh  air  contained  4*8  volumes 
of  carbonic  acid  in  10,000.  In  Drury 
Lane  the  average  of  three  analyses  was 
25'9.  You  must  not  think  that  because 
these  were  taken  in  the  upper  part  of 
the  house  that  down  below  there  was 
any  great  difference.  In'  a  private  box, 
for  instance,  the  space  is  so  enclosed 
that  the  air  very  often  there  is  worse 
than  in   the   gallery,  especially   at  the 


back  of  the  box.  In  the  stalls  of  Cov- 
ent Garden,  between  the  acts,  when  the 
curtain  is  down,  the  air  is  then  very  hot 
and  very  impure.  I  have  not  made  an 
analysis  of  that,  but  one  can  feel  it  when 
the  curtain  is  down;  the  supply  of  fresh 
air  is  practically  cut  off,  because  the 
supply  of  fresh  air  comes  from  behind 
the  scenes,  all  other  entrances  being 
carefully  closed  by  swing  doors,  and 
there  being  a  great  want  of  openings  to 
supply  fresh  air  from  the  outside.  There 
is  no  doubt  the  large  amount  of  gas 
burnt  in  a  theatre,  if  ventilation  had  free 
play,  would  considerably  facilitate  the 
entrance  of  pure  air.  We  have  heard 
great  complaints  about  public  offices, 
more  especially  the  British  Museum; 
and  last  summer  I  made  some  experi- 
ments on  the  air  of  an  office  of 
which  great  complaints  had  been  made, 
namely,  in  the  money-order  office  in 
Aldersgate  Street.  In  one  room  where 
there  were  a  large  number  of  clerks,  a 
tolerably  high  room,  with  large  windows, 
the  proportion  was  22.2  and  something 
over,  in  fact  it  reached  up  to  25,  this 
being  the  average  of  two  or  three  analy- 
ses. This  is  as  bad  as  a  theatre.  In  the 
same  office,  on  another  occasion,  without 
the  gas  lighted,  it  was  17 '6.  In  the 
same  office,  with  the  windows  open, 
there  were  4*2  volumes,  that  is  to  say,  it 
was  practically  the  outside  air.  This 
gives  you  a  tolerable  notion  of  the 
amount  of  carbonic  acid,  and  conse- 
quently the  amount  of  pollution  in  the 
air  in  various  buildings. 

Now,  with  regard  to  the  amount  of 
fresh  air  which  is  necessary  for  each 
person.  This  is  far  more  considerable 
than  you  would  imagine.  The  amount 
of  carbonic  acid  given  off  by  an 
average  size  man  in  an  hour,  from 
the  lungs  and  skin,  is  about  7-10ths 
of  a  cubic  foot,  and  if  we  take 
it  at  6-10ths  we  shall  be  below  the 
quantity.  A  good  oil  lamp,  or  a  couple 
of  good  candles,  will  also  give  6-10ths 
of  a  cubic  foot.  Therefore,  a  man  in  a 
room  with  a  lamp  or  two  candles,  gives 
one  and  one-fifth  of  a  cubic  foot  in  an 
hour.  Now  I  have  told  you  before  that 
the  amount  of  allowable  pollution  in  the 
air  was  6  volumes  in  10,000;  beyond 
that  the  atmosphere  becomes  unwhole- 
some. Therefore,  in  order  to  keep  the 
air  fresh  with  two  men  in  a  room,  or  one 


AIR  AND  VENTILATION. 


115 


with  a  lamp  or  two  lighted  candles, 
would  have  to  require  this  amount  of 
carbonic  acid  produced  with  5,000  vol- 
umes of  air.  He  would  therefore  require 
6,000  cubic  feet  of  fresh  air,  and  one 
man,  therefore,  in  occupying  a  bed-room 
for  instance,  would  require  3,000  cubic 
feet  for  his  own  use.  This  is  pure  calcu- 
lation. What  does  the  experiment  show? 
In  some  experiments  made  in  Paris  to 
determine  the  amount  of  fresh  air  which 
should  be  supplied  to  hospitals  it  was 
found,  by  pure  experiment,  not  by  cal- 
culation at  all,  that  this  should  be  from 
3,120  to  2,470  cubic  feet  in  an  hour. 

Cubic  feet. 

Hospitals 2,120 

for  wounded 3,530 

"        for  epidemics 5,300 

Workshops 2,120 

"        for  unhealthy  trades  3,530 

Barracks,  day 1,060 

night 12,410  ..  1,765 

Large  rooms  for  long  meetings. .  2,120 
short       "       ..  1,060 

Schools  for  children 424  ..      530 

"      for  adults 880  . .  1,060 

Now,  in  order  to  get  this  3,000  cubic 
feet  of  air  in  an  hour  supplied  to  a  large 
audience  in  any  public  building,  it  is 
absolutely  necessary,  as  far  as  I  know  at 
present,  to  resort  to  some  special  means 
of  supplying  fresh  air,  and  a  very  good 
instance  of  that  is  afforded  at  the  Royal 
Institution.  Very  great  care  was  taken, 
there  four  or  five  years  ago  by  arranging 
with  upright  cylinders  going  to  the  roof 
from  under  the  gallery,  in  which  gas-jets 
were  burnt,  and  passages  connected  with 
windows  which  entered  underneath  the 
seats  and  above  the  heads  of  the  audi- 
ence underneath  the  gallery,  to  admit 
fresh  air;  but,  nevertheless,  on  a  night 
when  there  is  a  large  audience  at  the 
Royal  Institution  the  ah-  is  undoubtedly 
bad.  It  is  not  so  much,  perhaps,  the 
contamination  by  the  breath  as  by  the 
gas  and  heat — it  feels  extremely  hot. 
To  estimate  whether  the  place  is  close 
or  the  air  is  polluted  by  breath,  it  is 
necessary  to  enter  from  the  outside  di- 
rectly. That  I  have  not  done.  I  have  gone 
in  at  the  commencement,  when  the  audi- 
ence was  arriving,  and  remained  there 
to  the  end.  Still,  there  is  no  doubt  peo- 
ple complain  continually  about  the  air 
in  the  upper  part  of  the  building  being 
extremely  bad.     There  is  no  doubt  that 


not  advisable  to 
room  more  than 
course  of  an  hour. 


the  Royal  Institution,  from  the  very  fact 
that  such  care  was  taken  in  the  ventila- 
tion, is  far  better  than  other   buildings 
of  the  same  kind,  but  it  shows  that,  in 
order  to  supply  fresh  air  to  a  building 
crowded  in  that  way,  some  mechanical 
means  must  be  resorted  to.    Such  mechan- 
ical means  are,  so  far  as  I  know,  a  rotat- 
ing fan,  which  drives  air  forward  through 
pipes  and  distributes  it  to  the  building, 
and  such  a  rotating  fan  is  applied  in 
America  to  the  ventilation  of  hospitals 
on  a  large  scale.     In  summer,  when  the 
air  is  hot,  it  is  passed  through  ice  to  cool 
it;  and  when  in  winter  it  is  cold,  it  is 
passed  over  hot- water  pipes  to  warm  it; 
and  so  a  regular  supply  of  fresh  air  is 
driven  into  the  building,  and  allowed  to 
find  its  way  out  where  it  can.     In  the 
Stamp  Office  at  Somerset  House,  which 
is  below  the  level  of  the  ground,  this 
means  is  resorted  to,  and  I  should  imag- 
ine, in  consequence  of  their  having  such 
a  contrivance,  that  the  air  was  in  such  a 
place  wholesome.     In  this  country  it  is 
change  the  ah*  of   a 
4   to  6  times  in  the 
It  is  therefore  neces- 
sary, generally  speaking,  to  have  a  suffi- 
cient supply  of  fresh  air  to  begin  with, 
in  order  to  prevent  the  air  being  changed 
too  rapidly,  and  it  has  been  calculated, 
as  stated  by  Dr.  Parkes  in  his  book  on 
"Practical  Hygiene,"  that  from  750  to 
1,000  cubic  feet  per  head  per  hour  is 
necessary.    In  a  crowded  building  where 
mechanical  ventilation  could  be  resorted 
$o,  the  air  could  be  so  warmed  as  to 
produce  no  feeling  of  draught.     I  may 
as  well   mention   what  this   feeling   of 
draught  is,  and  why  it  is  that  diffusion 
through  the  walls  is  unf  elt.     When  the 
air  travels  at  a  lower  rate  than  nineteen 
inches   per   second,  generally  speaking, 
that  is  to  say,  if  it  is  not  very  cold,  it  is 
unfelt.     There  are  around  us  continued 
currents  of  air  pouring  upwards  by  the 
heat  of  the  body,  causing  the  an*  sur- 
rounding us  to  become  warm  and  rise  up 
with  fresh  air  coming  against  us;    still 
these  currents  we  are  unconscious  of.    It 
is  only  by  an  extremely  delicate  instru- 
ment placed  under  your  top-coat   that 
these  currents  can  be  detected.     Then 
on  a  day  when  not  a  leaf  is  stirring,  not 
a  ripple  on  the  water,  there  are  constant- 
ly currents  playing  about;  these  are  un- 
felt, and  are  produced  at  a  rate  of  some- 


116 


VAN   NOSTRAND'S   ENGINEERING   MAGAZINE. 


thing  less  than  nineteen  inches  per 
second.  That  this  rate  is  unfelt  may  be 
proved  by  passing  the  hand  through  the 
air  at  a  speed  somewhat  less;  and,  of 
course,  passing  the  hand  through  the  air 
is  jnst  the  same  as  passing  the  air  over 
the  hand  if  it  were  stationary. 

Ventilation  then  may  be  considered, 
generally  speaking,  as  the  'passage  of 
fresh  air  to  an  apartment  at  a  rate  of 
less  than  19  inches  per  second,  so  as  to 
reduce  the  carbonic  acid  in  the  air  to  6 
volumes  ha  10,0(X).  Dr.  Angus  Smith, 
who  has  done  such  valuable  work  in  the 
matter  of  air  and  ventilation,  gives  us  a 
means  whereby  we  can  estimate  whether 
the  air  of  a  room  is  wholesome  or  not, 
whether  the  vitiation  is  increased  to  an 
extent  which  is  unwholesome,  and  that 
is  a  very  simple  test.  It  consists  in  tak- 
ing a  bottle,  which  holds  10-J  oz.  of  air 
when  the  stopper  is  placed  in  the  bottle. 
If  I  blow  the  air  into  this  with  the  bel- 
lows, and  then  take  %  oz.  of  saturated 
lime-water,  the  test  consists  of  this,  that 
if  there  is  more  carbonic  acid  in  the  air 
of  that  bottle  than  6  in  10,000,  shaking 
up  this  ^  oz.  of  lime-water  in  it  will 
cause  the  lime-water  to  become  turbid. 
Trying  the  experiment  with  the  air  of 
this  room  it  becomes  just  turbid,  and 
that  is  all.  I  should  not  think  from  this 
experiment  that  there  were  more  than  6 
volumes  in  10,000.  It  just  shows  the 
slightest  trace  of  turbidity  and  that  is 
all.  By  taking  a  smaller  bottle  and  the 
same  amount  of  lime-water  the  amount 
of  carbonic  acid  in  the  air  may  be  told 
to  the  extent  of  one  volume  in  10,000, 
and  by  means  of  a  flexible  bottle  and 
the  lime-water  contained  in  another  ap- 
paratus, we  may  determine  the  amount 
with  some  degree  of  accuracy. 

I  will  pass  over  the  determination  of 
the  carbonic  acid  in  the  air,  and  I  will 
go  to  another  matter,  a  very  important 
one,  which  is  the  carbonic  acid  in  the 
soil.  Pettenkofer  has  shown  that  if  we 
take  a  gravelly  soil,  cut  a  piece  out,  and 
measure  the  amount  of  water  that  we 
can  pour  into  it,  the  amount  of  water  it 
will  take  up  will  amount  to  one-third  the 
space  occupied  by  the  soil.  Therefore, 
the  soil  consists  of  one-third  of  air. 
Now  Boussingault  has  shown  that  the 
amount  of  carbonic  acid  in  the  air  con- 
tained in  the  soil  was  very  much  more 
than  that   contained  in  the  air  of  the 


atmosphere.     He  found  that  in  a  field 
recently  manured  it   amounted   to  221 
parts  in  10,000  of  ah',  and   in   another 
field  974,  and  in  a  field  of  carrots  98,  a 
vineyard  96,  forest  land  86,  loamy  sub- 
soil 82,  sandy  subsoil  24,  garden  soil  36, 
prairie  179.      You  see  then  that  what 
may  be  called  the  ground-air  is  highly 
charged  with  carbonic  acid.     When  we 
warm  a  house  by  a  fire  it  creates  an  up- 
ward draught,  and  undoubtedly  the  air 
from  the  soil  passes  into  the  house.     If 
you  doubt  this,  a  very  good  case  to  prove 
it  is  the  one  Pettenkofer  mentions  at 
Munich  of  a  house  in  which  there  was 
no  gas  laid  on  or  any  gas  pipe  within 
twenty  yards  of  the  house,  yet  the  peo- 
ple in  the  house  were  poisoned  by  an 
escape  of   gas.     This   escape  from   the 
main    traveled   through  the   earth   and 
gained  admission  to  the  house.     Nearer 
home  there  has  occurred  a  case  of  a  still 
more   striking   character    at  Southgate, 
Colney  Hatch,  where  one  or  two  small 
houses  were  completely  wrecked  in  No- 
vember   last  by   an   explosion    of   gas. 
This  gas  was  not  laid  on  to  the  houses 
at   all,   the    main  .passed    through  the 
street,  the  houses  stood  back  from  the 
street    some    distance;     the    main   was 
cracked,  the  gas  traveled  through   the 
soil,  gained  admission  to  the   house,  it 
smelt  for  several  days,  and  finally  ex- 
ploded  one   evening  on   a   lamp   being 
lighted,   and    completely    wrecked    the 
building.     Here,   then,   is   striking  evi- 
dence of  gas  passing  through  the  soil. 
What  does  this  teach  ?     It  teaches  that 
the  air  of  the  soil  should  be  as  far  as 
possible  prevented  from  being  polluted. 
If  the  soil  is  polluted  by  a  leaky  drain 
pipe  we  have  that  communicated  to  the 
soil  which,  if  it  gains  admission  to  the 
house,  may  lead   to   disastrous  results, 
the  breaking  out  of  typhoid  fever,  and 
those  other  diseases  which  are   always 
traceable  to  contaminated  air  and  water, 
which  are  fjamiliar  to  every  one.     It  is 
therefore    highly    important    that    this 
matter  should  have  attention  called  to 
it.     It  is  not  at  all  an  unusual  thing  in 
the  neighborhood  of  London  for  specu- 
lating builders  to  build  houses  and  make 
drain -pipes  which  have  no  outlet;  they 
put  drain-pipes  below  the  house,  which 
lead  nowhere;    the  consequence  is,  that 
after  the  house  is  let  the   unfortunate 
tenant  is  perfectly  ignorant  of  the  fact 


EAILWAY   GAUGES. 


117 


that  everything  which  escapes  by  the 
drain-pipes  is  lodged  in  the  earth.  Of 
course,  after  a  time,  this  cannot  fail  to 
be  found  out,  but  frequently  only  when 
it  is  too  late. 

Having  mentioned  this  matter,  I  think 
I  must  now  conclude  my  paper,  and  I 
hope   sincerely   that   I  may  succeed  in 


drawing  attention  to  these  matters  which 
are  undoubtedly  of  the  highest  import- 
ance. In  preparing  my  experiments,  I 
have  to  give  my  best  thanks  to  my 
friend,  Mr.  Thomson,  who  undertook  the 
trouble  for  me  this  afternoon,  otherwise 
I  do  not  think  I  could  have  performed 
them. 


.  EAILWAY  GAUGES. 

From  "Engineering." 


Under  the  title  of  "  Some  Notes  on 
the  Early  History  of  the  Railway  Gauge," 
Dr.  William  Pole  has  lately  read  a  paper 
in  which  he  strongly  attacks  the  reaction 
towards   narrow  gauges   now  being   so 
strongly   shown   in  all  countries  where 
cheap  railways  are  a  necessity,  and  he 
goes  so  'far  as  to  state  his  belief  that 
"the  late  official  Indian  narrow  gauge 
movement  will  be  pointed  to  by  posterity 
as  a  blot  on  the  mechanical  character  of 
the  British  nation.  It  will  not  only  show, 
as  Oxenstiern  said,  '  with  how  little  wis- 
dom the  world  is  governed,'  but  it  will 
serve  as  an  illustration,  added  to  many 
others,  of  how,  in  spite  of  the  general 
spread  of  scientific  knowledge,  the  most 
incomprehensible  delusions  may  prevail." 
Further,  Dr.  Pole,  after  speaking  of  the 
introduction    of    the  broad   gauge,   by 
Brunei,  says:    "Would   any   one,  with 
this  history  before  him,  believe  that  a 
great  economical  policy  had  been  based 
on  the  uneconomical  proposal  to  push 
the  wheels  closer  together  under  a  car- 
riage  body?     Yet   the   records   of   the 
past  few  years  show  that  this  has  actu- 
ally been  done.     It  is  said  that  a  narrow 
gauge  is  cheaper;  but  this  argues  simply 
a    misunderstanding     of     what     gauge 
means,  and  what  significance  it  has   in 
railway  construction."    These   are  forci- 
ble opinions,   and  coming  from   an  en- 
gineer of  Dr.  Pole's  position,  they  merit 
a  reply,  notwithstanding  that  the  errors 
they  include  have  been  fully  shown  by 
the  results  of  practical  experience. 

We  have  no  intention  of  discussing 
the  historical  portion  of  Dr.  Pole's  paper, 
but  in  order  to  explain  the  matter  more 
clearly  it  would  be  necessary  to  state 
briefly  the  steps  by  which  Dr.  Pole  ar- 


rives at  the  conclusions  we  have  quoted. 
The  4  ft.  8|  in.  gauge  Dr.  Pole  states  to 
have  been  adopted  from  the  accidental 
circumstance  of  the  Northumberland  col- 
liery lines  being  made  to  that  gauge,  and 
he  goes  on  to  remark  that  in  the  earlier 
rolling  stock  all  the  bodies  were  situated 
between  the  wheels,  and  that  it  was  not 
until  the  traffic  had  been  somewhat  de- 
veloped on  the  Liverpool  and  Manchester 
Railway  that  bodies  extending  over  the 
wheels  and  axles  with  outside  bearings 
came  into  use.  This  form  of  vehicle  Dr. 
Pole  characterizes  as  an  "  abnormal 
type,"  and  "inherently  defective  in  a 
mechanical  point  of  view,  and  differing 
essentially  from  that  which  the  experi- 
ence of  the  world  in  all  preceding  ages 
had  established  as  the  proper  one  for 
wheel  carriages."  According  to  Dr.  Pole, 
in  fact,  things  were  in  a  very  bad  state 
when  Brunei  stepped  in  to  revolutionize 
matters  by  introducing  the  broad  gauge. 
Brunei,  he  asserts,  intended  to  place  the 
bodies  of  his  carriages  between  the 
wheels  and  to  make  the  latter  of  larger 
diameter  than  usual  with  a  view  of 
diminishing  friction,  and  under  these  cir- 
cumstances the  width  of  the  gauge  was 
determined  so  as  to  allow  of  placing  be- 
tween the  wheels  a  private  carriage, 
which  was  the  broadest  article  ordinarily 
requiring  to  be  transported  by  rail.  As 
a  matter  of  fact,  however,  the  construc- 
tion of  carriages  which  Dr.  Pole  terms 
an  "  abnormal  type  "  was,  except  in  some 
of  the  earlier  vehicles,  adopted  on  the 
Great  Western  as  on  other  lines,  and 
the  history  of  this  point  is  judiciously 
referred  to  in  the  paper  under  notice,  as 
"  somewhat  obscure."  Dr.  Pole,  however, 
adheres  to  his  proposition  that  the  ordi- 


118 


VAN  nostrand's  engineering  magazine. 


nary  type  of  railway  carriage  with  out- 
side bearings  is  mechanically  wrong, 
that  narrow  gauge  railways  are  a  mis- 
take, and  that  the  gradual  disappearance 
of  Brunei's  gauge,  which  he  so  highly 
commends,  has  been  brought  about  not 
by  any  inherent  defects  in  the  gauge 
itself  but  simply  from  the  evils  of  break 
of  gauge  which  the  Great  Western  Com- 
pany had  to  suffer.  On  these  points  we 
propose  to  have  something  to  say. 

In  the  first  place,  as  regards  the  con- 
struction of  railway  vehicles  which  Dr. 
Pole  calls  "  abnormal,"  we  entirely  dis- 
agree from  the  conclusions  at  which  he 
arrives.  More  than  four  years  ago,  in 
dealing  with  the  stability  of  rolling 
stock  {vide  vol.  x.,  page  439),  we  showed 
that  when  vehicles  are  "  carried  on  bear- 
ings situated  inside  the  wheels,  the  re- 
sistance to  the  overturning  of  the  upper 
part  of  the  vehicle  on  the  springs  is 
always  less  than  that  opposed  to  the 
overturning  of  the  whole  vehicle  on  the 
rails,"  and  it  thus  follows  that  if  the 
type  which  Dr.  Pole  so  admires  be 
adopted,  the  full  stability  due  to  the 
width  of  the  gauge  cannot  be  obtained. 
It  also  follows,  as  a  collateral  deduction 
from  the  above  fact,  that  with  inside 
bearings  the  springs  used  must  be 
much  stiffer  than  with  outside  bearings, 
to  maintain  the  same  control  of  the 
oscillations  of  the  body,  and  that  hence 
the  outside  bearings  afford  the  means  of 
producing  a  more  easily  riding  carriage. 
Under  the  ordinary  arrangement,  too, 
the  bearings  need  be  made  only  about 
two-thirds  of  the  diameter  which  would 
be  necessary  were  they  placed  inside  the 
wheels,  and  this,  of  course,  proportion- 
ately reduces  the  axle  friction.  A  third 
advantage  is  that  by  extending  the  body 
of  the  wagon  or  carriage  beyond  the 
wheels,  a  vehicle  can  be  constructed 
having  a  less  proportion  of  dead  weight 
to  paying  load,  than  if  the  body  was 
kept  between  the  wheels,  while  the 
former  mode  of  construction  also  enables 
a  greater  number  of  passengers  to  be 
carried  per  foot-length  of  train,  and 
thus  enables  an  economy  to  be  effected 
in  length  of  platforms  at  stations,  etc. 
Altogether  theory,  as  well  as  ■  practice, 
points  to  the  ordinary  type  of  railway 
vehicle  as  being  advantageous  rather 
than  "  abnormal,"  while  we  are  unaware 
of  a  single  point  of  real  superiority  pos- 


sessed by  the  type  which  Dr.  Pole  so 
strongly  advocates. 

We  now  come  to  the  question  as  to 
the  advantages  of  the  narrow  gauge 
lines  which  are  now  being  so  extensively 
built  in  almost  every  part  of  the  world 
where  railways  are  known.  Respecting 
these  lines  our  opinions  are — as  our  read- 
ers scarcely  need  to  be  reminded — diam- 
etrically opposed  to  Dr.  Pole's,  and  we 
have  on  many  occasions  entered  into  the 
matter  so  fully  that  it  will  only  be  neces- 
sary for  us  to  speak  concerning  the 
salient  points  here.  Dr.  Pole  insists  that 
so  long  as  the  rolling  stock  is  made  to 
suit  a  given  traffic  the  width  of  the  gauge 
can  make  no  material  difference  in  the 
cost  of  the  line,  for  he  says,  "  the  cost  of 
the  permanent  way  must  depend  upon 
the  weight  to  be  carried,  while  that  of 
the  overworks  can  only  be  governed  by 
the  dimensions  of  the  loaded  vehicles, 
into  neither  of  which  elements  does  the 
gauge  necessarily  enter."  That  he  should 
insist  upon  such  a  statement  as  this  is, 
we  think,  a  remarkable  exemplification 
of  his  own  words  already  quoted,  "  how, 
in  spite  of  the  general  spread  of  scien- 
tific knowledge,  the  most  incomprehensi- 
ble delusions  may  prevail."  We  should 
have  thought  that  everybody  conversant 
with  railway  construction  and  working 
was  aware  that  the  fact  of  a  given  traffic 
having  to  be  accommodated  by  no  means 
at  once  fixes  the  best  proportions  of  the 
rolling  stock  to  be  employed.  The  pro- 
portions, in  fact,  are  to  a  large  extent  de- 
pendent on  the  gauge,  and  are  not,  as  Dr. 
Pole  appears  to  suppose,  dominant  over 
the  latter.  It  is  quite  true  that  in  some 
intances  the  fact  of  certain  articles  hav- 
ing to  be  transported  may  fix  the  mini- 
mum width  of  vehicle  admissible,  but  in 
all  ordinary  cases  the  width  thus  de- 
manded is  well  within  that  which  can 
be  provided  on  such  narrow  gauge  lines 
as  we  advocated,  and  such  as  are  being 
made  in  India,  so  that  this  point  does 
not  enter  into  the  discussion.  As  far  as 
general  merchandise  is  concerned  the 
proportions  of  the  vehicle  used  for  con- 
veying it  can  be  varied  within  wide 
limits  without  introducing  any  practical 
inconveniences.  It  thus  by  no  means 
follows,  as  Dr.  Pole  appears  to  suppose, 
that  to  accommodate  a  given  traffic,  the 
vehicles  will,  or  ought  to  be,  made  of  a 
certain  widtb;   whatever  the  width  of 


RAILWAY  GAUGES. 


119 


the  gauge  may  be.  On  the  contrary,  it 
will  be  found  that  for  every  gauge  there 
is  a  certain  width  of  vehicle  which  gives 
the  most  beneficial  results  as  regards 
proportion  of  dead  weight  to  paying 
load,  and  necessarily  this  width  becomes 
less  as  the  gauge  is  reduced.  This  being 
so,  Dr.  Pole's  assertions  about  the  cost 
of  permanent  way  and  overworks  at 
once  fall  to  the  ground,  for  the  narrower 
the  rolling  stock  the  less  is  the  weight 
per  foot  of  train,  and  hence  the  less  is 
the  strain  thrown  upon  the  permanent 
way,  while,  of  course,  with  a  reduced 
width  of  wagons  the  less  can  be  the 
span  of  the  over-bridges.  In  other 
words,  the  adoption  of  a  narrow  gauge 
enables  a  certain  weight  of  train  to  be 
distributed  over  a  greater  length  of  line 
than  would  be  possible  with  a  wider 
gauge,  unless  in  the  latter  instance  vehi- 
cles of  a  type  which  may  be  justly 
characterized  as  "  abnormal "  were  em- 
ployed. 

Dr.  Pole  absolutely  ignores  the  facili- 
ties which  narrow  gauge  lines  afford 
for  economical  management  and  working. 
Yet  these  matters  are  quite  as  important 
as  the  reduction  of  first  cost.  A  reduc- 
tion of  the  gauge  is  accompanied  by  a 
reduction  in  the  size  of  vehicle  which 
can  be  most  profitably  employed,  and 
hence  narrow  guage  rolling  stock  is  not 
only  more  frequently  run  with  full  loads 
than  the  stock  on  a  wider  gauge  could 
be,  but  the  vehicles,  whether  loaded  or 
unloaded,  are  more  easily  handled  at 
stations,  and  thus  a  source  of  economy 
is  introduced,  which  all  who  have  had  to 
do  with  railway  management  can  well 
appreciate.  As  we  have  pointed  out  on 
former  occasions,  in  fact,  the  lightness 
and  handiness  of  narrow  gauge  stock 
leads  to  numerous  sources  of  economy 
which  it  is  impossible  to  enumerate  here, 
but  which  should  by  this  time  be  well 
understood  by  all  who  have  studied  the 
question. 

Perhaps,  however,  the  best  answer  to 
Dr.  Pole's  assertions  respecting  the  poli- 
cy adopted  by  the  Indian  Government 
regarding  their  new  lines,  is  to  be  found 
in  the  every-day  experience  now  being 
gained  with  narrow  gauge  railways. 
Everywhere  almost  we  find  such  lines 
spreading.  In  the  United  States  up- 
wards of  2,000  miles  of  such  lines  have 
already  been  laid,  while  in  Canada,  South 


America,  and  our  Australian  colonies, 
narrow  gauge  railways  have  taken  deep 
root.  Nearer  home,  too,  we  find  such 
lines  constructed  and  in  course  of  con- 
struction, in  France,  Germany,  Italy, 
Russia,  Norway,  and  Switzerland,  and 
everywhere  we  hear  good  accounts  of 
the  results  obtained  from  them.  In  a 
paper  on  the  Rigi  Railway,  read  before 
the  Institution  of  Civil  Engineers  in 
1873,  Dr.  Pole  remarked  that,  although 
the  railway  in  question  "  is  in  every  re- 
spect a  special  and  exceptional  line,  and 
intended  for  the  very  lightest  character 
of  traffic,  the  Swiss  with  their  usual 
good  practical  sense  have  avoided  the 
foolish  fallacy  of  narrowing  the  gauge;" 
it,  may,  however,  interest  Dr.  Pole  to 
know  that  the  Swiss  "  with  their  usual 
good  practical  sense  "  are  not  only  now 
building  metre  gauge  lines,  but  are  also 
contemplating  the  introduction  of  narrow 
gauge  tramways.  The  fact  is  that  with 
very  few  exceptions  narrow  gauge  lines 
have  one  great  source  of  attraction  de- 
nied to  many  of  their  more  pretentious 
brethren.     They  pay. 

It  was  at  one  time  considered  that  it 
would  be  impossible  for  narrow  gauge 
lines  to  provide  the  engine  power  neces- 
sary for  carrying  heavy  loads  or  for 
working  steep  gradients.  This,  however, 
has  now  long  been  proved  to  be  entirely 
a  fallacy,  the  Fairlie  system  affording 
the  means  of  placing,  on  even  the  nar- 
rowest lines,  really  powerful  locomotives. 
Thus  the  Festinoig  Railway  of  1  ft.  llf 
in.  gauge  has  now  a  Fairlie  engine  with 
730  square  feet  of  heating  surface,  while 
Mr.  Fairlie  has  built  engines  with  829 
square  feet  of  surface,  for  the  Patillos 
Railway,  Peru,  a  line  of  2  ft.  6  in.  gauge, 
and  others  with  1,325  square  feet  of  sur- 
face for  the  3  ft.  6  in.  Livny  Railway, 
Russia.  We  have  merely  mentioned 
these  out  of  numerous  examples  of  nar- 
row gauge  Fairlie  engines  to  show  the 
capabilities  of  the  system  as  already 
proved;  but  we  may  add  that  none  of 
these  examples  represent  the  most  that 
can  be  done  on  the  respective  gauges. 
If  required,  Mr.  Fairlie  would  no  doubt 
undertake  the  construction  of  still  more 
powerful  loc6motives,  and  we  may  in 
fact  say  that  the  capabilities  of  the  nar- 
row gauge  are  now  practically  not  in 
any  way  limited  by  the  question  of  en- 
I  gine    power.    As  we  have    frequently 


120 


VAN   NOSTRAND'S   ENGINEERING   MAGAZINE. 


pointed  out,  too,  the  Fairlie  system  and 
narrow  gauge  lines  are  intimately  associ- 
ated in  several  ways,  for  not  only  does 
the  Fairlie  system  enable  an  engine 
power  to  be  provided  to  an  extent 
almost  unattainable  in  any  other  way, 
but  it  also  enables  engines  to  be  con- 
structed which  are  eminently  adapted 
for  traversing  the  sharp  curves  generally 
to  be  met  with  on  railways  where  first 
cost  is  an  important  consideration.  This 
system  of  locomotive  in  fact  enables  the 


capabilities  of  narrow  gauge  railways  to 
be  fully  developed,  and  we  are  glad  to 
find  that  this  fact  is  now  being  daily 
recognized,  and  that  the  advantage  of 
narrow  gauge  are  being  appreciated  by 
those  who  formerly  regarded  it  as  of 
very  limited  application,  but  who,  throw- 
ing aside  prejudice,  have  by  further  in- 
quiry made  themselves  acquainted  with 
the  real  truth  of  the  case.  In  this  num- 
ber Dr.  Pole  does  not  at  present  appear 
to  be  included. 


RAILWAY    ACCIDENTS. 

JBy  feed.  chas.  danvers,  c.  e. 

From  "  Quarterly  Journal  of  Science." 


So  much  attention  has  of  late  been 
given  to  the  subject  of  railway  accidents, 
and  the  best  means  of  preventing  them, 
and  so  important  is  it  in  the  interest  of 
the  public  generally,  that  a  few  pages 
of  the  "Quarterly  Journal  of  Science" 
may,  with  advantage,  be  devoted  to  a 
consideration  of  how  far  all  known  and 
practicable  means  for  the  mitigation  of  the 
dangers  of  railway  traveling  have  been 
adopted.  In  investigating  this  question 
we  must  refer  briefly,  in  the  first  instance, 
to  the  early  history  of  railway  legisla- 
tion, with  a  view  to  trace  what  steps 
have  been  taken  by  the  Government  for 
the  protection  of  travelers,  prior  to  en- 
quiry as  to  what  action  had  been  taken 
by  the  railway  companies  themselves 
with  the  same  object. 

The  earliest  railway  or  tramway  Act 
was  passed  in  1801,  for  the  construction 
of  a  railway  from  Wandsworth  to  Croy- 
don, for  "  the  advantage  of  conveying 
coals,  corn,  and  all  goods  and  merchan- 
dise to  and  from  the  metropolis  and  other 
places."  From  this  period  new  tramways 
or  railways  were  sanctioned  in  almost 
every  session.  The  Acts  by  which  the 
earlier  railway  companies  were  estab- 
lished followed  very  closely,  in  their 
general  scope,  the  provisions  which  had 
been  applied  to  canal  companies.  The 
promoters  of  the  project  were  constituted 
a  corporation,  and  were  authorized  to 
raise  such  money,  either  by  shares  or  by 
borrowing,  as  they  required  for  complet- 


ing their  undertaking;  and  they  were 
empowered  in  their  corporate  capacity 
to  take  lands  compulsorily,  and  to  charge 
tolls  at  their  discretion  for  the  use  of 
their  railway,  within  the  limits  of  certain 
prescribed  rates,  for  various  classes  of 
goods.  In  the  Act  for  the  Liverpool  and 
Manchester  Railway,  passed  in  the  year 
1825,  and  in  other  subsequent  similar 
Acts,  a  further  provision  was  introduced, 
that  if  the  dividends  should  exceed  10 
per  cent,  an  abatement  should  be  made 
from  the  maximum  tonnage  rates  of  5 
per  cent,  on  the  amount  thereof  for  each 
1  per  cent.,  which  the  Company  might 
divide  over  and  above  a  dividend  of  10 
per  cent,  on  its  capital.  In  their  capacity 
as  owners  of  a  road,  railway  companies 
were  not  intended  by  Parliament  to  have 
any  monopoly  or  preferential  use  of  the 
means  of  communication  on  their  lines 
of  railway;  on  the  contrary,  provision 
was  made,  in  all  or  most  of  the  Acts  of 
Incorporation,  to  enable  all  persons  to 
use  the  road  on  payment  of  certain  tolls 
to  the  company,  under  such  regulations 
as  the  company  might  make  to  secure 
the  proper  and  convenient  use  of  the 
railway.  But  no  sooner  were  railways 
worked  on  a  large  scale  with  locomotive 
power  than  it  was  found  impracticable 
for  the  public  in  general  to  use  the  lines, 
either  with  carriages  or  locomotive  en- 
gines; and  the  railway  companies,  in 
order  to  make  their  undertakings  re- 
munerative?   were   compelled,  with  the 


EAILWAY   ACCIDENTS. 


121 


assistance  of  the  persons  who  had  been 
previously  engaged  in  the  carrying  trade 
of  the  country,  to  embark  in  the  business 
of  common  carriers  on  their  lines  of  rail- 
way, and  conduct  the  whole  operation 
themselves. 

In  consequence  of  the  increasing  num- 
ber of  Railway  Bills  annually  coming 
before  Parliament,  and  the  necessity  of 
securing  consistency  in  private  bill  legis- 
lation, the  House  of  Commons,  in  1837, 
appointed  a  select  committee,  to  which 
were  referred  all  petitions  for  private 
bills,  and  it  was  the  duty  of  this  com- 
mittee to  decide  how  far  the  standing 
orders  had  been  complied  with  in  each 
case. 

In  1840,  another  Select  Committee  of 
the  House  of  Commons,  appointed  to 
report  on  the  railway  system,  came  to 
the  conclusion  that  the  right  secured  to 
the  public  by  the  Railway  Acts,  of  run- 
ning their  engines  and  carriages  on  the 
railways,  was  practically  a  dead  letter. 
In  consequence  of  their  recommendation 
that  the  executive  government  should 
be  entrusted  with  the  duty  of  inspecting 
new  lines  of  railway,  and  of  exercising  a 
general  supervision  over  the  manner  in 
which  the  railway  companies  used  their 
powers,  an  Act  was  passed  by  which  it 
was  provided  that  no  new  railway  for 
the  conveyance  of  goods  or  passengers 
should  be  opened  without  previous  no- 
tice to  the  Board  of  Trade,  and  the 
Board  were  empowered  to  appoint  offi- 
cers to  inspect  all  new  railways.  The 
Board  was  also  empowered  to  require, 
under  a  penalty,  that  every  railway 
company  should  deliver  to  them  returns, 
in  whatever  form  they  might  prescribe, 
of  the  traffic  in  passengers  and  goods, 
as  well  as  of  accidents  attended  with 
personal  injury,  and  a  table  of  tolls  and 
rates  from  time  to  time  levied  on  passen- 
gers and  goods.  All  by-laws  already 
made  by  companies  were  to  be  certified 
to  the  Board,  and  no  new  ones  were  to 
be  made  without  its  sanction.  The  Board 
was  also  constituted  the  guardian  of  the 
public  interests,  being  empowered  at  its 
discretion  to  certify  to  the  law  officers 
of  the  Crown  any  infraction  of  the  law, 
and  the  law  officers  of  the  Crown  were 
thereupon  required  to  take  the  requisite 
legal  proceedings.  The-  power  which 
had  been  conferred  upon  proprietors  of 
and  adjoining  railways  by  their  private 


Acts  of  Parliament,  for  making  junc- 
tions, was  placed  under  the  control  of 
the  Board  of  Trade,  with  a  discretion  to 
regulate  the  manner  in  which  it  should 
be  exercised. 

In  1842,  the  returns  of  the  accidents 
required  to  be  made  to  the  Board  of 
Trade  were  extended  to  all  cases,  whether 
or  not  they  were  attended  with  personal 
injury;  and  in  1844  parliamentary  trains 
were  established  by  law,  and  the  powers 
of  the  Board  of  Trade  to  compel  railway 
companies  to  comply  with  the  law  were 
extended  to  all  unauthorized  proceedings 
on  the  part  of  the  railway  companies. 
In  1846  an  Act  was  passed  establishing 
a  Board  of  Commissioners  of  Railways, 
to  whom  the  powers  possessed  by  the 
Board  of  Trade  were  transferred;  but  in 
1851  the  Board  of  Commissioners  was 
abolished,  and  its  powers  and  duties 
were  re-transferred  to  the  Board  of 
Trade. 

In  1857  a  Select  Committee  on  Acci- 
dents on  Railways  was  appointed,  who 
in  their  Report  of  the  25  th  June,  1858, 
classified  the  causes  of  accidents  under 
the  three  following  heads:  Inattention 
of  Servants;  Defective  Material,  either 
in  the  works  or  rolling  stock  ;  and  Ex- 
cessive Speed.  Much  stress  was  laid  by 
the  Committee  on  the  necessity  for 
punctuality  in  the  departure  and  arrival 
of  trains;  they  considered  that  it  should 
be  imperative  on  every  railway  compa- 
ny to  establish  a  means  of  communica- 
tion between  guards  and  engine-drivers, 
and  that  a  system  of  telegraphic  com- 
munication on  the  lines  should  be  en- 
forced, in  order  that  they  might  be 
worked  on  the  block  system;  and  they 
concluded  by  recommending  that, with  re- 
spect to  signals,  breaks,  and  other  pre- 
cautions, such  details  should  be  left  to 
the  management  of  the  railway  boards, 
but  that  the  Board  of  Trade  should  be 
invested  with  further  powers  to  enable 
them  the  more  effectually  to  control  the 
working  of  railways  with  a  view  to 
diminishing  the  number  of  railway  acci- 
dents. 

Bills  have  at  various  times  been  intro- 
duced with  the  object  of  compelling 
railway  companies  to  adopt  some  precise 
system  of  working,  but  they  were  not 
passed;  and  in  1866,  in  a  bill  of  this 
nature,  it  was  for  the  first  time  pro- 
posed, to  compel  railway  companies  to 


122 


VAN  NOSTRAND'S   ENGINEERING  MAGAZINE. 


adopt  a  means  of  communication  be- 
tween passengers  and  guards,  and  be- 
tween guards  and  engine-drivers  of  all 
trains.  This  Bill,  however,  did  not,  at 
the  time,  become  a  law,  but  was  with- 
drawn. 

In  1865  a  Royal  Commission  was  ap- 
pointed to  enquire  generally  into  the 
subject  of  railways,  and  to  report, 
amongst  other  matters,  whether,  with  a 
due  regard  to  the  progressive  extension 
of  the  railway  system,  it  would  be  prac- 
ticable by  means  of  any  changes  in  the 
laws  relating  to  railways,  "more  effect- 
ually to  provide  for  securing  the  safe, 
expeditious,  punctual,  and  cheap  transit 
of  passengers  and  merchandise  upon  the 
said  railways." 

Up  to  this  date  the  legislation  upon 
railways  directed  that  no  line  should  be 
opened  until  it  had  first  been  approved 
and  passed  by  the  Board  of  Trade  In- 
spectors, but  after  it  had  been  once 
opened  for  traffic  the  manner  of  working 
was  left  entirely  in  the  hands  of  the 
railway  company,  power  being,  however, 
reserved  to  the  Board  of  Trade  to  cause 
the  railways,  the  engines,  and  the  car- 
riages to  be  inspected  by  their  officers 
whenever  they  might  think  fit,  and  they 
might,  when  applied  to,  make  regula- 
tions for  the  safe  working  of  the  traffic 
at  the  junction  of  the  lines  of  two  compa- 
nies. The  railway  company,  in  under- 
taking the  duty  of  carriers,  became 
liable  under  the  common  law  to  compen- 
sate persons  injured,  and  under  Lord 
Campbell's  Act  to  compensate  the  rela- 
tives of  persons  killed  by  the  company's 
negligence  or  by  that  of  their  servants. 
Thus  Parliament  relied  upon  the  princi- 
ple of  leaving  the  responsibility  of  the 
safe  working  of  railways  with  the  com- 
panies rather  than  upon  giving  the 
Board  of  Trade  the  power  and  duty  of 
interfering  in  the  details  of  management. 
The  Royal  Commission  of  1865,  in 
their  Report,  expressed  the  opinion  that 
the  plan  of  relying  for  the  safe  working 
of  railways  upon  the  efficiency  of  the 
common  law  and  of  Lord  Campbell's 
Act,  had  been  more  conducive  to  the 
protection  of  the  public  than  if  the 
Board  of  Trade  had  been  empowered  to 
interfere  in  the  detailed  arrangements 
for  working  the  traffic.  They  recom- 
mended, however,  that,  on  the  one  hand, 
railway  companies  should  be  absolutely 


responsible  for  all  injuries  arising  in  the 
conveyance  of  passengers,  except  those 
due  to  their  own  negligence;  and  that, 
on  the  other  hand,  the  liability  of  the 
railway  companies  be  limited  within  a 
maximum  amount  of  compensation  for 
each  class  of  fares;  but  that  any  passen- 
ger should  be  entitled  to  require  from 
the  company  any  additional  amount  of 
insurance  he  might  desire,  on  paying 
for  it  according  to  a  fixed  tariff.  They 
also  recommended  that  claims  for  com- 
pensation should  not  be  admitted  unless 
made  within  a  certain  period,  and  that 
the  railway  companies  should  have  the 
right  of  medical  examination  of  the 
claimant ;  and,  further,  that  to  the  power 
already  possessed  by  the  Board  of  Trade 
of  appointing  officers  to  inspect  railways 
and  rolling  stock,  should  be  added  a 
power  for  the  inspecting  officer  to  re- 
quire the  attendance  of  the  officers  and 
servants  of  the  company  as  witnesses, 
and  the  production  of  books  and  docu- 
ments bearing  on  enquiries  directed  by 
the  Board  of  Trade;  and  that  the  reports 
of  the  inspecting  officers  on  accidents 
should  be  made  public. 

In  1870  a  Select  Committee  of  the 
House  of  Commons  was  appointed  to 
enquire  into  the  law  and  the  administra- 
tion of  the  law  of  compensation  for  acci- 
dents as  applied  to  railway  companies, 
and  also  to  enquire  whether  any,  and 
what,  precautions  ought  to  be  adopted 
by  railway  companies  with  a  view  to 
prevent  accidents.  On  the  second  point 
the  Committee  pointed  out  that  on 
those  lines  where  the  block  system  had 
been  adopted  it  had  materially  conduced 
to  the  safety  of  the  public,  and  they 
recommended  the  evidence  collected  by 
them  on  this  subject,  as  well  as  that  in 
favor  of  the  principle  of  the  interlocking 
of  signals  and  points,  and  concerning 
continuous  breaks,  to  the  careful  consid- 
eration of  railway  boards  of  directors. 

Last  year  (1873)  a  Bill  was  introduced 
into  Parliament  for  the  "Regulation  of 
Railways,"  with  a  view  to  the  prevention 
of  accidents.  This  Bill  had  for  its  object 
the  enforcing  upon  all  railway  companies 
the  obligation  of  securing  an  interval  of 
space  between  trains  following  each 
other  on  the  same  line  of  rails,  which  is 
now  generally  effected  by  what  is  known 
as  the  block  system,  and  it  further  pro- 
posed to  enforce  the  interlocking  sys- 


KAILWAY  ACCIDENTS. 


123 


tern.  A  Select  Committee  was  appointed 
by  the  House  of  Lords  to  consider  this 
Bill,  but  whilst  strongly  recommending 
the  adoption  of  both  the  block  system 
and  the  interlocking  system  on  all  im- 
portant lines  of  railway,  yet,  relying  on 
the  great  exertions  recently  and  very 
generally  made  by  different  railway  com- 
panies to  extend  both  systems,  and  other 
great  improvements  now  in  progress,  the 
.Committee  recommended  that  the  Bill 
should  not  then  be  proceeded  with. 
They  recommended,  however,  that  the 
Board  of  Trade  should  call  for  such  in- 
formation as  might  enable  the  inspect- 
ors, in  their  annual  reports,  to  state 
specially  the  progress  made  in  their 
adoption  on  all  passenger  lines,  after 
which,  it  was  considered,  Parliament 
would  be  in  a  condition  to  decide  wheth- 
er or  not  it  would  be  right  to  require  the 
further  and  more  prompt  extension  of 
these  systems  on  those  lines  where  they 
might  still  be  necessary. 

Another  Commission  is  at  the  present 
time  occupied  in  considering  how  rail- 
way accidents  may  best  be  prevented, 
and  what  legislation,  if  any,  is  desirable 
on  the  subject  in  the  interests  of  the  pub- 
lic at  large.  It  will  be  observed  that, 
hitherto,  the  action  of  Parliament  has 
been  rather  to  recommend  and  advise 
than  to  pass  coercive  measurers  to  com- 
pel railway  companies  to  adopt  improved 
means  for  the  protection  of  their  passen- 
gers. At  the  same  time,  additional 
powers  have  been  vested  in  the  Board  of 
Trade  from  time  to  time  for  the  more  ef- 
ficient inspection  of  lines  open  to  the 
public,  and  there  can  be  no  doubt  that 
the  duties  devolving  upon  that  branch  of 
public  service  have  hitherto  been  con- 
ducted satisfactorily  in  the  general  inter- 
ests, but  it  is  hardly  to  be  supposed  that 
its  action  should  meet  with  universal  ap- 
probation, or,  indeed,  that  it  should  be 
always  free  from  blame.  It  is  very  ob- 
vious that  the  officers  of  the  Board  of 
Trade  are  not  in  good  odor  with  the 
present  President  of  the  Institution  of 
Civil  Engineers  ;  and,  as  his  observations 
may  probably  be  taken  to  represent  the 
feelings  of  railway  officials  generally 
towards  them,  we  quote  the  following 
remarks  made  by  him  in  his  inaugural 
address  on  the  13th  of  January  last : 

"  There   is   also   a  '  popular  delusion  ' 
which  I  think  ought  to  be  corrected. 


The  public  believe  that  the  various  re- 
commendations made  to  the  railway 
companies  from  time  to  time  by  the 
officers  of  the  Board  of  Trade,  such  as 
the  block  system,  interlocking  of  points, 
&c,  are  really  inventions  of  those  offi- 
cers, whereas  the  fact  is  that  not  one 
of  these  systems  or  inventions,  or  any 
new  idea  in  connection  with  the  workings 
of  railways,  has  ever  really  been  sug- 
gested by  them. 

"  The  railway  companies  also  are  at  a 
great  disadvantage  with  the  public  in  re- 
spect to  the  reports  which  are  from  time 
to  time  made  by  the  Government  inspect- 
ing officers — their  dictum  is  never  ques- 
tioned by  the  public  ;  and  although  rail- 
way officers  of  great  experience  constantly 
differ  from  those  officials  in  the  conclu- 
sions at  which  they  arrive,  the  railway 
companies  feel  that  any  appeal  against 
these  reports  is  useless,  and  practically 
judgment  is  allowed  to  go  by  default. 

"  In  making  their  reports,  the  officers 
of  the  Board  of  Trade  are  in  the  position 
of  ex 'post  facto  judges,  and  I  need  hardly 
point  out  that  there  is  a  great  difference, 
to  use  an  expression  of  our  late  Presi- 
dent, Mr.  Hawksley,  between  looking  in- 
to the  events  of  the  week  that  is  past, 
and  looking  into  middle  of  next  week  ; 
and  should  the  country  at  any  time  be- 
come the  purchasers  of  the  railways, 
these  officers  will  soon  find  the  difference 
in  their  position  when  the  responsibility 
of  working  the  lines  devolves  upon  them. 

"  Captain  Tyler,  in  his  valuable  Report 
on  Railway  Accidents  in  1872,  says : 
'  Whatever  be  the  amount  of  care  taken, 
the  item  of  human  fallibility  will  still 
remain,  and  will  always  be  the  cause  of 
a  certain  number  of  accidents.'  And  he 
states  that  in  180  cases  of  accidents  out 
of  238,  'negligence,  want  of  care,  or 
mistakes  of  officers,  were  apparent.' 

"  This  is  a  subject  to  which  for  years 
past  I  have  devoted  a  great  deal  of  at- 
tention and  anxious  thought,  and  I  attach 
much  more  importance  to  the  item  of 
'human  fallibility'  than  Captain  Tyler 
appears  to  do." 

To  these  remarks  Captain  Tyler  replied 
as  follows,  in  a  paper  read  by  him  before 
the  Society  of  Arts  in  May  last : 

"When  Mr.  Harrison  attributes  to  the 
author  that  he  does  not  sufficiently  ap- 
preciate the  element  of  human  frailty  as 
contributing  to   accidents   on  railways, 


124 


VAN   NOSTRAND'S   ENGINEERING   MAGAZINE. 


and  leaves  it  to  be  understood  that  im- 
proved arrangements  will  not  materially 
lessen  the  number  of  accidents  and  their 
serious  results,  the  author  would  venture 
to  reply  that  he  estimates  that  cause  of 
accident  at  no  more  and  no  less  than  has 
actually  been  found  by  experience  of 
many  years  to  attach  to  it." 

This  subject  also  was  referred  to  by 
the  Select  Committee  of  the  House  of 
Lords,  who,  in  their  report  of  last  year, 
remarked  : 

"It  may  be  confidently  stated  that  the 
general  safety  of  railway  traveling 
would  be  increased  by  the  more  extensive 
employment  of  the  block  and  of  the  in- 
terlocking systems.  Some  witnesses 
stated  that  these  precautionary  arrange- 
ments and  mechanical  appliances  tend  to 
lessen  the  sense  of  responsibility  in  the  en- 
gine drivers.  Such  an  effect  may  have 
been  produced,  but,  nevertheless,  the  ad- 
vantages resulting  from  the  introduction 
of  these  systems  are  practically  admit- 
ted by  all  the  witnesses,  and,  in  the  judg- 
ment of  the  Committee,  decidedly  pre- 
ponderate." 

We  do  not  propose  to  follow  up  this 
subject  further  at  present,  beyond  re- 
marking that,  whilst  fully  admitting  the 
element  of  human  frailty,  which  must 
exist  wherever  the  hand  of  man  is  en- 
gaged, we  entirely  concur  in  the  conclu- 
sion arrived  at  by  the  Select  Committee 
of  the  House  of  Lords,  that  the  intro- 
duction of  improved  machanical  contri- 
vances for  the  more  efficient  and  safe 
working  of  railways  is  likely  to  overbal- 
ance in  its  advantages  the  evils  likely  to 
arise  from  the  element  of  "  human 
frailty,"  which  must  be,  at  all  times,  in- 
separable from  their  introduction. 

The  next  subjects  for  consideration  are 
the  extent  to  which  railway  passengers 
are  liable  to  accidents,  and  how  far  for- 
mer risks  are  increased  or  diminished  in 
proportion  to  the  number  of  travelers, 
and  to  the  adoption  of  means  with  a 
view  to  their  prevention.  A  general  re- 
view of  the  number  of  fatal  accidents  to 
passengers  from  all  causes  beyond  their 
own  control,  between  the  years  1847  and 
1873  inclusive,  is  contained  in  Captain 
Tyler's  General  Report  to  the  Board  of 
Trade  on  the  accidents  which  have  oc- 
curred on  the  railways  of  the  United 
Kingdom  during  the  year  1873,  from 
which  the  following  extract  is  taken  : 


"The  total  number  of  persons  record- 
ed at  the  Board  of  Trade  as  having  been 
killed  on  railways  during  the  year  was 
1372,  and   the   number   of  injured   was 
3110.     Of  these,  160  persons  killed,  and 
1750  persons  injured,  were  passengers  ; 
and  the  remainder,  1212  killed  and  1360 
injured,  were  officials  or  servants  of  the 
railway   companies,    or    trespassers,    or 
others  who  met  with  accidents  at  level 
crossings,  or  from  miscellaneous  causes. 
Of  the  passengers,  40  were  killed,  and 
1522  were  injured,from  causes  beyond 
their  own  control.     The  total  number  of 
passenger-journeys  having  been  455,272,- 
000,   it   follows   that   the  proportion  of 
passengers  killed  was,  in  round  numbers, 
1  to  2,845,450,  and  of  passengers  injured 
1  to  260,155  ;  and  that  the  proportions 
of   passengers  killed  and  injured  from 
causes   beyond  their  own  control  were 
respectively,  1   in  11,381,800,   and  1  in 
299,127.     This   was   a   deorease   on  the 
average  of  the  number  killed,  and  an  in- 
crease   of    the   number    injured,     from 
causes  beyond  their  own  control,  in  the 
previous  three  years,  in  which  the  pro- 
portions were  1  to  11,123,931  killed,  and 
1  to  357,000  injured.     Of  the  officers  and 
servants  of  railway  companies  there,  have 
during  the  past  year,  in  proportion  to  the 
total  number  employed,  as  nearly  as  they 
can  be  estimated(say  250,000),  been  killed 
from  all  causes  1  out  of  323,  and  injured 
1  out  of  213  ;  but  accidents  to  servants 
do  not  appear,  in  many  cases,  even  now 
to  have  been  reported  by  certain  of  the 
railway  companies,    and   their   numbers 
would,  if  the  whole  truth  could  be  ascer- 
tained, be  considerably  increased. 

"  The  following  statement  shows  the 
proportion  of  passengers  killed  to  pass- 
enger-journeys for  the  three  years  ending 
1849,  the  four  years  ending  1859,  the 
four  years  ending  1869,  and  the  four 
years  1870,  1871,  1872,  and  1873, 
respectively  :  (See  table  next  page.) 

From  these  figures  it  appears  that  the 
average  of  fatal  accidents  for  the  last 
four  years  was  higher  than  in  the  similar 
cycle  immediately  preceding  ;  and  the 
conclusion  that  would  naturally  be 
formed  at  first  thought  is,that  a  maximum 
of  safety  in  railway  traveling  has  been 
arrived  at.  On  a  closer  examination, 
however,  it  does  not  in  any  way  seem 
that  this  is  the  case.     No  doubt  traffic 


RAILWAY  ACCIDENTS. 


125 


Number  of  pas- 

sengers killed 

Number  of  passenger- 

Proportion  killed 

Year. 

from  all    causes 

journeys,  exclusive   of 

to 

beyond  their 

journeys  by  season- 

number  carried. 

own      control. 

ticket  holders. 

1847) 

1848  [ 

1849 

18561 

.    36 

173,158,772 

1  in    4,782,188 

1857  I 
.     1858  f 

64 

557,338,326 

1  in    8,708,411 

1859  J 

18661 

1867  1 

1868  f 

91 

1,177,646,573 

1  in  12,941,170 

1869  J 

1870 

66 

336,545,399 

1  in    5,099, 172 1 

1871 

12 

375,220,754 

1  in  31,268,396  1 

2  ^3   '5  ^  OB 

1872 

24 

422,874,822 

1  in  17,619,784  [ 

P  **  o  _,  CO 

1873 

40* 

455,272,000 

1  in  11,381,800  J 

<5  oeo     " 

has  increased  on  may  lines  in  a  more 
rapid  ratio  than  the  development  of  in- 
creased accommodation  for  such  traffic. 
But  the  accidents  in  1870  were  consider- 
ably in  excess  of  the  proportion  given  in 
the  above  table  since  1856  ;  but  if  we 
omit  that  bad  year,  and  take  only  the 
average  of  the  last  three  years,  it  will  be 
seen  that  the    number    of    passengers 
killed  from  all  causes  beyond  their  own 
control  was  only  1  in  20,089,993,   which 
shows  a  considerable  improvement  upon 
any  of  the  earlier  periods  referred  to. 
The  year  1871  was,  it  appears,  exception- 
ally free  from  fatal  accidents  ;  but  Cap- 
tain Tyler  shows  that  it  is  not  desirable 
to  lay  too  much  stress  on  the  results  of 
working  in  the  case  of  any  particular 
year,  either  as  to  the  number  of  sufferers 
or  as  to  the  number  of  accidents.     More 
returns  of  accidents  than  formerly  have 
been  rendered  by  the  companies  within 
the  last  two  years.     Inquiries  have  also 
been  instituted  during  those  two  years 
into  a  greater  proportion  of  cases,  and 
there  is,   humanly   speaking,   much    of 
chance  in  both.     A  dangerous  or  defec- 
tive mode  of  working  is  frequently  car- 
ried on  for  a  great  length  of  time  with- 
out bad  results,  while  there  are  accidents 
and  loss  of   life  where   greater   precau- 
tions have  been  adopted,  or  less  risk  is 
apparently  incurred.     A  comparatively 
trifling  defect  may  in  one  case  lead  to 
much  loss  of  life,  whilst  important  de- 


*  The  deaths  of  two  of  this  number  were  not  the  results 
of  train  accidents. 


f  ects  may,  in  another  case,  be  unattended 
with  accident. 

Setting  aside  considerations  of  human- 
ity, the'railway  companies  have  a  positive 
and  direct  pecuniary  interest  in  the 
avoidance  of  accidents,  and  capital  laid 
out  with  that  object  in  view  is  not  likely 
to  be  wholly  unproductive.  Under  Lord 
Campbell's  Act  the  railway  companies 
are  pecuniarily  liable  to  those  to  whom 
any  injury  is  caused  by  accidents,  <fcc, 
on  their  lines,  and,  during  the  ten  years 
from  1848  to  1857  inclusive,  there  was 
paid  as  compensation  on  account  of  pas- 
sengers and  goods  injured  on  fourteen 
lines  of  railway,  no  less  a  sum  than 
£414,440,  or  at  the  rate  of  over  £40,000 
a  year.  For  the  five  years  ending  with 
the  year  1871,  there  was  similarly  paid 
£2,348,568?  of  which  £1,622,370  was  as 
compensation  for  personal  injury,  and 
£726,198  as  compensation  for  damage  to 
goods.  These  sums  do  not,  however, 
include  anything  on  account  of  injury  to 
the  servants  of  the  railway  companies, 
to  whom  the  latter  are  not  liable  by  law 
in  the  same  way  that  they  are  towards 
their  passengers  or  goods  traffic. 

The  following  table  shows  the  number 
of  train  accidents  that  have  formed  the 
subject  of  inquiry,  and  have  been  report- 
ed on,  by  officers  of  the  Board  of  Trade, 
during  the  past  four  years.  The  number 
of  cases  inquired  into  during  the  preced- 
ing five  years  averaged  83  per  annum, 
upon  which  those  for  the  year  1870  show 
an  increase  of  57  per  cent : 


126 

VAN  NOSTRAND's   ENGINEERING   MAGAZINE. 

18T0. 

1871. 

1872. 

1873. 

CAUSE  OP  ACCIDENT. 

9 

19 

21 

24 

From  engines  or  vehicles  meeting  with,  or  leaving  the 
rails  in  consequence  of  obstructions,  or  from  defects  in 
connection  with  the  permanent  way  or  works. 

10 

22 

17 

23 

From  boiler  explosions,  failures  of  axles,  wheels,  tyres, 
or  from  other  defects  in  the  rolling  stock. 

r 

22 

18 

From  collisions  between  engines  and  trains  following 
one  another  on  the  same  line  of  rails,  excepting  at  junc- 

61 

1 

tions,  stations,  or  sidings. 

[63 

91 

98 

From  colisions  within  fixed  signals  at  stations,  or 
sidings,  &c. 

18 

19 

32 

20 

From  collisions  at  junctions. 

3 

2 

5 

3 

From  collisions  between  trains,  &c. ,  meeting  in  oppo- 
site directions. 

1 

— 

— 

3 

From  collisions  at  level  crossings  of  two  railroads. 

14 

12 

34 

36 

From  passenger-trains  being  wrongly  turned  or  run  into 
sidings,  or  otherwise  through  facing  points. 

— 

2 

7 

5 

From  trains  entering  stations  at  too  great  speed. 

6 

11 

9 

11 

On  inclines. 

9 

12 

8 

6 

Miscellaneous. 

131 

171 

246 

247 

An  examination  of  this  table  will  show 
that  the  more  serious  classes  of  accidents 
are  evidently  upon  the  increase,  more 
particularly  from  collisions  within  fixed 
signals  at  stations  or  sidings,  and  from 
passenger  trains  being  wrongly  turned, 
or  run  into  sidings,  or  otherwise  through 
facing  points.  But  it  must  be  observed 
that  the  accidents  are  in  no  respect  pro- 
portionate to  either  the  length  of,  or  the 
amount  of  traffic  on,  any  particular  line 
of  railway,  some  lines  being  particularly 
unfortunate  in  this  respect,  while  others 
enjoy  comparative  immunity  from  acci- 
dents. Increase  of  traffice,  high  speed, 
and  variations  of  speed,  tend  materially 
to  increased  risk,  to  greater  numbers  of 
accidents,  and  to  more  severe  accidents 
when  there  is  insufficient  accommodation 
in  lines  and  sidings,  when  signal  and 
point  arrangements  are  defective,  when 
the  means  of  securing  intervals  between 
the  trains  are  defective,  without  sufficient 
break-power,  without  good  construction 
and  high  maintenance,  and  when  the 
appliances  and  apparatus  are  not  adapted 
to  the  exigencies  of  the  traffic.  But 
when,  on  the  other  hand,  the  accommo- 
dation is  sufficient  to  enable  the  traffic 
to  be  worked  under  safe  conditions, 
when  high  speed  is  employed  only  over 
a  good  permanent  way  in  suitable  por- 
tions of  railway,  and  under  proper  cir- 
cumstances, and  when  good  arrange- 
ments are  made  to  preserve  intervals  be- 


tween the  trains,  of  whatever  class,  then 
such  extra  risk  may  be  in  a  great  meas- 
ure obviated.  Some  of  the  great  railway 
companies  have  made,  and  others  are 
making,  great  progress  in  providing  the 
necessary  remedies.  It  was  stated  by  Mr. 
T.  B.  Farrer,  in  his  evidence  before  the 
Select  Committee  of  the  House  of  Lords 
last  year,  that  the  railway  companies  had 
then  already  spent  upon  the  introduction 
of  the  block  system  and  the  system  of  in- 
terlocking signals,  between  £700,000  and 
£800,000,  and  that  they  were  proposing 
to  spend  a  great  deal  more ;  on  a  previous 
occasion,  however,  it  had  been  stated  be- 
fore the  same  Committee,  by  Mr.  J.  S.Far- 
mer,  that,  in  his  opinion,  a  great  deal  of 
expense  had  been  thrown  away  in  tink- 
ering at  -the  signals,  in  trying  to  do  as 
little  as  possible,  instead  of  grasping 
the  thing  comprehensively  in  the  first 
place. 

However  much  has  already  been  ac- 
complished, a  good  deal  yet  remains  to 
be  done,  especially  on  certain  railway 
systems;  and  Captain  Tyler  expresses  it 
as  his  opinion  that  it  is  partly  on  ac- 
count of  sufficient  attention  not  having 
been  paid  in  previous  years  to  the  vari- 
ous means  of  safety  that  some  of  the 
great  railway  companies  now  appear  so 
unfavorably  at  the  head  of  the  accident 
list,  and  partly  also  because  they  have 
found  it  difficult,  with  constantly  in- 
creasing traffic,  simultaneously  to  make 


RAILWAY  ACCIDENTS. 


127 


np   for  past  omissions  and  to  keep  up 
with  present  requirements. 

In  a  circular  letter  addressed  by  the 
President  of  the  Board  of  Trade  to  the 
several  railway  companies  in  November, 
1 873,  on  the  subject  of  the  great  increase 
in  the  number  of  railway  accidents  dur- 
ing 1872,  Mr.  Chichester  Fortescue  re- 
marked that  a  large  proportion  of  these 
casualties  appeared  to  have  been  due  to 
causes  within  the  control  of  the  railway 
companies.  "  If  it  may  be  contended," 
the  circular  goes  on  to  state,  "  that  the 
traffic  on  many  lines  has  very  greatly 
increased,  and  with  it  the  risks  of  rail-' 
way  traveling,  it  is  no  less  true  that  it  is 
within  the  power  of  the  companies  to 
take  care  that  the  permanent  way,  the 
rolling  stock,  and  the  station  and  siding 
accommodation,  are  kept  up  to  the  re- 
quirements of  the  traffic;  that  the  offi- 
cers and  servants  are  sufficient  in  num- 
ber and  quality  for  the  work  to  be  done, 
and  that  proper  regulations  for  their 
guidance  are  not  only  made,  but  en- 
forced; that  pains  are  taken  to  test 
every  reasonable  invention  and  expedi- 
ent devised  for  the  purpose  of  prevent- 
ing danger;  and  that  such  of  those  expe- 
dients as  experience  proves  to  be  effective 
are  adopted  without  undue  delay. 

"  In  the  face  of  the  facts  collected  and 
analyzed  by  Captain  Tyler,  and  of  the 
numerous  accidents  of  the  present  year 
(many  of  them  the  subject  of  Board  of 
Trade  inquiries)  it  is  difficult  to  suppose 
that  such  is  the  case. 

"There  can  indeed  be  no  doubt  that 
methods  of  working  and  mechanical 
.contrivances,  the  value  of  which  has 
been  thoroughly  ascertained,  have  been 
too  slowly  introduced,  and  that  there  is 
great  reason  to  believe  that  sufficient 
provision  has  not  been  made  for  the  safe 
working  of  the  increased  traffic  by  the 
enlargement  or  re-arrangement  of  sta- 
tions and  sidings,  and  the  laying  down 
of  additional  lines  of  rail. 

"  But  whatever  may  be  thought  of 
these  and  other  causes  as  contributing 
to  the  result,  the  present  insecurity  of 
railway  traveling  imposes  upon  the  rail- 
way companies  the  grave  responsibility 
of  finding  appropriate  remedies  for  so 
great  an  evil." 

On  the  subject  of  the  frequent  un- 
punctuality  of  trains  it  was  remarked, 
"The   inconvenience,  vexation,  and  loss 


caused  to  passengers  by  this  breach  of 
the  conditions  upon  which  the  companies 
profess  to  carry  them,  constitute  in 
themselves  a  s^ious  subject  of  com- 
plaint. But  the  evil  arising  from  un- 
punctuality  does  not  end  here.  The 
surface  of  the  line  is  disarranged;  the 
chances  of  accident  are  multiplied;  the 
trains  are  foreed,  in  order  to  make  up 
for  lost  time,  to  travel  at  excessive  speed 
through  complicated  stations,  or  under 
other  circumstances  where  such  traveling 
may  be  equally  dangerous." 

It  is  further  remarked  that  the  returns 
of  accidents  to  railway  servants  show  a 
lamentable  number  of  casualties,  often 
fatal,  in  proportion  to  the  numbers  em- 
ployed; and,  finally,  a  hope  is  expressed 
that  the  railway  companies  themselves 
"  will  make  every  effort  to  meet  the  rea- 
sonable demands  of  the  public  and  of 
Parliament." 

The  Board  of  Trade,  as  the  branch 
of  the  Government  which  has  to  look 
after  the  interest  of  the  public  in 
respect  to  railway  traveling,  for  which 
purpose  it  has  been  invested  with 
special  powers,  could  not  with  any 
degree  of  propriety  have  passed  over, 
without  some  special  notice,  the  alarm- 
ing increase  in  the  number  of  railway 
accidents  recorded  in  1872,  which  had 
increased  nearly  44  per  cent,  over  1871, 
88  per  cent,  over  1870,  and  196  per 
cent  over  1869.  It  is  not  proposed  to 
consider,  separately,  the  replies  to  this 
circular  which  were  sent  to  the  Board  of 
Trade,  as  the  remarks  which  they  con-* 
tained  with  reference  to  the  principal 
causes  of  accident  prevailing  on  rail- 
ways, will  be  noticed  further  on  under 
the  different  headings  to  which  they  re- 
spectively belong. 

The  means  of  safety  which  the  acci- 
dents occurring  last  year  show  to  be  re- 
quired, are  thus  given  in  the  last  General 
Report  to  the  Board  of  Trade: 

1.  The  judicious  selection,  training, 
and  supervision  of  officers  and  servants, 
and  the  preservation  of  good  discipline. 

2.  Maintenance  in  high  condition  of 
the  permanent  way. 

3.  Good  design,  construction,  and  ma- 
terial of  axles. 

4.  The  application  of  tyre  fastenings 
which  will  prevent  the  tyres  from  fiying 
off  the  wheels  in  the  event  of  fracture. 


128 


VAN  NOSTRAND's   ENGINEERING  MAGAZINE. 


5.  Improved  coupling  of  vehicles  in 
trains. 

6.  Signal  and  point  arrangements  with 
modern  improvements,*  including  con- 
centration and  interlocking  of  the  signal 
and  point  levers,  and  locking-bolts  and 
locking-bars  for  facing  points. 

7.  Safety  points  to  goods  or  siding 
connections  with  passenger  lines. 

8.  Increased  use  of  the  telegraph, 
with  block-telegraph  systems  for  securing 
intervals  of  space  instead  of  illusory  in- 
tervals of  time  only  between  trains. 

9.  Sufficient  siding  accommodation  for 
the  collection,  distribution,  and  working 
of  goods  traffic,  so  that  goods  trains 
may  be  shunted  and  marshalled  inde- 
pendently, and  kept  out  of  the  way  of 
passenger  trains,  and  may  not  encumber 
and  endanger  the  traffic  on  the  main 
lines. 

10.  Continuous  breaks,  to  be  worked 
by  the  engine-drivers  as  well  as  the 
guards,  as  occasion  may  require. 

We  propose  to  consider  these  several 
means  for  providing  increased  security 
to  railway  traffic  under  the  following 
headings,  viz. — 1.  Efficiency  of  Staff.  2. 
Maintenance  of  Permanent  Way.  3. 
Maintenance  of  Rolling  Stock.  4.  Sig- 
nals and  Points.  5.  Telegraph,  and  the 
Block  System.  6.  Siding  Accommoda- 
tion. 7.  Break  Power, 

1.  Efficiency  of  Staff. — It  will  be 
readily  understood  that,  all  mechanical 
appliances  for  ensuring  safety  being 
perfect,  the  efficiency,  both  as  regards 
strength  of  establishment  and  individual 
intelligence,  on  the  part  of  the  railway 
staff  is  yet  necessary  in  order  to  secure 
freedom  from  accident  and  danger. 
Even  under  the  most  perfect  organization, 
however,  the  fallibility  of  human  nature 
must  ever  be  a  bar  to  the  attainment  of 
absolute  security,  but  the  risk  may  be 
lessened  to  the  last  practical  limit  by 
the  maintenance  of  a  fully  efficient  staff, 
and  the  strict  enforcement  of  all  regula- 
tions laid  down  for  their  guidance.  In  a 
paper  on  "  Railway  Accidents,"  read  be- 
fore the  Institution  of  Civil  Engineers 
as  far  back  as  April,  1862,  Mr.  James 
Brunlees,  the  author,  observed  that  the 
negligence  of  servants,  their  payment, 
and  their  hours  of  working,  were  matters 
of  the  greatest  importance,  and  he  re- 


marked that  most  of  the  accidents 
caused  by  negligence  might  be  traced  to 
ignorance  or  to  inefficiency.  The  wages 
usually  given  by  railway  companies  were 
too  small  to  command  the  services  of 
men  of  intelligence,  steadiness,  and  self- 
reliance,  and,  in  consequence,  inferior 
men  were  employed,  who  were  incapable 
of  appreciating  the  importance  and  ne- 
cessity of  executing  their  duty  with 
promptness  and  exactitude.  In  the  offi- 
cial report  to  the  Board  of  Trade  on 
railway  accidents  for  the  year  1870,Cap- 
tain  Tyler  remarked,  after  enumerating 
the  accidents  of  the  year  under  their 
respective  headings:  "Accidents  from 
all  the  above  causes  are  more  or  less  pre- 
ventible,  except  in  so  far  as  it  will  never 
be  possible,  under  the  best  arrangements, 
altogether  to  avoid  accidents  from  negli- 
gence or  mistakes  on  the  part  of  em- 
ployees, although  it  is  practicable,  under 
good  arrangements  and  systems,  and 
with  good  discipline,  very  much  to  re- 
duce their  number." 

In  the  year  1871,  out  of  171  investi- 
gated accidents,  there  had  been  in  121 
cases  of  negligence,  want  of  care,  or 
neglect  of  servants;  in  1872,  out  of  238 
cases,  180  were  due  to  negligence  or 
mistakes  of  officers  or  servants;  and  in 
1873,  out  of  241  accidents,  a  similar 
negligence  was  apparent  in  182  cases. 

Whatever  be  the  means  and  appli- 
ances provided,  or  the  amount  of  care 
taken,  the  item  of  human  fallibility 
will  always  be  the  cause  of  a  certain 
number  of  accidents.  But  the  number 
of  accidents  from  this  cause,  as  was  re- 
marked by  Captain  Tyler  in  his  report 
for  1873,  may  be  very  much  reduced  by 
"  improvements  in  regulations  and  dis- 
cipline, by  greater  care  in  the  selection, 
training,  payment,  and  employment  of 
competent  men  in  sufficient  numbers  and 
for  reasonable  hours,  and  by  providing 
them  with  the  requisite  siding  and  other 
accommodation,  with  proper  signal  and 
point  apparatus,  with  the  best  means  of 
securing  intervals  between  trains,  with 
sufficient  break-power,  and  with  other 
necessary  appliances."  It  has  been  argued 
that  railway  servants  are  apt  to  become 
more  careless  in  the  use  of  these  im- 
provements, in  consequence  of  the  extra 
security  which  they  are  believed  to 
afford;  but,  whilst  Captain  Tyler  re- 
marks that  by  the  results  of  more  ex- 


RAILWAY   ACCIDENTS. 


129 


tended  experience  this  argument  has  re- 
ceived further  confutation,  Mr.  Harrison, 
the  President  of  the  Institution  of  Civil 
Engineers,  and  no  mean  authority  on 
railway  matters,  stated,  in  his  inaugural 
address,  that  there  was  an  undoubted 
tendency  on  the  part  of  engine  -  men 
and  other  railway  servants  to  believe 
that  all  these  arrangements  of  the  block 
system  and  additional  signals  do,  in  fact, 
provide  for  their  safety,  and  that  conse- 
quently they  do  not  keep  the  same  look 
out,  or  use  the  same  care  that  they 
would  do  on  a  line  apparently  less  pro- 
tected, "and  that  this  is  the  case,"  he 
remarked,  "observation  and  inquiry  have 
clearly  demonstrated." 

Here,  then,  we  find  two  leading  au- 
thorities at  issue  in  regard  to  a  state- 
ment of  fact,  and  it  is,  of  course,  very 
difficult  to  draw  a  fair  conclusion  be- 
tween the  two.  The  result  of  Mr.  Harri- 
son's experience  seems  to  prove  that,  at 
present,  railway  servants  have  not  be- 
come sufficiently  experienced  in  respect 
to  the  true  value  of  signals,  and  other 
means  of  safety  on  railways,  but  there 
is  surely  reason  to  hope  that,  as  a  body, 
they'  possess  sufficient  intelligence  to 
enable  them  in  time  to  appreciate  more 
fully  the  extent  to  which  these  safeguards 
are  valuable,  and  how  much  also  depends 
upon  thek  individual  discretion. 

In  respect  to  enforcing  discipline,  Mr. 
Harrison  observes  that  the  difficulty  is 
becoming  constantly  greater,  as  dismissal 
is  no  longer  a  punishment,  when  employ- 
ment can  at  once  be  had  elsewhere;  and 
a  reprimand  is  constantly  met  with  the 
reply,  "Oh!  very  well,  I'll  go."  This 
gentleman  has  found  that  nothing  at- 
taches men  more  to  the  service  of  a 
railway  company  than  giving  them  com- 
fortable cottages,  with  gardens  to  culti- 
vate. 

The  efficiency  of  a  staff  on  a  railway 
depends  mainly  upon  three  circum- 
stances: First,  the  selection  of  none  but 
respectable  and  tolerably  educated  men; 
secondly,  the  establishment  of  a  fixed 
code  of  rules  for  their  guidance,  and 
seeing  that  those  rules  are  strictly  en- 
forced; and,  thirdly,  the  maintenance 
of  an  efficient  number  of  men  to  do  the 
required  work;  the  payment  of  liberal 
wages,  so  as  to  keep  them-  in  the  service; 
the  holding  out  of  prospects  of  promo- 
tion to  the  most  efficient;  and  the  proper 
Vol.  XIII.— No.  2—9 


treatment  of  them  whilst  in  the  ser- 
vice. 

No  doubt  all  modern  improvements 
on  railway  working  tend  to  increase  the 
expense  to  the  railway  companies,  but 
this  is  a  matter  for  which  there  is  ap- 
parently no  remedy.  "  The  question  of 
the  effect  of  the  labor  market  on  rail- 
ways, both  in  their  construction  and 
working,"  says  Mr.  Harrison,  "has  come 
forcibly  home  to  every  one  connected 
with  them.  It  is  not  too  much  to  say 
that  all  new  works  are  now  costing  from 
30  to  40  per  cent,  more  than  they  did  a 
few  years  ago,  and  nearly  double  the 
time  is  required  to  complete  them." 

As  will  be  shown  further  on,  the 
adoption  of  the  block  system  on  all  lines 
will  necessitate  a  considerable  increase  of 
staff  for  working  it,  and  with  these  addi- 
tional elements  of  "  human  frailty " 
there  will  evidently  exist  an  increase  in 
the  numbers  of  those  to  whom  the  safety 
of  the  traveling  public  will  be  entrusted, 
and  increased  safety  can  therefore  only 
be  expected  to  result  if  the  rules  laid 
down  for  the  guidance  of  the  companies' 
servants  are,  in  the  first  instance,  judi- 
ciously framed,  and  afterwards  rigidly 
enforced. 

2.  Maintenance  of  Permanent  Way. — 
The  accidents  caused  by  defects  in  per- 
manent way  are,  happily,  not  nearly  so 
numerous  as  they  were  in  former  years. 
The  art  of  constructing  railways,  in  the 
first  instance,  and  of  properly  maintain- 
ing them  afterwards,  is  so  much  better 
understood  now  than  formerly,  that  ac- 
cidents arising  from  defects  in  its  ob- 
servance would  be  a  great  slur  upon  the 
professional  officers  of  any  company.  In 
the  year  1854,  thirteen  accidents  oc- 
curred from  the  defective  condition  or 
neglect  of  the  permanent  way.  In  the 
following  year  thirty-one  cases  arose 
from  the  same  causes,  but  in  the  year 
1856  there  were  fewer  accidents  of  this 
description,  which  fact  maybe  attributed 
to  the  greater  attention  given  by  engi- 
neers to  the  permanent  way,  and  to  the 
introduction  of  the  fished  joint,  and  of 
other  improved  methods  of  connecting 
rails.  In  the  year  1857  twenty  accidents 
were  caused  by  the  neglect,  or  imperfect 
condition,  of  the  permanent  way;  in  four 
of  these  the  permanent  way  had  been 
neglected,  and  in  five  it  had  been  con- 


130 


VAN  NOSTRAND'S   ENGINEERING   MAGAZINE. 


structed  in  a  defective  manner.  In  1S58, 
twenty-nine  accidents,  and  in  1859  four- 
teen accidents,  were  due  to  the  state  of 
the  permanent  way. 

In  commenting  on  this  class  of  railway 
accidents,  due  to  permanent  way  defects, 
which  occurred  during  1870,  Captain 
Tyler  stated  that  onlj*  nine  were  attrib- 
utable to  the  conditions  of  the  way  and 
works,  or  to  obstructions  on  the  perma- 
nent way,  etc.  "  This,"  he  observed,  "  is 
a  great  improvement  upon  former  years, 
when,  say  ten  years  ago,  16  per  cent,  of 
railway  accidents  were  caused  principally 
by  defects  of  permanent  way;  and  the 
improvement  is  due,  partly  to  the  in- 
creased strength  in  some  cases  of  rails 
and  chairs,  partly  to  placing  the  sleepers 
in  some  cases  nearer  together,  and  espe- 
cially to  the  disuse  of  wooden  trenails 
for  attaching  the  chairs  to  the  sleepers, 
and  to  the  now  almost  universal  employ- 
ment of  fish-joints  for  fastening  the  ends 
of  the  rails  together."  As  to  the  remedy 
suggested  for  this  class  of  accidents,  it 
is  remarked  that  next  in  importance  to 
proper  maintenance,  and  even  as  part  of 
it,  is  the  question  of  discipline  amongst 
those  employed  in  repairs,  with  a  view 
to  ensure,  as  far  as  possible,  that  due 
warning  shall  be  given  to  engine-drivers 
when  a  rail  has  to  be  taken  out,  while 
the  road  is  being  lifted,  or  whenever  the 
line  is  not  in  a  fit  condition  to  be  run 
over  at  speed. 

Twenty-six  accidents  occurred  in  1871 
owing  to  defects  of  construction.  These 
defects,  it  was  then  pointed  out,  were 
not  as  promptly  corrected  as  they  ought 
to  have  been,  as  new  materials  were 
supplied,  on  many  lines  of  railway;  each 
company,  or  each  individual  officer, wait- 
ing too  often  to  buy  his  own  experience, 
and  profiting  too  little  by  the  experience 
of  other  companies.  Defects  of  main- 
tenance, which  appeared  in  nineteen 
cases,,  occurred  partly  from  the  over-work 
of  materials,  and  partly  from  the  want 
of  more  careful  supervision,  and  of  more 
careful  record  and  comparison,  from 
which  much  valuable  information  might 
be  obtained.  The  number  of  accidents 
due  to  defective  construction  of  road  or 
works  was  four  in  1872,  and  six  in  1873, 
and  to  defective  maintenance  of  the 
same,  sixteen  in  1872,  and  twenty-four 
in  1873. 

It   may   perhaps   be   considered   that 


forty  accidents  in  one  year,  upon  all  the 
railways  in  the  United  Kingdom,  due  to 
defective  construction  or  maintenance, 
is  hardly  above  the  number  that  might 
be  expected  to  occur  from  such  causes, 
considering  the  vast  amount  of  traffic 
which  now  takes  place  in  the  neighbor- 
hood, more  particularly,  of  large  towns 
and  cities,  but  it  must  be  remembered 
that  these  constitute  a  class  of  accident 
which  is  preventible  by  the  exercise  of 
due  care  on  the  part  of  the  permanent 
way  staff,  and  proper  supervision  during 
construction.  It  is,  therefore,  one  which 
should  not  be  seen  in  the  official  returns, 
unless  accompanied  by  some  such  causes 
as  exceptional  floods,  or  other  reasons  to 
show  that  they  were  not  occasioned  by 
any  laxity  of  duty  or  neglect  of  ordinary 
precautions  on  the  part  of  the  railway 
company  or  their  officials. 

Maintenance  of  Moiling  Stock. — With 
regard  to  locomotives,  instances  do  rarely 
occur — and  they  were  more  common  in 
former  than  in  recent  years — of  boiler 
explosions,  due  in  some  instances  to 
want  of  proper  care  in  the  selection  of 
water  for  their  use,  and  in  others,  to  a 
faulty  mode  of  staying  the  boiler.  These 
causes  of  accident  are  to  be  avoided  by 
frequent  inspection,  by  which  the  earliest 
intimation  of  any  deterioration  may  be 
obtained,  and  the  employment  of  weak- 
ened or  worn-out  boilers  be  discontinued. 
During  the  seven  years  from  1854  to 
1860  twenty-one  locomotives  exploded, 
but  in  the  annual  returns  to  the  Board 
of  Trade  only  two  accidents  from  this 
cause  are  stated  to  have  taken  place  in 
1870,  and  two  in  1873  ;  no  record  of  a 
similar  accident  appearing  in  the  two  in- 
tervening years. 

The  most  common  accidents  to  rolling 
stock  are  the  breaking  of  the  axles  and 
wheel  tyres.  These  cases  may  be  traced 
generally  to  one  or  other  of  the  follow- 
ing causes  :  sometimes  they  occur  in  the 
winter  months,  owing  possibly,  in  some 
degree,  to  the  rigid  state  of  the  perma- 
nent way  in  frosty  weather  ;  some  are 
due  to  the  use  of  bad  iron  or  steel,  and 
others  to  defects  either  in  the  welding  of, 
or  in  the  mode  of  attaching,  the  tyres  of 
wheels.  The  existence  of  flaws  in  either 
axles  or  tyres  may  completely  escape  de- 
tection until  they  are  discovered  upon 
the  occurrence  of  an  accident,  and  such 


RAILWAY   ACCIDENTS. 


131 


cases  must  be  included  amongst  the  risks 
which  cannot  be  foreseen  or  avoided. 
The  high  speed  at  which  trains  travel 
as  a  general  rule  must  subject  both  tyres 
and  axles  to  very  severe  blows  and  jerks, 
especially  when  passing  over  points,  or 
portions  of  line  that  are  out  of  repair, 
and  uneven,  and  it  is  in  such  cases  that 
flaws  or  cracks  are  most  likely  to  result 
in  a  complete  fracture.  "  There  is  no 
satisfactory  test,"  said  Captain  Tyler,  in 
his  report  for  1870,  "to  which  axles  can 
be  subjected  from  time  to  time  in  the 
course  of  running,  as  far  as  is  known,  by 
which  flaws  can  be  detected."  With  re- 
gard to  fracture  of  tyres,  it  was  stated 
in  the  same  report  that  in  two  cases  the 
tyre  was  attached  to  the  wheel  by  means 
of  rivets  through  holes  bored  in  the 
tyre,  and  it  was  remarked  that  the  "  old 
system  of  boring  holes  through  the  tyres 
is  essentially  a  vicious  one,  and  is  par- 
ticularly undesirable  in  the  case  of  steel 
tyres.  It  affords  no  security  in  the  event 
of  fracture,  and  even  leads  to  increased 
risk  of  fracture,  in  consequence  of  the 
weakening  of  the  tyre  at  the  sides  of  the 
rivet  holes. 

In  1871  there  were  twenty-two  acci- 
dents of  this  class,  in  which  three  per- 
sons were  killed  and  thirty-four  were  in- 
jured ;  in  1872  there  were  seventeen 
accidents,  occasioning  the  death  of  two 
passengers  and  five  servants  of  compa- 
nies, and  injury  to  forty  passengers  and 
eight  servants  of  companies,  whilst  in 
1873  there  were  twenty-three  accidents 
owing  to  the  same  causes,  killing  ten 
passengers  and  two  servants  of  compa- 
nies, and  injuring  fifty-four  passengers 
and  seventeen  servants  of  companies. 
The  chief  methods  recommended  for 
adoption  with  a  view  to  avoiding  acci- 
dents from  the  breaking  of  tyres,  consist 
in  the  use  of  improved  modes  of  fasten- 
ing them  to  the  rims,  so  as  to  prevent 
them  from  flying  off  the  wheel.  They 
may  fail  from  the  brittle  nature  of  the 
material,  or  from  defects  of  manufacture, 
or  from  being  too  tightly  shrunk  on  the 
wheel,  and  they  have  frequently  failed 
from  one  of  these  causes,  or  from  a  com- 
bination of  them.  The  danger  consists, 
not  in  the  fracture,  or  in  the  tyre  becom- 
ing divided,  whilst  running,  into  two  or 
more  parts,  but  in  the  probability  of  the 
tyre,  which  is,  or  ought  to  be,  in  a  state 
of  tension  on  the  wheel,  flying  suddenly 


and  violently  from  it  when  fracture  oc- 
curs, and  this  danger  is  greater  with 
steel  than  with  iron  tyres. 

3.  Signals  and  Points. — During  the 
seven  years  from  1854  to  I860  inclusive, 
as  many  as  eighty-eight  accidents  hap- 
pened from  the  use  of  improper  or  in- 
efficient signals.  Accidents  have  been 
caused  by  the  total  want  of  signals,  es- 
pecially at  sidings,  others  have  arisen 
from  their  defective  form,  or  from  their 
bad  position.  Many  accidents  have  oc- 
curred in  connection  with  distance  sig- 
nals; in  some  cases  they  have  been  placed 
so  near  to  the  station  that  the  engine- 
driver  has  been  unable  to  stop  within 
the  space  allowed.  It  was  observed  by 
Captain  Tyler  in  1870,  that  out  of  sixty- 
one  collisions,  independent  of  the  colli- 
sions at  junctions  or  level  crossings, 
thirty-one,  or  more  than  half  of  them, 
were  due  to  defective  arrangements  with 
regard  to  signals  or  points,  but  that  in 
twenty-eight  cases  out  of  these  negli- 
gence was  combined  with  the  defects, 
and  that  the  latter  contributed  more  or 
less  to  the  negligence  ;  and  out  of  eight- 
een collisions  at  junctions  there  were 
ten  cases  in  which  defective  signal  and 
point  arrangements  were  the  cause.  In 
1871  there  were  fifty-three  acciderfts 
caused  by  defective  signal  and  point  ar- 
rangements, or  want  of  locking  appar- 
atus ;  in  1872  the  number  of  accidents 
due  to  similar  causes  was  seventy-one, 
and  last  year  it  was  seventy-eight,  so 
that  this  cause  of  accident  would  appear 
to  be  growing  rapidly  in  importance. 

When  trains  were  few,  and  the  speed 
at  which  they  traveled  was  moderate,  a 
comparatively  crude  method  of  signal- 
ing sufficiently  answered  every  purpose; 
with  the  increase  of  trains,  the  complica- 
tions of  junctions,  and  the  greater  diffi- 
culty that  consequently  existed  in  con- 
trolling a  number  of  signals  at  any  one 
point,  it  became  necessary  to  place  all 
the  signals  and  point  levers  in  or  around 
the  signal  cabins;  and,  in  order  to  afford 
a  better  view  to  the  signal  man,  the 
cabins  were  raised  to  a  greater  or  less 
height  above  the  ground,  and  placed  in 
convenient  situations,  according  to  local 
circumstances.  But  even  then,  when  the 
control  was  more  conveniently  placed 
in  the  hands  of  one  man,  there  was  still, 
as  the  levers  in  or  near  a  cabin  became 


132 


VAN   NOSTRAND'S   ENGINEERING   MAGAZINE. 


more  numerous,  a  liability  to  mistake, 
from  the  signalman  pulling  over  a  wrong 
lever  ;  or  the  levers  were  fastened  over 
by  blocks  of  wood,  which  the  signalman 
forgot  to  remove  ;  and  to  prevent  such 
mistakes,  and  serious  accidents  resulting 
from  them,  it  became  further  necessary 
to  interlock  the  levers  with  one  another. 
By  1860  many  improvements  had  been 
introduced  upon  the  interlocking  system, 
and  the  inspecting  officers  of  the  Board 
of  Trade  began  to  insist  on  the  use  of 
locking  apparatus  at  the  junctions  of 
new  branches  with  existing  lines. 

By  the  application  of  locking  and 
other  apparatus  it  is  possible  to  prevent 
nearly  all  accidents  from  collision  occur- 
ring, in  the  ordinary  way  of  working,  in 
consequence  of  any  mistake  of  the  sig- 
nalman. Conflicts  between  signals,  and 
conflicts  between  points  and  signals,  may 
alike  be  avoided  ;  and  a  good  combina- 
tion of  locking-bar  and  bolt  may  be 
made  to  insure  that  the  facing  points 
are  completely  over  before  the  proper 
signal  is  lowered,  and  may  also  prevent 
them  from  being  moved  during  the  pas- 
sage of  a  train.  It  is,  of  course,  impos- 
sible to  provide  against  all  the  contin- 
gencies which  may  arise — such  as,  in  cer- 
tain cases,  against  the  absolute  neglect 
of  ^drivers  to  pay  attention  to  the  signals 
made  to  them  ;  or  such  as  a  signalman, 
when  two  trains  are  running  towards  a 
junction  at  one  time,  setting  his  points 
and  lowering  his  signals  first  for  one  of 
them,  and  then  altering  them  and  pre- 
paring for  the  second  train,  without  al- 
lowing time  for  the  first  train  to  stop 
short  of  the  junction.  But  provision 
may  be  made,  and  is  made  to  some  ex- 
tent, even  for  the  contingency  of  an  en- 
gine-driver neglecting  to  obey  signals. 

In  a  paper  recently  read  before  the  In- 
stitution of  Civil  Engineers,  by  Mr.  R. 
C.  Rapier,  a  detailed  description  of  sig- 
nals and  points  was  given,  besides  an 
account  of  different  methods  of  inter- 
locking the  two,  so  as  to  avoid  accidents 
which  might  occur  in  the  event  of  wrong 
signaling.  It  would  be  impossible  to 
follow  out  that  paper  in  detail  here,  but 
we  may  briefly  state  that  it  was  there 
shown  that  the  mere  connection  of 
switches  and  signals  was  not  sufficient, 
but  that  effective  interlocking  required 
the  movement  of  the  switches  to  be 
completed  before  the  alteration  of  the 


signals  could  be  made,  and  vice  versa; 
whilst,  as  regards  facing-points,  it  was 
stated  that,  although  it  was  desirable  to 
avoid  tlrem  as  much  as  possible  on  a  line 
of  light  traffic,  the  use  of  facing-points, 
properly  controlled,  might  be  made  one 
of  the  greatest  safeguards  where  trains 
were  frequent,  aud  traveled  at  different 
rates  of  speed. 

5.  Telegraph  and  the  Block  System. — 
In  two  papers  on  "  Railway  Accidents," 
by  Mr.  Brunlees  and  by  Captain  Galton, 
read  at  the  Institution  of  Civil  Engineers 
in  1862,  it  was  deduced  from  statistical 
tables  that  the  great  majority  of  acci- 
dents were  attributable  to  preventible 
causes,  and  that,  of  these,  27  per  cent, 
were  due  to  the  absence  of  the  electric 
telegraph.  The  advantages  of  the  tele- 
graph in  connection  with  the  working  of 
railways  were  dealt  with  in  an  able 
paper  by  Mr.  W.  II.  Preece,  which  was 
read  at  the  Institution  of  Civil  Engineers 
as  far  back  as  January,  1863,  and  al- 
though all  the  views  expressed  by  him 
on  the  subject  at  that  time  have  not  met 
everywhere  with  approval  or  adoption, 
the  system  generally  has  come  to  be 
recognized  as  absolutely  necessary  for 
the  safe  working  of  any  line  of  railway, 
and  it  forms  a  most  important  element 
in  the  now  universally  adopted  block 
system. 

The  first  attempt  of  a  block  system 
introduced  on  railways  was  by  maintain- 
ing a  presumed  time  interval  between 
trains;  this  plan,  however,  failed,  because 
those  intervals  could  not  in  practice  be 
observed;  and  the  permissive  system  for 
reducing  the  time  intervals  by  the  aid 
of  the  telegraph,  and  sending  trains 
timed  to  travel,  and  capable  of  traveling, 
at  various  speeds,  one  after  another,  into 
the  sections,  with  a  caution  to  each,  may 
also  be  considered  to  have  failed,  because 
it  does  not  afford  sufficient  protection  to 
the  traffic.  Under  these  time  systems 
collisions  have  occurred  from  engine- 
drivers  slackening  their  speed  to  avoid 
collision  with  trains  in  front  of  them, 
and  being  run  into  by  trains  behind 
them.  The  greater  the  variety  of  speed 
between  the  trains,  the  more  does  the 
weakness  of  such  systems  become  ap- 
parent. 

The  proposal  to  divide  the  line  of  rail- 
way into  telegraphic  sections,  and  thus 


RAILWAY   ACCIDENTS. 


133 


to  preserve  space  intervals  between 
trains,  was  made  by  Mr.  (now  Sir  Wil- 
liam) Cooke,  as  far  back  as  1842,  and 
was  first  practised,  it  is  believed,  on  a 
portion  of  what  is  now  the  Great  Eastern 
Railway,  in  1844;  and,  subsequently,  a 
train  telegraph  system  was  established 
on  portions  of  the  London  and  North- 
Western  Railway.  This  latter,  however, 
was  not  a  block  system,  or  a  space  sys- 
tem, but  a  time  system  worked  with  the 
aid  of  telegraph  instruments,  and  it  is 
now  known  as  the  permissive  system. 
As  regards  the  block  system,  there  are 
many  descriptions  of  instruments  for 
working  it,  and  various  rules  and  regula- 
tions applicable  to  it  on  different  lines  of 
railway.  The  main  principle  involved  is 
simply  by  the  division  of  a  line  into 
block  sections,  and  allowing  no  engine  or 
train  to  enter  a  block  section  until  the 
previous  engine  has  quitted  it,  to  pre- 
serve an  absolute  interval  of  space  be- 
tween engines  and  trains.  This  may  be 
done  mechanically  or  electrically.  Any 
means  of  communication  with  which  the 
signalmen  may  be  provided  will  enable 
them  to  inform  one  another  of  the  ap- 
proach of  a  train,  of  its  entrance  into  a 
block  section  at  one  end,  and  of  its  exit 
from  that  block  section  at  the  other  end. 
Mr.  Harrison,  the  President  of  the  In- 
stitution of  Civil  Engineers,  has  stated 
that  the  block  system  will,  as  soon  as  ,it 
is  possible  to  complete  the  necessary 
works,  be  introduced  throughout  the 
whole  of  the  railways  in  England.  It 
was  stated  by  Mr.  Farrar,  before  the 
Select  Committee  of  the  House  of  Lords 
last  year,  that  the  railway  companies 
had  already  spent  upon  introducing  the 
block  system,  and  the  system  of  inter- 
locking signals,  between  £700,000  and 
£800,000,  and  they  were  proposing  to 
spend  a  great  deal  more.  Besides  this 
expense  there  is  a  considerable  annual 
cost  to  be  incurred  in  working  those  sys- 
tems; the  increased  cost  of  the  staff  alone 
is  estimated  for  the  Great  Eastern  Rail- 
way at  £13,860,  and  on  the  Midland  at 
£130,000  per  annum.  In  the  case  of  the 
North  Eastern  Railway  it  is  calculated 
that  on  the  completion  of  the  block  sys- 
tem, the  number  of  signalmen  will  be 
increased  from  500  to  2,000.  Mr.,  Rapier, 
in  his  paper  to  which  we  have  already 
referred,  shows  that  the  probable  cost  of 
the   interlocking   and   block   system  on 


fourteen  of  the  principal  railways  would 
be  about  {  per  cent,  on  the  whole  cost 
of  the  lines,  and  that  then  their  carrying 
power  might  be  so  increased  that  three 
times  as  many  trains  could  be  run  on 
the  block  system  as  without  it,  and  with 
greater  safety.  The  probable  cost  of 
maintaining  the  block  system  was  stated 
to  be  about  2^  per  cent,  on  the  traffic  re- 
ceipts, and  this  comparative  percentage 
was  less  on  the  lines  which  had  a  great 
number  of  points  to  protect  than  on 
some  of  the  light  traffic  railways. 

6.  /Siding  Accommodation.— It  was 
pointed  out  in  the  Report  to  the  Board 
of  Trade  on  Accidents  that  occurred 
during  1871,  that  collisions  at  stations 
often  occurred  from  the  want  of  accom- 
modation at  the  stations  or  sidings,  pas- 
senger lines  being  unduly  obstructed 
from  the  want  of  sidings  in  which  to 
place  slow  or  stopping  trains,  or  in  which 
shunting  may  be  performed.  The  same 
deficiency  of  accommodation  may  also 
be  the  indirect  cause  of  collisions  on  the 
line  between  stations,  when,  for  instance, 
from  the  want  of  siding  accommodation, 
a  slower  train  is  despatched  in  advance 
of  a  faster  one,  without  a  sufficient  inter- 
val between  them  to  allow  of  its  pro- 
ceeding forward  to  the  next  place  of 
refuge  before  it  is  overtaken,  and  it  is 
stated  that  the  want  of  improvement  in, 
and  addition  to,  the  siding  accommoda- 
tion, combined  with  the  want  of  modern 
appliances  for  working  the  points  and 
signals  from  suitable  cabins,  and  inter- 
terlocking  the  levers  with  one  another, 
and  of  telegraph-working  for  assisting 
in  protecting  an  obstructed  station,  have 
principally  to  answer  not  only  for  the 
accidents  themselves,  but  also  for  the 
negligence  of  the  servants  by  which 
those  accidents  were  more  or  less  directly 
occasioned. 

7.  Brake  Power. — The  subject  of  brake 
power  is t  one  of  especial  importance, 
many  lives  and  much  property  being 
hourly  dependent,  in  a  greater  or  less 
degree,  on  the  power  and  efficient  state 
of  the  brakes.  It  has  been  found  that 
most  of  the  collisions  which  have  occur- 
red might  have  been  prevented  had 
those  in  charge  of  the  trains  posses- 
sed the  power  of  stopping  within  a 
few  hundred  yards.     This  is  more  par- 


134 


VAN   NOSTRANO'S   ENGINEERING   MAGAZINE. 


ticularly  necessary  on  account  of  the 
high  speeds  and  heavy  trains  now  adopt- 
ed on  all  lines.  It  is  thei*efore  essential 
that  there  should  he  ample  brake  power 
to  each  train,  and,  whatever  system 
may  be  adopted,  it  should  be  powerful, 
simple,  and  capable  of  being  applied  in 
the  shortest  possible  time.  On  certain 
railways,  where  the  necessities  or  con- 
venience of  the  companies  have  been  the 
means  of  inducing  more  rapid  improve- 
ments in  this  respect,  systems  of  continu- 
ous brakes  have  for  many  years  been  in 
successful  operation ;  and  the  experi- 
ence of  these  lines  has  left  no  doubt  of 
the  value  of  such  systems  of  brakes. 
Amongst  the  simpler  means  of  providing 
extra  brake  power  are  :  increasing  the 
numbers  of  guards  and  of  brake  vehicles; 
enabling  a  guard  or  brakesman  to  apply 
the  brakes  of  two  adjacent  vehicles; 
allowing  the  guards  and  brakesmen  to 
walk  through  the  trains,  and  to  apply  the 
brakes  of  the  various  vehicles  provided 
with  them  ;  or  by  such  a  system  as  may 
enable  a  guard  from  his  own  van  to 
apply  the  brakes  of  several  vehicles,  in 
which  may  be  combined  an  economy  in 
guards  with  efficiency  in  brake  power. 
In  the  use  of  any  good  system  of  this 
description,  it  becomes  unnecessary  to 
skid  the  wheels  of  brake-vehicles,  and 
flat  places  in  the  wheel  tyers  are  thus 
avoided.  Perhaps  the  most  perfect  sys- 
tem of  continuous  brakes  yet  introduced 
is  that  which  enables  the  engine  driver 
to  control  the  train,  and  by  means  of 
compressed  air  to  apply  all  the  brakes 


at  once  without  the  development  of  any 
manual  exertion. 

The  limit  of  space  to  which  we  are 
necessarily  confined  for  a  single  article 
has  prevented  any  detailed  account  of 
the  various  methods  of  intercommunica- 
tion in  trains,  which,  by  the  Regulation 
of  Railways  Act  of  186S,  is  directed  to 
be  provided  in  every  train  carrying  pas- 
sengers and  traveling  more  than  twenty 
miles  without  stopping,  or  of  the  several 
other  minor  arrangements  suggested  or 
introduced,  with  the  view  of  more  effec- 
tually securing  the  safety  of  passengers. 

With  the  adoption  of  the  improved 
methods  of  interlocking  signals  and 
points,  and  of  the  block  system,  no 
doubt  very  considerable  addition  is  made 
to  the  safety  of  travelers,  but  the  com- 
panies are  thereby  put  to  great  addition- 
al expense,  both  in  first  cost  and  for  sub- 
sequent maintenance,  for  which  the  only 
return  they  can  look  to  is  an  increased, 
immunity  from  accidents.  To  insure 
absolute  security  is  not,  however,  pos- 
sible, by  the  adoption  of  any  means 
hitherto  suggested.  The  introduction  of 
the  block  system  necessitates  the  main- 
tenance of  a  considerably  increased  staff 
of  signalers,  and  at  the  same  time  it  in- 
troduces so  many  additional  elements  of 
human  fallibility,  whose  liability  to  err 
can  only  to  a  limited  extent  be  guarded 
against  by  the  employment  only  of  com- 
petent men,  and  the  strict  enforcement 
of  such  rules  and  regulations  as  it  may, 
in  each  case,  be  considered  advisable  to 
frame  for  their  guidance. 


THE  FUTURE  OF  ARCHITECTURE. 


From  "The  Builder." 


Recent  discussions  have  shown  that 
there  is  no  desire  on  the  part  of  the  pro- 
fession to  disguise  the  defects,  the  de- 
merits and  the  failures,  which  have  in  so 
large  a  measure  exhibited  themselves  in 
connection  with  our  modern  architecture, 
and  the  system  to  which  we  are  indebted 
for  our  architects.  The  main  practical 
conclusion  we  have  now  to  face  is  that 
the  production  of  our  architecture  has 
passed  into  the  hands  of  an  immense 
multitude  throughout  the  country,  of 
whom  it  is  impossible  to  say  that  they 


are  the  fittest  minds  for  the  task  they 
have  undertaken,  or,  that  if  so,  there  is 
any  guarantee  of  their  qualifications. 
This  is  a  condition  of  things  with  which 
it  is  impossible  immediately  to  deal;  any 
amelioration  must  be  gradual,  progres- 
sive and  prospective.  No  system  of 
compulsory  examinations  could  be  set 
up,  or  the  absolute  necessity  of  a  diploma 
before  practice  enforced,  as  things  now 
are  ;  and  we  fear  that  the  offer  of  volun- 
tary examination,  and  the  advantages 
which     might     accrue     in    professional 


THE  FUTURE   OF   ARCHITECTURE. 


135 


status  by  being  fortified  by  such  a  guar- 
antee  would    be   responded   to    a   very 
slight  extent.     Hence,  as  we  have  said, 
any  remedial  measures  must  be  regarded 
chiefly     in     their     prospective     aspect. 
What   we    have  now  to   determine   is, 
whether  we  can  fairly  and  safely  hope 
that  there  are  elements  in  the  present 
condition  of  things,  which  will,  if  slow- 
ly, yet  surely,  work  their  own  cure.     In 
the  present  intermingling  and   jostling, 
as   it   were,    of    engineer,    builder,    and 
architect  on  the   same  field,  may  it  be 
hoped  that  the  gradual  improvement  of 
public  taste,  and  a  higher  tone  in  the 
patronage  upon  which  architecture  de- 
pends,   will    eventuate     in    a    demand 
which  will   be   unable   to   tolerate  that 
which  now  passes  for  sufficiently  good 
architecture,  and  in  the  end  so  far  elim- 
inate the  bad,  that  false,  mediocre,  and 
pretentious  work  will  sink  to  its  level, 
and  that  which  the  true   architect  can 
alone  supply  meet  with  its  fitting  place  ? 
We  are  very  distinctly  of  opinion  that 
it  is  fallacious  to  indulge  such  a  hope. 
It  must  be  a  fact  within  the  knowledge 
of  all  who  have  thought  upon  fine  art  in 
any  of  its  branches,  be  it  architecture, 
painting,    sculpture,    music,   or    poetry, 
that  "taste"  is  a  most  variable  quality, 
and  grows  by  that  which  it  feeds  upon. 
Illustrations  innumerable  might  be  given 
as  to  this,  but  we  will  confine  ourselves 
to  a  single  cognate  instance.     Can  there 
be  a  question  that,  even  among  minds  of 
an  average  range  of  culture  and  suscept- 
ibility to  aesthetic  influence,  that  after 
being  accustomed  to  a  low  type  of  art, 
say  in  architecture,   and  perfectly  satis- 
fied with  this,  because  knowing  no  higher 
or  better,  the  sight  of  indubitably  finer 
buildings  would  at  once  raise  the  taste, 
and   render  that   before   tolerated  with 
complaisance  almost  insufferable.     Now, 
this  we  take  to  be  the  key  of  the  whole 
question   of    an   advance   in   the  public 
taste  as  to  art,  and  it  decides  at  once 
what  we  believe  must  be  found  to  be  the 
truest  ground  upon  which  any  hope  can 
be  built,  that  the  "  architecture  of  the 
future  "  will  prove  any  positive  advance 
upon  what  is  now  in  its  main  extent  a 
somewhat  mongrel  and  unsatisfying  state 
of  things.     The  public  taste  can  become 
debauched  or  perverted  by  showy,  pre- 
tentious work,  which  will  not  bear  in- 
vestigation upon  any  principles  of  true 


architecture  ;    and  which,  if  capable  of 
startling  and  creating  a  "  sensation,"  will 
not  answer  to  that  one  criterion  of  true 
art,  it  sufficing  to  afford  an  abiding  source 
of  pleasure.     All  this  character  of  art  is 
increasingly  abundant  around  us,  for  evi- 
dence of  which  we  have  only  to  point  to 
the  majority  of  new  edifices  which  arise 
in  the  process  of  rebuilding  now  so  rap- 
idly going  on.     The  issue  of  all  this  can- 
not be  such  a  purifying  and  ennobling  of 
public   taste   and   art-patronage  as  will 
lead  to  the  production  of  works  which 
will  stand  the  test  of  lasting  admiration, 
but  rather  their   degradation,    and  will 
leave  few  precedents  to  posterity  such 
as  the  thoughtful,  noble  works  of  Greek 
and  Mediaeval  times  have  been  to  subse- 
quent ages.     How,  then,  are  these  ten- 
dencies to  be  corrected  and  the  founda- 
tion laid  for  a  pure  and  noble  system  of 
art-culture   and   development  ?      While 
our  architects,  or  the   large  body  who 
undertake  our  architectural  works,  are 
either  incapable  of  anything  better,  or 
persist  in    pandering  to   a   false   taste, 
there  can  be  no  improvement,  and  the 
present  conditions  of  patronage  are  such 
that  the  chances  are  that  the  meretri- 
cious will  outbid  a  higher  and  truer  class 
of  art.     Nor  will  improvement  come,  as 
some  fondly  imagine,  by  a  dissemination 
among  all  classes  of  some  knowledge  of 
the  principles  and  practice  of  art.     The 
utmost  that  can  be  done  in  this  way  will 
go  so  little  towards  forming  a  correct 
taste  that  it  cannot  be  taken  into  reckon- 
ing with  what  we  have  stated  to  be  the 
practical   means   which    creates,   fosters 
and  maintains  true  taste  in  art,  viz.,  the 
exhibition   of    instances   of    such   noble 
works  as  gradually,  if  not  at  once,  make 
themselves  felt,  and  adjust  the  standard 
of  what  is  satisfying  against  inferior  and 
ignoble  work.     The  consideration  of  this 
question  has  often  been  before  us,  and 
we  can  only  resort  to  what  we  have  al- 
ready stated,  that,  in  the  present  condi- 
tion of  English  architecture,  the  admit- 
ted failure  of  the  pupil-system,  the  im- 
possibility of  enforcing  a  system  of  ex- 
aminations and   degrees,    and   the   fact 
that  our  present   architecture  is  in  the 
hands  of  such  a  numerous  band  of  prac- 
titioners and  aspirants,  there  is  no   im- 
mediate prospect  of   the  application  of 
any  means  which    can    act   as    a  direct 
remedy.     But  there  is  a  prosgieetive  one, 


136 


VAN   NOSTRAND'S   ENGINEERING   MAGAZINE. 


and  this  we  think,  to  all  who  give  the 
subject  a  candid  and  thoughtful  atten- 
tion in  its  present  aspects  and  bearings, 
will  be  found  to  consist  in  the  establish- 
ment of  architectural  colleges.  These 
would  provide  an  arena  for  the  combined 
and  sustained  study  of  architecture  in 
all  its  fulness  as  a  fine  art  unaffected  by 
the  chance  influences  of  misapplied  pat- 
ronage and  misinformed  public  taste  to 
which  our  architects  are  now  necessarily 
subject,  and,  if  rightly  organized,  would 
attract  only  that  class  of  minds  which 
find  in  architecture  an  expression  of  the 
art-faculty  with  which  they  are  endowed. 
The  cultivation  of  any  art  beyond  the 
limits  of  those  who  can  enter  upon  it 
with  some  sort  of  original  creative 
faculty  is  a  mistake  and  waste  of  effort, 
and  in  modern  times  has  given  us  that 
plethora  of  mediocrity  in  nearly  all  the 
fine  arts  which  has  been  their  bane  and 
misfortune.  But  architectural  colleges 
of  the  nature  we  have  in  view,  would 
send  forth  trained  bands  of  men  agreed 
upon  the  common  principles  at  the  base 
of  all  architectural  practice  in  varying 
constructive  modes  and  the  unity  of 
decorative  effects  ;  which,  as  matters  of 
ascertained  truth  could  not  be  diverged 
from,  as  now,  at  the  dictate  of  any  ca- 
price ;  while  leaving  a  full  field  for  the 
exercise  of  that  individuality  and  orig- 
inality which  must  ever  form  a  consider- 
able factor  in  all  true  art. 

It  is  comparatively  easy  to  point  out 
the  defects  of  our  present  architecture 
and  the  system  which  promotes  them, 
and,  by  a  converse  process,  to  arrive  at 
what  might  be  regarded  as  an  ideal 
condition  of  things,  which  might  well 
be  taken  to  be  such  a  state  of  the  public 
taste  as  could  not  tolerate  the  exhibition 
of  bad  architecture  ;  and  hence  the  ne- 
cessity that  our  architects  should  be  only 
those  who  could  satisfy  such  a  high  de- 
mand. But,  as  we  have  seen,  the  culti- 
vation of  the  public  taste  is  the  direct 
product  of  that  which  is  placed  before 
it,  and  higher  results  can  only  be  attain- 
ed by  beginning  with  those  in  any  age 
and  nation  best  calculated  to  be  the  pur- 
veyors of  art  to  those  who  have  it  not. 
There  is  one  all-important  point  in  re- 
gard to  architecture  which  applies  with 
less  force  to  the  other  fine  arts.  An 
architectural  work,  whether  we  will  or 
not,  must  come  under  our  notice,   and 


must  exercise  an  influence  from  which 
we  cannot  escape,  either  for  good  or 
evil,  in  the  elevation  or  lowering  of  our 
taste.  Herein  lies  the  raison  d'etre  for 
seeking  to  confine  the  production  of  our 
architecture  to  the  best  minds  and  hands; 
and,  after  the  fullest  consideration  of 
the  whole  subject,  in  view  of  the  actual 
condition  of  things  amongst  us,  there 
seems  nothing  which  offers  any  prospect 
of  a  remedy  other  than  the  combining 
of  the  best  contemporary  genius  and 
talent  in  the  study  of  architecture  in 
such  a  form  as  shall  be  able  so  to  take 
the  lead  that  the  public  will  not  be  long 
in  judging  what  are  the  true  art-jn-o- 
ducts  and  what  are  not,  and  in  rendering 
honor  and  aid  to  those  alone  entitled  to 
deserve  them.  A  system  of  architectural 
colleges  effecting  this  result  would  soon 
winnow  the  chaff  from  the  wheat,  and 
be  able  to  dispense  all  those  distinctions 
that  are  now  wanting  in  the  architectural 
profession. 

We  cannot  but  regard  the  present  as 
a  time  of  crisis  in  the  history  of  archi- 
tecture in  this  country,  and  though  we 
have  before  in  a  detailed  manner  pointed 
out  the  place  and  special  value  of  some- 
thing of  an  architectural  collegiate  sys- 
tem for  the  satisfactory  cultivation  of 
the  art,  and  the  formation  of  a  genuine 
architectural  profession  in  the  midst  of 
the  divided  heterogeneous  influences  of 
the  present  time,  we  would  again  com- 
mend this  aspect  of  the  subject  to  the 
earnest  attention  of  our  thoughtful  pro- 
fessional readers.  Art  now  stands  in  a 
different  relation  to  society  to  what  it 
did  in  any  former  time  ;  we  cannot  re- 
store old  conditions,  but  must  meet  the 
new  ones  as  best  we  may,  and  the  two 
points  which  have  now  to  be  conciliated, 
are  the  providing  scope  for  the  best  art- 
faculty  amongst  us,  and  such  a  cultiva- 
tion of  the  public  taste  as  shall  reduce 
patronage  of  the  inferior  and  mediocre 
to  a  minimum.  A  well-organized  sys- 
tem of  colleges,  whether  affiliated  to  the 
universities  or  not,  would  effect  the  one, 
and  general  art-congresses  in  their  public 
and  popular  aspects  would  do  not  a  little 
in  effecting  the  other.  It  is  to  be  hoped 
that  the  admirable  bequest  of  Chantrey 
for  the  encouragement  of  the  highest 
art  in  painting  and  sculpture  may  meet 
with   some   imitator  in   the  interests  of 


BREECIILOADING   ORDNANCE. 


137 


architecture  ;  a  similar  sum  in  trust  in 
the  hands  of  a  few  of  our  most  devoted 
and  distinguished  architects  and  connois- 
seurs would  go  a  long  way  towards  set- 


ting on  foot  an  influence  upon  our  archi- 
tecture such  as  the  present  mercantile 
and  fictitious  repute  notions  which  gov- 
ern its  patronage  can  never  afford. 


BREECHLOADING  ORDNANCE. 

Prom  "Engineering." 


In  a  recent  communication  to  the 
Times,  through  Mr.  Alfred  Longsdon, 
Herr  Friedrich  Krupp,  of  Essen,  has 
contributed  some  valuable  information 
upon  the  subject  of  cast  steel  breech- 
loading  guns,  information  which  no  one 
was  in  a  position  to  supply  but  himself, 
the  largest  private  maker  of  ordnance  in 
the  world.  The  main  object  of  this  let- 
ter was  to  throw  some  light  on  the  con- 
fused notions  existing  as  to  the  powers 
of  resistance  of  cast  steel  guns,  and  the 
reliability  of  the  breech  mechanism  em- 
ployed. With  respect  to  the  rumors 
that  in  the  course  of  the  Franco-German 
war  200  field  pieces  failed,  we  are  as- 
sured that  not  one  gun  burst  during  the 
whole  of  the  campaign  on  the  German 
side,  which  was  supplied  wholly  from 
the  works  at  Essen,  while  the  breech 
mechanism  in  all  cases  showed  its  com- 
plete efficiency,  and  not  a  single  failure 
of  it  is  recorded. 

Mr.  Longsdon  next,  taking  wider 
ground,  gives  us  statistics  as  to  the  fail- 
ures which  have  taken  place  among  the 
13,000  steel  guns  manufactured  by  the 
magnificent  establishment  he  represents. 
These  failures,  he  assures  us,  are  limited 
to  seventeen.  Out  of  this  extremely 
small  number  eleven  may  be  fairly 
thrown  out  of  consideration;  they  were 
imperfect  guns  as  far  as  the  breechload- 
ing  mechanism  was  concerned,  having 
been  made,  tested,  and  destroyed  before 
the  present  highly  efficient  system  of 
breechloading  had  been  adopted.  Of 
the  remaining  six  guns  Mr.  Longsdon 
gives  us  a  record  as  follows: 

In  1865  a  9-in.  gun  burst  explosively 
in  Russia  after  the  410th  round.  This 
gun  was  a  converted  muzzleloader,  and 
failed  under  excessive  charges. 

In  1866  a  second  9-in.  gun  burst  explo- 
sively in  Russia  after  the  56  th  round. 


In  1869  an  8-in.  gun  burst  explosively 
in  Berlin  after  the  650th  round. 

In  1871  an  11 -in.  gun  burst  at  Fort 
Constantine . 

In  1872  a  15-pounder  burst  in  Berlin 
after  557  rounds. 

Mr.  Longsdon  has,  however,  omitted 
to  mention  several  other  failures  of  his 
guns,  which  we  may  add  to  the  above 
list.  We  take  them  from  a  paper  read 
by  Major  Haig  before  the  Royal  Artil- 
lery Institution. 

In  1865  a  Krupp  9f-inch  steel  gun 
burst  with  a  moderate  charge  of  powder, 
a  Prussian  committee  attributing  the 
failure  to  inferiority  of  the  metal. 

In  the  same  year  a  9^-in.  gun  of 
Krupp's  steel  burst  in  Russia  at  the 
66th  round. 

In  the  same  year  an  8^-in.  similar  gun 
burst  at  the  96th  round. 

In  1866  a  Krupp  field  gun  burst  ex- 
plosively at  Berlin,  killing  three  cadets. 

In  1866,  during  the  Austro-Prussian 
war,  six  Prussian  steel  field  guns  burst. 

In  January,  1867,  a  7-in.  Krupp  gun 
burst  at  the  second  round  of  proof  at 
Woolwich. 

In  the  same  year  a  4-pounder  burst  at 
Tegal,  near  Berlin. 

In  1868  an  8-in.  Krupp  gun  burst  on 
board  a  Russian  frigate  very  destruct- 
ively, killing  and  wounding  in  all  12 
men. 

In  1872  an  11 -in.  Krupp  gun  burst  at 
the  chase,  and  blew  about  3  ft.  off  the 
muzzle. 

The  correctness  of  the  above  list  is 
easy  of  verification,  and  it  is  somewhat 
to  be  regretted  that  Mr.  Longsdon 
should  have  overlooked  these  important 
instances  of  dangerous  failures,  as  they 
modify  considerably  the  inferences  to  be 
drawn  from  his  letter.  In  statistics  of 
this  kind  nothing  is  so  necessary  as  un- 
assailable accuracy;    and  we  should  be 


138 


VAN   NOSTRAND'S   ENGINEERING   MAGAZINE. 


glad  to  learn  that  Major  Haig's  state- 
ments are  incorrect,  although  we  have 
not  the  slightest  doubt  that  the  failures 
enumerated  by  him  did  take  place,  and 
the  value  of  Mr.  Longsdon's  communi- 
cation to  the  Times  will  lose  all  its  value 
if  we  find  that  the  assurances  it  contains 
are  unreliable.  And  before  accepting 
the  assurance  that  no  Krupp  field  guns 
failed  during  the  Franco-German  war, 
we  are  obliged  to  hesitate,  because  since 
the  publication  of  Mr.  Longsdon's  letter, 
the  public  is  assurred  that  in  numerous 
instances  the  Krupp  field  guns  have 
burst  during  that  period. 

One  correspondent,  replying  to  Mr. 
Longsdon's  letter,  states  that  in  1871  he 
was  assurred  by  an  officer  on  the  Head- 
quarters staff  of  the  German  army,  that 
out  of  70  long  breechloading  24-pound- 
ers,  36  became  unserviceable  during  15 
days'  firing,  and  that  had  the  bombard- 
ment been  continued  for  another  week, 
the  German  batteries  would  have  been 
silenced  owing  to  failure  at  the  breech. 
Again  on  the  Loire  and  in  Brittany  24 
field  guns  became  unserviceable,  chiefly 
through  their  own  fire.  A  second  writer 
goes  further  and  maintains  that  about 
200  field  guns  were  wholly  or  partially 
disabled,  two  or  three  through  the  ene- 
my's fire,  and  the  rest  through  defects 
in  the  breech 'mechanism  and  bursting  of 
shells  in  the  bore.  It  is  only  fair  to 
state,  however,  that  these  damaging  alle- 
gations are  advanced  anonymously,  and 
require  corroboration. 

We  have  to  assume,  therefore,  despite 
Mr.  Longsdon's  assurances  to  the  con- 
trary, that  a  considerable  number  of  ex- 
plosive failures  of  Krupp  guns  have 
taken  place;  but  we  would  call  attention 
to  the  fact  already  recorded  by  us,  that 
none  of  them  are  proved  to  have  failed 
by  reason  of  the  breech  mechanism  (after 
it  had  attained  its  present  form),  but 
through  the  unreliability  of  the  metal 
itself. 

From  the  experience  thus  gained  it 
may  be  fairly  assumed  that  the  steel 
employed  in  the  heavy  ordnance  on  the 
Continent  is  not  so  reliable  as  the  steel 
and  iron  used  in  combination  in  our 
Woolwich  guns.  A  steel  gun  may  show 
very  high  powers  of  endurance,  as  evi- 
denced by  many  admirable  examples  of 
Krupp's  work,  but  it  is  impossible  to  be 
absolutely  sure  of  the  absence  of   any 


flaw  or  other  unseen  element  of  weak- 
ness, and  when  it  does  yield,  it  almost 
certainly  yields  with  violence.  Sir  Joseph 
Whitworth  claims,  and  indeed  has  shown 
by  numerous  experiments,  that  the  homo- 
geneous metal  he  manufactures  is  entirely 
reliable,  that  it  exhibits  very  high  powers 
of  resistance,  and  when  forced  to  yield  by 
the  overwhelming  nature  of  the  powder 
charge  it  does  not  break  with  violence. 
But  for  all  practical  use  to  this  country 
the  employment  of  this  metal  has  not 
gone  beyond  the  stage  of  experiment, 
and  we  fail  to  understand  why  it  has 
not  been  tested  in  the  A  tube  of  one  of 
our  large  Woolwich  guns.  The  Wool- 
wich authorities  are,  we  feel  sure,  anx- 
ious to  adopt  superior  materials  when- 
ever possible,  and,  therefore,  they  can 
scarcely  be  responsible  for  not  having 
tried  a  metal,  which  is,  according  to  the 
high  authority  of  Sir  Joseph  Whitworth, 
far  superior  to  any  that  has  ever  before 
been  employed. 

But  even  with  the  materials  at  their 
disposal  the  guns  made  at  Woolwich 
show  no  such  annals  of  explosive  failure 
as  do  those  of  Essen  manufacture.  In- 
deed, the  great  merit  of  our  heavy 
ordnance  is  its  almost  perfect  non-liabil- 
ity to  burst  explosively,  but  that  it 
yields  gradually,  giving  timely  warning 
of  approaching  failure.  The  admirable 
combination  and  arrangement  of  mate- 
rial used  in  the  Woolwioh  guns  is 
equalled  nowhere,  and  in  our  present 
state  of  knowledge  cannot  be  surpassed, 
and  the  reasoning  in  the  Text-Book  of 
the  Construction  aud  Manufacture  of 
Rifled  Ordnance,  published  in  1872, 
holds  equally  good  to-day.  "  Steel  from 
its  hardness,  high  tensile  strength,  and 
freedom  from  flaws  and  defects,  is  better 
suited  than  wrought  iron  for  the  inner 
barrel  of  a  gun,  while  its  brittleness  and 
uncertainty  render  it  unsuitable  for  the 
exterior  portions.  The  construction 
adopted  in  the  service  is,  therefore, 
founded  on  correct  principles,  as  far  as 
the  materials  and  their  arrangements  are 
concerned,  and  the  correctness  of  the 
principles  has  been  proved  by  twelve 
years'  experience,  during  which  period 
thousands  of  guns  have  been  manufact- 
ured and  issued,  and  in  no  one  instance 
has  a  gun  burst  explosively  on  service, 
nor  has  a  single  life  been  sacrificed."  Of 
the  ordnance  of  no  other  great  power  in 


BREECTILOADING   ORDNANCE. 


139 


the  world  can  this  be  said,  and  whether 
we  compare  our  guns  with  the  composite 
cast  iron  and  steel  structures  of  France, 
the  steel  guns  of  Germany  and  Russia, 
or  the  obsolete  cast  iron  pieces  of  the 
United  States,  our  superiority  of  design, 
of  materials,  and  of  workmanship,  is  as 
marked  as  it  is  reassuring.  That  re- 
forms may  have  to  be  made  in  our  mode 
of  rifling,  and  that  possibly,  nay  proba- 
bly, we  shall  follow  the  practice  of  Con- 
tinental nations,  and  abandon  muzzle  in 
favor  of  breechloading  for  large  calibres, 
does  not  alter  the  main  fact  of  the  supe- 
riority of  our  heavy  guns. 

The  durability  of  the  breechloading 
system,  which  we  have  described  and 
illustrated  on  previous  occasions,  has,  as 
we  have  stated,  been  called  into  question 
by  the  correspondents  to  the  Times, 
whose  letters  was  called  forth  in  reply 
to  Mr.  Longsdon's  communication.  The 
evidence  on  this  point,  however,  is  very 
vague,  and  on  the  other  hand  there  is 
very  powerful  testimony  in  favor  of  the 
system.  To  apply  it  to  one  of  our  heavy 
guns  will  be  (if  such  a  decision  be  ar- 
rived at)  but  a  small  matter,  and  we 
shall  then  have  ample  opportunity  of 
judging  for  ourselves  of  the  actual 
merits  of  the  mechanism  as  carried  out 
at  Woolwich. 

At  the  close  of  his  letter  to  the  Times 
Mr.  Longsdon  refers  -to  the  claims  of 
Mr.  L.  W.  Broadwell,  of  Carlsruhe,  to 
the  invention  of  the  breechloading  me- 
chanism associated  with  Mr.  Krupp's 
name,  and  as  we  have  on  previous  occa- 
sions referred  to  the  same  subject,  his 
remarks  have  a  special  interest  for  us. 
But  as  Mr.  Longsdon  has  favored  us 
with  a  communicttion  touching  the  same 
question,  and  dealing  with  it  in  much 
detail,  we  propose  only  to  make  a  passing 
reference  to  the  matter  now,  and  to  defer 
our  criticism  of  the  letter  addressed  to 
ourselves  until  Mr.  Broadwell  himself 
has  been  allowed  time  to  reply. 

Mr.  .Krupp,  writing  by  Mr.  Longsdon, 
accedes  to  Mr.  Broadwell  the  invention 
of  a  detail  originally  connected  with  the 
system,  a  detail  obsoletf  indeed,  but 
which  at  the  time  was  of  considerable 
importance.  "  To  Mr.  Broadwell  be- 
longs the  merit  of  inserting  the  ring  in 
the  face  of  the  breech  block,  a  very  useful 
invention."  The  italics  are  our  own. 
This  detail  was  patented  by  Mr.  Broad- 


well in  1861,  yet  in  1862  we  find  precise- 
ly similar  rings  inserted  in  the  breech 
blocks  shown  in  Mr.  Krupp's  specifica- 
tion. Thus  while  a  clear  acknowledg- 
ment is  made  of  the  fact  that  Mr.  Broad- 
well was  the  originator  of  the  idea  for 
placing  the  ring  in  the  face  of  the  breech 
block,  endorsing  our  own  statement,  we 
have  no  explanation  why  the  same  detail 
was  patented  by  Mr.  Krupp  more  than 
a  year  after. 

But  we  are  assured  that  the  "  Broad- 
well ring  "  is  a  misnomer,  it  "  wrongly 
goes  by  his  name,"  and  should,  by  infer- 
ence, be  called  the  Krupp  ring.  Refer- 
ence must  be  made  here,  we  presume, 
to  the  perfected  form  of  ring,  patented 
by  Mr.  Broadwell  in  1865,  and  improved 
subsequently.  Yet  in  Mr.  Krupp's  spec- 
ification dated  February,  1865,  two 
months  before  that  of  Mr.  Broadwell's 
just  referred  to,  we  only  find  drawings 
of  the  ring  inserted  in  the  face  of  the 
breech  block,  the  "  very  useful  modifica- 
tion," the  merit  of  which  belongs  to  Mr. 
Broadwell.  In  the  latter  gentleman's 
specification  dated  April,  1865,  the  first 
arrangement  of  a  specially  formed  ring 
fitting  in  a  suitable  channel  in  the  bore 
of  the  gun,  and  bearing  at  the  back  upon 
a  circular  plate  in  a  recess  in  the  breech 
block,  is  shown.  For  many  months  be- 
fore this  patent  was  applied  for,  Mr. 
Broadwell  had  been  in  St.  Petersburg, 
discussing  his  plans  for  breechloading 
ordnance  with  the  Minister  of  War,  and 
it  was  while  there  that  he  introduced 
this  improvement  on  his  original  idea. 
In  July,  1865,  about  three  months  after 
his  application  for  a  patent,  the  Russian 
Government  had  accepted  his  system, 
with  a  formal  declaration  of  which  the 
following  is  a  translation.  "  After  numer- 
ous experiments  made  by  the  Imperial 
Russian  Government  in  the  gas  check 
ring,  the  invention  of  Mr.  L.  W.  Broad- 
well, citizen  of  the  United  States,  this 
ring  has  been  recognized  as  perfectly 
attaining  its  object  of  preventing  the 
gases  from  the  burning  powder  to  escape 
through  the  transverse  opening  in  the 
breech,  through  which  the  closing  me- 
chanism is  introduced,  and  it  is  in  con- 
sequence of  these  highly  satisfactory  re- 
sults that  the  said  Broadwell  ring  has 
been  introduced  in  the  Imperial  Artillery, 
for  use  in  cast-steel  breechloading  guns. 
(Signed)  Barantzoff,  Aide-de-Camp  Gen- 


140 


VAN  NOSTRAND  S  ENGINEERING    MAGAZINE. 


eral."  Thus,  while  Mr.  Krupp  freely 
acknowledges  the  originality  of .  Mr. 
Broadwell's  insertion  of  the  ring  in  the 
face  of  the  breech  block,  dates  and  un- 
questionable authority  award  him  the 
undoubted  merit  of  the  improved  ring, 
universally  known  by  his  name. 

"We  have  dwelt  at  some  length  upon 
this  point,  having  been  led  to  do  so  by 


the  remark  we  have  quoted  from  Mr. 
Longsdon's  letter  to  the  Times,  and  here 
we  leave  the  subject  for  the  present. 

We  would,  however,  take  this  oppor- 
tunity of  assuring  Herr  Krupp  and  Mr. 
Longsdon  that  the  only  object  we  have 
in  view,  is  to  arrive  at,  and  place  on 
record  the  exact  truth  connected  with 
this  interesting  question. 


ENGLISH  LIGHT-HOUSES. 

From  "  Illustrated  Washington  Chronicle." 


Without  question  the  noblest  monu- 
ments of  civilization  are  those  created  to 
promote  the  happiness  and  protect  the 
lives  of  people.  It  has  been  justly  ob- 
served that  a  government,  which  guar- 
antees unto  its  citizens  unrestrained  free- 
dom, and  neglects  to  provide  the  safe- 
guards that  insure  the  enjoyment  of  life, 
is  far  inferior  to  that  which,  though  ex- 
ercising a  proper  and  even  severe  firm- 
ness in  the  administration  of  its  laws, 
uses  the  means  at  its  command  to  in- 
crease the  safety  and  consequently  the 
prosperity  of  those  it  governs. 

For  proof  of  this  we  need  but  glance 
at  the  respective  conditions  of  two  dif- 
ferent classes  of  nations.  Those  which 
have  acknowledged  the  importance  of 
securing  the  welfare  of  their  inhabitants 
by  a  wise  system  of  public  benefits,  and 
the  governments  which  have  practically 
allowed  the  affairs  of  the  people  to  take 
care  of  themselves.  • 

Of  the  public  benefits  referred  to  there 
is  none  greater  than  that  which  insures 
the  safety  of  the  mariner — the  light- 
house. Without  it  commerce  would 
ever  remain  dwarfed  in  its  proportions ; 
for  the  perils  of  the  deep,  unless  lessened 
by  these  humane  contrivances,  would 
prove  too  appalling  for  those  hardy 
enough  to  brave  its  mitigated  dangers. 
The  countries  which  have  paid  the  most 
attention  to  this  important  matter  are 
those  that  have  attained  the  highest 
position  in  the  commercial  scale.  It  may 
be  asserted  that  light-houses  were  con- 
structed by  these  nations  because  the 
safety  of  their  vessels  depended  upon 
their  existence.  But  it  may  be  assumed 
with  equal  certainty  on  the  other  hand 


that  a  nation  with  harbors  difficult  of 
access,  and  unprovided  with  the  warnings 
necessary  for  the  security  of  ships  in  ap- 
proaching or  departing,  can  never  become 
a  great  maritime  power,  for  the  reason 
that  circumstances  combine  to  prevent 
its  growth  in  that  direction. 

This  fact  has  been  recognized  since 
the  birth  of  enterprise,  although  it  was 
reserved  for  the  moderns  to  bring  the 
light-house  system  to  its  present  com- 
plete and  efficient  condition.  Foremost 
among  the  nations  that  have  distinguish- 
ed themselves  in  the  erection  of  these 
valuable  assistants  to  navigation  are 
France,  England,  Scotland,  and  the 
United  States.  The  peculiar  conforma- 
tion of  the  English  coast  rendered  the 
construction  of  many  of  her  light-hruses 
an  imperative  necessity  ;  without  them 
it  would  have  been  impossible  to  create 
or  preserve  after  having  created,  the 
vast  navy  of  vessels  bearing  her  flag 
that  find  their  way  to  and  from  her  ports 
every  day  in  the  year. 

The  growth  of  the  light-house  system 
of  the  countries  mentioned  to  its  present 
effectiveness  has  not  been  precipitate. 
It  is  the  result  of  centuries  of  patient 
work,  fortified  by  a  continued  determina- 
tion to  achieve  excellence  in  this  direc- 
tion. 

In  this  number  of  the  Chronicle  we 
give  illustrations  of  a  few  of  the  most 
prominent  light-houses  of  England.  We 
are  mainly  indebted  for  the  accompany- 
ing descriptions  to  an  interesting  public 
document  embodying  the  results  of  Maj. 
Elliot's  corps  of  engineers,  United  States 
army,  tour  through  Europe,  made  for 
the  purpose  of  examining  and  reporting 


ENGLISH   LIGHT-HOUSES. 


141 


upon  the  light-house  systems  of  foreign 
nations.  At  the  time  of  the  first  appear- 
ance of  the  report  we  took  occasion  to 
refer  to  it  as  a  document  worthy  the 
most  careful  study  on  account  of  the 
quantity  and  value  of  the  carefully-pre- 
pared information  it  contained,  but  as 
the  work  is  inaccessible  to  the  general 
public  we  reproduce  such  illustrations 
and  exti'acts  as  may  prove  most  enter- 
taining. We  regret  that  limited  space 
precludes  our  copying  more  extensively, 
for  we  seldom  come  across  a  public 
document  from  which  so  many  and 
valuable  extracts  can  be  made. 

The  Roman  Pharos,  now  one  of  the 
most  precious  relics  of  ancient  England, 
is  situated  within  the  walls  of  the  Castle 
of  Dover.  The  antiquity  of  this  monu- 
ment no  doubt  exceeds  that  of  any 
light-house  in  Great  Britain.  It  has  not 
been  used  since  the  Conquest  as  a  warn- 
ing tower  to  mariners.  From  the  time 
of  its  erection,  which  was  supposed  to 
have  been  during  the  reign  of  the  Em- 
peror Claudius,  about  A.  D.  44,  up  to 
the  period  of  the  invasion  by  the  Con- 
querors, large  fires  of  wood  and  coal 
were  maintained  upon  it.  This  method 
was  the  earliest  adopted  to  guide  sailors, 
and  it  finally  gave  way  to  the  reflector, 
which  was  in  turn  supplanted  by  that 
triumph  of  skill,  the  Fresnel  lens.  The 
Pharos  is  built  of  brick,  of  a  light  red 
color,  about  fourteen  inches  in  length 
and  not  more  than  one  and  a  half  inches 
thick,  but  little  more  than  the  thickness 
of  the  joints,  which  are  filled  with  a 
mortar  composed  of  lime  and  finely- 
powdered  brick.  Its  preservation  is 
doubtless  owing  to  the  circumstance  that 
the  tower  was  converted  into  a  belfry 
for  the  church  of  St.  Mary,  and  was 
surrounded  by  walls  of  stone,  which 
have  nearly  succumbed  to  the  action  of 
the  elements,  and  have  exposed  the  old 
Roman  work. 

The  great  electric  light  at  Souter 
Point,  three  miles  below  the  mouth  of 
the  River  Tyne,  is  a  modern  scientific 
triumph.  Its  location  is  such  as  to  pre- 
sent serious,  obstacles  to  the  effective 
construction  of  a  proper  guide  to  marin- 
ers owing  to  the  smoke  from  the  cities 
and  towns  on  the  river,  including  New- 
castle, combining  with  the  frequent  fogs, 
but  these  have  been  overcome  in  a  great 
measure  by  the  introduction  of  a  light 


which  sends  over  the  North  Sea  its 
flashes,  each  of  which  is  equal  in  inten- 
sity to  the  combined  light  of  eight  hun- 
dred thousand  candles.  The  lenticular 
apparatus  is  of  the  finest  possible  work- 
manship, and  utilizes  every  ray  of  light 
generated  by  the  electrical  machines  in 
the  tower. 

The  Outer  Fame  or  Longstone  Light- 
house, better  known  to  the  public  as  the 
home  of  Grace  Darling,  is  situated  at 
the  mouth  of  the  Tweed.  It  is  the  most 
northerly  of  the  sea  lights  of  England, 
on  the  shore  of  the  North  Sea,  and  is 
in  plain  view  from  the  light  at  St.  Alb's 
Head,  the  first  of  the  Scottish  lights. 
It  is  a  rock  light-house,  and  its  peculiar 
construction  is  well  illustrated  in  our 
engraving.  The  sea  rolls  with  great 
violence  in  the  vicinity,  and  for  this 
reason  it  was  found  necessary  to  sur- 
round the  tower  with  high  walls  to  pro- 
tect it  from  the  encroachments  of  the 
waves  in  time  of  storm.  The  daring  act 
of  Grace  Darling  in  rescuing  nine  men 
from  the  wrecked  vessel  Forfarshire, 
when  she  struck  Hawkin's  Reef,  must 
ever  throw  around  this  spot  a  poetic 
glamor.  The  house  that  sheltered  hero- 
ism of  this  kind  must  always  be  interest- 
ing to  those  who  have  a  sympathetic 
heart  in  their  bosoms. 

The  Eddystone  Light-house,  off  the 
coast  of  Devonshire,  is  famous  for  its 
great  strength.  The  first  light-house  on 
the  Eddystone  was  completed  in  1698. 
Its  existence  was  brief,  however,  as  it 
was  destroyed  in  a  violent  storm  in  1703. 
The  keepers  and  the  builder  lost  their 
lives  by  the  catastrophe.  A  second 
light-house  was  constructed  herein  1709, 
which  was  destroyed  by  fire  in  1755. 
The  present  Eddystone  was  commenced 
by  John  Smeaton  in  1756,  and  completed 
in  1759.  It  is  a  marvel  of  solidity  and 
strength.  •  The  material  employed  in  its 
construction  is  stone.  The  joints  are 
dovetailed,  rendering  it  simply  impos- 
sible to  move  one  stone  without  displac- 
ing the  rest.  This  has  proved  the  model 
for  all  light-houses  subsequently  erected, 
except  in  immaterial  details.  The  science 
of  illumination  as  applied  to  the  Eddy- 
stone was  far  behind  the  science  of  con- 
struction, and  while  Smeaton  sprang  at 
once  from  the  prejudice  of  his  time  to  a 
full  conception  of  the  true  principles 
which  should  govern  the  construction  of 


142 


VA1ST  nostrand's  engineering  magazine. 


a  work  of  this  character,  it  remained 
lighted  for  many  years  as  at  first,  by 
"twenty-four  candles  burning  at  07ice, 
five  whereof  weighed  two  pounds."  The 
quaint  expression  in  italics  are  extracted 
from  Smeaton's  narrative  of  the  build- 
ing of  the  Eddystone  Light-house.  Re- 
flectors were  not  introduced  until  early 
in  the  present  century,  and  in  1845  these 
in  turn  gave  way  to  a  second  order  Fres- 
nellens,  the  beam  from  which,  with  its 
Douglass  burner,  is  equal  to  4,650  can- 
dles. 

This  was  the  first  catadioptric  ap- 
paratus ever  constructed. 

The  Wolf  Rock  Light,  ten  miles  from 
Land's  End,  was  commenced  in  1862, 
and  its  construction  finished  in  1869.  It 
is  built  on  a  rock  two  feet  below  high 
water.  This  rock  for  centuries  was  the 
dread  of  mariners,  as  in  violent  weather 
the  sea  sweeps  completely  over  it.  But 
since  the  erection  of  the  staunch  house 
it  has  been  shorn  of  all  its  terrors,  and 
that  which  was  once  a  serious  evil  is  now 
converted  into  a  positive  good,  the  loca- 
tion and  its  distance  from  the  land  ren- 
dering it  a  most  valuable  guide  for  en- 
trance into  the  English  Channel.  There 
is  no  light-house  in  existence,  however, 
that  has  cost  more  labor  than  this.  The 
fury  of  the  elements  in  the  neighborhood 
is  such  as  to  render  work  impossible  for 
long  periods.  To  illustrate  this,  in  con- 
structing a  day -beacon  on  this  rock  in 
five  years  only  seventy  days  were  suffi- 
ciently calm  to  permit  work.  The  re- 
mainder of  the  time  the  weather  was  too 
boisterous  to  allow  a  stroke  of  work  to 
be  performed.  The  rock  is  completely 
submerged  at  high  water,  and  is  but 
little  larger  than  the  base  of  the  tower, 
forty-one  feet  eight  inches.  The  tower 
is  one  hundred  and  sixteen  feet  high, 
and  solid  from  the  base  to  the  height  of 
thirty-nine  feet.  The  thickness  of  the 
walls  at  the  doorway  is  seven  feet  nine 
and  a  half  inches.  Four  keepers  are 
employed  to  take  charge  of  the  light, 
and  three  of  these  are  constantly  on 
duty. 

The  off  man  is  supposed  to  spend 
four  weeks  on  the  mainland  with  his 
family,  but  it  frequently  happens  that 
eight  weeks  elapse  before  a  landing  can 
be  effected.  The  difficulty  of  reaching 
the  lighthouse  and  entering  it  is  graphi- 
cally  described  by   Major  Elliot,  who 


visited  it  on  his  tour,  and  the  description 
carries  the  conviction  that  the  feat  is  one 
attended  with  no  small  hazard,  as  can  be 
well  understood  from  the  engraving.  The 
derrick  employed  for  landing,  except 
when  in  use,  is  taken  down  and  fastened 
in  deep  channels  in  the  rock  ;  otherwise 
it  would  be  swept  away  by  the  sea.  The 
light  is  an  excellent  one,  and  gives  out 
alternate  red  and  white  flashes. 

The  South  Stock  Light-house,  at  the 
extreme  westerly  point  of  Holyhead,  the 
extremity  of  Anglese,  is  remarkable  for 
the  ingenious  contrivance  which  has 
been  adopted  to  obviate  the  drawback 
of  its  elevated  position.  A  sliding  light 
has  been  constructed,  which  is  made  to 
ascend  or  descend,  as  the  exigency  de- 
mands. By  this  means  when  the  fog 
clouds  hang  over  the  land  and  obscure 
the  light  of  the  tower  a  light  is  run 
down  to  the  foot  of  the  cliff,  and  there 
gives  warning  to  avoid  the  dangerous 
point. 

In  conclusion  we  cannot  refrain  from 
remarking  that  France  and  our  own 
Government  have  done  much  to  add  se- 
curity to  commerce.  In  fact,  the  French 
nation  to-day  stands  practically  ahead  of 
either  England  or  the  United  States. 
"We  have  merely  selected  the  light-houses 
mentioned  because  they  are  the  more 
striking  of  those  found  in  Major  Elliot's 
book.  We  regret,  however,  that  the 
brevity  of  the  article  will  not  allow  us  to 
refer  to  some  of  the  lights  of  France 
and  other  countries  visited  by  him. 


Axle  Boxes. — Mr.  J.  A.  Longridge, 
of  Clapham,  has  patented  some  improve- 
ments in  axle  boxes  for  locomotive  and 
other  railway  vehicles.  The  invention 
consists  in  dispensing  with  the  so-called 
"  rolling  brass."  Mr.  Longridge  makes 
the  cheeks  or  flanges  on  the  axle  box 
in  which  the  axle  guides  or  horns  work 
so  as  to  present  two  convex  surfaces  to 
the  axle  guides  or  horns,  instead  of  a 
parallel  groove  as  hitherto,  the  narrow- 
est part  of  the  groove  being  in  the 
centre  line  of  the  bearing,  and  widened 
out  above  and  below. 

— London  Mining  Journal. 


MANUFACTURE   OF   BESSEMER  STEEL   TN   BELGIUM. 


143 


ON  THE  MANUFACTURE  OF  BESSEMER  STEEL  IN  BELGIUM.* 

By  M.  JULIEN  DEBY,  C.E.,  Brussels. 
Prom  "Engineering." 


The  members  of  the  Iron  and  Steel 
Institute  of  Great  Britain  were  the  first 
to  promulgate  the  economic  doctrine 
that  it  is  more  to  the  benefit  of  the  man- 
ufacturer and  of  the  trader  in  general  to 
exchange  freely  the  results  of  practice 
and  of  experience,  than  to  lock  up  their 
proceedings  from  fellow-workers,  and  to 
live  on  hereditary  secrets. 

I  am  happy  to  have  it  in  my  power  to 
affirm  that  this  great  idea,  worthy  of  the 
century,  is  rapidly  extending  its  benefi- 
cial influence  beyond  the  contracted 
limits  of  the  United  Kingdom. 

In  America,  Belgium,  Germany,  and 
even  in  France,  most  workshops  of  in- 
dustry are  now  thrown  open  to  the  in- 
spection of  competitors,  with  a  generosi- 
ty which,  a  few  years  back,  was  quite 
unheard  of. 

As  a  slight  proof  of  the  truth  of  the 
above  assertion,  I  come  before  you  this 
day  with  a  full  statement  of  what  our 
Bessemer  Steel  Works,  in  Belgium,  are 
now  doing,  and  of  how  they  a*re  doing  it. 
M.  E.  Sadoine,  the  able  director  of 
the  John  Cockerill  Works,  at  Seraing, 
at  my  request,  has  given  me  full  leave 
to  divulge  to  the  members  of  this  Insti- 
tute the  whole  of  the  results  obtained  at 
his  new  works,  without  any  restrictions 
whatever,  as  to  what  I  may  communi- 
cate. 

I  shall,  in  consequence,  proceed,  in  as 
few  words  as  possible,  to  exhibit  a  con- 
densed summary  of  the  most  important 
facts  which  I  think  may  interest  you. 

At  Seraing,  the  iron  is  most  success- 
fully and  regularly  run  direct  from  the 
blast  furnace  into  the  converters — a 
most  economical  process,  which,  to  my 
knowledge,  has  not,  as  yet,  been  put 
into  practice  in  Great  Britain,  but  which 
I  believe  ought  to  become  universal. 

Belgium  lays  no  claim  whatever  to 
originality  in  the  matter  of  this  direct 
process.  As  early  as  1857,  the  Swedish 
works  had  used  it,  and  they  continue  to 
do  so  to  this  day,  adding  iron  to  the 
charge  when  the  production  of  the  fur- 

*  Kead  before  the  Iron  and  Steel  Institute. 


nace  is  insufficient.  In  1863,  the  same 
process  was  introduced  into  the  Styrian 
Works,  of  Turrach,  and  in  1864,  into 
those  of  Heft,  in  Carinthia.* 

In  1864,  the  Neuberg  Company,  in 
Styria,  applied  it  also,  and  this  Com- 
pany, as  well  as  that  of  Heft,  have  since 
that  period  considerably  enlarged  their 
works  on  the  same  basis. 

In  1867,  Terre  Noire,  in  France,  em- 
ployed the  direct  run  from  the  furnace, 
and,  if  I  am  not  mistaken,  the  Creusot 
has  also  lately  adopted  the  same  princi- 
ple. 

The  new  steel  works,  at  Seraing,  con- 
stitute one  of  the  most  important  de- 
partments of  that  extensive  establish- 
ment. Very  few  in  Europe,  if  any,  are 
better  organized  at  the  present  time  for 
the  economical  transformation  of  iron 
ore  into  steel  on  a  large  scale. 

The  whole  plant  was  devised,  and  the 
plans  put  into  execution,  by  the  com- 
bined efforts  of  two  intelligent  young 
engineers  of  the  company,  MM.  Greiner 
and  Philippart,  to  whose  kindness  I  owe 
to  have  been  able  to  examine  minutely 
all  details,  and  to  have  had  access  to 
official  documents,  from  whence  I  have 
derived  most  of  the  figures  contained  in 
this  paper. 

The  foundation-stone  of  the  steel 
works  of  Seraing  was  laid  in  March, 
1873,  and  on  the  1st  of  February,  1S74, 
the  first  blow  was  made  in  the  Bessemer 
converters. 

In  order  to  simplify  the  subject,  I 
shall  proceed  methodically  and  follow 
the  ores  in  their  successive  transforma- 
tion: 

1.  Into  pig  iron  in  the  blast  furnace. 

2.  Into  steel  ingots  in  the  Bessemer 
converters. 

3.  Into  rails,  tyres,  axles,  etc.,  in  the 
forge. 

But,  before  doing  so,  I  must  give  a 
short  account  of  the  plant  and  of  its 
distribution. 


*  These  works  were  fully  described  as  early  as  1S66, 
by  M.  Habets,  of  Liege,  from  official  documents  in  the 
Revue  Universellc  dea  Mints,  vol.  xx.,  p.  273,  where  the 
advantages  of  the  process  were  enumerated. 


144 


VAN   NOSTRAND'S   ENGINEERING   MAGAZINE. 


When  the  whole  works  are  completed, 
they  will  comprise  four  blast  furnaces 
(of  which  two  are  already  finished)  united 
by  bridges,  and  between  which  are 
placed  atmospheric  lifts. 

Each  furnace  is  furnished  with  four 
Whitwell  stoves  placed  hi  a  square, 
forming  thus  two  parallel  rows  of  eight 
stoves  each. 

The  principal  dimensions  of  the  blast 
furnaces  are  as  follows: 

Metres.  Feet. 

Diameter  of  hearth 1.60        =  5.248 

"           bosh 5             =  16.40 

top 3.50        =  11.48 

Total  height 18.50        =  60 

Inclination  of  boshes 67£  deg. 

Capacity. .  225  cubic  metres=7,942  cubic  feet. 

Three  blast  engines  of  the  special  verti- 
cal type  of  Seraing,  so  well  known  on 
the  Continent,  and  of  which  123  are  now 
in  operation  in  various  places,  furnish 
the  necessary  blast,  at  a  pressure  which 
attains  30  centimetres  or  12  in.  of  mer- 
cury. 

The  blowing  cylinders  of  the  engines 
have  a  diameter  of  3  metres,  or  9.84  ft., 
and  a  stroke  of  2.44  metres,  or  1  ft. 
The  steam  cylinders  are  on  the  Woolf 
condenser  principle. 

The  normal  number  of  revolutions  of 
the  engines  is  13  per  minute.  This  fur- 
nishes 400  cubic  metres,  or  14,120  cubic 
feet  of  blast,  the  quantity  needed  for  the 
combustion  of  120  metric  tons  of  coke 
in  24  hours. 

To  the  right  and  left  of  the  blowing 
engines  are  situated  the  mixing  sheds 
for  ore,  and  outside  of  these  again  are 
the  pumping  engines  for  the  whole  of 
the  hydraulic  apparatus  of  the  establish- 
ment. 

The  sheds,  where  the  charges  of  ore 
are  prepared,  are  supplied  with  hydraulic 
lifts,  which  raise  the  ore  to  the  proper 
height,  and  allow  of  its  being  thrown 
into  separate  boxes  or  compartments, 
where  an  intimate  mixture  of  raw  mate- 
rial can  be  easily  effected. 

In  front,  and  to  the  north,  is  placed  a 
group  of  boilers,  made  from  Bessemer 
steel  plate,  1.60  metres,  or  5,248  feet  in 
diameter,  and  15  metres,  or  49  feet  in 
length.  They  each  carry  a  large  re- 
heater  3.28  feet  in  diameter,  and  49  feet 
in  length  below  them.  The  boilers  are 
heated  by  the  escaped  gases  from  the 
blast  furnaces. 


On  the  south  side,  the  blast  furnaces 
are  situated  alongside  the  Bessemer 
foundry,  which  is  divided  into  three 
separate  compartments  by  a  series  of 
cast-iron  columns. 

The  first  compartment  comprises  the 
pig  bed,  and  also  receives  the  ladles  and 
the  hydraulic  lifts,  which  carry  the  mol- 
ten metal  from  the  furnaces  to  the  con- 
verters. 

The  second  compartment  contains  the 
cupolas,  where  the  re-smelting  of  the  pig 
iron  is  effected  when  at  any  time  or 
from  any  cause  it  is  thought  advisable 
to  work  by  the  old  process. 

The  third  compartment  comprises  the 
converter  compartment.  Here  we  find 
six  converters,  two  to  each  pit,  receiving 
alternately  the  iron  from  the  furnace  or 
from  the  cupolas  as  the  case  may  be, 
these  last  being  furnished  with  hot  air 
receivers  for  keeping  the  liquid  metal 
hot. 

Parallel  with  these  buildings,  and  on 
the  south  side,  are  situated  the  blast  en- 
gines for  the  converters,  the  pumps  and 
the  accumulators  having,  to  the  right 
and  to  the  left,  a  group  of  eight  boilers 
each,  of  exactly  the  same  make  as  those 
employed  for  the  blast  furnace  engines. 

The  Bessemer  blast  engines  belong  to 
the  class  constructed  as  a  specialty  by 
the  Seraing  Works,  and  were  designed 
by  M.  Kraft,  the  well  -  known  chief- 
engineer  of  the  Cockerill  Company,  and 
whose  name  must  also  be  honorably 
attached  to  the  whole  mechanical  de- 
partment of  the  steel  works.  These  en- 
gines are  of  the  compound  vertical 
type,  realizing  a  very  great  economy 
in  fuel.  The  consumption  of  coal  being 
only  If  kilogs.,  or  2|  lbs.,  per  indicat- 
ed horse  power  per  hour.  We  next 
come  to  the  rolling  mill,  the  length  of 
which  is  82  metres,  or  270  ft.,  and  which 
comprises  two  divisions,  each  18  metres, 
or  59  ft.,  wide,  and  united  by  a  row  of 
columns  33  ft.  in  height. 

In  the  first  division  are  placed  six 
large  sized  Ponsard  and  Bicheroux  fur- 
naces, whose  bottom  measures  4.50  by 
5  metres,or  about  12  ft.  by  16  ft., and  are 
sufficient  to  hold  the  ingots  needed  for 
the  two  rail  mills  situated  in  the  next  or 
third  compartment. 

The  first,  or  blooming  mill,  has  two 
pair  of  30-in.  rolls,  and  is  actuated  by  a 
reversible  engine  running  45  turns  per 


MANUFACTURE   OF   BESSEMER  STEEL   TN  BELGIUM. 


145 


minute  by  means  of  gearing.  This  has 
a  separate  engine  for  the  condenser. 

The  steam  cylinders  are  32  in.  in 
diameter,  and  have  4  ft.  stroke,  the 
pinions  being  in  proportion  of  1  to  2  J. 

The  second  or  finishing  mill,  has  two 
housings  with  24-in.  rolls,  and  is  worked 
by  a  direct-acting  reversible  engine  run- 
ning 80  to  90  revolutions  per  minute. 
This  engine  has  two  steam  cylinders  40 
in.  in  diameter,  and  acts  directly  on  a 
crank  from  12  in.  to  14  in.  in  diameter, 
placed  on  the  axis  at  the  end  of  the 
combination. 

Special  condensers  are  applied  to  this 
engine  in  order  to  avoid  the  inevitable 
counter-pressure  so  prejudicial  to  the 
working  of  engines  of  this  class.  As  a 
complement  to  the  rolling  mill,  a  special 
rail-finishing  shop  is  established,  which 
will  contain  all  the  most  modern  and 
improved  appliances  for  the  purposes 
required.  All  the  buildings  of  the  works 
are  simple,  light,  and  airy,  iron  being 
largely  used  in  their  construction.  They 
constitute  a  very  harmonious  and  sym- 
metrical whole. 

I. — Blast  Furnace  Practice. 

As  an  example  of  the  working  of  the 
new  plant,  we  cannot  do  better  than 
transcribe  the  results  obtained  in  furnace 
No.  1,  during  each  week  of  the  months 
of  March  and  April  last.  These  are  as 
follows : 


1875. 


Metric  tons. 


March    1    to   7....  417 


759 


(( 

7  "  14  . 

.  424 

771 

218 

(« 

14  "  21.. 

.  415 

773 

183 

c« 

21  "  28. . 

.  475 

910 

184 

II 

28  "  Apr. 

4  468 

913 

208 

April 

4  "  11.. 

..  459 

869 

198 

n 

11  "  18.. 

. .  455 

868 

172 

Weekly  average  . . .  445 


838 


211  370 
360 
369 
433 
434 
449 
447 

196   409 


The  mean  composition  of  the  charges 
was  as  follows: 

Coke 1650  kilogs.=3630  lbs.  Eng.  avdp. 

Ore 3100      "       =6820   "  " 

Limestone.     725      "       =1595   "  " 

The  ores  specially  employed  were  Al- 
gerian and  Spanish,  and  the  mixture 
consisted  of: 

Vol.  XIII— No.  2— 19, 


Water 6.50 

Carbonic  acid 2.50 

Silica 15.00 

Alumina 4.00 

Lime., 3.00 

Magnesia 1.50 

Oxide  of  iron 64.00.    . .  .Iron     45.08 

Oxide  of  manganese  .. .     4.25 Mang.    3.00 

Sulphur 0  10 

Phosphoric  acid 0.075 

99.925 

The  practical  product  being  49  per 
cent,  of  pig  iron. 

The  proportion  of  limestone  added 
was  23.50  per  cent.  The  coke  was  all 
made  in  Appolt  ovens,  and  was  very 
regular  in  quality,  leaving  from  8  to  10 
per  cent,  of  ash. 

With  the  above  mixture  the  iron  ob- 
tained contained  on  an  average: 

Silicon 2.25 

Carbon 4.50 

Sulphur 0.04 

Phosphorus 0.06 

Manganese 3.75 

Iron..... 89.40 


100.00 


A  considerable  percentage  of  slag  was 
produced.  This  slag  is  generally  of  a 
white  color  with  a  greenish  tinge,  and 
falls  promptly  to  dust  when  exposed  to 
the  air.     Its  composition  is  as  follows : 

Silica 37.00 

Alumina 13. 50 

Lime 43.00 

Magnesia 1.50 

Oxide  of  iron 0.59 

Manganese 3.50 

Sulphur 1.25 

100.25 

The  preceding  figures  show  that  the  con- 
sumption of  coke  has  never  exceeded 
110  lb.  to  the  100  lb.  of  iron  produced. 
This  good  result  is  attributable  to  the 
great  care  taken  throughout  the  whole 
of  the  metallurgical  processes,  and  to 
the  high  heat,  600  deg.  Centigrade,  main- 
tained in  the  blast. 

It  is  also  interesting  to  note  what  be- 
comes of  the  reduced  oxide  of  manga- 
nese which  was  contained  in  the  charge 
of  mixed  ores.  Of  this,  two-thirds  are 
found  in  the  pig  iron  and  one-third  go 
into  the  slas:. 


146 


VAN   NOSTRAND'S   ENGINEERING  MAGAZINE. 


II. — The  Bessemer  Foundry. 

The  molten  metal  is,  immediately  it 
has  run  from  the  blast  furnace  into  the 
tilt-ladle,  taken  to  the  converters  by 
means  of  hydraulic  lifts  and  the  station- 
ary bridge  on  which  it  is  carried  on  rails. 
It  is  weighed  in  a  very  simple  manner 
while  on  the  lift,  by  means  of  the  indica- 
tions of  an  ordinary  pressure  gauge 
placed  in  communication  with  the  water 
in  the  hydraulic  cylinder  of  the  lift. 

No  inconvenience  is  suffered  if  the 
iron  be  left  for  even  one  and  a  half 
hours  in  the  ladle,  beyond  the  presence 
of  a  small  solid  bottom,  which  can  be  re- 
melted  afterwards  in  one  of  the  cupolas. 

The  whole  operation  of  conversion  of 
iron  into  steel  lasts  from  15  to  22  min- 
utes. 

In  the  middle  of  the  decarburation, 
from  10  to  25  per  cent,  of  rail  ends  are 
added,  the  quantity  varying  according 
to  the  temperature  of  the  bath. 

The  most  remarkable  fact  connected 
with  the  whole  process  at  Seraing  is 
that  no  spiegel  whatever  is  introduced 
into  the  converter  at  the  end  of  the 
blow,  it  having  been  found  that  the  iron 
contained  sufficient  manganese  to  render 
this  addition  quite  useless. 

As  soon  as  the  bands  of  the  spectro- 
scope have  all  disappeared,  the  slag  is 
essayed  in  a  very  simple  and  practical 
manner,  the  end  of  the  operation  be- 
ing determined  simply  by  a  color  test. 
The  modus  operandi  is  as  follows:  The 
blow  is  momentarily  stopped  and  the 
converter  inclined;  a  paddle  is  then  in- 
troduced through  the  mouth  and  dipped 
into  the  bath.  This  is  then  drawn  out, 
steeped  at  once  in  water,  and  the  thin 
sheet  of  investing  slag  taken  off  and 
compared  to  a  standard  scale. 

A  lemon  yellow  slag  corresponds  to  a 
very  hard  steel  containing: 

0.75  of  carbon  or  more. 

Orange  yellow 0.60         "  " 

Light  brown 0.45         " 

Dark  brown 0.30         " 

Bluish  black 0.15 

The  small  metallic  globules  imbedded 
in  the  samples  of  slag,  and  resembling 
blow-pipe  beads,  may  also  be  tried  by 
hammering  them  on  a  small  anvil.  A 
very  short  expeiience  soon  teaches  the 
nature  of  the  steel,  by  the  degree  of 
malleability  of  the  globule.    If  too  hard, 


it  requires  several  blows  of  the  hammer 
to  form  a  small  starred  disc,  by  the 
splitting  of  the  edges;  if  too  soft,  it 
flattens  down  at  the  very  first  blow  of 
the  hammer.  These  are  two  extremes 
to  be  avoided,  unless  for  quite  special 
purposes. 

As  soon  as  the  metal  in  the  converter 
has  reached  the  desired  degree  of  hard- 
ness, which,  as  we  have  seen,  can  be  regu- 
lated at  will,  by  prolonging  or  shorten- 
ing the  blow,  it  is  run  into  the  moulds 
in  the  usual  way,  and  the  ingots  are 
taken  to  the  forge  as  soon  as  crj^stalliza- 
tion  has  taken  place,  and  before  they 
have  had  time  to  cool. 

Three  very  light  hydraulic  cranes  to 
each  pit  lift  out  the  ingots  rapidly,  and 
without  any  kind  of  difficulty.  The  pit 
itself  is  very  wide,  10  metres,  or  33  ft., 
in  diameter,  and  is  very  shallow,  only 
0.90  metres,  or  3  ft.,  deep,  and.  the 
moulds  being  placed  side  by  side,  plenty 
of  space  is  left  for  circulation  in  the 
centre. 

The  general  distribution  of  the  Besse- 
mer foundry  brings  to  mind  the  Ameri- 
can works,  and  nowhere  on  the  Conti- 
nent, nor  in  England,  does  there  exist 
any  establishment  where  the  practical 
facilities  are  greater,  nor  their  results 
more  economical,  than  they  are  here. 
Having  visited  nearly  every  steel-work 
in  Europe,  and  many  in  America,  I  can 
speak  with  confidence  in  this  respect. 

At  present,  the  production  reaches  100 
tons  of  ingots  for  each  pair  of  6 -ton  con- 
verters in  24  hours,  but  this  figure  will 
be  largely  increased  when  the  new  rail 
mills  are  finished,  and  rails  of  two  or 
three  lengths  are  rolled  at  once. 

The  economy  realized  by  the  direct 
run  from  the  blast  furnace  is  easy  of 
calculation.  It  consists  in  a  reduction 
in  the  quantity  of  iron  used,  added  to  a 
saving  in  fuel,  and  to  a  diminution  in 
labor. 

Since  iron  has  been  run  from  the  new 
Seraing  blast  furnaces,  not  a  single  case 
of  black  slag  has  occurred,  which  gives 
sufficient  proof  that  the  iron  produced  is 
fit  for  the  manufacturer  of  first-class 
steel. 

A  very  remarkable  fact,  as  yet  quite 
unexplained,  is  the  undeniable  one,  that 
the  direct  product  of  the  blast  furnace 
works  better  in  the  mill  and  gives  much 
tougher  steel  than  that  obtained  by  the 


WATER   SUPPLY   AND   DRAINAGE. 


147 


resmelting  of  the  same  iron  in  the  cu- 
pola. 

The  chemical  composition  being  iden- 
tical, the  steel  from  the  direct  process 
has  stood  the  ordinary  tests  for  rails  and 
tyres  much  better  than  that  which  has 
been  obtained  from  the  cupolas. 

III.— The  Bail  Mill. 

Until  the  present  day,  the  ingots  have 
been  taken  to  the  old  rail  mill,  and 
•rolled  into  single  length  rails.  Even 
here,  the  advantages  and  economy  of 
rolling  the  ingot  while  still  hot  have 
been  fully  appreciated.  A  very  ordinary 
mill  produces,  in  this  case,  600  tons  of 
20  ft.  rails,  weighing  above  70  lb.  to  the 
yard,  per  week. 

No  doubt  whatever  can  be  entertained 
that  the  new  mill,  now  in  course  of 
erection,   and   which   will   wprk    ingots 


two  or  three  times* heavier  than  at  pres- 
ent, will  turn  out  1,200  tons  per  week 
without  any  difficulty. 

As  it  takes  30  hours  for  the  conversion 
of  iron  ore  in  the  blast  furnace  into  pig 
iron,  and  as  the  operation  in  the  con- 
verter lasts  about  one  hour,  including 
carriage  of  ingots,  handling,  etc.,  and  as- 
suming that  after  one  hour  of  heating 
the  rail  may  be  rolled;  we  confidently 
affirm  that,  in  the  short  space  of  36 
hours  after  the  arrival  of  the  ore  at  the 
works,  a  rail  may  be  ready  for  shipment, 
and  during  the  whole  process  the  mate- 
rial will  not  have  been  allowed  to  get 
cool. 

This  appears  to  me  about  as  complete 
a  solution  of  the  problem  of  producing 
steel  direct  from  the  ore  as  has  yet  been 
proposed  by  many  of  the  ingenious 
searchers  of  the  day. 


WATER  SUPPLY  AND  DRAINAGE.* 

By  W.  A.  CORFIELD,  Esq.,  M.A.,  M.D. 
I. 


It  will  be  our  purpose  in  this  course 
to  discuss,  in  the  first  place,  the  sources 
and  the  kind  of  water  that  are  required 
for  large  communities — the  kind  in  the 
first  place,  the  quantity  in  the  next,  the 
places  to  get  it  in  the  third,  and  then 
the  ways  to  convey  it  to  the  community. 

It  is  only  one  part  of  the  fuel  of  a 
community  that  we  have  to  consider. 
We  shall  then  consider  what  are  the 
wastes  from  a  large  community,  and 
whether,  although  useless  for  the  pur- 
pose for  which  the  original  fuel  was 
supplied,  they  can  be  made  useful  for 
other  purposes,  and  if  so,  how  ?  Whether 
again  there  is  any  necessity  of  getting 
rid  of  them,  and  if  so,  how  this  can  be 
done  most  effectually,  and  most  cheaply, 
and  without  prejudice  to  other  commu- 
nities. 

Now  then  as  regards  water.  Water  is 
required  in  a  large  community  for  a 
great  variety  of  uses.  These  uses  were 
divided  by  the  Romans,  and  they  have 
been  divided  ever  since,  into  public  and 

*  Abstracts  from  a  course  of  lectures  delivered  before 
the  School  of  Military  Engineering  at  Chatham,  England. 


private  uses.  The  public  uses  are  such 
as  for  cleaning  streets,  extinguishing 
fires,  for  fountains,  for  public  baths,  and 
so  on.  The  private  uses  are  for  drinking, 
washing,  cooking,  etc.  Thus  water  you 
see  at  once  from  the  mere  examination 
of  its  uses  comes  to  the  community  to 
be  soiled.  It  comes  in  order  that  the 
community  may  be  supplied  with  one  of 
the  necessities  of  life.  It  comes  to  wash 
communities,  places,  and  habitations.  It 
comes,  I  repeat,  to  be  soiled.  It  is, 
therefore,  generally,  when  soiled,  useless 
for  the  purpose  it  was  originally  wanted 
for.  It  has  either  to  be  purified  or  got 
rid  of.  A  community  requires  pure 
water  for  some  purposes,  and.  those  are 
especially  for  drinking  and  cooking. 
Pure  water — I  do  not  mean  chemically 
pure,  but  we  shall  see  directly  what  is 
meant  hygienically  by  pure  water — is  not 
necessary  for  every  purpose  such  as  for 
washing  the  streets,  extingTiishing  fires, 
etc.  However,  practically  speaking,  only 
one  kind  of  water  can  as  a  rule  be  sup- 
plied to  a  community,  and  so  it  becomes 
necessary  for  us  to  know  where  we  can 


148 


VAN   NOSTRAND'S   ENGINEERING   MAGAZINE. 


get  this  sufficient  supply  of  water  of  a 
certain  quality,  viz.,  sufficiently  good  for 
drinking. 

Now,  roughly  speaking,  a  drinking- 
water  should  be,  in  the  first  place,  trans- 
parent. In  the  second  place,  it  should 
be  transparent  to  white  light:  that  is  to 
say,  it  should  be  transparent  and  with- 
out color.  It  must  be  without  taste  and 
without  smell,  and  it  must  deposit  no 
sediment  on  standing,  and  have  no  par- 
ticles suspended  in  it.  Those  are  the 
rough  qualities  of  water  which  anybody 
can  examine  for  himself  ;  the  best  way 
to  look  at  it  is  to  look  through  about  a 
foot  or  18  inches  of  it  in  a  long  glass 
cylinder,  placed  on  a  piece  of  white 
paper.  It  must  be  aerated  to  be  fit  for 
drinking,  and  cool.  Now,  if  the  water 
you  are  examining  does  not  fulfil  these 
conditions,  it  must  be  rejected  at  once, 
or  brought  to  satisfy  them.  We  have  to 
consider  how  these  conditions  are  to  be 
fulfilled,  and  we  ought*  to  satisfy  them 
on  a  large  scale.  But  a  water  may  com- 
ply with  all  these  conditions,  and  yet  not 
be  a  safe  water  to  drink.  It  may  con- 
tain substances  which  you  cannot  tell  in 
any  of  these  ways,  and  practically  speak- 
ing, all  waters  do.  Substances  whether 
in  solution  or  suspension  may  be  hurt- 
ful, or  they  may  be  harmless,  and  now  I 
want  to  tell  you  how,  if  you  have  a 
chemical  analysis  of  a  sample  of  water 
before  you,  you  can  tell  whether  that 
water  is  suitable  for  your  purpose  or  not. 
That  is  a  thing  you  do  not  generally  find 
in  engineering  books.  It  is  necessary 
for  you  to  know  it,  because  if  a  report 
is  brought  up  upon  a  particular  water, 
you  ought  to  be  able  to  know  whether 
that  will  be  a  satisfactory  water  or  not. 

Natural  waters  contain  dissolved  (in  the 
first  place  especially)  carbonic  acid  gas. 
They  contain  all  the  constituents  of  air 
in  solution,  but  the  gases  are  not  in  the 
proportion  in  which  they  are  in  atmos- 
pheric air.  There  is  often  a  great  quan- 
tity of  carbonic  acid  gas,  and  oxygen 
being  more  soluble  than  nitrogen  is  gen- 
erally in  larger  proportion  than  in  atmos- 
pheric air.  Now  the  carbonic  acid  gas 
is  the  one  that  I  am  going  to  speak  of 
first.  Water  containing  carbonic  acid 
in  solution  has  the  property  of  holding 
in  solution  quantities  of  certain  salts 
that  it  would  not  dissolve  otherwise,  or 
only  in  much  smaller  quantities,  and  the 


chief  of  these  is  carbonate  of  lime. 
Natural  waters  often  contain  then,  in 
the  first  place,  salts  of  lime,  especially 
the  carbonate,  dissolved  in  carbonic  acid. 
They  contain  often  the  sulphates  of 
lime,  soda,  magnesia,  iron,  and  so  on— in 
fact,  different  salts  of  these  and  other 
bases.  Phosphates  they  all  contain,  and 
also  chlorides  and  nitrates.  All  natural 
waters  contain  the  latter  in  certain  pro- 
portions—even rain  water.  Almost  all 
of  them  contain  salts  of  ammonia.  The 
question  arises  which  of  these  may  be 
allowed  in  water,  and  which  may  not,  or 
which,  at  any  rate,  may  not  be  allowed 
above  a  certain  quantity,  and  what  is 
the  quantity  ?  Beyond  those  simple 
characters  for  pure  water  which  I  gave 
you  a  few  minutes  ago,  there  is  a  prop- 
erty of  natural  Avaters  which  can  be 
easily  ascertained  by  any  one,  and  which 
constitutes  one  of  the  best  known  differ- 
ences between  various  specimens  of 
water,  and  that  is  the  quality  of  hard- 
ness. What  does  that  mean  ?  Hardness 
is  tested  in  this  way.  Pure  water  dis- 
solves soap,  which  is  a  combination  of 
soda  with  some  of  the  fatty  acids.  Pure 
water  dissolves  soap  perfectly  and  forms 
a  lather  at  once.  Now  water  containing 
certain  salts  in  solution,  and  notably  salts 
of  lime,  magnesia,  and  iron,  does  not  do 
so,  because  these  salts  form  insoluble  pre- 
cipitates with  the  soap.  That  is  what  is 
meant  by  the  water  being  hard.  If  a 
water,  instead  of  lathering  with  soap 
immediately,  takes  a  great  deal  of 
trouble  to  make  a  lather,  does  not  do  it 
till  after  some  time,  and  causes  a  curdy 
precipitate,  then  it  is  a  hard  water. 
That  is,  of  course,  a  very  rough  way  of 
putting  it;  but  the  amount  of  soap  that 
is  required  before  a  water  will  lather, 
gives  a  test  of  the  amount  of  salts  which 
cause  the  hardness  of  the  water,  and  the 
chemist  takes  a  standard  solution  of 
soap  and  tries  how  much  of  this  solution 
is  required  before  he  can  get  a  lather 
with  water,  and  he  says  that  the  water 
has  so  many  degrees  of  hardness.  What 
is  meant  by  a  degree  of  hardness  ?  That 
each  gallon  of  the  water  contains  in  so- 
lution an  amount  of  salts  which  will  pre- 
cipitate as  much  soap  as  a  'grain  of  car- 
bonate of  lime  would  precipitate.  What 
is  the  importance  of  this  ?  Hard  water 
is  as  a  general  rule  less  wholesome  than 
soft,  and  often  much  less  so,  it  is  not  so 


WATEK   SUPPLY   AND   DRAINAGE. 


149 


good  for  household  purposes,  nor  for 
use  in  engines,  and  it  entails  an  enormous 
waste  of  soap.  It  is  therefore  objection- 
able, even  if  the  hardness  is  caused  by 
the  presence  of  harmless  salts.  The 
total  amount  of  hardness,  the  degree  of 
hardness  of  a  water  before  anything  is 
done  to  it,  is  called  the  "  total  hardness," 
and  if  the  total  hardness  of  a  water  is 
greater  than  six  degrees  on  what  is  called 
"  Clark's  Scale  "  (the  value  of  a  degree 
of  which  I  have  already  explained)  it.  is 
called  a  hard  water  ;  if  less,  it  is  known 
as  a  soft  water.  Now  hard  water  (sup- 
posing you  have  only  got  hard  water, 
and  cannot  get  a  supply  of  soft  water)  is 
made  softer,  in  the  first  place,  by  boiling. 
That  can  be  done  on  a  small  scale.  If 
you  boil  hard  water,  of  course  the  car- 
bonic acid  is  driven  off,  and  the  salts 
held  in  solution  by  it,  especially  carbon- 
ate of  lime,  are  precipitated.  There  is 
another  way  of  rendering  hard  water 
soft,  and  this  can  be  applied  on  a  large 
scale  ;  it  is  known  as  "  Clark's  process." 
The  carbonate  of  lime  is  held  in  solution 
in  the  water  by  carbonic  acid  ;  you  can 
precipitate  it  by  boiling,  or  prevent  its 
being  held  in  solution  by  causing  the 
carbonic  acid  to  combine  with  something 
else,  as  with  more  lime,  and  Clark's  pro- 
cess which  is  now  used  on  an  extensive 
scale  (and  ought  to  be  used  very  much 
more  than  it  is)  consists  in  adding  to  the 
hard  water  milk  of  lime.  This  milk  of 
lime  combines  with  the  excess  of  car- 
bonic acid,  forming  carbonate  of  lime, 
which  falls  down  as  precipitate  together 
with  the  carbonate  of  lime  that  was  pre- 
viously held  in  solution,  thus  leaving  the 
water  softer.  If  you  boil  water,  and 
then  determine  the  hardness  that  remains, 
that  is  called  the  "permanent  hardness;" 
an  extremely  important  matter.  The 
importance  of  it  consists  in  this,  that  it 
cannot  be  removed  at  any  rate  on  a  large 
scale,  and,  in  the  second  place,  that  it  is 
due  to  salts  sev.eral  of  which  are  injuri- 
ous, so  that  a  large  degree  of  permanent 
hardness  indicates  a  bad  water.  Now 
this  permanent  hardness  (the  hardness 
that  is  lost  by  boiling  is  called  "  tempo- 
rary hardness  ")  is  due  chiefly  to  the  sul- 
phate of  lime  and  chloride  of  calcium, 
and  to  magnesian  salts.  These  are  all 
objectionable  in  a  water.  Let  me  give 
you  some  examples  of  degrees  of  hard- 
ness of  various  specimens  of  water  so  as 


to  give  you  a  definite  idea  of  hard- 
ness. 

The  hardness  of  the  Thames  water 
above  London  is  14  degrees  of  Clark's 
scale.  That  is  a  hard  water.  The  hard- 
ness of  the  New  River  water  is  15-£  de- 
grees. That,  too,  is  a  hard  water.  The 
water  of  Bala  Lake  has  only  \  of  a  de- 
gree of  hardness,  and  of  course  that  is 
an  exceedingly  soft  water.  I  must  tell 
you  before  going  on  (because  it  is  very 
likely  that  you  may  take  up  one  of  the 
Registrar  General's  Reports  and  see 
what  he  says  about  the  water  supply  to 
London)  that  it  is  now  very  usual  to  ex- 
press hardness  in  another  way.  That  is 
to  say,  instead  of  saying  so  many  grains 
per  gallon  as  is  done  in  Clark's  scale, 
hardness  is  now  very  generally  ex- 
pressed by  parts  in  100,000,  and  I  men- 
tion this  at  once,  because  the  results  of 
most  of  the  analyses  that  we  shall  have 
to  refer  to  during  the  lectures  are  given 
in  parts  per  100,000.  Of  course,  if  you 
are  given  the  hardness  of  water  in  parts 
per  100,000,  you  can  convert  it  into  de- 
grees of  hardness  in  Clark's  scale  by 
multiplying  by  seven  and  dividing  by 
ten,  because  Clark's  scale  gives  the  re- 
sults in  grains  per  gallon;  a  grain  per 
gallon  is  one  part  in  70,000.  On  this 
new  scale,  as  an  example,  the  hardness 
for  the  last  week  of  last  year  of  the  five 
Thames  companies  was  about  20  de- 
grees, that  is  to  say,  about  14  degrees 
by  Clark's  scale. 

The  hardness,  again,  of  the  water  sup- 
ply which  is  derived  from  deep  borings 
in  the  chalk  was  29.4  on  this  scale,  or 
20.58  of  Clark's  scale.  Of  course  that 
is  a  very  hard  water  indeed.  Btit  the 
hardness  of  these  two  waters  is  quite 
different,  because  the  permanent  hard- 
ness of  Kent  water  is  very  little  indeed. 
The  total  hardness  of  that  water  is  al- 
most entirely  due  to  the  carbonate  of 
lime,  whereas,  much  of  the  hardness  of 
the  water  supply  to  London  by  the 
Thames  companies  is  due  to  salts  other 
than  carbonates,  especially  to  sulphates. 
Therefore,  you  get  ranch  information 
about  the  quality  of  water  by  its  hard- 
ness. If  you  know  water  has  a  high  de- 
gree of  permanent  hardness,  you  know 
it  has  a  very  good  chance  of  being  a  bad 
water.  It  contains  probably  sulphate  of 
lime  and  chloride  of  calcium,  and  per- 
haps  magnesian   salts.     The   latter   are 


150 


VAN  nostrand's  engineering  magazine. 


especially  objectionable  to  water,  and 
any  water  which  gives  even  a  small 
amount  of  salts  of  magnesia  is  to  be  re- 
jected. Water  containing  these  salts 
causes  diarrhoea;  when  drunk,  and  it  ap- 
pears to  be  from  the  presence  of  these 
salts  in  drinking  waters  that  the  swelling 
of  the  neck  known  as  goitre  is  produced 
in  Switzerland  and  other  countries. 

The  next  thing  to  which  I  wish  to 
draw  your  attention  with  regard  to  sub- 
stances dissolved  in  water,  is,  the  amount 
of  chlorides  that  may  be  present.  I  may 
say  broadly,  that  if  you  see  in  a  report 
on  the  quality  of  a  water  that  it  contains 
much  chlorine,  or  much  common  salt 
(chloride  of  sodium),  you  may  at  once 
put  it  down  as  a  suspicious  water,  and 
you  will  see  why  in  a  minute.  Where 
do  you  get  chlorides  in  a  water  ?  They 
may  come  from  an  infiltration  from  the 
sea.  They  may  come  again  from  strata 
containing  a  quantity  of  common  salt. 
But  another  source  of  chlorides  in  a 
water  is  pollution  by  sewage.  All  sew- 
age contains  a  considerable  proportion 
of  common  salt.  This  is  one  of  the  ne- 
cessities of  life,  it  is  contained  in  many 
of  our  foods,  and  in  excretal  matters, 
especially  in  the  urine,  and  so  sewage 
contains  it.  The  average  amount  in  the 
sewage  of  water-closeted  towns  is  ten 
parts  of  chlorine  in  the  100,000.  Pure 
natural  waters  contain  less  than  a  grain 
of  chlorine  in  a  gallon,  or  about  ]  part 
in  100,000.  So,  if  in  a  sample  of  water 
for  which  you  get  the  analysis  sent,  you 
see  more  than  a  grain  in  a  gallon  of 
chlorides,  you  must  at  once  know  the 
reason  why.  London  drinking  water 
contains  2  parts  in  100,000.  That  is  not 
very  bad  water,  and  as  it  is  got  from  the 
Thames  we  know  that  it  has  been  pol- 
luted by  sewage.  The  water  derived 
from  the  chalk — the  Kent  water — actu- 
ally contains  more  than  that,  but  we 
have  a  very  good  reason  for  not  object- 
ing to  it  on  that  account,  inasmuch  as 
we  know  that  it  is  not  rendered  impure 
by  sewage.  The  well  waters  of  London 
mostly  contain  more  chlorine  than  sew- 
age, they  are  in  fact,  a  concentrated 
form  of  sewage  which  has  gone  through 
certain  alterations.  1  am  not  here  allud- 
ing to  the  Artesian  Wells,  but  only  to 
those  which  are  supplied  by  the  subsoil 
water  above  the  London  clay.  The 
amount  of  chlorine  is  a  very  good  test 


of  the  purity  of    a   water,  except   that 
you  must  always  allow  for  the  possibil- 
ity  of    chlorides   being   present   in   the 
soil  through  which  that  water  has  gone. 
Nitrates  and  nitrites  are  given  you  in 
the  Registrar  General's  Reports  as  the 
test  for  what  is  called  "previous  sewage 
contamination?     What  does  that  mean? 
It  means  that  the  nitrates,  &c,  that  are 
dissolved  in  water  come  in  a  great  major- 
ity of  cases  (if  not  in  all)  from  the  oxyda- 
tion  of  organic  matter  at  some  time  or 
other,  or  in  some  place.     Now  to  show 
you  how  plain  it  is  that  water  must  not 
be  rejected  merely  because  it  contains 
nitrates,  I  must  tell  you  that  there  are 
nitrates  and  nitrites  in  all  waters,  even 
in  small  quantities  in  rain  water.     What 
amount   of    nitrates   may  be   found   in 
water  without  giving  a  suspicion  of  pre- 
vious   contamination  ?      Allowing    that 
they  are  not  injurious  in  themselves,  yet, 
inasmuch  as  they  at  once  make  you  sus- 
pect that  the  water  containing  them  in 
solution  has,  at  some  time  or  other,  been 
contaminated  with  organic  matters  to  a 
large  extent,  which  organic  matters  have 
been  oxydized,  the  result  being  the  pro- 
duction of   nitrates   and  nitrites ;    inas- 
much  as   that   is   the   case,  if  you  get 
much   nitrates,    &c,   represented    in    a 
water,  you  must  at  once  see  if  that  water 
is  derived  from  a  source  where  it  is  likely 
to  get  contaminated  with  refuse  matters; 
because  if  it  is,   although   the  nitrates 
are   harmless,   and   although   it  is .  very 
desirable  that  these  matters   should  be 
oxydized  to  that  state,  still  you  are  al- 
ways liable  to  its  happening  some  day 
that  the  water  is  contaminated  by  the 
solution  of  these  organic  matters  in  their 
crude  unoxydized  form,  in  which    case 
they  are  very  often,  if  not  always  danger- 
ous.    Let  us  see  what  amount  of  nitrates 
is  found  in  various  waters.    In  the  drink- 
ing water  we   get  in  London  from  the 
Thames  there  are  about  2  parts  in  a  mil- 
lion (or  0.2  in   100,000).     In  the  New 
River  Water  (North   London  water)  a 
little   more   than  3    parts  ;   and  in  the 
Kent  water  4  parts  in  a  million,  so  that 
the  deep  chalk  waters  (which  we  know 
must  be  very  pure)  contain  more  nitrates 
than   the   others    do,   a  sufficient   proof 
that  the  presence  of  nitrates  is  not  of 
itself  a  sufficient  reason  for  rejecting  a 
water.     The  waters  from   the  Cumber- 
land Lakes  contain  very  much  less.     To 


WATER  SUPPLY   AND   DPvAINAGE. 


151 


give  you  an  example  of  a  water  contain- 
ing a  great  deal,  I  may  cite  the  instance 
of  a  well  at  Liverpool  which  was  found 
to  contain  more  than  8  parts  in  100,000 
of  nitrates  and  nitrites,  which  were  all 
derived  (or  in  all  probability  derived) 
from  the  oxydation  of  sewage  that  had 
traversed  the  ground  round  that  well. 
If  nitrates  be  present  in  large  quantities 
it  must  be  regarded  as  a  suspicious  cir- 
cumstance, unless  you  have  good  reason 
to  know  that  the  water  comes  from  a 
source  which  is  beyond  the  suspicion  of 
contamination.  There  are  quantities  of 
nitrates  in  many  soils.  The  presence  of 
nitrates  in  water  got  from  such  soils 
would  not  justify  you  in  having  the 
water  condemned  as  a  source  of  supply 
if  there  were  no  other  reason. 

Salts  of  ammonia.  These,  too,  are 
contained  in  natural  waters  in  exceed- 
ingly small  quantities.  They  do  no 
particular  harm  in  themselves,  but  they 
frequently  come  directly  from  sewage. 
The  numbers  in  a  drinking  water  repre- 
senting salts  of  ammonia  ought  to  be  in 
the  third  place  of  decimals  for  parts  in 
100,000,  or  if  in  the  second  place  of  dec- 
imals, ought  to  be  small.  Now  the  water 
supply  of  London,  filtered  Thames  water, 
contains  .001  to  .005  parts  in  100,000. 
That  is  pretty  good.  The  water  at  Bala 
Lake  contains  .001  parts,  and  rain  water 
contains  the  same  amount;  so  that  we 
may  expect  salts  of  ammonia  to  be  con- 
tained in  all  natural  waters.  Sewage 
contains  about  6  parts  in  100,000.  Well 
water  often  contains  large  quantities, 
four  parts  for  instance;  the  pump  water 
in  London  contains  nearly  one  part  in 
100,000,  and  the  water  of  the  Thames  at 
London  Bridge  0.1  part  in  100,000;  these 
are  all  bad  waters,  so  that  when  you  see 
ammonia  mentioned  in  an  analysis  of 
water  in  greater  quantity  than  is  repre- 
sented on  the  second  place  of  decimals 
in  parts  per  100,000,  you  may  always 
safely  condemn  it,  for  on  looking  fur- 
ther you  will  find  what  I  am  now  going 
to  speak  of,  namely,  organic  matters. 

Now  the  actual  organic  matters  pres- 
ent in  a  water  may  be  in  suspension  or 
solution.  If  there  are  organic  matters 
in  suspension  a  water  may  be  safely  con- 
demned, because  they  may  even  by  agi- 
tation pass  into  solution,  and  so  the  fact 
of  your  trying  to  separate  them  may 
cause  more  of  them  to  get  into  solution. 


Organic  matters  you  will  find  in  analysis 
represented  in  two  different  ways.     In 
one,  as  for  instance  in  the  analysis  given 
by  the  Registrar  General,  you  will  find 
organic  matters  represented  in  this  way: 
so  much  organic  carbon,  and  so  much 
organic  nitrogen  in  the  100,000,  and  the 
Rivers   Pollution    Commissioners    have 
given  this  as  a  standard,  not  of  drinking 
water,  but  of  a  water  that  shall  be  con- 
sidered to  pollute  any  water  course  to 
which  it  is  turned.  Two  parts  of  organic 
carbon  in  100,000  or  3  parts  of  organic 
nitrogen   in    100,000.      What   does   the 
London  drinking  water  contain  again  ? 
From  3  to  4  in  100,000  of  organic  carbon 
(I  take  this  from  the  Registrar  General's 
reports),  and  about  .05  of  organic  nitro- 
gen.     Now   we  shall   see   at   once   the 
difference  between   drinking  water   de- 
rived from  such  a  source  as  the  Thames 
and  filtered,  and  drinking  water  derived 
by   boring   into    deep    strata — into   the 
chalk.     The  chalk  water  only  contains 
.06,  that  is  the  fifth  of  the  quantity  of 
organic  carbon,  and  .01,  a  fifth  of  the 
quantity   of   organic  nitrogen  that   the 
water  supplied  by  the  Thames  Compa- 
nies contains;  so  that  when  you  come  to 
organic  matters,  you  see  the  difference 
at  once  between  a  water  that  is  derived 
from  a  pure  source,  and  one  from   an 
impure.     The  other  method  that  I  have 
to  mention  to  you,  which  is  used  for  ex- 
pressing the  amount  of  organic  matters 
in  water,  is  called  "  Wanklyn's  method  " 
from   the    chemist   who   discovered    it. 
This  method  consists  in  the  conversion 
of  the  nitrogen  contained  in  the  organic 
matter  in  the  water,  or  a  considerable 
part  of  it,  into  ammonia,  and  then  it  is 
estimated  as  so  much  ammonia.     I  dare 
say  you   all  know   that   the   test   that 
chemists  have  for  ammonia  is  perhaps 
the  most  delicate  test  with  which  we  are 
acquainted.     This  ammonia  you  will  see 
mentioned  in  the  records  of  analysis  as 
"  albuminoid  ammonia,"  and  to  a  certain 
extent  it  does  represent  the  amount  of 
organic  matter  in  the  water.  This  album- 
inoid ammonia  in  a  drinking  water  must 
not  be  allowed  to  be  above  the  third 
place  of  decimals.     If  it  appears  higher 
than  the  third  place  of  decimals  in  parts 
of  100,000,  if  in  the  second  place,  or  if 
hi  the  first,  it  is  bad.     If  in  the   first 
place  it  is  decidedly  bad  water,  and  con- 
tains a  considerable  amount  of  organic 


152 


VATS'  NOSTRAND'S   ENGINEERING  MAGAZINE. 


matter  in  a  state  of  solution.  You  may 
consider  that  the  albuminoid  ammonia 
represents  about  ten  times  its  weight  of 
dry  organic  matter,  and  about  forty  times 
its  weight  of  moist  organic  matter.  So 
that  .05  of  albuminoid  ammonia  in  100,- 
000  represents  about  2  parts  of  moist 
organic  matter  in  the  water.  You  see 
that  when  you  have  an  analysis  of  water 
before  you,  you  must  consider  the  differ- 
ent things  together.  The  nitrates  help 
to  condemn  a  water  with  much  organic 
matter  in  it.  The  ammonia  does  the 
same,  and  the  chlorides  especially  so, 
and  chlorides  are  to  be  regarded  as  a 
suspicious  indication  in  water,  if  you 
have  not  good  reason  to  suppose  that 
they  come  from  some  other  source  than 
the  one  I  have  indicated.  The  danger 
of  organic  matter  in  drinking  water  con- 
sists in  this  fact  (of  course  organic  mat- 
ters are  necessary  to  us  for  our  food,  and 
it  is  not  the  mere  fact  of  its  being  organic 
matter  that  renders  it  dangerous)  that  it 
is  organic  matter  in  a  state  of  rapid 
change;  in  a  state  of  putrefactive 
change,  and  then  that  it  may  contain, 
and  often  does  contain  (especially  if  it  is 
derived  from  excremental  matter)  the 
poison  of  specific  diseases,  which  may 
be  distributed  in  the  drinking  water  to  a 
population  and  cause  an  outbreak  of 
cholera,  typhoid  fever,  etc.  We  know 
now  what  sort  of  water  must  be  got  for 
drinking.  The  above  are  its  character- 
istics, and  the  water  supply  must  either 
comply  with  these  conditions,  or  be 
made  to  do  so  artificially. 

Now  how  much  of  it  is  wanted? 
You  can  look  at  this  in  two  ways.  You 
can  get  to  know  by  experience  how 
much  bodies  of  men  and  towns  always 
have  wanted.  The  amount,  of  course, 
varies  immensely  with  the  use  of  baths, 
whether  they  are  public  baths  or  not, 
with  the  amount  used  for  washing  the 
streets,  and  for  manufactures,  and  also 
with  the  amount  of  waste,  because  that 
is  a  very  important  item.  Now,  for 
washing,  drinking,  and  domestic  pur- 
poses generally,  you  may  put  it  down 
(if  there  is  reasonable  amount  of  bath- 
ing) at  about  ten  gallons  a  head  a  day, 
and  then  you  must  add  nine  or  ten 
more  for  flushing  the  sewers  and  washing 
the  streets.  Much  of  this  will  be  added 
through  the  water-closets.  Thus  you 
may  say  20  gallons  a  day  without  waste 


may  be  taken  as  a  kind  of  average. 
For  trades  you  must  allow  10  gallons 
more  as  a  rule.  If  there  are  public 
baths,  and  where  there  are  many  ani- 
mals, as  horses,  which  require  about  12 
or  15  gallons  a  head  for  washing  and 
drinking,  you  must  make  a  greater  al- 
lowance. You  will  see  that  about  30 
gallons  a  head  a  day  is  the  least  even 
where  there  is  no  extra  demand,  and 
that  is  about  the  amount  provided  in 
London,  and  that  is  about  the  least  that 
you  should  aim  at.  Professor  Rankine 
tells  you  that  35  gallons  is  the  greatest 
amount  necessary.  However,  they  don't 
think  so  everywhere.  New  York  man- 
ages to  get  through  300  gallons,  and 
does  not  find  it  too  much.  In  ancient 
Rome  (to  show  you  that  these  matters 
have  been  thought  of  a  long  time  ago) 
they  had  nine  aqueducts  to  bring  water 
to  the  city.  They  thought  it  of  so  much 
importance  that  several  of  these  aque- 
ducts were  from  42  to  49  miles  long, 
and  one  of  them,  the  •  Marcian,  was  54 
miles  long.  Frontinus,  who  was  the 
superintendent,  and  who  wrote  a  most 
excellent  work  about  them,  giving  accu- 
rate descriptions  and  measurements  of 
them,  tells  us  the  two  most  recent  were 
made  because  the  seven  already  in  exist- 
ence "  seemed  scarcely  sufficient  for  pub- 
lic purposes  and  private  amusements." 
Now  the  sectional  area  of  the  water 
supply  to  Rome  by  these  aqueducts  was 
1120  square  feet,  and  it  is  pretty  sure 
that  there  were  not  more  than  332,000,- 
000  gallons  daily  brought  to  Rome  by 
them.  I  suppose  there  were  not  more 
than  a  million  people  ;  that  gives  you 
about  332  gallons  a  day  that  they  found 
necessary. — (Mr.  James  Parker  on  the 
"  Water  Supply  of  Rome.") 

Now,  let  me  give  you  one  or  two 
points  about  the  measurement  of  water 
that  you  will  find  useful.  The  measure- 
ment of  water  you  will  often  find  given 
in  cubic  metres.  '  A  cubic  metre  is  35^ 
cubic  feet  or  220  gallons.  That  is  to 
say,  a  cubic  metre  of  water  is  220  gal- 
lons, and  as  a  ton  of  water  contains  224 
gallons,  a  cubic  metre  of  water  is  almost 
exactly  equal  to  a  ton  by  weight  (or  tun 
by  measure).  A  cubic  foot  is  rather 
more  than  6  gallons,  and  100  gallons 
are  just  about  16  cubic  feet.  Let  me 
just  give  you  an  example  of  this.  Lon- 
don during  December,  1872  (I  find  from 


WATER   SUPPLY   AND   DP.AINAGE. 


153 


the  Registrar  General's  report),  was  sup- 
plied daily  with  100  millions,  nine  hun- 
dred thousand,  and  something  odd,  gal- 
lons of  water.  That  is  to  say  458,577 
cubic  metres,  or  about  the  same  amount 
of  tons  by  weight  or  tuns  by  measure  ; 
that  is,  201.8  gallons  to  each  house,  or 
rather  less  than  a  cubic  metre  to  each 
house,  and  28.4'  gallons  to  each  person. 
I  told  you  it  was  30.  Well  it  varies  a 
little.  It  is  a  little  under  30  very  often. 
Of  the  total  amount  of  water  supplied 
to  a  place,  you  may  take  it  as  a  general 
rule  that  80  or  82  per  cent,  is  required 
for  domestic  purposes,  so  that  during 
that  month  of  December  in  London, 
there  were  about  23^  gallons  used  for 
domestic  purposes.  Hence  the  conclu- 
sion about  the  quantity  is,  that  the 
least  you  must  endeavor  to  get  is  30 
gallons  a  head  a  day  without  any  very 
extra  demands.  Of  this  about  80  per 
cent,  will  be  required  for  domestic  and 
the  rest  for  public  purposes. 

So  much  for  the  quality  of  drinking 
water,  and  the  quanty  to  be  supplied. 
We  have  now  to  go  on  to  consider  the 
places  where  water  of  this  quality  and 
in  sufficient  quantity  can  be  procured. 
The  main  sources  of  water  are  rain,  and 
the  sources  that  are  subordinate  to  rain- 
fall— wells,  springs,  streams  and  rivers. 
Some  other  sources  which  are  used  occa- 
sionally, and  which  are  of  very  little  use 
for  a  great  supply,  are  such  as  the  dew, 
ice,  snow  and  distilled  water.  These 
latter  we  may  dismiss  with  a  word  or  two 
as  only  of  exceptional  utility.  Dew  has 
been  used  in  deserts  and  at  sea.  Ice  and 
snow  furnish  enormous  quantities  of 
water  in  certain  places  where  they 
abound.  Ice  furnishes  an  exceptionally 
pure  water,  because  in  freezing  the  salts 
are  separated  out,  and  the  gases  too  ; 
such  water  therefore  requires  aeration. 
Snow  and  ice  if  used  should  not  be  col- 
lected near  to  dwellings,  because  of  the 
risk  of  contamination.  Distilled  water 
is  an  important  water  supply  now,  espe- 
cially at  sea.  Its  chief  fault  is  that  it 
requires  aeration.  To  give  it  this  Nor- 
mandy's apparatus  may  be  used,  or  it 
may  be  allowed  to  fall  from  one  vessel 
to  another  like  a  shower.  It  has  been 
said  that  cases  of  lead  poisoning  have 
occurred  at  sea  "  partly  from  the  use  of 
minium  in  the  apparatus,  and  partly 
from  the  use  of  zinc  pipes  containing 


lead  in  their  composition,"  (Dr.  Parkes.) 
So  much  for  the  subordinate  sources, 
which  are  all  of  little  importance  to  us. 

We  now  come  to  rain,  which  is  the 
original  source  of  all  great  supplies. 
Rain,  which  we  are  going  to  consider, 
is,  of  course,  caused  by  the  fact  that 
when  two  air  currents  come  together, 
both  saturated  with  moisture  one  having 
a  lower  temperature  than  another,  the 
mixed  air,  though  it  has  a  mean  tempera- 
ture, has  not  the  mean  capacity  for 
water,  but  a  capacity  less  than  the  mean, 
and  so  some  of  it  falls  as  rain.  Is  rain, 
as  it  falls,  sufficiently  pure  to  be  used  as 
a  source  of  drinking  water  ?  In  the 
first  place  it  is  very  soft.  In  the  second 
place  it  is  well  aerated.  It  dissolves 
especially  carbonic  acid  and  oxygen  from 
the  air — the  former  being  about  three 
per  cent,  of  the  total  dissolved  gases, 
and  the  latter  from  30  to  40  per  cent.  It 
contains  nitrates  and  nitrites,  especially 
during  thunderstorms.  It  contains  salts 
of  ammonia,  which  render  it  more  alka- 
line when  collected  in  the  country.  Near 
towns  it  contains  most  of  the  impurities 
that  are  found  in  the  air  of  towns,  and 
especially  it  becomes  acid  instead  of 
alkaline,  absorbing  a  large  amount  of 
the  sulphuric  acid  that  is  in  the  air.  It 
contains  organic  matter,  and  this  in  in- 
creased amount  near  towns.  Rain  half 
a  mile  from  the  extreme  south-west  of 
Manchester,  although  the  wind  was 
blowing  from  the  west,  tasted  flat,  in- 
sipid, oily  and  nauseous — deposited  or- 
ganic matters,  and  even  organized  bodies 
in  considerable  quantities,  and  left  a 
clear  water  above,  containing  more  than 
two  grains  of  organic  matter  in  the  gal- 
lon. Dr.  Angus  Smith,  who  examined 
this  water,  makes  the  following  remarks: 
"  It  becomes  clear  from  the  experiments 
that  rain-water  in  town  districts,  even  a 
few  miles  distant  from  a  town,  is  not  a 
pure  water  for  drinking  ;  and  that  if  it 
could  be  got  direct  from  the  clouds  in 
large  quantities,  we  must  still  resort  to 
collecting  it  on  the  ground  in  order  to 
get  it  pure.  The  impurities  of  rain  are 
completely  removed  by  filtration  through 
the  soil ;  when  that  is  done,  there  is  no 
more  nauseous  taste  of  oil  or  of  soot, 
and  it  becomes  perfectly  transparent." 
He  is  therefore  of  opinion,  that  rain  col- 
lected directly  from  the  air  cannot,  at 
any  rate  near  to  towns,  afford  a  proper 


154 


VAN   NOSTRAND'S   ENGINEERING   MAGAZINE. 


water  supply.  However,  since  rain  is 
the  source  of  all  the  supplies  that  we 
get,  it  becomes  necessary  and  of  great 
importance  in  estimating  the  amount  of 
water  that  can  be  got  in  a  district  to 
measure  the  rain-fall  of  that  district. 
Now  the  depth  of  the  rain-fall  of  a  dis- 
trict has  extraordinary  varieties,  both  as 
to  place  and  time.  For  instance,  as  re- 
gards time,  the  tropical  rain-fall  is  almost 
all  at  one  part  of  the  year.  With  us  it 
is  variable.  The  rain-fall  is  measured 
in  England  by  its  depth  in  inches.  The 
rain-fall  is  greater  in  mountainous  dis- 
tricts, and  on  the  leeward  side  of  moun- 
tains, if  they  are  not  high  enough  to 
penetrate  the  clouds,  but  if  they  are,  it 
is  on  the  windward  side,  because  the 
clouds  do  not  get  over  the  tops  of  the 
mountains.  Now,  for  the  supply  of 
water,  the  important  points  to  be  known 
about  the  rain-fall  are  these.  The  first 
is  the  least  amount  of  rain  that  has  ever 
been  known  to  fall  in  a  year  in  a  district ; 
the  minimum  annual  fall.  Then  it  is  im- 
portant to  know  the  distribution  of  the 
rain  throughout  the  year,  and  especially 
the  longest  drought,  because  you  have 
got  to  provide  for  that  time  as  well  as 
for  any  other  time,  and  the  observations 
on  the  rain-fall  of  a  district  should  ex- 
tend over  not  less  than  20  years.  Of 
course  it  is  not  often  that  you  can  get 
observations  at  any  locality  that  have 
been  maintained  for  20  years,  and  so  we 
shall  have  to  consider  in  an  instant  or 
two  how  we  are  to  get  over  that  diffi- 
culty. 

The  machine  used  for  measuring  the 
depth  of  rain-fall  is  called  a  rain  gauge. 
It  is  essentially  a  funnel,  the  area  of  the 
top  of  which  is  known  very  accurately. 
The  top  of  this  funnel  is  provided  with 
a  vertical  rim  to  catch  the  splashings  so 
that  none  may  be  lost.  Below  the  fun- 
nel there  is  a  glass  vessel  placed  to  re- 
ceive the  water.  The  height  of  the 
water  in  it  may  be  indicated  by  a  float, 
or  its  quantity  may  be  ascertained  at 
given  intervals  of  time  by  measuring  or 
weighing  it,  and  that  is  the  best  plan. 
Of  course  the  number  of  cubic  inches  of 
water,  which  is  the  same  as  the  number 
of  square  inches  of  the  area  of  the  fun- 
nel, gives  you  one  inch  of  rain  over  that 
area.  Suppose  the  area  of  your  funnel 
it  20  square  inches,  20  cubic  inches  of 
water  will  obviously  be  the  result  of  one 


inch  of  rain-fall  over  that  20  inches.  It 
is  most  convenient  to  measure  the  water, 
and  the  measuring  glass  is  constructed  in 
the  following  way  : — At  the  place  where 
that  amount  of  cubic  inches  of  water 
stands  which  is  equal  to  the  number  of 
square  inches  in  the  area  of  your  funnel 
a  line  is  drawn,  and  this  represents  one 
inch  of  rain-fall.  If  the  area  of  your  fun- 
nel is  20  square  inches,  then  you  take  20 
cubic  inches  of  water  which  you  have 
weighed  or  measured  accurately,  place  it 
in  your  glass  vessel  and  mark  one  at  the 
level  where  it  stands,  because  that 
amount  is  equal  to  a  depth  of  one  inch 
of  water  over  the  area  you  are  observing 
One  cubic  inch  of  water  weighs  252£ 
grains,  almost  exactly.  That  one  inch 
is  divided  into  tenths  and  hundreds  ;  and 
with  this  vessel  you  are  able  to  measure 
the  amount  of  rain  that  has  fallen 
through  the  funnel  in  a  given  time.  The 
top  of  the  gauge  must  be  placed  nearly 
level  with  the  ground  ;  the  instrument 
must,  in  fact,  be  sunk.  It  must  be 
placed  in  an  open  situation,  and  a  fence 
put  round  it  if  necessary.  One  is  very 
frequently  placed  at  a  height  above  the 
ground,  and  one  on  the  ground  to  show 
the  difference  in  the  amount  of  rain  that 
falls  at  the  two  levels.  The  amount  of 
rain  that  falls  at  the  level  of  the  ground 
(leaving  hills  out  of  the  question)  is 
always  greater  than  the  amount  that 
falls  at  any  height  above  the  ground. 
If  you  have  got  records  of  the  rain-fall 
of  a  district  for  a  considerable  number 
of  years  your  work  is  to  a  great  extent 
done,  because  then  you  have  merely  to 
take  out  the  facts  that  you  want.  If 
you  have  not,  the  only  -way  to  do  it 
(with  a  limited  time)  is  to  place  rain 
gauges  at  convenient  situations,  and  as 
many  as  possible  all  over  the  district  you 
are  examining,  and  if  there  are  any  hills 
in  or  near  the  district  some  of  them 
ought  to  be  placed  on  their  tops,  and 
each  of  these  rain  gauges  ought  to  be 
carefully  and  regularly  examined  at  cer- 
tain fixed  times.  Then  you  must  com- 
pare the  records  of  all  these  gauges  with 
the  results  given  by  the  nearest  rain 
gauge  that  has  been  observed  for  a  con- 
siderable number  of  years,  to  get  a  kind 
of  relation  between  the  rain  that  falls  at 
these  different  stations  on  your  district, 
and  the  rain  that  falls  at  the  nearest 
place  from  which  you  can  get  any  re- 


WATER   SUPPLY   AND   DRAINAGE. 


155 


liable  data,  and  from  this  comparison 
you  must  calculate  what  will  probably 
be  the  longest  drought  in  your  district, 
and  what  is  probably  the  least  annual 
rain-fall.  Now,  the  average  in  different 
parts  of  England  is  from  22  inches  to 
100,  or  even  120  per  annum  ;  in  some 
countries,  as  Burmah,  180  to  220,  and  it 
is  even  said  to  be  as  much  as  600  inches 
in  one  place.  This  useful  rule  was  given 
by  Mr.  Hawkesley  (and  certainly  the 
tables  show  that  it  is  a  very  accurate 
rule)  that  if  you  take  the  average  rain- 
fall of  a  place  for  20  years,  and  substract 
a  sixth  from  it,  that  will  give  you 
the  average  annual  rain-fall  of  the 
three  driest  years  during  that  period. 
If  you  take  the  average  annual  rain -fall 
for  20  years,  and  take  a  third  part  from 
it,  that  will  give  you  the  amount  of  rain 
in  the  driest  year  of  these  20  almost 
exactly,  and  if  you  take  the  average  of 
20  years,  and  add  a  third  to  it,  then  that 
will  give  you  pretty  nearly  the  amount 
of  rain  in  the  wettest  year. 

So  you  get  with  a  considerable  amount 
of  accuracy  the  quantity  of  rain  ;  the 
least  amount  of  rain  you  are  likely  to 
get,  and  the  greatest  as  well.  Then,  of 
course,  you  want  to  know  the  area  of  the 
district,  and  besides  the  actual  amount 
of  the  rain-fall,  you  must  also  know  the 
amount  which  is  available.  In  the  first 
place,  a  great  deal  of  the  rain-fall  is  lost 
by  evaporation  and  absorption.  Evapo- 
ration from  the  surface,  and  absorption 
by  plants,  &c.  Then,  if  the  ground  is 
very  porous  to  a  great  depth,  a  consider- 
able amount  will  be  sbsorbed  so  fast  that 
you  cannot  collect  it.  Most  of  the  rain- 
fall is  at  once  available  from  or  near  the 
surface  in  steep  countries,  and  especially 
those  which  are  formed  of  primitive  and 
metamorphic  rocks,  as  granite,  clay-slate, 
&c,  and  generally  from  impervious 
rocks  that  are  steep-sided.  Almost  all 
the  rain-fall  in  these  cases  is  available  at 
once.  It  runs  off  the  surface  and  col- 
lects in  lakes,  and  is  available  directly. 
And  then,  on  hilly  pasture  lands  in  lime- 
stone and  sandstone  regions,  something 
like  two-thirds  of  the  rain  may  be  con- 
sidered available,  and  on  flat  pasture 
countries  something  like  one-half*.  For 
instance,  on  the  green  sand,  Mr.  Prest- 
wich  estimated  that  from  36  to  60  per 
cent,  is  available.  On  chalk  and  loose 
sand  there  is  very  little  indeed  available. 


Now  one  of  the  most  important  things, 
if  not  the  most  important  thing  to  know, 
is  the  geological  character  of  the  rocks 
of  the  district  you  are  examining,  be- 
cause that  will  tell  you  a  very  great  deal 
about  the  amount  of  available  water, 
and  about  the  way  to  get  it.  We  are 
told  that  in  chalk  countries  the  rivers 
and  streams  carry  off  at  once  about  a 
fifth  of  the  rain-fall  ;  that  the  evapora- 
tion and  absorption  by  vegetables  and 
animals  amounts  to  as  much  as  a  third, 
and  that  the  remainder  (i.e.,  the  greater 
part  of  the  total  rain-fall)  sinks  into  the 
ground.  In  less  absorbent  strata  you 
may  put  down  that  it  is  about  equally 
divided — that  one-third  is  carried  off  by 
the  streams,  &c. ;  another  third  absorbed 
by  plants  and  animals,  or  lost  by  evapo- 
ration, while  a  third  sinks  into  the 
ground. 

Well  now,  let  us  consider  what  means 
have  been  taken  to  get  at  this  water  that 
sinks  into  the  ground.  Of  course  it  is 
got  at  by  digging  down,  and  now  we 
must  consider  in  what  strata  we  are  likely 
to  be  successful  in  digging  wells  or  mak- 
ing borings  to  get  underground  water. 
In  the  first  place,  wells  in  sands  lying 
over  impervious  strata,  over  clays  es- 
pecially, if  they  are  not  deep,  do  not,  as 
a  rule,  afford  much  water.  They  may, 
however,  afford  a  fair  supply  as  to  quan- 
tity, but  very  often  afford  a  bad  supply 
as  to  quality.  For  instance,  'the  wells 
sunk  into  the  sands  and  gravels  over  the 
London  clays  afford  a  very  impure  water. 
If  water  of  this  description  has  come  di- 
rectly from  the  surface,  and  especially  in 
the  neighborhood  of  towns,  it  is  contam- 
inated in  all  sorts  of  ways.  The  water 
in  these  wells  never  overflows  or  spouts 
up.  Wells,  on  the  other  hand,  sunk 
through  impervious  strata  to  pervious 
ones  below,  generally,  though  not  always, 
supply  excellent  water.  At  any  rate, 
they  have  much  greater  chance  of  sup- 
plying excellent  water,  becaiise  they  sup- 
ply the  water  that  has  come  from  the 
high  grounds  at  a  considerable  distance. 
For  instance,  the  borings  that  are  made 
through  the  London  clay  down  to  the 
chalk,  supply  some  of  the  best  water  in 
London.  The  Kent  water  is  still  better, 
and  is  supplied  in  large  quantities  by 
borings  which  pass  through  the  chalk, 
through  the  upper  green  sand,  and 
through  the  gault  (an  impervious  stratum) 


156 


VAN  nostrand's  engineering  magazine. 


into  the  lower  green-sand.  These  wells 
are  known  as  Artesian  wells.  The  water 
rises  up  a  considerable  height  in  them, 
and  may  overflow.  It  is  often  thought 
that  Artesian  wells  always  overflow,  but 
they  don't.  The  water  rises  up  to  a  cer- 
tain height,  which  height  is  of  course 
determined  by  several  considerations, — 
for  instance,  by  the  height  it  came  from 
originally.  Of  coui-se  the  water  that 
you  get  from  under  Kent  is  the  water 
that  has  fallen  upon  the  outcrop  of  the 
green  sand  at  a  very  considerable  dis- 
tance round  the  London  basin. 

Mr.  Prestwich,  who  has  paid  the  great- 
est attention  to  the  water  supply  of  Lon- 
don, and  to  thearrangement  of  the  strata 
around  London,  has  calculated  that,  from 
the  lower  green-sand  underneath  the 
London  basin,  there  is  to  be  got  an  enor- 
mous supply  of  water  for  the  metropolis, 
that  is  to  say,  on  the  presumption  that 
this  lower  green-sand  is  continuous  under- 
neath London.  It  would  not  be  fair  if  I 
did  not  tell  you  here  that  the  lower 
green  sand  does  not  appear  to  be  con- 
tinuous underneath  the  London  basin. 
Some  of  the  older  strata  are  brought  into 
contact  with  the  chalk,  so  that  the  lower 
green-sand  is  missing,  probably,  under- 
neath a  great  part  of  the  district.  This 
we  know  from  deep  borings  which  have 
been  made  at  several  places.  Of  course 
the  chalk  and  also  the  green-sand  are 
merely  instances.  You  want  to  know 
the  alternation  of  the  strata  right  away 
down  the  whole  geological  series,  so  as 
to  be  able  to  say,  if  you  go  into  a  coun- 
try and  study  the  maps  and  sections  for 
a  short  time,  "  If  we  make  a  well  here 
and  bore  down,  we  shall  probably  go 
through  a  band  of  clay  into  a  pervious 
stratum,  and  get  a  supply  of  water." 
You  want  for  this  purpose  to  study  the 
geological  maps,  and  to  have  ample  time 
to  do  it.  If  we  go  below  the  chalk  into 
the  oolitic  series,  we  have  similar  alter- 
nations of  pervious  and  impervious 
strata.  "When  we  go  below  this  we 
come  to  the  new  red  sandstone,  and  I 
mention  this,  because  there  is  an  im- 
portant point  connected  with  it.  The 
new  red  sandstone  is  (to  a  great  extent) 
a  pervious  stratum.  It  contains  enor- 
mous quantities  of  water,  but  the  cau- 
tion about  it  is,  that  in  many  countries 
it  holds  immense  salt  deposits.  It  is  in 
the   new   red   sandstone   of  "Worcester- 


shire (for  instance)  that  the  salt  deposits 
of  Droitwich  are  found ;  so  that  borings 
in  the  new  red  sandstone  (although  it  is 
true  that  some  towns  are  supplied  from 
that  stratum),  are  frequently  found  to 
give  a  brackish  water.  Below  this  come 
the  Permian  strata,  in  which  you  have 
the  magnesian  rocks,  that  I  mentioned 
last  time,  and  it  is  a  mischievous  thing 
to  bore  into  these  strata,  because  you 
may  get  water  containing  large  amounts 
of  magnesian  salts.  Towns  which  are 
placed  upon  these  strata  are  best  sup- 
plied (like  Manchester)  from  older  for- 
mations, such  as  mountain  limestone, 
and  so  on,  which  generally  afford  excel- 
lent water.  The  best  supplies  are  ob- 
tained from  them,  not  by  boring  or 
by  wells,  but  from  springs.  There  is 
one  thing  I  must  mention,  before  I  leave 
the  wells,  and  that  is,  that  the  sinking 
of  deep  wells  may  lower  the  level  of  the 
water  in  the  country  above  considerably, 
and  that  is  a  point  that  has  often  to  be 
taken  into  consideration.  For  instance, 
Mr.  Clutterbuck  showed  that  wells  at  a 
considerable  distance  from  London  have 
been  seriously  affected  by  the  pumping 
of  the  green-sand  water  below  London. 
He  showed  that  the  level  of  the  water  in 
these  wells  was  affected  so  much,  that 
you  could  tell  by  the  levels  of  the  well 
waters  at  a  considerable  distance  from 
London,  whether  the  pumping  had  been 
going  on  in  London  on  the  previous  day 
or  not.  There  is  another  thing  that  re- 
quires to  be  known,  especially  about 
borings  in  the  chalk,  and  that  is,  that 
some  of  the  borings  will  give  an  inex- 
haustible supply  of  water,  practically 
speaking,  while  borings  close  by  will 
give  you  next  to  none.  This  Mr.  Prest- 
wich accounts  for,  by  stating  that  the 
water  in  chalk  runs  chiefly  through 
crevices,  and  does  not  infiltrate  through 
the  mass  of  rock.  Before  I  say  a  few 
words  to  you  about  the  construction  of 
wells,  I  have  something  to  say  about 
springs,  and  the  amount  of  water  they 
supply.  Now  springs  occur  where  you 
have  an  impervious  stratum  cropping 
out  from  beneath  a  pervious  one,  and 
this  may  happen  in  various  ways. 

The  water  in  springs,  and  also  that  in 
wells,  varies  very  much  in  quality  accord- 
ing to  the  place  that  it  is  taken  from. 
Spring  water  differs  from  rain  water  in 
that  it  has  passed  through  certain  rocks, 


WATER  SUPPLY   AND   DRAINAGE. 


157 


and  dissolved  more  or  less  considerable 
quantities   of    substances    on    its    way. 
Spring   water  resembles   rain  water   in 
containing  a  considerable  amount  of  car- 
bonic  acid   in   solution.     This   has   the 
property  of  dissolving  many  substances, 
one  of  the  chief  of  which  is  the  carbon- 
ate  of  lime.     The  water  then   passing 
through   the  rocks   dissolves   carbonate 
and  sulphate  of  lime,  salts  of  iron,  &c. 
It  is  important  to  know  this  for  many 
reasons.     In    the    first   place,  some    of 
these  waters  dissolve,  in  mountain  lime- 
stone districts  for  instance,  so  much  car- 
bonate of  lime   as  to  become  what  is 
known  as  petrifying  springs.     Of  course 
if  you  take  a  petrifying  spring  and  bring 
it  along  an  acqueduct,  under  certain  con- 
ditions your  supply  is  stopped  up :  and 
one  of  the  acqueducts  at  Rome  is  to  be 
seen  to  this  day  perfectly  closed  for  a 
considerable   length   with   a   deposit  of 
carbonate  of  lime  and  other  salts,  be- 
cause  the   contractor  took  in  a  spring 
that  he  was  not  told  to  tap — a  mineral 
spring.     Now  the  purest  spring   water 
you  can  get  comes  from  the  igneous,  the 
metamorphic,    and   the   older    stratified 
rocks.     Many  of  these  hard  rocks  yield 
a  very  pure  water  without  a  great  deal 
of  salts  in  solution.    The  mountain  lime- 
stone,  the   oolitic   limestones,    and    the 
chalk  rocks  also   yield  a  good  supply, 
and  these  waters  are  fit  for  drinking  so 
long  as  they  do  not  contain  any  quantity 
of  magnesian  salts.    Water  from  sand- 
stones, especially  the  new  red  sandstone, 
I  have  told  you,  often  contains  common 
salt.  Waters  in  clay  countries  very  often 
contain   considerable   quantities   of   the 
sulphate   of  lime.     The   waters   of  the 
London  and  Oxford  clays  do,  as  also  the 
water  of  the  lower  lias  clay.     These  are 
bad  waters.   They  are  permanently  hard 
and  unwholesome.     Well   waters    have 
partly  the  same  qualities,  unless  they  con- 
tain additional  impurities  from  the  causes 
I  have  mentioned  before.     River  water 
is  often  purer  than  spring  water;  that  is 
to  say,  it  often  contains  less  total  solids 
in  solution.     The  permanent  hardness  is 
generally  greater.     It  contains  less  sub- 
stances in  solution,  because  much  of  the 
carbonic  acid  has  escaped,  and  the  sub- 
stances it  held  in  solution  have  been  de- 
posited.    River  water  very   often   con- 
tains much  more  organic  matter,  espec- 
ially near  towns. 


Wells  sunk  in  hard  rocks  may  require 
no  lining  at  all;  if  they  pass  through 
sandy  strata  they  require  a  lining  of 
brickwork,  and  sometimes  part  or  the 
whole  of  it  must  be  set  in  cement.  For 
an  artesian  well,  an  ordinary  well  is  dug 
first  of  a  tolerable  breadth  and  depth, 
and  then  a  boring  is  made  which  varies 
from  twenty  down  to  three  or  four 
inches  in  depth.  As  soon  as  an  impervi- 
ous layer  is  bored  through,  and  a  pervi- 
ous stratum  reached,  the  water  rises 
through  the  boring  into  the  well  (which 
acts  as  a  sort  of  cistern),  and  has  to  be 
pumped  up,  or  it  may  rise  so  high  as  to 
overflow. 

The  ordinary  atmospheric  lifting  pump 
is  seldom  used,  but  a  kind  of  lifting  pump 
with  a  solid  piston  and  metallic  valves  is 
often  used.  In  fact,  the  cylinder  in 
which  the  solid  piston  slides  is  connected 
with  the  space  between  the  valves  above 
the  piston  instead  of  below  it.  So  that 
when  the  piston  is  raised  the  water  is 
lifted  through  the  upper  valve,  and  when 
it  is  depressed  water  is  drawn  from  the 
well  into  the  body  of  the  pump  through 
the  lower  valve.  Forcing  pumps  are 
also  used.  They  are  driven  by  engines, 
and  the  water  is  pumped  into  air  vessels, 
by  which  the  pressure  on  the  mains  is 
equalized  so  that  it  does  not  come  in 
jerks.  Let  me  mention  one  or  two  ex- 
amples of  artesian  wells,  and  the  amounts 
of  water  got  from  them  in  different 
strata.  From  the  well  of  Grenelle,  near 
Paris,  in  1860,  there  were  about  200,000 
gallons  daily.  This  well  when  first  sunk 
yielded  800,000  gallons  daily,  so  that 
you  see  the  supply  has  considerably 
diminished  with  time,  which  is  an  im- 
portant thing  to  take  note  of.  The  bor- 
ing of  this  well  of  Grenelle  began  at 
twenty  inches  in  width,  and  ends  at 
about  eight  or  somewhat  less.  It  is 
1,800  feet  deep  (being  one  of  the  deepest 
borings  ever  made),  and  more  than  1,700 
feet  of  it  is  lined  with  copper  tubing, 
which  was  placed  there  instead  of  some 
wrought-iron  tubing,  with  which  it  was 
originally  lined.  The  copper  tubing  be- 
gins at  12  inches  in  diameter  and  goes 
down  to  6^.  The  temperature  of  the 
water  in  this  well  at  about  1,S00  feet  is 
as  much  as  82  F.,  and  you  may  put  it 
down  that  as  a  rule,  the  temperature  of 
the  water  increases  1°  F.  for  every  50 
feet  below  the  surface.     Of  course  there 


158 


VAN  NOSTRAND's   ENGINEERING    MAGAZINE. 


are  certain  places  where  it  increases  very 
much  more  (about  Bath  for  instance), 
but  these  are  exceptional  cases.  The 
boring  in  the  well  at  Trafalgar-square  is 
sunk  384  feet  from  the  surface  into  the 
chalk,  and  it  yields  65  cubic  feet  in  a 
minute,  or  more  than  580,000  gallons  in 
the  24  hours.  There  is  a  well  in  Wool- 
wich in  the  chalk  580  feet  deep,  which 
yields  1,400,000  gallons  in  24  hours,  and 
the  last  I  am  going  to  mention  in  the 
chalk  is  a  well  near  London — the  Am- 
well  hill  well — close  by  the  source  of  the 
New  River.  That  is  only  171  feet  deep, 
and  it  is  said  to  yield  very  nearly  2£ 
million  gallons  in  the  24  hours.  (Hughes 
on  "Waterworks.")  As  all  this  water 
underneath  the  London  basin  comes 
originally  from  districts  at  some  distance 
from  London,  it  is  not  to  be  wondered 
at  that  the  pumping  at  London  lowers 
the  level  of  the  water  in  the  wells  in 
those  districts.  These  are.  examples  of 
successful  borings.  Now,  a  word  with 
regard  to  the  new  red  sandstone  wells  of 
Liverpool.  These  wells  you  will  find 
described  in  the  twelfth  volume  of  the 
proceedings  of  the  Institution  of  Civil 
Engineers.  One  of  them  called  the 
"  Bootle  Well  "  has  many  points  of  in- 
terest about  it.  Its  maximum  yield  was, 
in  1853,  about  1,100,000  gallons  in  the 
24  hours.  A  curious  point  about  it  is 
that  at  the  bottom  of  the  well  instead  of 
there  being  one  boring  there  are  16  or  17. 
These  16  or  17  borings  are  of  very  differ- 
ent depths,  and  it  became  very  interest- 
ing to  know  whether  the  whole  of  them 
were  of  any  use,  and  Mr.  Stephenson 
thought  of  blocking  them  up,  all  but 
one.  He  did  so,  and  found  that  one 
yielded  very  nearly  as  much  water  as  the 
16,  so  that  a  very  considerable  amount 
of  capital  had  been  wasted  in  the  boring 
of  these  holes.  That  is  worth  knowing. 
There  are  six  other  public  wells  at  Liver- 
pool in  this  new  red  sandstone,  and  the 
ordinary  yield  was  about  4-J-  million  gal- 
lons daily  from  them  all.  This  was  in 
1850.  Eighteen  years  afterwards,  evi- 
dence was  given  before  the  Commission- 
ers on  the  Water  Supply  for  the  Metrop- 
olis of  a  falling  off  in  the  water  supply 
of  these  wells.  In  fact,  the  continual 
pumping  had  diminished  the  supply.  In 
1854,  these  wells  in  the  new  red  sand- 
stone at  Liverpool  were  pronounced  fail- 
ures  by   Mr.  Rawlinson,   as   also   were 


others  in  England  and  America,  and  Mr. 
Piggott  Smith,  in  a  report  on  the  water 
supply  of  Birmingham,  confirmed  this, 
and  it  is  a  fact  that  they  have  had  to  be 
supplemented  by  a  supply  of  much  su- 
perior water  from  a  distance.  Mr. 
Stevenson  estimated  the  cost  of  a  pump- 
ing station  for  one  of  those  Liverpool 
wells,  including  shafts  and  steam  engines, 
at  £20,000,  and  the  annual  cost  per  mil- 
lion gallons  a  day  at  £1,324,  this  being 
without  interest  or  compensation,  but  in- 
cluding depreciation.  Generally,  well 
waters  are  liable  to  vrary  in  amount  from 
month  to  month,  and  from  year  to  year, 
as  witnessed  by  the  amounts  pumped 
from  these  Liverpool  wells,  and  by  the 
amounts  pumped  year  after  year  from 
the  Cornish  mines. 

After  wells,  the  next  thing  we  have  to 
consider  is  the  way  in  which  water  can 
be  collected  from  springs  and  streams 
over  a  large  area,  called  a  drainage  area. 
That  is  one  method  of  supply,  and  the 
other  method,  of  course,  is  pumping 
from  rivers.  We  tell  the  amount  of 
water  that  can  be  got  from  a  large  sur- 
face of  land,  in  the  first  place,  by  a  way 
I  spoke  to  you  about  before,  viz  : — by 
estimating  the  amount  of  available  rain- 
fall on  it.  Then  we  can  tell  it  in  another 
way,  by  correctly  measuring  the  amount 
of  water  that  is  brought  down  by 
streams  and  springs  ;  so  that  we  have  to 
consider  the  methods  used  for  gauging 
springs,  streams,  &c.  The  gauge  most 
commonly  in  use  is  the  one  known  as  the 
Weir  gauge.  Weir  gauges  are  made  by 
damming  up  the  stream,  and  making  it 
all  pass  over  a  sharp  ledge  or  through 
an  orifice  or  notch,  or  row  of  notches,  on 
a  vertical  board.  Then  from  formula 
you  can,  by  means  of  tables,  calculate 
the  amount  of  water  that  passes  through 
the  notch,  or  over  the  orifice  of  the  weir 
in  a  given  time.  You  determine  the 
height  of  the  still  water  by  means  of  a 
scale,  the  zero  of  which  is  level  with  the 
base  of  the  notch,  and  you  do  it  in  this 
way.  A  stick  is  planted  in  the  bed  of 
the  stream,  its  top  at  some  little  distance 
from  the  weir,  and  so  that  its  top  is  level 
with  the  base  of  the  notch,  or  row  of 
notches,  in  the  weir,  and  then  you 
measure  by  the  scale  from  the  top  of 
this  stick  to  the  level  of  the  water  from 
the  orifice.  That  is  one  way.  The  next 
plan  is  by  calculating  from  the  declivity. 


THE   IRON   ORES   OF   SWEDEN. 


159 


This  is  only  applicable  to  regular  chan- 
nels, like  the  New  River  for  instance, 
and  if  the  stream  is  small  you  can  make 
the  whole  of  it  pass  through  a  trough, 
and  then  calculate  the  velocity  from  the 
declivity.  Another  way  is  by  measur- 
ing the  maximum  surface  velocity, which 
is  done  by  means  of  floats  of  any  sort, 
or  by  means  of  fan  wheels,  and  various 
little  instruments  for  measuring  the 
surface  velocity  of  streams.  You  take 
the  maximum  surface  velocity,  and  about 
three-fourths  of  this  will  represent  the 
mean  velocity  of  the  section.  The  dis- 
charge of  springs  is  estimated  by  the 
time  taken  to  fill  a  vessel  of  known 
capacity.  A  word  about  the  permanence 
of  springs  and  streams,  which  is  an  ex- 
tremely important  point.  In  the  first 
place  you  must  try  and  get  evidence 
from  maps  and  trustworthy  sources  gen- 
erally. At  the  bases  of  hills  springs  are 
usually  permanent.  In  flat  countries 
you  may  put  it  down  that  the  reverse  is 
generally  the  case.  Springs  in  limestone 
countries  are  very  permanent.  Springs 
in  very  permeable  strata  are  very  gener- 


ally variable,  unless  they  are  tapped  at 
a  considerable  distance  from  the  surface, 
and  then  they  often  give  an  enormous 
yiekl  p 

Springs  in  primary  strata,  and  in 
granite  countries  are  very  often  very 
permanent  indeed,  and  it  is  in  these 
countries  you  have  some  of  the  large 
lakes  which  are  used  for  supplies  of 
water.  In  clay  basins  the  water  supply 
is  variable  as  a  rule,  being  very  great  in 
the  winter,  when  there  are  often  floods, 
and  very  small  in  summer.  In  chalk 
countries  the  springs  are  more  perma- 
nent, for  the  reason  that  they  draw  from 
considerably  beyond  the  actual  basin. 
Intermittent  springs  sometimes  occur, 
especially  in  the  chalk  ;  they  are  due  to 
the  gradual  collection  of  water  in  sub- 
terranean hollows,  which  when  filled 
above  a  certain  level  empty  themselves 
by  means  of  a  syphon  shaped  outlet ; 
it  is  obvious  that  they  must  not  be  re- 
lied on  as  sources  of  a  supply  of  water. 
This  will  end  our  consideration  of  the 
merits  of  different  localities  from  the 
water  supply  point  of  view. 


THE  IRON  ORES  OF  SWEDEN. 

By  Mr.  CHARLES  SMITH,  Barrow-in-Furness. 
Journal  of  the  Iron  and  Steel  Institute. 


Although  the  iron  trade  of  Sweden 
is  on  a  very  small  scale  compared  with 
that  of  England,  the  quality  of  much  of 
the  metal  manufactured  is  of  so  high  a 
character,  that  the  subject  has  an  import- 
ance far  beyond  the  mere  question  of  the 
quantity  produced.  In  round  numbers, 
England  makes  twenty  times  as  much 
iron  as  Sweden  ;  the  Furness  district 
alone  producing  more  iron  and  iron  ore 
than  the  whole  of  the  latter  kingdom. 
Notwithstanding  this  comparative  in- 
significance in  quantity,  the  Swedes, 
with  their  _  wonderfully  pure  ores,  have 
succeeded  in  manufacturing  iron  which, 
in  many  branches  of  trade,  appears  for 
the  present  to  be  a  necessity,  and  which 
is  perhaps  the  finest  in  Europe.  On 
these  considerations,  I  hope  that  a  brief 
account  of  the  Swedish  iron  ores  -may 
prove  not  uninteresting  to  many  mem- 
bers of  the  Institute. 


The  iron  ores  of  Sweden  are,  with  an 
insignificant  exception,  of  one  class  ; 
and  though  they  vary  considerably  in 
their  iron  percentage,  and  to  some  ex- 
tent in  other  constituents,  they  have  a 
very  great  external  similarity.  The  ore 
is  either  Magnetite  or  Red  Hematite, 
containing  every  percentage  of  metallic 
iron,  from  30  per  cent,  to  almost  chemi- 
cal purity,  which,  for  the  former  would 
be  72,  and  for  the  latter  70,  per  cent. 
The  hematite,  called  "  bloodstone,"  gives 
the  same  streak  as  the  English  red  hema- 
tites, but  is  externally  scarcely  distin- 
guishable from  the  magnetite  ;  both 
kinds  are  named  in  Swedish  "Mountain 
ores ; "  they  have  a  slightly  different 
aspect  from  the  Spanish  and  Algerian 
magnetites,  but  possess  nearly  the  same 
blue-black  color. 

A  small  varying  quantity  of  Brown 
Hematite   is   procured  in  the   south  of 


160 


van  nostrand's  engineering  magazine. 


Sweden,  from  the  large  bogs  of  Smaland; 
and  in  winter  a  similar  ore  is  dredged 
from  the  bottom  of  certain  lakes  in  the 
same  province.  The  average  of  this  ore 
would  probably"  not  exceed  25  per  cent, 
metallic  iron,  though  it  occasionly  con- 
tains 50  per  cent.;  frequently  it  is  so  in- 
termixed with  sand  as  to  be  of  little 
value;  phosphoric  acid  is  generally  pres- 
ent, sometimes  up  to  4  per  cent.;  man- 
ganese is  often  a  constituent,  and  in  a 
few  places  has  a  strength  of  20  per  cent. 
The  yearly  quantity  raised  of  this  ore  is 
as  varied  as  its  composition;  in  1855,  it 
was  12,000  tons  ;  in  1860,  20,000  tons; 
in  1866,  8,000  tons;  in  1867,  17,000  tons; 
in  1869,  6,000  tons;  in  1871,  15,500  tons; 
in  1872,  12,000  tons. 

The  other  ores  of  iron,  with  trifling 
exceptions,  do  not  occur  in  Sweden. 
The  red  and  brown  hematites  and  the 
oolitic  ores,  such  as  those  we  have  in 
England,  are  absent  altogether;  chaly- 
bite,  the  white  carbonate,  is  found  in 
hand  specimens  in  a  few  of  the  metal- 
liferous mines;  find  a  thin  insignificant 
bed  of  argillaceous  iron  ore  has  been 
met  with  in  the  Skane  coalfield. 

Judging  from  official  returns,  the  av- 
erage yield  of  the  "  Mountain "  ores, 
throughout  the  kingdom  is  under  50  per 
cent,  metallic  iron.  In  1872,  from  671 
mines,  718,000  tons  of  ore  were  raised, 
and  333,000  tons  of  iron  manufactured; 
but  of  the  former,  12,000  tons  were  bog 
and  lake  ores,  with  very  low  percentages, 
and  about  an  equal  quantity  of  the 
"  Mountain  "  ores  was  exported  to  Fin- 
land. Besides  the  iron  oxide,  the  main 
constituent  of  the  ores  is  almost  invari- 
ably silica.  Lime,  magnesia,  and  alumina 
are  generally  present;  the  last  usually 
in  the  smallest  quantity.  Phosphorus 
has  rarely  a  greater  strength  than  0.05; 
though  in  some  ores,  not  worked,  up- 
wards of  1  per  cent,  is  found  ;  and  it 
sinks  to  0.004  at  Persberg,  and  to  0.003 
at  Dannemora.  Sulphur,  with  a  few 
marked  exceptions,  is  not  generally 
present  to  a  much  greater  extent  than 
phosphorus. 

The  surface  of  Sweden  is  mainly  cov- 
ered by  plutonic  rocks,  of  which  granite 
is  the  most  abundant,  although  large 
areas  are  occupied  by  gneiss,  mica  slate, 
and  every  variety  of  porphyry;  there  is 
also  a  f  elspathic  rock  peculiar  to  Sweden, 
termed  "  Helleflinta,"  or  Leelite,  which, 


though  small  in  quantity,  is  of  great  im- 
portance in  reference  to  iron,  as  this 
metal  is  nearly  always  present  where 
Helleflinta  occurs.  Over  a  vast  area,  in 
these  granitiferous  rocks,  iron  ore  is 
found  in  greater  or  less  abundance; 
though,  doubtless,  the  iron  districts  are 
still  most  imperfectly  known,  as  so  much 
of  the  country,  especially  in  the  north,  is 
for  iron-making  purposes  inaccessible. 
Far  in  the  north,  beyond  the  head  of  the 
Gulf  of  Bothnia,  the  iron  deposits  of 
Gellivara  are  probably  the  richest  in  the 
world ;  but  the  rigor  of  the  long  winter 
has,  hitherto,  prevented  any  commercial 
success  in  the  working  of  the  mines; 
and,  according  to  the  Government  re- 
turns, the  annual  production  does  not 
reach  50  tons  of  ore.  More  to  the  south, 
a  few  small  mines  are  worked,  but  only 
on  the  most  limited  scale,  until  the  par- 
allel of  Gefle  is  reached.  We  may,  per- 
haps, assume  that  future  research  will 
prove  that  Sweden  possesses  the  greatest 
stores  of  her  purest  ore  in  her  most 
northern  provinces;  but  we  can  scarcely 
hope  that  these  can  be  made  available, 
without  changes  in  value  taking  place 
that,  at  present,  cannot  be  anticipated. 
In  the  southern  portion  of  the  kingdom 
very  little  ore  is  raised.  The  main  bulk 
is  obtained  from  the  central  provinces. 
The  counties  of  Kopparberg  and  Orebro 
alone  produce  50  per  cent.,  and  West- 
manland  and  Wermland  30  per  cent,  of 
the  whole  yield. 

Iron  ore  is  by  far  the  most  important 
Swedish  mineral.  The  "Mountain"  ores 
occur  in  veins,  which  are  sometimes 
regular,  but  more  generally  are  deflected 
from  a  straight  line,  and  occasionally 
even  form  a  semicircle.  Usually  they 
have  a  north-east  to  a  south-west  direc- 
tion, though  north  to  south  and  east  to 
west  veins  occur.  Their  width  varies 
from  mere  strings  up  to,  as  at  Schyss- 
hyttan,  200  feet.  Probably  30  to  50 
feet  would  be  the  general  strength  of 
the  veins  now  worked.  In  some  in- 
stances, these  can  be  traced  for  some 
distance  along  the  surface;  but,  com- 
monly, they  dip  down  at  a  steep  angle. 
As  so  many  are  known,  few  have  been 
thoroughly  explored  as  to  their  depth; 
when  worked  to  200  or  300  feet  deep, 
other  shallower  veins  have  been  started, 
except  in  the  more  important  depos- 
its. 


THE  IRON   ORES   OF   SWEDEN. 


161 


The  mode  of  formation  is,  as  yet,  an 
unsolved  problem.  Many  difficulties  pre- 
sent themselves  in  opposition  to  each  of 
the  more  popular  solutions.  The  veins 
are  occasionally  found  in  gneiss  ;  at 
other  times  in  granite;  but,  generally, 
they  are  separated  from  their  granitic 
surroundings  by  a  band  of  Helleflinta, 
which  is  usually  only  present  in  small 
quantities;  but  at  Persberg,  the  largest 
mine  in  Sweden,  the  surface  for  two 
miles  in  one  direction  is  composed  of  it. 
In  some  cases,  the  veins  descend  per- 
pendicularly; and  in  at  least  one  in- 
stance (at  Persberg),  the  vein,  after  so 
doing,  makes  an  elbow  at  right  angles 
and  lies  horizontally. 

It  is  commonly  believed  that  the  ore 
is  an  aqueous  deposit,  probably  from  hot 
water.  Though  numerous  facts  support 
this  theory,  many  will  not  coincide  with 
it ;  perhaps  the  chief  being  that  there  is 
not  the  slightest  external  appearance  of 
the  ore  being  a  water  deposit,  as  it  is  in 
solid  irregular  masses,  lying  in  equally 
solid  rock,  which  in  those  cases  where 
granite  overlies  is  unquestionably  plu- 
tonic.  Assuming  that  Helleflinta  is  an 
altered  clay,  which  has  by  no  means  been 
proved  absolutely,  and  that  both  it  and 
the  ore  were  deposited  simultaneously, 
there  would  be  some  mechanical  mixture 
of  the  two,  and  not  the  perfect  demarca- 
tion that  exists.  If  the  ore  were  an 
aqueous  deposition,  it  must  necessarily 
have  been,  at  some  time,  horizontal;  and 
whatever  the  convulsions  were,  which 
could,  as  in  the  Persberg  instance,  tilt 
up  one  end  of  the  vein  to  the  extent  of 
90°,  they  could  not  do  this  without  a 
great  dislocation  of  both  the  vein  and 
the  surrounding  rocks,  whether  it  hap- 
pened before  or  after  the  solidifying  of 
the  ore  and  the  Helleflinta,  and  this  is 
not  the  case. 

In  certain  instances  the  iron  oxide  is 
found  interspersed  in  grains  for  some 
distance  on  either  side  of  a  vein,  which 
becomes  more  and  more  rich  as  it  ap- 
proaches the  centre,  where  is  the  purest 
part.  It  is  difficult  to  account  for  this 
on  any  ordinary  aqueous  or  ingenious 
theory. 

The  peculiar  magnetic  properties  of 
much  of  the  "  Mountain  "  ore  offer  little 
assistance  to  the  solution  of  the  problem 
of  its  formation.  The  magnetite  and 
hematite  are  found  closely  intermixed, 
Vol.  XIII.— No.  2—11 


the  one  highly  magnetic,  the  other  not 
affecting  the  needle ;  the  ores  being  similar 
in  appearance  and  constituents.  Some 
masses  of  magnetite  are  much  more 
magnetic  than  others,  affecting  the  com- 
pass through  20,  or  even  50,  fathoms  of 
intervening  rock  ;  whilst  to  some  bodies 
of  equally  true  magnetite,  the  needle 
will  not  dip,  though  not  more  than  10 
fathoms  of  rock  intervene. 

In  several  districts,  especially  in  the 
Norberg  mines  and,  to  a  less  extent,  in 
those  near  Nora,  the  ore  has  a  very  sin- 
gular striped  appearance,  caused  by 
numerous  veins,  or  nearly  parallel  layers, 
of  crystallized  quartz  lying  amongst 
the  ore. 

May  I  be  allowed  to  suggest  that, 
perhaps  electricity  may  have  been  the 
chief  agent  in  the  formation  of  these 
mineral  deposits.  It  is  difficult  to  under- 
stand in  what  possible  way  they  could 
be  formed  by  volcanic  action ;  and 
it  appeared  to  me  to  be  equally  impos- 
sible to  understand  how  these  veins  of 
iron  ore,  which  dip  steeply  over  immense 
areas  of  countiy,  could  owe  their  origin 
to  water,  without  exhibiting  some  trace 
of  aqueous  deposition;  especially  when 
their  centres  are  the  purest  part,  whilst 
they  gradually  on  either  side  pass  im- 
perceptibly into  the  surrounding  rocks. 
It  seems  still  more  difficult  to  account, 
either  by  the  aqueous  or  igneous  theory, 
for  the  finely  veined  ores  of  Norberg, 
which  consist  of  thin  parallel  layers  of 
magnetite  and  crystallized  quartz.  But 
what  might  be  difficult  or  impossible  for 
fire  or  water  to  accomplish,  might  per- 
haps be  effected  by  electricity,  if  we  as- 
sume that  currents  may  have  acted,  in 
definite  directions,  for  long  periods  of 
time,  segregating  the  particles  of  iron 
oxide,  which  exist  in  a  slight  percentage 
throughout  vast  masses  of  many  Swedish 
rocks. 

Although  there  is  so  strong  a  similar- 
ity amongst  all  the  Swedish  "Mount- 
ain "  ores,  there  is  generally  a  sufficient 
divergence,  in  chemical  composition,  to 
give  a  separate  character  to  most  of  the 
districts,  and  to  some  of  the  individual 
mines. 

Pre-eminent  for  its  purity  is  the  best 
Bispberg  ore,  which  contains  up  to  70 
per  cent,  metallic  iron,  or  almost  a  chemi- 
cally pure  oxide  ;  only  a  small  propor- 
tion reaches  this  high  standard,  the  bulk 


162 


VAN   NOSTRAND'S   ENGINEERING   MAGAZINE. 


of  the  output  varying  from  50  to  60  per 
cent.  The  mines,  which  are  thirty  miles 
south-east  of  Fahlun,  claim  an  antiquity 
of  600  years  ;  they  are  very  small,  pro- 
ducing under  15,000  tons  per  annum. 
On  account  of  the  purity  of  the  ore  it  is 
much  esteemed  as  a  mixture,  but  from 
the  isolation  of  the  mines  it  becomes  very 
expensive  to  most  of  the  works  which 
use  it.  From  the  working  drawings,  it 
does  not  appear  as  if  the  production 
could  be  much  increased.  The  greatest 
depth  is  about  700  feet,  with  the  vein, 
which  lies  in  quartz  and  talc-schist,  dip- 
ping steeply. 

Much  the  largest  iron  mines  in  Sweden 
are  those  at  Persberg,  near  Filipstad,  in 
Wermland.      The   veins,    of  which   the 
largest  is  66  feet  at  its  greatest  width, 
lie  altogether  in  Helleflinta.     The  deep- 
est workings  are  over  600  feet  below  the 
surface,  the  largest  400  to  500  feet.  The 
annual  production  has   lately  been  be- 
tween 50,000  and  60,000  tons.     The  ore 
rarely  contains  less  than  50,  and  rises  to 
60  per  cent,  metallic  iron  ;    it  is  much 
valued   for    furnace    purposes,    for    its 
purity  and  freedom  from  deleterious  in- 
gredients;   it  commands  a  higher  price 
than  that  from  any  other  large  mines, 
and,   to    a   great   extent,   the   iron   ore 
market  of  that  part  of  Sweden  is  regu- 
lated by  its  selling  price.     Persberg  is 
said  to  have  been  worked  for  800  years. 
The  most  famous  of  the  Swedish  iron 
mines  are  those  at  Dannemora,  in  Upsala 
County,   away  from  the  main  iron  dis- 
tricts.    The  annual  production  is  under 
25,000  tons,  and  has  varied  but  little  for 
over   20  years.     The  ore  contains  from 
25   to  60  per  cent,  metallic  iron  ;  very 
little  has  over  50  per  cent.,  and  the  aver- 
age is  much  below;  most  contains  suffi- 
cient lime  and  silica  to  be  smelted  with- 
out a  flux;  it  has  also  about  2  per  cent, 
manganese.      The   highest   percentaged 
ore   does  not  make  the  best   pig  iron. 
The  mines  have  been  worked  steadily 
for  four  centuries;  the  largest  is  in  three 
sections,  the  centre,  an  open-work,  being 
the  chief.     The  main  vein  is  somewhat 
irregular;   it  has  an  average  width   of 
100  feet,  being  150  at  the  widest,  and 
has  been  explored  900  feet  in   length  in 
the  open-work,  which  is  200  feet  wide, 
with     walls,     either     perpendicular     or 
slightly  overhanging,  of  over  500  feet  in 
vertical  depth.     The  bottom  of  this  ex- 


traordinary mine  was  covered,  during 
my  visit  in  the  month  of  August,  with 
large  blocks  of  ice.  The  veins  lie  in 
Helleflinta,  of  which  there  are  several 
varieties;  different  trap  rocks  are  present, 
with  granite  and  gneiss.  The  produc- 
tion of  the  mines  might  be  greatly  in- 
creased, but  they  are  held  under  a  tenure 
that  prevents  more  than  a  certain  quan- 
tity being  raised.  The  ore  is  never  sold, 
but  goes  solely  to  the  furnaces  of  the 
different  joint  proprietors.  The  largest 
owner  is  Baron  De  Geer,  the  representa- 
tive of  a  Dutch  family,  who,  in  the  17th 
century^  acquired  a  practical  monopoly 
over  the  iron  trade  of  Sweden ;  most  of 
their  works  and  mines  have  passed  into 
other  hands,  but  they  still  retain  Lofsta, 
where  is  manufactured,  from  Dannemora 
ore,  the  L  iron,  the  dearest  in  Europe  of 
its  class. 

A  new  railway  will  shortly  open  up 
the  Grangesberg  district,  in  Dalecarlia, 
which,  it  is  considered,  may  prove  the 
most  productive  in  Sweden.  At  present 
the  mines  are  cramped  by  expensive 
transit.  The  ore  in  the  most  southern 
part  of  the  district  is  of  very  high  quali- 
ty, and  free  from  phosphorus;  but  this 
ingredient  increases  regularly  in  a  north- 
erly direction,  until  in  the  extreme  north 
the  ore  is  of  little  value. 

The  mines  round  Norberg,  in  West- 
manland,  produce  about  70,000  tons  per 
annum  of  ore,  which  contains  from  45  to 
50  per  cent,  metallic  iron.  The  striped 
appearance  of  this  ore,  caused  by  fine 
layers  of  quartz  amongst  the  iron  oxide, 
is  peculiar.  Notwithstanding  its  large 
percentage  of  silica,  it  makes  good  iron. 
The  veins  are  from  20  to  50  feet  wide, 
and  lie  in  gneiss,  but  are  separated  from 
it  by  bands,  on  either  side,  of  Helle- 
flinta. About  three  years  ago,  a  new 
ore  was  discovered  here,  containing  35 
per  cent,  iron  and  20  per  cent,  manga- 
nese, which  it  was  hoped  might  produce 
spiegeleisen;  but  it  is  understood  that 
the  experiments  have  not  been  success- 
ful. 

In  the  neighborhood  of  Nora,  in  Ore- 
bro  County,  there  are  many  mines;  those 
at  Striberg  are  second  only  to  Persberg 
in  production ;  but  the  ore  is  the  poorest 
in  the  district,  with  only  48  to  50  per 
cent.;  whilst  at  Dalkarlsberg,  which  is 
the  deepest  iron-mine  in  Sweden — about 
800  feet — the  best  ore  has  68  per  cent. 


THE   IE01ST   ORES   OF   SWEDEN. 


163 


metallic  iron,  and  very  much  rises  to  60 
per  cent.  Much  of  the  Nora  ore  con- 
tains manganese;  at  the  Wickers  mines 
up  to  9  per  cent.  The  manganiferous  ores 
almost  always  contain  mundic  (sulphuret 
of  iron) ;  in  some  cases  they  have  to  be 
calcined  twice  to  drive  off  the  sulphur; 
they  are  also  much  more  close-grained 
in  appearance  than  ordinary  magnetite, 
and  some  becomes  brown  with  two  or 
.three  days'  weathering.  Many  of  the 
Nora  veins  are  red  hematite,  which 
rarely  contains  over  55  per  cent,  metallic 
iron.  Some  of  the  magnetic  veins  have 
been  proved  over  a  thousand  vards  in 
length. 

For  the  Bessemer  steel  trade,  by  far 
the  most  important  mines  in  Sweden  are 
those  at  Schysshyttan,  10  miles  from 
Smedjebacken,  in  Delecarlia.  The  ore 
is  a  mixture  of  magnetite  and  knebelite ; 
the  latter,  a  very  rare  silicate  of  manga- 
nese and  iron,  met  with  at  Dannemora 
and  a  few  other  localities,  but  nowhere, 
except  at  Schysshyttan,  in  any  quantity. 
The  combined  minerals  contain  50  per 
cent,  iron  and  manganese;  they  produce, 
without  the  addition  of  any  other  ore, 
the  highest  class  of  spiegeleisen.  The 
vein,  which  has  more  the  appearance  of 
a  lode,  can  be  traced  along  the  surface 
for  a  considerable  distance;  it  is  200 
feet  in  breadth,  and  has  been  proved  to 
300  feet  in  depth,  without  any  appear- 
ance of  the  bottom  ;  the  centre  of  the 
lode  is  the  best;  at  the  edges  the  ore  is 
not  good. 

_  Far  to  the  south  of  the  general  iron 
district,  near  Jonkoping,  in  Smaland,  is 
the  remarkable  hill  of  Taberg.  As  far 
as  has  been  ascertained,  this  hill,  which 
rises  380  feet  above  the  level  of  the  sur- 
rounding country,  is  a  solid  mass  of 
close-grained  serpentine,  containing  on 
the  average  about  30  per  cent,  metallic 
iron,  and  which  is  in  appearance  very 
like  some  of  the  hematite  ores  of  the 
north.  Two  sides  of  the  hill  are  per- 
pendicular, and  form  quarries,  whence 
has  been  taken  for  years  the  supply  of 
ore  for  a  dozen  furnaces,  which  alto- 
gether have  only  an  annual  production 
of  3,000  tons  pig  iron.  This  iron  has 
been  found  well  suited  for  a  few  pur- 
poses, and  is  very  tough  ;  but  the  de- 
mand is  limited.  The  heavy  percentage 
of  magnesia  in  the  ore  has  hitherto  been 
an  insuperable   obstacle    to    any  lai-ge 


manufacture.  Were  this  difficulty  over- 
come, this  hill  would  be  one  of  the  most 
valuable  iron  mines  in  the  kingdom. 

The  foregoing  are  the  chief  represen- 
tative iron  mines  in  Sweden,  either  for 
quantity  of  production,  or  quality  of  ore. 
All  the  mines  are  much  alike  in  charac- 
ter, with  the  exception  of  Dannemora 
partly  and  Taberg  wholly,  as  the  mode 
of  working  is  almost  identical.  In  some 
cases  the  veins  of  ore  come  to  the  sur- 
face ;  but  generally  they  are  discovered 
by  a  magnet  of  peculiar  construction,  so 
made  that  the  needle  can  dip  as  freely  as 
turn  horizontally;  as  soon  as  these  mag- 
nets come  over  a  body  of  magnetite,  the 
needle  swings  round  and  points  down- 
wards to  the  mineral.  When  the  pres- 
ence of  the  ore  is  ascertained,  a  large 
hole  is  usually  made  down  to  the  vein, 
which  may  be  worked  open  for  a  short 
time,  but  as  most  dip  at  a  steep  angle, 
the  ore  is  mainly  obtained  by  mining. 
As  the  walls  are  solid,  only  a  trifling 
amount  of  timber  is  used,  often  none  at 
all.  The  surrounding  rocks  are  so  firm, 
that  it  rarely  happens  any  are  brought 
down  by  the  constant  blasting  ;  the  only 
one  that  I  saw,  during  a  lengthened  tour 
through  the  Swedish  Iron  districts, 
which  had  given  away,  or  become  unsafe, 
by  the  rock  crushing,  was  at  Guldsmed- 
shyttan,  in  Orebro  County.  The  whole 
of  the  "Mountain"  ores,  without  any 
exception,  have  to  be  blasted.  The 
small  shafts,  that  may  have  to  be  sunk 
through  overlying  granite  drift,  are  fre- 
quently of  very  rude  construction,  bound 
round  with  withes  and,  if  not  round,  of 
no  regular  shape.  The  drainage  of  the 
mines  gives  much  trouble  ;  except  where 
steam  is  unavoidable,  hydraulic  power  is 
always  used,  and  often  the  pumps  are 
worked  by  bobs  of  immense  lengths. 

Royalties  in  Sweden  belong  half  to  the 
landlord  and  half  to  the  discoverer  of  the 
mineral  ;  but  the  former  may  take  half 
the  mine,  if  he  elect  to  do  so.  On  finding 
any  deposit,  in  the  case  of  iron  by  mag- 
net or  otherwise,  an  application  is  made 
to  a  government  official,  termed  berg- 
master,  who  grants  a  certificate  of 
ownership,  should  no  adverse  claim  be 
presented  and  proved  within  a  given 
time.  These  bergmasters,  of  whom  there 
are  ten,  have  each  a  separate  district, 
the  whole  kingdom  being  divided 
amongst  them.     They  have  very  consid- 


164 


VAN   NOSTRAND  S   ENGINEERING   MAGAZINE. 


erable  power,   and  appear  to  settle  al- 
most all  mining  disputes. 

The  value  of  the  iron  ores  varies  to  a 
great  extent,  depending  not  only  on 
chemical  composition,  but  also  to  a  very- 
great  degree  on  local  position.  It  must 
be  remembered  that  the  key  to  the 
Swedish  iron  trade  is  not  the  mineral, 
but  the  fuel,  supply.  This  latter  has 
been  annually  growing  in  relative  impor- 
tance, until  lately  it  has  become  the  chief 
particular.  Charcoal  still  remains,  not- 
withstanding the  importation  of  foreign 
coal  and  coke,  the  main  fuel  of  the 
country ;  and  as  it  deteriorates  most 
materially  in  transit,  the  fuel  supply  de- 
termines the  locality  of  most  of  the 
Swedish  works.  Often  ore  is  carted  20 
or  30  miles,  or  transported  over  100 
miles  by  road,  canal,  and  railway  ; 
whilst  furnaces  have  been  built  in  Fin- 
land, where  there  is  but  little  native 
ore;  or  in  the  Hernosand  district,  up 
the  Gulf  of  Bothnia,  where  there  is 
scarcely  any,  to  save  carriage  on  the 
charcoal.  The  ore  in  this  way  has, 
often  to  bear  a  most  burdensome  car- 
riage, and  its  cost  varies  for  every 
works.  As  far  as  possible,  the  annual 
supply  is  laid  in  during  the  winter,  as  it 
is  more  cheaply  transported  over  the 
snow  and  ice,  than  by  road  in  summer. 
Many  furnaces  are  dependent  on  a  hard 
winter  for  obtaining  any  supply  at  all; 
and  such  during  a  winter  like  the  past 
mild  one,  when  there  was  scarcely  any 
snow,  are  obliged  to  be  blown  out. 
When  the  furnace  proprietor  raises  his 


own  ore,  the  cost  varies  probably  from 
3s.  to  16s.  per  ton,  delivered  at  the 
works;  and  some  of  the  best  ores  are 
worked  the  cheapest.  Norberg  ore,  with 
50  per  cent,  iron  and  much  silica,  is 
quoted  about  16s.  per  ton,  delivered  at 
Stromsholm,  on  the  Malar  Lake,  where 
sea-going  vessels  can  load.  Ordinary 
ores,  with  a  little  over  50  per  cent,  iron, 
are  sold  in  Wermland  and  in  the  Nora 
district,  at  about  27s.  per  ton,  delivered 
on  the  railway  or  at  some  mining  centre. 
Persberg  ore  would  be  more  expensive, 
and  is  quoted  on  a  sliding  scale  accord- 
ing to  percentage.  Dalkarlsberg  ore, 
when  containing  68  per  cent.,  is  quoted 
over  30s.  per  ton,  delivered  on  the  rail- 
way. The  majority  of  these  ores  would 
have  to  bear  heavy  carriage  in  addition 
to  these  prices,  which  are  from  50  to 
100  per  cent,  higher  than  in  1871. 

In  conclusion,  I  have  only  to  regret 
that  this  sketch  does  so  little  justice  to 
the  subject  undertaken,  but  I  shall  be 
satisfied  if  it  has  enabled  the  members 
of  the  Institute  to  obtain  a  clearer  per- 
ception of  the  marvelous  resources  in 
iron  ores  possessed  by  Sweden.  At 
present  the  iron  trade  in  that  country  is 
cramped  by  want  of  fuel,  labor,  capital, 
and  means  of  transit.  But  every  year 
now  should  lessen  these  deficiencies,  and 
we  may,  perhaps  not  without  reason, 
look  forward  to  a  not  distant  future, 
when  the  iron  trade  of  Sweden  will  be 
of  European  importance,  not  alone  from 
the  quality,  but  also  from  the  quantity, 
of  the  metal  produced. 


ELEMENTARY    DISCUSSION    OF    STRENGTH    OF    BEAMS 
UNDER    TRANSVERSE    LOADS. 

By  Prof.  W.  ALLAN. 
Written  for  Van  Nostrand's  Engineering  Magazine. 


I. 


In  the  following  discussion  the  ordi- 
nary cases  of  loaded  beams  are  treated 
without  resorting  to  the  higher  mathe- 
matics. It  is  an  attempt  to  compile 
from  various  sources  the  simplest  meth- 
ods of  treating  such  cases  as  arise  most 
frequently  in  practice. 

iransverse  stress  is  produced  by  a  load 
applied  to  a  beam  in  a  direction  perpen- 
dicular, or  inclined,  to  its  length.     A  D 


D 


)w 


Fig.  1. 


STRENGTH   OF   BEAMS   UNDER   TRANSVERSE   LOADS. 


J  65 


(Fig.  1)  is  a  beam  subjected  to  such  a 
stress. 

In  this  kind  of  stress  a  compression  of 
the  particles  or  fibres  on  one  side  of  the 
beam,  and  an  extension  of  those  on  the 
other,  are  produced.  In  consequence  of 
this  the  beam  bends.  Experiment  shows 
that  the  amount  of  compression  on  the 
the  one  side,  and  of  extension  on  the 
other,  diminishes  as  we  go  inwards  from 
the  top  or  bottom  towards  the  centre, 
and  at  some  intermediate  plane,  0  0', 
becomes  zero.  The  fibres  at  this  plane 
being  neither  lengthened  nor  shortened, 
it  is  called  the  neutral  plane,  and  its  in- 
tersection by  the  plane  of  vertical  sec- 
tion is  called  the  neutral  line  or  axis. 
Experiment  also  shows  that,  from  this 
plane  towards  the  top  and  bottom,  the 
amount  of  extension  and  compression 
may,  for  the  stresses  that  occur  in  ordi- 
nary practice,  be  considered  as  varying 
directly  with  the  distance "  from  the 
neutral  plane. 

The  extreme  top  and  bottom  fibres 
suffer  the  greatest  compression  and  ex- 
tension, and  in  case  of  rupture,  the  rup- 
ture begins  with  them.  Some  question 
exists  as  to  the  exact  location  of  the 
neutral  line  or  plane,  but  for  slight  de- 
flections it  passes  through  the  centre  of 


gravity  of  the  cross  section  of  the  beam, 
and  it  is  very  probable  that  it  never 
deviates  from  this  position. 

In  discussing  transverse  stress,  the  as- 
sumptions based  upon  experiment  may 
be  stated  as  follows  : 

1.  The  forces  on  the  fibres  are  directly 
as  the  amount  of  extension  or  compres- 
sion they  produce  ;  ( TJt  tensio  sic  vis,) 
and  since  the  extension  and  compression 
increase  as  the  distance  from  the  neutral 
axis,  the  forces  vary  in  the  same  propor- 
tion. 

2.  Within  elastic  limits  the  extension 
and  compression  at  equal  distances  from 
the  neutral  axis  are  equal,  and  the  forces 
producing  them  are  equal. 

3.  The  neutral  axis  passes  through  the 
centre  of  gravity  of  the  cross  section. 

RECTANGULAR   BEAMS. 

Let  us  now  discuss  the  relations  exist- 
ing between  the  forces  in,  and  on,  trans- 
versely loaded  rectangular  beams,  the 
load  being  supposed  to  be  vertical  in 
direction  and  the  beam  horizontal. 

Case  I. 

Let  AD  (Fig.  2)  be  a  beam  so  thin 
that  it  may  be  considered  as  composed 


>]E 


* 


Fig.  2. 


of  but  one  layer  of  fibres  or  particles. 
Let  it  be  fastened  in  a  wall  at  A  B,  and 
be  loaded  with  W  at  the  other  end. 
Neglect  for  the  time  the  weight  of  the 
thin  beam  itself,  which  is  small.  Imag- 
ine it  to  be  cut  by  a  vertical  plane  E  F 
at  any  point,  and  let  us  see  under  what 
forces  the  part  ED  is  held  in  equili- 
brium. 

The  only  external  force  on  E  D  is  W 
acting  at  D  downwards,  and  E  D  is  pre- 
vented from  falling  under  this  weight  by 


the  resistance  of  the  fibres  at  E  F.  To 
analyze  these  forces,  let  us  take  Oj  as  an 
origin  of  coordinates,  and  01 0'  as  the 
axis  of  x,  and  O^  E  as  the  axis  of  y,  and 
as  the  forces  are  all  in  one  plane,  find 
their  components  along  these  axes.  The 
internal  forces,  or  resistance  of  the  fibres 
at  E  F,  are  : 

1.  The  horizontal  forces  which  are 
tensile  above  and  compressive  below,  and 
which  increase  from  zero  at  01  just  in 
proportion   as   we   go   from  that  point 


166 


VAN   NOSTEAND'S   ENGINEEEING   MAGAZINE. 


towards  the  upper  or  lower  edge  of  the 
beam.     (Fig.  3.) 


.T 

-HE. 

<K 

tr- 

0 

> 

L 

W'y 

F 

Fig.  3. 


2.  The  vertical  force.  This  is  called 
the  shearing  force,  or  transverse  shearing 
force.  It  resists  the  tendency  of  the 
part  of  the  beam  ED  to  slide  down  on 
the  surface  E  F.  The  existence  of  this 
force  may  be  realized  if  we  conceive  the 
beam  to  be  divided  into  two  parts  by  the 
vertical  plane  E  F,  and  those  parts  to  be 
united  by  some  very  elastic  substance, 
as  india-rubber.  Then  the  beam  would 
take  the  form  shown  in  Fig.  4,  the  part 
FC  sliding  down  on  the  other.  The 
force  in  the  beam  that  resists  this  sliding 
is  represented  in  Fig.  3,  by  the  vertical 


Fig.  4. 


arrow  at  E.  Let  it  be  called  T.  In  Fig. 
3  are  represented  all  the  forces  we  have 
to  deal  with.  Since  this  system  of  forces 
is  balanced,  the  following  equations 
must  be  fulfilled  : 


^X=0     ^Y=0     ^M=0 


(1) 


That  is  :  the  sum  of  all  the  horizontal 
forces  (5X),  and  the  sum  of  all  the  ver- 
tical forces  (2Y)  must  each  be  equal  to 
zero,  and  the  sum  of  the  moments  about 
any  point  as  01  must  also  equal  zero. 

The  only  horizontal  forces  in  the  sys- 
tem are  the  two  triangular  groups  of 
forces  EOjH  and  F 01 L,  representing 
the  sum  of  the  tensile  and  compressive 


stresses  on  the  fibres.  As  the  group 
E  01 H  acts  in  a  direction  opposite  to 
that  of  the  group  FC^L,  and  as  the 
algebraic  sum  of  the  two  groups  is  zero 
(_2X  =  0),  the  groups  must  be  equal  to 
each  other.  This  is  indicated  in  the 
figure  by  the  equality  of  the  triangles 
E  01  H  and  F  O,  L. 

The  vertical  forces  are  W  and  the 
shearing  force  T  at  E  F,  and  since 

2Y=T-¥'=0.        We  have 

T=W  (2) 

Next  obtain  the  moments  of  all  the 
forces  about  Oj  and  place  the  sum  of 
these    moments  =  zero.       Replace    the 


A# 


< N 


G 

E- 


—~m 


w 


Fig. 


STRENGTH   OF   BEAMS   UNDER   TRANSVERSE   LOADS. 


167 


tensile  and  compressive  forces  by  their 
resultants.  The  resultant  or  sum  of  all 
the  tensile  forces  represented  by  the 
triangle  E  Ox  II  (Fig.  3)  may  evidently 
be  represented  by  the  area  of  the  triangle 
of  which  the  base  E  Oj  is  the  distance 
over  which  the  forces  are  distributed, 
and  the  altitude  E II  is  the  stress  in  the 
outside  fibre.     Let 

S  =  this  stress  =  E  H 
•and         df=E  F= depth  of  beam 

Then  area  E01H=|Sd=N  =  resultant 
of  tensile  forces.     Similarly 

Area  F  01  L=J  Sd=~N'=  resultant  of 
compressive  forces. 

These  resultants  will  pass  through 
the  centres  of  gravity  of  the  triangles 
EO,H  and  Ox  F  L,  since  the  little  forces 
of  which  they  are  composed  are  repre- 
sented by  these  triangles.  Hence  the 
direction  of  A7' will  intersect  01  E  at  a 
point  G  (Fig.  5),  whose  distance  from  Oj 

is  =  §  EO  =-.  -  =  -.     This  is  the  lever 
s         '323 

arm  of  N  about  O,.     That  of  JST  is  G'  01 

d 

also=-.     Hence  the  sum  of  the  moments 

of  these  two  forces  about  01  (since  they 
both  tend  to  produce  left-handed  rota- 
tion) is 


3      -      3 


■-S<f 
6 


The  force  T  since  its  direction  passes 
through  01  has  no  lever- arm,  and  hence 
its  moment  is  zero. 

If  the  distance  from  O'  to  Oj  be  called 
x,  the  moment  of  the  weight  W  is 
=  +  W  x  (since  it  tends  to  produce 
right-handed  rotation) 


W'z--$d2=2M=0 
6       1 


This  discussion  is  general  and  will 
apply  to  any  section  as  well  as  to  E  F.  S 
and  x  are  the  variables  in  eq.  (4),  and 
these  quantities  will  have  different  values 
at  the  different  sections,  which  values  in- 
crease as  we  go  towards  A  B  (Fig.  2), 
but  the  form  of  the  equation  will  evi- 
dently be  unchanged.  If  AC  (Fig.  2) 
be  =  I,  we  have  for  the  section  at  A  B 
(Fig.  2) 

(5) 


Wl  =  ^Sbd2 
6 


A  B  is  the  section  of  greatest  stress,  and 
the  beam  if  overloaded  will  break  there. 

The  quantity  -  S  b  d2  is  called  the  mo- 
ment of  resistance  of  the  fibres,  or  mo- 
ment of  the  internal  forces,  and  is  often 
written  M  for  brevity.  Wx  is  called 
the  moment  of  the  weight,  or  moment 
of  the  external  forces.  Let  the  maxi- 
mum value  of  -  Sbd2  (eq.  5)  be  called 
6 

M0. 

We  may  illustrate  geometrically  the 
variation  of  the  moments  M=Wa;,  and 
consequently  of  the  stresses  produced  on 
the  outside  fibres  from  A1  to  C. 

In  Fig.  6  let  A  C  be  the  beam.     Take 


(3) 


So  far  we  have  considered  a  beam 
whose  breadth  is  that  of  only  one  row 
of  fibres,  but  a  beam  of  any  breadth 
may  be  made  up  of  a  number  of  such 
slices  placed  side  by  side,  and  if  b  =  the 
number  of  slices,  or  breadth  of  the 
beam,  and  W  =  the  weight  hung  at  the 
end  of  it,  then  eq.  (3)  becomes 


Wx=^Sbd2 
6 


(4) 


Fig.  6. 

a  line  on  some  scale  to  represent  the 
value  of  M0=W£,  and  lay  it  off  from  A 
perpendicular  to  A  C.  Let  A  L  be  this 
line.  Draw  L  C.  Then  the  dotted  per- 
pendiculars in  the  triangle  LAC  will  rep- 
resent the  moments  of  resistance  in  the 
beam  at  the  several  points  at  which 
they  are  drawn. 

From  eq.  (2)  it  is  seen  that  the  shear- 
ing force  is  constant  at  every  section  of 
the  beam.  This  force  we  may  assume 
with  sufficient  accuracy,  for  our  present 
purpose,  to  be  uniformly  distributed  over 


168 


VAN   NOSTEAND'S   ENGINEERING   MAGAZINE. 


the  cross  section  of  the  beam  on  whic 
it  acts.     Hence  if  A  =  area  of  cross  sec- 
tion, and  t  =  shearing  force  on  a  unit  of 
the  surface, 

T=W=At  (6) 

Lay  off  AC  (Fig.  V)  =1  and  CP=W. 

Then  the  rectangle  AP  represents  geo- 
metrically the  shearing  stress  at  every 
point  of  the  beam. 

Corollary.     When  several  weights  as 
W  W,  W2  (Fig.  8)  are  suspended  from 


A 
L 


Fig.  V. 


Fig.  8. 


the  beam  at  different  points,  the  moment 
of  resistance  at  any  point  is  equal  to  the 
joint  moments  of  the  weights  at  that 
point.  Thus,  calling  distances  measured 
from  C,  G,  and  E  towards  A,  x,  xx  and  ai2 
respectively,  we  have  for  the  equation  of 
moments  for  points  between  C  and  G 


6 


Between  G  and  E 


Wa+W^^-SW2    While  at  K, 


for  instance,  it  is 

Wx  +  W.^  +  W.x  =^Sbd2      (7) 
The  shearing  force  at  K  is 

T=W  +  W1  +  W2  (8) 

Geometrically.  Let  A  C  (Fig.  8)  =  I 
AG=?1andAE=?a.  LayoffAL=WZ, 
LHrzzW,^  and  AI=W2Z2.  Draw  the 
triangles  as  in  Fig.  8.  Then  NP=total 
moment  at  K,  for  instance. 


'  TL 


% 


Fig.  9, 


STRENGTH   OF   BEAMS   UNDER   TRANSVERSE   LOADS. 


169 


The  shearing  force  is  represented  by 
the  rectangles  AP,  NO,  and  ST  (Fig. 
9),  and  at  any  point  in  the  beam  is  equal 
to  the  sum  of  the  weights  between  that 
point  and  C. 

EXAMPLES. 

(1.)  Suppose  the  safe  stress  per  square 
inch  to  be  1,000  lbs.  (=  S),  and  I  =  10 
ft.,  b=3  inches,  and  d=l2  inches,  what 
weight  will  the  beam  support  ? 

(2.)  Suppose  W=f  ton,  1=12  ft.,  b=2 
inches,  what  must  be  the  depth  (d)  of  a 
rectangular  cast  iron  beam,  so  that  S  shall 
not  exceed  4  tons  ? 

Case  II. 

Let  the  beam  be  as  in  the  last  case, 
but  with  the  load  distributed  uniformly 
over  it   (Fig  10).     Let  w= weight  on  a 


QQQ  QiQQQQ  qQQ  Q 
33! 


Fig.  10. 

unit  of  length,  W= total  weight  on  AC, 
l=A  C= length,  c?=AB=depth,  x=EC 
as  before.  Then  the  forces  to  be  con- 
sidered are  represented  in  Fig  11,  the 
little  arrows  along  E  0  representing  the 
weight  distributed  along  the  beam. 

Replace  the  weights  along  E  C  by  their 
resultant,  which  is  =  wx,  and  which 
should  be  applied  at  the  middle  point  of 
E  C,  since  the  little  weights  on  the  beam 
are  uniformly  distributed.  Then  putting 
the  resultants  N  and  N'  in  place  of  the 
tensile  and  compressive  force,  and  pro- 
ceeding as  before,  we  have 


Also 


T— wx=0 
T=iox 

wx.  - —  Sbd* 
2     6 


(9) 


=  0 


^-=Js-»cP=M  (10) 


At  AB  (Fig.  10)  these  equations  become 

%=wl=W  J 

wf     Wl     1„,  „     „   '        (11) 


2         G 


M, 


k 


umiiLiiU 


re 


■m 


3§- 


Fig.  11. 

By  comparing  the  last  equation  with 
eq.  (5),  we  see  that  if  the  weight  and 
beam  be  the  same  the  stress  on  the  fibres 
in  this  last  case  is  only  one-half  what  it 
was  in  the  former,  or,  what  amounts  to 
the  same,  the  beam  will  bear  twice  as 
much  distributed  over  it,  as  it  will  when 
the  weight  is  concentrated  at  the  extrem- 
ity. 

From  eq.  (9)  we  see  that  the  shearing- 
force  is  not  constant  as  in  the  last  case, 
but  varies  as  x.     It  is  greatest  at  A. 


Fig.  12. 


170 


VAN   NOSTRAND'S   ENGINEERING   MAGAZINE. 


Geometrically.  The  equation  M  =  \ 
wcc2  corresponds  with  that  of  a  parabola 
with  vertex  at  C  and  axis  vertical.  Lay 
off  AL  (Fig.  12)  =&tor,  and  through 
L  and  C  draw  a  parabola.  The  ordinates 


of  this  parabola  (dotted  in  the  figure) 
will  represent  the  moments  at  the  several 
points. 

The  equation  T=wk  is  rej)resented  by 
the    triangle    APC    (Fig.    13),    which 


i    i    M    1    II    i  l^ 
Ml    \J>^, 

Fig.  13. 

therefore  gives  the  shearing  stress  at 
every  point  of  the  beam  when  AP  is 
taken  =  w  I. 


Corollary  1.  When  the  load  is  dis- 
tributed over  only  a  part  of  the  beam 
as  in  Fig.  (14),  let  R  C=m=the  loaded 


sE 

o  Q  q  ®  a 

| 

„L              "CO' 

R< 

» — ^ 

i 

&-£"* 

D 


Fig.  14. 


part,  and  take  the  other  letters  as  before. 
Then  the  equations  for  any  section  in 
the  loaded  part  are  evidently  the  same 
as  those  just  obtained,  viz.  : 


£  10  x 


Sbd*=M 


AtR 

And 


6 

-J  JJffl'rM 


(12) 


But  at  any  section  E  F  between  A  and 
R  the  moment  of  the  load  is  =  w  m 
(%—%m),  the  latter  factor  being  the  dis- 
tance from  the  centre  of  gravity  of  the 
load  to  the  section  E  F.  The  moment  of 
resistance  having  the  same  form  as  be- 


fore, we  have  for  the  equation  of  mo- 
ments for  any  section  in  R  A 


lsbd*=M      (13) 

6  v     ' 


wm  (x— \  m) 

At  A  this  becomes 

w  m  i}—\  rn)  =M0  the  greatest  moment. 

The  shearing  force  at  E  F  being  equal 
in  amount  and  opposite  in  direction  to 
the  whole  load  between  E  F  and  C  will 
be 

T=wm  (14) 

Geometrically.  For  the  moment  S :  lay 
off  A  C  =  I  and  C  R  =  m  (Fig.  15).     At 


Fig.  15. 


STRENGTH   OF   BEAMS   UNDER  TRANSVERSE    LOADS. 


171 


R  erect  DR  = 


wm 


and  at  A  make  A  L 


=M0.  Through  C  and  D  draw  a  para- 
bola as  in  the  last  case,  and  (since  eq. 
[13]  is  of  the  first  degree)  through  D 


A 


and  L  draw  a  straight  line.  Then  from 
C  to  R  the  ordinates  of  the  parabola 
represent  the  moments,  and  from  R  to 
A  they  are  represented  by  the  ordinates 
of  the  trapezoid  RL.  For  the  shearing 
stress  (Fig.  16),  lay  off  from  R,  RN —wrru 


Fig.  16. 


Draw  CNandN P.  Then  the  triangle 
CRN  (corresponding  to  the  equation 
T=w  x)  gives  the  shearing  force  at  each 
point  in  CR  while  the  rectangle  RP 
(corresponding  to  the  equation  T=wm) 
gives  the  force  in  the  remaining  segment 
of  the  beam. 

Corollary  2.  When  there  is  a  load  W 
at  the  extremity  C,  in  addition  to  the 
load  uniformly  distributed  over  the  beam 
(Fig.    11),   we  have   a   combination   of 


Fig.  17. 


Cases  I.  and  II.  and  the  moment  of  the 
external  forces  at  any  section,  E  F,  is 

i  w  x*  +  W  x 
Hence  the  equation  of  moments  is 

1  SbcF=iiox*  +  Wx 


M: 


o 


This  is  greatest  at  A,  or 

M=lQsbcr=itor+wi 

The  shearing  force 

T=iox  +  W 
At  A 

T=wl+W 


(15) 

(16) 

(18) 


Geometrically.     The   simplest  way  of 

representing  the  moments  is  to  construct 

those  due  to  each  kind  of  weight,  and 

to  x 
then  combine  them.     Thus,  let  M'=— - 

and  M"=Wa;.  Construct  M'  as  in  Case 
II.,  it  being  represented  by  a  parabola 
with  vertex  at  C  and  axis  vertical,  and 
M"as  in  Case  I.,  it  being  represented  by 


Fig.  18. 


172 


van  nostkand's  engineeking  magazine. 


a  triangle  (placed  under  A  C  for  con- 
venience). Since  M  ==  M'  +  M"  from  eq. 
(15)  we  have  the  total  moment  at  any 
point  E  (Fig.   18)  represented   by   the 


sum  of  the  ordinates 
ures=NPFia-.  (18.) 


of  these  two  ho:- 


The  moments  may  also  be  represented 
by  the  parabola   corresponding   to    eq. 


Fig.  19. 


(15)  as  in  Fig.  (19.)  This  parabola  has 
its  vertex  at  C  and  not  at  C.  Of  course, 
only  that  part  of  the  curve  between  C 
and  A  is  applicable  to  our  purpose. 


The  shearing  force  is  represented  by 
adding  the  triangle  N  PP'  Fig.  (20) 
representing  the  variable  part  w  x  of  T 
to  the  rectangle  C  P  which  represents 
the  constant  part  W  of  T. 


A 


Fig.  20. 


EXAMPLE. 

Discuss  the  forces  when  the  load  is 
distributed   as   shown  in   Fig.  (21)    as- 


L  Q  Q   Q    Q   Q  K 


Q>   Q  Q   Q   Q 


W 


Fig.  21. 


suming  various  values  for  L  N  and  N  0 
as  well  as  for  w  and  W. 

Case  III. 
Let  the  beam  whose  length  is  I  rest 
upon  supports  at  B  and  D  (Fig.  22)  and 

G  r 


& 


V 

I 


I 

I 


o 


Fig.  22. 


let  it  be  loaded  at  some  point  G  with  a 
single  weight  W.     Let  m  and  n  be  the 


STRENGTH  OF  BEAMS  UNDEE  TRANSVERSE  LOADS. 


173 


segments  into  which  the  beam  is  divided 
at  the  point  G  of  the  application  of  the 
weight. 

First  find  the  proportions  of  the 
weight  supported  at  B  and  D,  or  in 
other  words,  the  reactions  of  the  sup- 
ports. By  the  principle  of  the  lever  the 
respective  portions  of  the  weight  sup- 
ported at  B  and  D  are  inversely  propor- 
tional to  the  distances  of  these  points 
from  G.  Thus,  let  W=reaction  at  D 
and  W"=reaction  at  B  and  then 


W  :  W";  \m  :  n 
W"  +  W  :  W'yjn  +  n  : 
But  W'  +  W"=:W  and  m  +  n=l 


m 


(19) 


And  so 


W": 


w 


Now  apply  the  conditions  of  equilib- 
rium to  any  part  A  E  of  the  beam  count- 
ing from  A.     Fig.  (23). 


c 


D 


'> 


Fig.  23. 


1st,  Between  A  and  G.  2X.=0  merely 
indicates  the  equality  of  N  and  N',  as 
these  are  the  only  horizontal  forces. 
.2Y=0  shows  that  the  shearing  force 
at  the  section  E  F  is  downwards 


and=W" 


(20) 


2  M=0.  The  joint  moment  of  N  and 
N'  is  as  before =-  S  b  d\  That  of  T  is 
zero.     The  only  other  force  acting  on 


A  E  is  W",  the  reaction  of  the  abutment. 
Let  O  O  =£.     Then  the  moment  of  W" 


is 


Hence 


n 


Wx 


7.Wx--Sbd> 

I  6 


n 


.  •,'jWx=^Bbda=M  (21) 
2d,  Between  G  and  C  (Fig.  24).  Here, 


4^  -■_.. 


N*r 


K- 


tO 


w° 


D 


Fig. 


between  A  and  E  are  the  two  external 
forces  W"  at  B  and  W  at  G.  Hence  the 
shearing  force  at  EF  is  upwards  and 


T=W"-W=  -W'= 


W. 


(22) 


24. 

For  2  M— 0  we  have 
1 


6 


Sfttf  +  Ws-W  (x-m)  =  0 


.  ■ .  -Wx-W{x-m)==j-  S  bd* =M    (23) 


174 


VAN   NOSTRAND'S   ENGINEERING   MAGAZINE. 


The  greatest  value  of  eq.  (21)  is  at  G, 
where"  it  becomes  identical  with  eq.  (23) 
for  the  same  point.     This  value  is 

^W=^Sbd2=Mti  (24) 

At  A  and  C  the  moments  are  zero. 


Geometrically.  From  eq.  (21),  which 
is  of  the  first  degree,  it  is  seen  that  the 
moments  vary  in  AG  as  they  did  in 
Case  I.  Hence  they  may  be  represented 
by  the  ordinates  of  the  triangle  A  L  G. 
(Fig.  25). 


Fig.  25. 


Eq.  (23)  is  also  that  of  a  straight  line 
cutting  the  axis  of  X  at  C.     Hence  the 


moments  in  G  C  are  represented  by  the 
triangle  GLC  (Fig.  25).     The   shearing 


p  r 

:     i      i     i     i 

i       ; '      |      !       j 


n 


Fig.  26. 


force  in  A  G  is  represented  by  the  rect- 
angle A  P  and  that  in  G  C  by  the  rect- 
angle C  P'. 

Note,  That  the  maximum  moment  (at 
G)  corresponds  to  the  point  where  the 
shearing  force  passes  through  zero. 

Corollary  1.  When  the  weight  W  is 
at  the  middle  of  the  beam  we  have 


n  =  m  =  \l 
Then  eq.  (21)  becomes 


x  Wx=  -Sbd2 
2  6 


M 


and  (24)  is 

l'W(J- 


(25) 


;      6 


=M 


STRENGTH   OF   BEAMS   UNDER  TRANSVERSE   LOADS. 


175 


At  the  centre    M  =4 W. £  £=£  W  Z  (26) 

The  triangles  A  L  G  and  G  L  C  (Fig, 
27)  represent  the  moments  in  this  case. 


G  L  having  been  laid  off 


:£WJ. 


The  shearing  force  throughout  the 
beam  is  then  T=£  W  (27)  as  is  shown 
in  the  rectangles  (Fig.  28). 

Comparing  the  value  of   M0  given  in 


A 


Fig.  28. 


eq.  (5)  Case  I.  with  that  of  M0  in  eq. 
(26)  we  see  that  the  load  and  the  length 
being  the  same,  a  beam  will  bear  four 
times  as  much  with  both  ends  supported, 
and  the  load  placed  in  the  middle  as  it 


will  do  with  one  end  fixed  and  the  other 
loaded. 

Corollary  2.  When  there  are  several 
weights,  as  in  Fig  (29),  the  moment  of 
the  external  forces  at  any  section  is  that 


A 


Gr' 


G-" 


$(- 


■— > 

JKU 


r 


■yr 


w, 


■Wa 


Fig.  29. 


due  to  the  action  of  all  the  weights. 
Let  the  segments  into  which  the  weights 
W,  W,  and  W2  divide  the  beam  be  »* 
and.  n  for  W,  m1  and  n1  for  W,  and 
m2  and  n^  for  Ws. 

Let  R:= reaction  of  abutment  at  B  and 
R2= reaction  of  abutment  at  D  and 
£=length  and  let  xbe  counted  from 
A  as  before. 

The  reaction  of  the   abutment   at  B 
due  to  these  weights  is 


-,-^  7t/    -  -  —  ft.    -r-r-r  *vn 


w. 


1 


SoatD  R^W  +  ^W^W, 


(28) 


The  shearing  force  is 


T=R, 


(30) 


For  every  section  between  G  and  G' 
the  weight  W  is  to  be  taken  into  consid- 
eration and  the  equations  are: 


Rlx-W(x-m)=-Sbdi=M     (31) 


T=R-W 


(32) 


For  any  section  between  A  and  G,  Ra 
is  the  only  external  force  and  hence  the 
equation  of  moments  is 


6 


M 


(29) 


For  any  section  between  G'  and   G") 
we  have: 

(33) 

B,1x-^W(x—m)—W1(x—m1)=-  S  bd*=M 
T=R1-W-W1 
For  any  section  between  G"  and  C 
R,  x-W(x—rri>-WJ(#—m1)—'Wt  ] 

U-m5)=Js^(-r=M  j-    (34) 

T=R1-W-W1-WS  j 

The  location  of  the  greatest  moment 


176 


VA1ST  nosteand's  engineering  magazine. 


is  most  readily  determined  by  geometrical 
construction. 

Geometrically .    The  moments  are  rep- 
resented  in   Fig.    (30)   by  constructing 


separately  those  due  to  each  weight  and 
then  combining  them.  Thus,  the  mo- 
ments produced  at  every  point  in  the 
beam  by  the  weight  W  are  represented 


Fig.  30. 


by  the  triangle  ALC  (Fig.  30),  in  which 
G  L  equals  the  greatest  moment  due  to 

Similarly  AL'C  represents 


MjWx. 


those  due  to  W1}  G'  1/  bemg=3  W1 


and  A  L"  C  gives  those  due  to  W2,  G"  L" 
being==y  W2  x. 

Now,  if  at  every  point  we  add  to- 
gether the  ordinates  of  these  three  tri- 
angles for  that  point,  and  lay  them  off 
above  A  C  we  shall  get  a  polygon  A  H 


WW  G,  which  represents  eqs.  (29)  (31) 
(33)  and  (34)  and  gives  the  total  moment 
at  any  section .  The  greatest  ordinate  of 
this  polygon  will,  of  course,  show  the 
location  of  the  maximum  moment.  This 
will  be  at  G  or  G'  or  G",  according  to 
the  relative  amounts  and  positions  of 
the  weights  W,  Wn,  and  W2.  In  the 
fig.  it  is  at  G'.     Hence  from  eq.  (31) 

Ps  m-W(m-m)=^  S  5<P=M0  (35) 

The  shearing  force  may  be  represented 
as  in  Fig.  (31).     It  is  greatest  in  that 


fi 


Fig.  31. 


J L_i 


one  of  the  two  end  segments  which  cor- 
responds to  the  greater  of  the  two  quan- 
tities Rj  and  R2. 

Note,  That  in  this  case  the  simplest 
way  of  finding  the  point  of  maximum 
moment  is  to  construct  the  figure  repre- 
senting the  shearing  force,  and  the 
point  when  the  shearing  force  passes 
through  zero  (G'  Fig.  31)  is  the  point 
sou  edit. 


EXAMPLES. 

1.  Let  1=20  ft.  m=5  ft.»w1=10  ft.  m2= 
15  ft.W=l  ton  W=2  tons  W2=3  tons. 

Find  the  maximum  moment. 

2.  Find  the  size  of  a  rectangular  wooden 

beam  where 

1=15  ft.  m=3  ft.   m=Q  ft.  ra2=14  ft. 

W=l  ton  W=%  ton  W2=2  tons 

S=1,000  lbs.  and  d=4  b. 


EXTEACTIOIST  OF  THE  PRECIOUS  METALS. 


177 


EXTRACTION  OF  THE  PRECIOUS  METALS  CONTAINED  IN 

COPPER  PYRITES. 

Translated  from  the  French  of  P.  Claudet,*  by  ED.  DAVID  E.EARN. 
From  the  "  Mining  Journal." 


Sulphuric    acid,    which    occupies    a 
prominent  position  among  the  chemical 
products  employed  in  industrial  pursuits, 
was  long  made  almost  exclusively  from 
the  sulphurs  of  Sicily  ;  but  on  the  one 
hand    fiscal   measures   which   interfered 
with  their  exportation,  and  on  the  other 
the  progressive  increase  in  the  consump- 
tion of  sulphuric  acid,  led  the  manufac- 
turers   to    substitute    for    sulphur    the 
pyrites   which   is   found   in   almost    all 
countries.     It  is  from  Spain  and  Portu- 
gal that  the  English  manufacturers  draw 
the  greater  part   of  the   pyrites  which 
they  use,  and  as  they  are  more  or  less 
cupi'iferous,  the  residuum  after  the  ex- 
traction of  the  sulphur  was  principally 
sold  to  the  copper  smelters,  who,  owing 
to  oxide  of  iron  constituting  the  greater 
part   of  the  residuum,   employed  it  as 
flux  for  the  smelting  of  quartzose  copper 
ore  ;  in  this  operation  the  copper  in  the 
pyrites  was  recovered,  but  naturally  all 
the  iron  was  lost  in  the  slag.     The  ex- 
traction of  copper  from  its  ores  by  the 
wet  way,  first  practiced  by  Mr.   Long- 
maid,  then  applied  by  Mr.  W.  Henderson 
to  the  pyrites  of  Spain  and  Portugal,  no 
longer  caused  this  loss  of  iron  ;  this  pro- 
cess has  been  largely  developed,  result- 
ing in  a  constant  increase  in  the  impor- 
tation of  pyrites,  which  now  reaches  to 
from  400,000  to  500,000  tons  per  year,  and 
goes    on   increasing.     The   pyrites  sells 
according  to  its  produce^  for  sulphur  and 
for  copper;  manufacturers  who  only  buy 
it  for  te  sulphur  re-sell  the  burnt  ore  to 
works  in  which  the  copper  is  extracted. 
It  is  a  work  of  this  kind  that  I  and  Mr. 
J.  A.  Phillips,  both   graduates   of   the 
School  of  Mines   of  #  Paris,  have    estab- 
lished at  Widnes,  near  Liverpool.     The 
pyrites  of  Spain  and   Portugal  is    com- 
posed   (the  *  proportions    only    varying 
within  very  small  limits)  of  the  different 
elements  of  which  the  following  analysis 
will  give  an  example,;  it  is  that  of  a  sam- 


ple from  the  San  Domingo  Mines  from 
the  working  of  which,  ably  developed 
by  Mr.  J.  Mason,  about  one-half  of  the 
pyrites  are  supplied. 

Sulphur 49 .00 

Arsenic 0 .47 

Iron 43.55 

Copper 3.20 

Zinc 0.35 

Lead 0.93 

Lime 0.10 

Water 0.70 

Quartzos^  residue 0. 63 

Oxygen  and  Loss 1.07 


100.00 


In  the  last  item  of  1.07  traces  of  a 
large  number  of  metals  are  found.  This 
pyrites,  after  having  been  burnt  for  the 
manufacture  of  sulphuric  acid,  is  the 
material  which  is  treated  for  the  extrac- 
tion of  the  copper;  it  then  contains, 
with  but  slight  variation:  — 

Sulphur 3.76 

Arsenic 0.25  peroxide. 

Iron 58.25=     83.00 

Copper 4.14 

Zinc 0.37 

Cobalt Traces. 

Silver Traces. 

Lead 1.14 

Lime 0.25 

Insoluble  residue 1.06 

Water 3.85 

Oxygen  and  loss 26.93 


100.00 


*  "  Nouveau  Proc6d6  pour  l'Extraction  des  M6taux 
Pr6cieux  contenus  dans  les  Pyrites  Cuivreuses."  Par  F. 
Claudet,  Presente  a  l'Academie  des  Sciences.  Paris, 
Hennuyer. 

Vol.  XIII— No.  2—12 


As  to  the  silver  which  is  only  men- 
tioned as  "  traces,"  it  is  very  difficult  to 
assay  it  precisely  in  this  kind  of  ore  ; 
however,  the  numerous  assays  that  I 
have  made  have  enabled  me  to  estimate 
the  quantity  between  0.0020  and  0.0028, 
or  from  20  to  28  grammes  to  the  ton. 
But  small  though  this  proportion  may 
be,  I  did  not  doubt  that  we  could  suc- 
ceed in  extracting  it  with  profit,  and  this 
I  have  done  by  a  process  allied  to  that 
of  the  extraction  of  copper  by  the  wet 
way,  a  short  description  of  which  I  will 
now  give  : — We  commence  by  stamping 
and  washing  the  residue  of  the  pyrites, 
'  then  they  are  roasted  with  chloride  of 


178 


VAN  nostrand's  engineering-  magazine. 


sodium  in  a  reverberatoiy  furnace  at  a 
very  low  temperature  ;  the  oxidation  of 
the  metallic  sulphides  and  the  decompo- 
sition of  the  chloride  of  sodium  which 
follows  give  rise  to  the  formation  of  sul- 
phate of  soda  and  soluble  chloride  of 
copper.  When  we  are  satisfied  by  trial 
of  samples  that  the  ore  has  been  prop- 
erly roasted  it  is  taken  out  of  the  fur- 
nace, and  when  it  has  sufficiently  cooled 
it  is  thrown  in  to  about  three-fourths  fill 
a  large  wooden  tank,  with  a  double  bot- 
tom forming  a  filter,  and  is  washed  with 
several  waters  slightly  acidulated  with 
hydrochloric  acid  until  the  copper  is 
taken  up.  There  remain  in  the  tank  the 
insoluble  portions  which  consist  almost 
entirely  of  oxide  of  iron,  and  of  which 
the  subjoined  analysis  will  give  an  ex- 
ample : — 

Peroxide  of  iron. . .  96.20=67.35  metallic  iron. 
Lead,  as  sulphate. .     0.86 

Copper 0.18 

Cobalt Traces. 

Alumina 0.45 

Lime 0.46 

Soda 0.10 

Phosphoric  acid No  traces. 

Arsenic  acid Traces. 

Sulphuric  Acid. .  .     0.49 

Sulphur 0.16 

Chlorine 0.03 

Silica 1.22=100.15. 

This  oxide  of  iron  in  consequence  of 
its  uniform  composition  and  fine  state  of 
division,  is  sold  to  the  iron  manufac- 
turers, who  use  it  with  advantage  for 
fettling  the  puddling  furnaces. 

Returning  to  the  mother  liquid  from 
which  the  copper  has  to  be  extracted,  it 
is  run  into  other  tanks,  in  which  frag- 
ments of  iron,  such  as  scrap  iron,  have 
been  placed  ;  chloride  of  iron  is  formed, 
and  the  copper  is  thrown  down,  taking 
with  it  the  small  quantity  of  silver  of  the 
ore  which  was  dissolved  in  the  liquor. 
The  copper  precipitate  is  then  melted 
and  refined  to  bring  it  to  the  state  of 
marketable  copper.  In  the  water  from 
which  the  copper  has  been  separated 
there  are  also  found  salts  of  iron  mixed 
with  alkaline  salts  which  are  not  acted 
upon,  but  by  subsequent  operations  we 
have  been  able  in  our  works  to  obtain, 
and  profitably,  too,  on  the  one  hand, 
sulphate  of  soda  in  a  state  of  almost 
absolute  purity,  and  on  the  other,  oxide 
of  iron  in  so  fine  a  state  of  division  that 
it  is  applicable  to  the  polishing  of  look- 


ing-glasses. The  waters  before  the  pre- 
cipitation of  the  copper  by  the  iron  con- 
tains, as  we  mentioned,  the  silver  of  the 
ore  dissolved  in  the  state  of  chloride;  to 
extract  it  we  first  naturally  think  of  pre- 
cipitating it  by  metallic  copper,  but  sil- 
ver, being  soluble  in  a  mixture  of  chloride 
of  sodium  and  deutochloride  of  copper, 
the  precipitation  cannot  take  place  so 
long  as  all  the  deutochloride  is  not  con- 
verted by  the  metallic  copper  into  a  pro- 
tochloride,  and  then  the  small  quantity 
of  silver  is  probably  found  precipitated 
with  the  copper  in  excess,  and  also  with 
the  protochloride  of  copper  which  the 
chloride  of  sodium  is  no  longer  sufficient 
to  dissolve.  We  must  then  have  re- 
course to  a  fresh  process  of  separation, 
and  the  expense  of  this  complicated 
operation  absorbs  more  than  the  value  of 
the  silver  ;  the  process  then  is  not  com- 
mercial. There  is  another  means  of 
separating  the  silver  from  the  copper, 
which  consists  in  making  a  sulphate  of 
copper  of  the  precipitate  ;  but  the  great 
aim  in  the  treatment  of  the  mineral  is  the 
production  of  metallic  copper,  and  not 
sulphate  of  copper,  the  consumption  of 
which  is  very  limited,  so  that  the  process 
is  only  applicable  within  narrow  limit. 

I  had  then  to  seek  another  mode  of 
separation,  and  I  succeeded,  after  numer- 
ous trials,  to  discover  and  put  in  practice 
a  process  which  I  will  now  describe;  it 
is  founded  on  the  fact  that  iodide  of  sil- 
ver is  almost  entirely  insoluble  in  a  solu- 
tion of  chloride  of  sodium  at  the  ordinary 
temperature.  The  ore  roasted  with  com- 
mon salt  undergoes,  as  we  have  said, 
several  washings,  yet  but  little  else  than 
the  three  first  waters  contain  a  sufficient 
quantity  of  silver  to  be  worth  treating. 
We  have  ascertained  by  experiment 
that  the  two  first  waters  contain  83  per 
cent,  and  the  three  first  waters  95  per 
cent,  of  all  the  silver  dissolved.  Ac- 
cording to  the  analysis  of  one  of  these 
waters,  marking  1.24  of  the  aerometer,  a 
cubic  metre  of  this  liquor  contained: 

Sulphate  of  soda Kilos.  144.171 

Chloride  of  sodium 63. 914 

Chlorine    in    combination 

with  metals 66. 143 

Copper 52.855 

Zinc 6.857 

Lead 0.571 

Iron 0.457 

Lime 0.743 

Silver 0.0437=335.7547 


EXTK ACTION   OF  THE  PRECIOUS   METALS. 


179 


We  have  neglected  in  this  analysis  the 
small  quantities  of  arsenic,  bismuth,  &c. 
This  result  is  only  given  by  way  of  ex- 
ample, for  the  silver  which  we  quote 
43.7  grammes  varies  in  our  operations 
from  25  to  27  grammes  per  cubic  metre, 
according  to  the  richness  of  the  mineral 
and  the  degree  of  concentration  of  the 
liquor.  It  is  then  the  water  from  the 
three  first  washings  only  that  we  use. 
We  run  them  into  a  wooden  tank,  where 
they  are  left  to  settle,  so  that  solid  mat- 
ters held  in  suspension  may  separate, 
and,  in  order  not  to  employ  more  iodide 
of  potassium  than  is  absolutely  necessary, 
we  first  assay  the  silver  contained  in  the 
liquor.  For  this  purpose  we  take  a 
fixed  measure  of  it,  dilute  it  with  water, 
adding  a  little  hydrochloric  acid,  to 
keep  all  the  copper  in  solution;  then  we 
pour  in  a  few  drops  of  a  weak  solution 
of  iodide  of  potassium,  which  changes 
the  soluble  chloride  of  silver  into  the 
insoluble  iodide  of  silver  at  the  same  time 
that  by  the  addition  of  a  solution  of 
acetate  of  lead  we  cause  the  formation 
of  a  strong  plombiferous  precipitate, 
which  contains  all  the  silver.  This  pre- 
cipitate is  dried,  and  then  melted  with  a 
flux  to  which  metallic  iron  is  added;  the 
resulting  argentiferous  lead  is  cupelled, 
and  from  the  weight  of  the  button  of 
silver  the  quantity  contained  in  the 
liquor  is  determined. 

The  clear  titrated  liquor  is  then  passed 
into  another  tank,  and  the  quantity  of 
iodide  of  potassium  found  to  be  neces- 
sary by  the  assay  is  added,  and  it 
is  diluted  with  a  quantity  of  water  equal 
to  about  a  tenth  of  that  of  the  cupreous 
liquor ;  the  whole  of  the  liquor  is  then 
shaken  and  left  to  settle  for  48  hours; 
the  supernatant  liquor  is  then  clear;  it 
is  drawn  off,  and  the  tank  is  refilled 
for  repeating  the  operation,  and  so  on.* 

Once  a  fortnight  we  collect  all  the  de- 
posit which  has  accumulated;  it  is  prin- 
cipally composed  of  sulphate  of  lead, 
iodide  of  silver,  and  salts  of  copper. 
These  latter  are  readily  separated,  by 
washing  with  weak  hydrochloric  acid. 
The  deposit,  cleansed  from  the  salts  of 
copper,    is    decomposed    with    metallic 


*  These  liquors,  which  are  drawn  off,  still  contain  a 
small  proportion  of  silver  in  solution,  about  5  grammes 
per  cubic  metre,  for,  as  we  have  mentioned,  the  iodide  of 
silver  is  not  absolutely  insoluble  in  these  liquors.  It  is 
scarcely  necessary  to  add  that  they  re-e  .ter  again  in  the 
ordinary  working  for  the  extraction  of  the  copper. 


zinc,  which  in  the  presence  of  water 
rapidly  and  completely  reduces  the  sil- 
ver by  uniting  with  the  iodine,  and 
forming  soluble  iodide  of  zinc.  There 
is  thus  produced — 1.  Soluble  iodide  of 
zinc,  which,  separated  by  filtration,  is 
titrated,  and  used  as  a  substitute  for  the 
iodide  of  potassium  in  subsequent  opera- 
tions to  precipitate  fresh  quantities  of 
silver. — 2.  A  deposit  rich  in  silver,  com- 
posed in  a  great  part  of  lead  in  the  me- 
tallic state,  and  as  a  sulphate  containing 
besides  various  substances,  of  which  the 
subjoined  analysis  of  a  dried  sample 
may  be  given  as  an  example: 

Silver 5.95 

Gold 0.06 

Lead 62.28 

Copper 0. 60 

Oxide  of  zinc 15.46 

Oxide  of  iron 1.50 

Lime 1.10 

Sulphuric  acid 7.68 

Insoluble  residue 1.75 

Oxygen,  and  loss. ......     3. 62 = 100. 00 

This  analysis  shows  that  all  the  iodine 
of  the  iodide  of  silver  has  entered  into 
combination  with  the  zinc,  and  re-become 
soluble,  since  the  deposit  contains  none 
or  only  traces.  Gold,  which  has  not 
before  been  mentioned,  appears  here  for 
the  first  time,  and  we  may  ask  how  this 
happens  ?  It  exists  then  in  the  ore,  and 
it  would  appear  that  in  the  operation  of 
roasting  it  forms  chloride  of  gold, which, 
rendered  more  stable  by  the  presence  of 
chloride  of  sodium,  is  not  reduced  at  the 
low  temperature  of  the  roasting;  it  then 
enters  into  solution  with  the  silver,  and, 
like  it,  it  is  precipitated  by  the  iodine. 
It  is  now  easy  to  separate  from  this  pro- 
duct the  precious  metals  by  the  ordinary 
processes  employed  by  smelters  who 
treat  gold  and  silver  matters.  It  will, 
no  doubt,  be  interesting  to  know  the  re- 
sults we  have  obtained  by  the  application 
of  the  process  during  a  year.  The  process 
was  applied  in  1S71  (the  paper  was  read 
in  1872)  to  16,300  tons  of  burnt  pyrites, 
from  which  we  extracted  of  silver 
333.242  kilos.,  and  of  gold  3.172  kilos., 
representing  a  little  more  than  20 
grammes  of  the  precious  metal  per  ton, 
and  producing  £3,232  after  deducting 
the  cost  of  melting  and  refining.  The 
expenditure  directly  connected  with  the 
precious  metals  amounted  to  £4 16, which 
includes  the  cost  of  137  kilos,  of  iodine, 
representing  the  loss  of  that  material, 


180 


VAN  NOSTRAND's  ENGINEERING   MAGAZINE. 


and  1,900  kilos,  of  zinc,  and  it  is  re- 
markable that  the  gold  which  exists  in 
the  ore  in  appreciable  quantity  suffices 
to  cover  the  whole  cost  of  the  process. 
The  cost  of  the  iodine,  already  large, 
has  become  much  more  considerable 
through  the  abnormal  increase  in  the 
price  of  the  product,  and  has  called  my 
attention  to  the  direct  employment  that 
might  be  made  of  the  lye  from  the  ashes 
of  seaweeds  instead  of  iodide  of  potassi- 
um. The  recent  experiments  we  have 
made  in  this  direction  have  answered 
my  expectations,  and  not  only  have  we 
succeeded  in  utilizing  by  this  means  all 
the  iodine  contained  in  the  seaweed,  and 
great  part  of  which  is,  as  we  know,  at 
present  lost,  but  the  trials  have  suggest- 
ed to  me  the  idea  of  an  inverse  oper- 
ation, to  which  I  am  now  giving  atten- 
tion, for  making  iodine,  and  which  con- 
sists in  precipitating  this  metalloid  from 
the  seaweed  lye  by  means  of  a  salt  of 
silver.  This  extraction  of  20  grammes 
of  precious  metal  from  the  ton  of  burnt 
pyrites  is,  I  admit,  not  very  considerable; 
but  when  we  consider  that  the  process 
could  be  applied  to  350,000  tons  of  ore, 


and  thus  produce,  with  a  good  profit, 
too,  7,200  kilos,  of  the  precious  metals, 
of  the  value  of  £68,000,  it  will  be  seen 
that  it  is  an  annual  result  not  to  be 
neglected. 

This  process  can  also  be  employed  for 
various  other  copper  ores  susceptible  of 
treatment  by  the  wet  way,  and  we  have 
begun  to  apply  it  to  the  copper  ores  of 
Cornwall,  which  generally  contain  more 
silver  than  the  Spanish  pyrites,  and 
which  hitherto  have  been  worked  by  the 
dry  way,  and  solely  for  the  extraction  of 
the  copper.  The  results  which  we  have 
just  recorded  show  how  highly  important 
it  is,  in  metallurgical  operations,  to  deal 
with  large  masses ;  we  thus  obtain  profits 
where  the  same  process  applied  to  limited 
quantities  could  only  result  in  loss.  We 
will  make  the  further  remark  upon  this 
subject  that  large  quantities  of  the 
precious  metals  have  been  lost,  and  are 
still  lost  daily,  in  metallurgic  operations, 
and  we  do  not  doubt  that  many  of  the 
residues 'in  various  parts  of  the  globe 
which  have  been  neglected  as  too  poor 
will  one  day  be  re-treated  to  separate 
the  gold  and  silver  which  they  contain. 


THE  DRAINAGE  OF  CALCUTTA. 


From  "The  Builder." 


Ten  years  ago  Sir  John  Strachey  de- 
clared that  the  capital  of  British  India 
was  "  a  scandal  and  a  disgrace  to  a  civ- 
ilized Government,"  and  asserted  that  it 
was  literally  unfit  for  the  habitation  of 
civilized  men.  He  declared  that  the 
most  important  streets  and  thorough- 
fares of  the  northern  division  of  the  city 
formed  to  all  intents  and  purposes  a 
series  of  huge  public  latrines,  the  abomi- 
nation of  which  could  not  be  adequately 
described.  And  he  vehemently  added, 
the.  other  cities  and  towns  of  India  were 
almost  faultless  when  compared  with  the 
metropolis.  Yet  at  that  time  sanitary 
questions  were  altogether  unknown  in 
India,  and  Miss  Nightingale  had  reported 
that  no  one  of  the  presidential  cities  of 
India  had  arrived  at  that  degree  of  civ- 
ilization in  their  sanitary  arrangements 
which  the  worst  parts  of  our  worst 
towns  had  reached  before  healthy  re- 
form in  such  matters  sprang  up  in  Eng- 


land at  all.  This  reproach  has  now  been 
wiped  away  from  the  Indian  capital,  and 
there  are  signs  that  Bombay  and  Madras 
will  soon  be  rendered  salubrious.  At 
Norwich,  in  November  last,  Miss  Night- 
ingale was  able  to  state  that  "the 
drainage  of  Calcutta  bids  fair  to  be  a 
wonder  of  the  world,  and  said  that  the 
city  had  become  more  healthful  than 
Manchester  or  Liverpool,  and  might  even 
be  considered  a  sanitarium  compared 
with  Vienna  or  Berlin."  How  has  the 
change  been  accomplished  ? 

Calcutta  lies  in  close  proximity  to  a 
vast  stagnant  marsh,  known  as  the  Salt 
Water  Lake.  Even  in  its  infancy  the 
settlement  was  unhealthy,  and  as  it 
grew  in  size  its  insalubrity  increased. 
Cholera  continually  haunted  it,  fevers 
and  dysentery  made  it  their  home,  and 
when  it  had  come  to  be  termed  the  City 
of  Palaces,  it  was  equally  well  known  as 
the  City  of  Pestilence.     But  the  traders 


THE  DRAINAGE   OF   CALCUTTA. 


181 


who. frequented  its  bazaars  risked  their 
health  for  the  sake  of  the  rupees  which 
flowed  into  their  coffers;  the  servants 
and  officers  of  John  Company  had  too 
many  wars  on  hand,  and  too  many 
States  to  annex,  to  pay  much  heed  to 
the  healthiness  of  the  town,  and  to  the 
soldiery  the  chances  of  death  on  the 
field  or  under  the  friendly  guns  of  Fort 
William  were  about  the  same.  But  at 
length  the  mortality  of  Calcutta  became 
so  notorious  that  the  Government  could 
no  longer  overlook  it,  and  a  committee 
was  appointed  to  inquire  into  the  causes 
of  the  prevalence  of  perennial  fever,  and 
to  propose  remedial  measures.  This 
committee  sat  for  several  years  previ- 
ously to  1840,  amassed  a  great  amount 
of  repulsive  evidence,  and  in  the  end 
proposed  the  establishment  of  a  fever 
hospital.  The  Medical  College  Hospital 
was  accordingly  founded  ;  but  while  it 
afforded  relief  to  the  afflicted,  and  did 
save  a  few  lives,  such  a  solitary  institu- 
tion could  not  materially  diminish  the 
death-rate.  At  that  time,  and  for  many 
years  afterwards,  the  affairs  of  the  city 
were  managed  by  a  Conservancy  Board, 
composed  of  two  European  and  two  na- 
tive commissioners;  but  although  these 
gentlemen  were  anxious  to  do  their 
duty,  they  lacked  professional  skill  to 
direct  their  efforts,  and  wasted  their  en- 
ergies in  futile  projects.  The  night  soil 
was  collected  from  house  to  house  by 
scavengers,  and  conveyed  in  open  carts 
to  the  river,  into  which  it  was  thrown  at 
a  point  above  the  harborl  The  stable 
refuse  and  house  rubbish  were  shot  into 
the  streets  and  road-ways,  and  subse- 
quently carted  away  to  fill  up  disused 
tanks  and  ponds,  and  to  raise  the  fore- 
shore of  the  river ;  while  the  surface 
water  of  the  thoroughfares  and  com- 
pounds, the  slops  from  the  houses,  in- 
cluding urine,  and  the  storm  water  were 
allowed  to  find  their  way  by  surface 
gutters  into  the  Hooghly  and  into  the 
Circular  Canal — a  deep  cutting  which 
almost  surrounds  Calcutta  to  the  east- 
ward. The  whole  subsoil  of  the  city 
was  saturated  with  filth  which  had 
spread  from  innumerable  cesspools,  and 
with  water  which  had  percolated  through 
from  the  Hooghly,  or  had  fallen  during 
the  monsoons.  Only  vile  drinking-water 
was  needed  to  render  the  Indian  capital 
the  permanent  abode  of  plague  and  pes- 


tilence— and  this  was  also  provided;  for 
wells  and  the  river  alike  were  impreg- 
nated with  sewage  matter.  In  the  trop- 
ics with  so  much  of  the  results  of  de- 
composition in  air,  earth,  and  water,  it 
is  surprising  that  life  was  at  all  endura- 
ble, and  that  the  people  submitted  to 
the  nuisance  so  long.  But  although  the 
European  inhabitants  grumbled,  the  na- 
tive Commissioners  opposed  all  schemes 
for  extensive  reform;  and  affairs  rolled 
on  on  the  filthy  old  groove  until,  in 
1855,  Sir  Frederick  Halliday  was  ap- 
pointed to  the  new  office  of  Lieutenant- 
Governor  of  Bengal.  An  administrator 
so  able  at  once  detected  the  foul  spot, 
and  succeeded  in  convincing  the  Com- 
missioners that  they  were  personally  in- 
capable of  superintending  the  work  of 
reform.  By  his  advice  a  professional 
adviser  was  called  in,  and  Mr.  William 
Clark,  C.  E.,  was  appointed  to  the  post. 
In  the  following  year  that  gentleman 
submitted  a  scheme,  with  estimates  at- 
tached, for  the  drainage  of  the  city,  and 
a  committee  was  appointed  to  report 
upon  it.  After  deliberations  extending 
over  eighteen  months,  the  committee  re- 
ported favorably  upon  the  project,  and 
it  was  sent  on  with  their  endorsement 
to  the  Government.  To  make  assurance 
doubly  sure,  the  plans,  about  which  little 
difference  of  opinion  then  existed,  were 
handed  over  for  supervision  to  Mr.  Ren- 
del,  C.  E.,  who  happened  to  be  in  India 
at  the  time.  By  him  they  were  carried 
to  England;  but  after  considering  them 
for  ten  months  he  reported  unfavorably 
with  regard  to  them,  and  proposed  a 
counter  scheme  of  his  own.  Then  the 
mutiny  broke  out;  people  had  other 
work  to  do  ;  and  the  whole  affair  was 
shelved  for  a  time.  However,  when  the 
rebellion  had  been  suppressed  the  Gov- 
ernment at  an  early  date  returned  to  its 
previous  intentions,  the  rival  projects 
were  compared;  the  proposals  of  Mr. 
Clark  were  preferred,  and  orders  were 
given  to  begin  the  work.  It  was  in  1859 
that  the  undertaking  was  commenced, 
and  it  is  not  quite  complete  now. 

Mr.  Clark's  scheme  comprised  outfall 
works  and  large  brick  sewers  in  every 
part  of  the  town,  which  lay  within  1,000 
feet  of  the  main  drainage  lines,  leaving 
minor  pipe  sewers  for  fuUire  considera- 
tion. The  large  sewers,  five  in  number, 
and  varying   from   6   feet  to  8   feet  in 


182 


VA1ST  NOSTRAISTD'S   ENGINEERING  MAGAZINE. 


height,  extended  from  the  river  to  the 
east  at  right  angles  across  the  town;  and 
these  sewers  were  connected  at  their 
eastern  extremity  by  an  8%  feet  sewer 
placed  beneath  what  is  known  as  the 
Circular  Road.  From  the  middle  of  this 
road  the  outfall  branched  off  in  a  due 
easterly  direction  in  the  bed  of  what 
was  formerly  the  Entally  Canal,  which, 
being  useless,  was  filled  up  for  the  pur- 
pose. The  outfall  sewer,  16  feet  high, 
was  continued  to  a  length  of  3,284  feet, 
to  a  channel  cut  in  the  marsh  or  salt 
water  lake  before  referred  to,  and  thence 
it  is  eventually  to  be  conducted  to  a  dis- 
tance of  ten  miles  from  the  city,  and 
there  discharged  into  the  tidal  stream  of 
Sunderbund.  From  the  river,  eastward, 
the  level  of  the  surface  of  the  land  falls 
at  the  rate  of  3  feet  per  mile,  and  even- 
tually forms  the  Salt  Water  Lake.  The 
waters  of  the  Hooghly  can  thus  be  util- 
ized at  discretion,  in  flushing  the  sewers 
during  the  dry  season  ;  while,  at  other 
times,  the  storm  water  can  be  discharged 
into  the  river  at  low  tide. 

The  perfection  of  the  drainage  scheme 
necessarily  involved  one  for  water  sup- 
ply. Accordingly,  Mr.  Clark  proposed 
to  take  water  from  the  Hooghly,  seven- 
teen miles  above  Calcutta,  pump  it  into 
large  settling  reservoirs,  filter  it,  and 
pass  it  down  to  the  city  in  iron  mains,  42 
inches  in  diameter.  Thence  it  was 
meant  to  pump  it  during  the  night  into 
a  large  reservoir  in  the  centre  of  the 
town,  from  which  it  could  be  pumped  for 
distribution  during  the  following  day. 
This  project  was  sanctioned  in  1865;  the 
works  were  commenced  at  the  end  of 
1866,  and  were  completed  in  three  years. 
The  daily  delivery  is  about  eight  million 
gallons  for  a  population  of  about  500,000 
inhabitants.  It  is  distributed  under  a 
pressure  of  50  feet  by  engines  fixed  near 
the  central  reservoir.  Stand-posts  are 
fixed  in  the  streets  for  supplying  the 
poorer  classes,  while  house-pipes  may  be 
connected  with  the  mains  if  it  be  so  de- 
sired. The  cost  of  these  works  was 
about  £600,000,  which  was  advanced  by 
the  Government  to  the  Municipality  at 
4^  per  cent.  After  having  served  do- 
mestic purposes  the  eight  million  gallons 
of  water  are  discharged  into  the  sewers 
by  the  drains;  this  water  flows  by  gravi- 
tation, with  the  subsoil  water  and  the 
light  shower  water,  to  the  pumping-sta- 


tion,  where  it  is  disposed  of  as  described. 
The  sewers  are  divided  into  three  classes. 
First,  the  large  ones  branching  off  from 
the  river  to  the  Circular  Road,  and  ulti- 
mately to  the  pumping-station.  There 
are  ten  miles  and  three-quarters  of  this 
sort.  The  second-class  are  also  brick 
sewers  from  3  feet  to  5  feet  high,  and 
are  laid  along  the  principal  streets  at 
right  angles  to  those  of  the  first-class. 
These  sewers  are  twenty-three  miles 
long,  and  both  these  and  those  of  the 
first-class  are  finished.  The  third-class, 
which  will  drain  the  narrow  lanes  and 
the  interior  of  the  blocks  of  buildings 
surrounded  by  the  first  and  second- 
class,  will  consist  of  stoneware  piping. 
They  also  are  very  nearly  complete,  and 
their  total  length  is  estimated  at  seventy- 
nine  miles.  Thus,  when  the  whole  net- 
work is  finished  there  will  be  113  miles 
of  sewers,  which  represent  the  road 
mileage  of  the  city. 

Considerable  difficulties  attended  the 
execution  of  the  scheme,  and  there  were 
some  differences  of  opinion  as  to  the 
mode  of  carrying  it  out,  but  they  were 
overcome,  one  after  another.  Native 
bricks  were  employed;  a  large  brick- 
making  establishment  was  set  on  foot  at 
a  place  nine  miles  above  Calcutta,  and 
the  native  brickmakers  soon  succeeded 
in  producing,  with  their  simple  appa- 
ratus, bricks  as  good  as,  and  less  expen- 
sive than,  those  turned  out  by  the  Euro- 
pean machines  which  had  been  imported. 
For  many  years  the  brickfield  had  pro- 
duced about'  8,000,000  of  hand-made 
bricks.  As  brick-dust,  or  what  is  known 
locally  as  "  soorkie,"  is  employed  instead 
of  sand  with  lime  in  making  mortar, 
about  500  maunds  of  it  were  supplied 
every  day.  Stoneware  pipes,  varying 
from  6  inches  to  12  inches  in  diameter, 
were  supplied  from  Doulton's  potteries 
at  Lambeth  ;  and  when  laid  down  the 
lowermost  half  of  the  openings  was 
united  by  cement,  and  the  upper  half  by 
puddled  clay,  through  which  the  subsoil 
water  was  permitted  to  percolate.  The 
saturated  subsoil  was  a  great  obstruc- 
tion to  progress.  A  trench,  dry  over- 
night, would  be  found  to  be  more  than 
half  full  of  water  in  the  morning  ;  and 
no  amount  of  pumping  was  equal  to  the 
task  of  keeping  the  trenches  dry  enough. 
After  many  abortive  attempts,  Mr. 
Clark  adopted  the  plan  that  has  been  f  ol. 


THE   DKAINAGE   OF   CALCUTTA. 


183 


lowed  in  London  of  laying  a  stoneware 
pipe  at  the  bottom  of  the  trench,  and 
covering  it  with  a  bed  of  concrete,  upon 
which  the  brick  sewer  was  built.  The 
lowermost  part  of  the  inner  circumfer- 
ence of  the  sewer  was  coated  with  Port- 
land cement,  and  made  water  tight,  but 
the  other  half  was  unprotected.  The 
walls  varied  according  to  the  size  of  the 
sewers  from  5  inches  to  20  inches  of 
brick-work  in  rings.  The  subsoil  water 
enters  the  sewers  either  at  the  bottom, 
by  means  either  of  the  small  stoneware 
pipe  or  by  percolation  through  the  upper 
half  of  the  brickwork  ;  and  the  plan  has 
been  so  successful  that  its  level  has  been 
reduced  by  7  feet  or  8  feet.  The  sewers 
are  employed  to  remove  the  subsoil  water, 
the  drainage  of  the  houses,  and  the  rain 
water.  In  a  tropical  country,  the  rain- 
fall is  a  most  important  consideration, 
that  of  Calcutta  varying  from  75  inches 
to  90  inches  per  annum.  Hence  the 
sewers  had  to  be  made  of  exceptionally 
large  size,  and  it  is  said  they  can  take 
the  equivalent  of  a  quarter  of  an  inch 
of  rain  per  hour,  which,  if  collected, 
would  be  represented  by  a  running- 
stream  40  feet  wide,  8  feet  deep,  and 
flowing  at  a  velocity  of  4  feet  per 
second. 

During  the  monsoons,  when  the  storm- 
water  falls  in  sufficient  quantities  to 
over-power  the  pumps  at  the  pumping- 
stations,  it  is  discharged  by  special  out- 
lets into  the  Circular  Canal,  adjoining 
the  Circular  Road,  whence  it  flows  off 
into  the  natural  streams  of  the  country 
eastward.  It  is  admitted  into  the  sew- 
ers by  gully-gratings  placed  at  the  sides 
of  the  footpaths,  which  gratings  cover  a 
deep  pit  provided  to  intercept  the  road 
grit,  which  is  removed  by  manual  labor. 
Such  of  the  grit  as  finds  its  way  along 
the  sewers  to  the  pumping-stations  is 
intercepted  there.  The  stable  -  litter, 
kitchen-stuff,  and  other  more  solid  refuse 
of  the  town  are  removed  from  every 
house  by  municipal  carts  daily  to  a  rail- 
way that  runs  along  the  Circular  Road, 
carried  by  it  to  the  Salt  Water  Lake,  and 
there  deposited.  There  have  been  vari- 
ous proposals  for  utilizing  the  sewage- 
matter  and  litter  at  the  place  of  their 
deposit,  but  no  action  has  yet  been 
taken,  atlthough  it  is  very  unlikely  that 
such  a  profitable  deposit  will  remain  long 
without  being  turned  to  good  account. 


The  Calcutta  justices  are  empowered 
to  compel  householders  to  connect  their 
premises   by   suitable   drains   with    the 
public  sewers,  but  they  are  reluctant  to 
enforce  their  authority,  and  prefer  leav- 
ing every  man  to  his  own  discretion.     It 
is   very  questionable  whether  their  lax- 
ity is  to   be  commended,  for  much   of 
their  outlay  is  thereby  rendered  unpro- 
ductive, and  the  health  of  the  whole  city 
suffers.     The   city  death-rate,    however, 
has  been  reduced  by  more  than  one  half. 
When  the  public  sewers  are  not  used  the 
householders  allow  the  drainage  of  their 
dwellings  to  gravitate  into  cesspools  and 
ditches,  and  it  is  only  when  they  have 
become   an  intolerable   nuisance   and   a 
source  of  pestiferous  exhalation  which 
cannot  be  endured  that  they  are  cleaned 
out,  and  the  contents,  in  a  state  of  active 
decomposition,  are  carted  away  and  shot 
into  the  sewers.     It  is  gratifying,  how- 
ever, to  state  that  the  natives  are  begin- 
ning of  their  own  accord  to  appreciate 
the  advantages  of  the  public  sewers,  and 
to   understand    the    dangers    attendant 
upon  the  accumulations  of  filth,  within 
and   about    their   dwellings.      Hitherto 
the  cost  of  connections  and  other  private 
drainage  works  has  acted  as  a  deterrent 
to  the  smaller  owners  and  holders.     Re- 
cently, however,  a  shrewd  native  justice 
suggested  that  the  English  system  should 
be  adopted,  by  which  such  persons  can 
have  their  premises  drained  by  the  muni- 
cipal authorities,  and  pay  off  the  com- 
bined interest  and  cost  at  a  fixed  annual 
rate.    The  project  has  been  adopted,  and 
it  is  anticipated  will  become  popular. 

The  total  cost  of  the  drainage  works 
of  Calcutta,  when  completed,  will  be 
about  £800,000,  of  which  nearly  £600,- 
000  have  already  been  expended.  The 
money  has  been  raised  partly  by  muni- 
cipal debentures  bearing  6  per  cent,  in- 
terest, and  latterly  by  a  Government 
loan.      The    benefits,    however,    amply 

compensate  for  all  the  expenditure. 


New  Signaling  Apparatus. — Mr.  "W.  Leach, 
of  Wigan,  has  patented  an  invention 
which  relates  to  the  construction  of  a  signal 
apparatus  for  collieries,  mines,  and  other 
underground  works,  the  object  being  to  com- 
bine visible  and  audible  signals  from  the  per- 
sons at  the  bottom  of  the  shaft  to  the  engineer 
at  the  pit  mouth,  such  signals  remaining  visible 
until  the  engine  has  commenced  to  wind  up, 
[  and  then  returning  automatically  to  zero. 


184 


VAN  NOSTRANO'S   ENGINEERING   MAGAZINE. 


REPORTS  OF  ENGINEERING  SOCIETIES. 

King's  College  Engineering  Society. — 
At  a  meeting  of  this  society,  held  on  June 
11th,  Mr.  E.  L.  Hesketh,  A.K.C.,  read  a  paper 
on  some  experiments  in  centrifugal  pumps, 
made  at  the  works  of  Messrs.  Easton  and  An- 
derson, of  Eirth.  The  author  commenced  by 
describing  the  pumps  which  were  experimented 
with.  The  first  was  a  10  in.  pump  with  trunk 
engine  attached,  and  the  second  was  a  vertical 
spindle  pump  with  2ft  6in.  fan.  He  described 
the  way  in  which  the  experiments  were  con- 
ducted, and  also  the  method  of  finding  the 
throw.  The  best  results  were  obtained  when 
the  case  was  made  of  a  spiral  form  inside  by 
the  temporary  introduction  of  a  curved  piece 
of  wood.  A  pump  is  now  being  constructed 
which  will  have  the  case  cast  in  a  spiral  form. 
In  the  other  pump  two  other  forms  of  fan 
were  used,  viz. ,  Rankine's  and  the  involute. 
The  latter  gave  by  far  the  best  results,  but 
still  not  satisfactory,  as  the  water  rotated  in- 
side the  pump  at  such  a  rate,  but  the  notion 
was  conceived  of  having  curved  blades  placed 
in  such  a  position  as  to  utilise  the  rotary  mo- 
tion of  the  water  and  convert  it  into  a  vertical 
one.  The  paper  was  illustrated  by  several 
diagrams,  photographs,  and  models. 


IRON  AND  STEEL  NOTES. 

Brightening  Iron. — A  Bavarian  serial  con- 
tains a  method  of  brightening  iron  recom- 
mended by  Boden.  The  articles  to  be  bright- 
ened are,  when  taken  from  the  forge  or  the 
rolls,  in  the  case  of  such  articles  as  plates,  wire, 
&c,  placed  in  dilute  sulphuric  acid  (1  to  20), 
where  they  remain  for  about  an  hour.  This 
has  the  effect  of  cleansing  the  articles,  which 
are  then  washed  clean  with  water  and  dried 
with  sawdust.  They  are  then  dipped  for  a 
second  or  so  in  nitrous  acid,  washed  care- 
fully, dried  in  sawdust,  and  rubbed  clean.  It 
is  said  that  iron  goods  thus  treated  acquire  a 
bright  surface,  having  a  white  glance,  without 
undergoing  any  of  the  usual  polishing  oper- 
ations. This  is  a  process  that  those  interested 
can  easily  test  for  themselves,  but  care  should 
be  taken  with  the  nitrous  acid  not  to  inhale  any 
of  its  fumes.  Boden  states  that  the  action  of 
the  sulphuric  acid  is  increased  by  the  addition 
of  a  little  carbolic  acid,  but  it  is  difficult  to  see 
what  effect  this  can  have,  and  it  may  very  well 
be  dispensed  with. — English  Mechanic. 

The  Danks  Furnace  est  America. — Infor- 
mation of  a  later  date  than  Mr.  I.  L.  Bell's 
visit  to  the  United  States  has  been  received  in 
Staffordshire  relative  to  the  working  of  the 
Danks  furnace  in  the  States.  The  ex-president 
of  the  Iron  and  Steel  Institute  in  his  ' '  Notes 
of  a  Visit  to  Coal  and  Iron  Mines  and  Iron- 
works in  the  United  States,"  said  that  two  es- 
tablishments at  which  the  Dank  system  was 
still  in  use  were  the  Railroad  Mill  at  Cincin- 
nati, under  the  personal  superintendence  of 
Mr.  Danks,  and  the  Mill  of  Messrs.  Graff, 
Bennett  &  Co.,  of  Pittsburgh.  Mr.  Bennett 
and  his  Manager — Mr.  Williams— Mr.  Bell  de- 


clared to  be  equally  sanguine  with  Mr.  Danks 
as  to  the  ultimate  success  of  the  system.  The 
later  information  is  that  Messrs.  Graff,  Ben- 
nett &  Co.  are  increasing  their  number  of  fur- 
naces, that  they  are  taking  the  bloom  direct  to 
the  Universal  Rolling  Mill— which  has  reverse 
motion — and  that  upon  coming  out  of  the 
rolls  the  hot  iron  is  slit  to  varied  widths  by 
powerful  cutters.  When  the  Danks  process 
was  discussed  by  the  Staffordshire  mill  and 
forge  managers,  on  the  occasion  of  their  visit 
to  the  Ravensdale  Works  in  North  Stafford- 
shire, certain  of  them  expressed  doubt  as  to 
the  practicability  of  dealing  with  such  large 
blooms  as  were  produced  by  the  rotary  fur- 
nace, so  as  to  make  from  them  the  smaller 
sizes  of  finished  iron  for  which  South  Stafford- 
shire is  best  known  ;  and  it  was  pointed  out 
that  the  difficulty  might  be  met  by  slitting  the 
blooms  immediately  they  left  the  forge  rolls. 
It  would  seem  as  though  Messrs.  Graff,  Ben- 
nett &  Co.  are  leading  the  way  in  an  adapta- 
tion of  the  Danks  process  to  the  making  of  the 
smaller  sizes.  If  they  are  successful  in  this 
work,  what  they  are  doing  is  of  considerable 
importance  to  South  Staffordshire.  Though 
nothing  is  known  of  any  present  attempt  to 
lay  down  the  Danks  plant  in  South  Stafford- 
shire, yet  there  is  a  rumor  that,  at  least  in  one 
instance,  there  is  a  disposition  to  test  the 
Crampton  furnace.  Nevertheless,  the  proba- 
bility that  one  or  the  other,  or  it  may  be  both, 
will  be  forced  upon  the  district  at  no  distant 
day  is  pretty  generally  conceded. — Engineer. 

PRODUCTION  OF  PlG  IRON  TN  THE  UNITED 
,  States  in  1874. — The  American  Iron  and 
Steel  Association  has  received  from  the  pro- 
ducers and  from  its  correspondents  full  statis- 
tics of  the  production  of  pig  iron  in  the  Unit- 
ed States  in  1874.  The  total  production  was 
2,689,413  net  tons,  against  2,868,278  net  tons 
in  1873,  and  2,854,558  net  tons  in  1872,  show- 
ing a  decrease  of  178,865  tons  as  compared 
with  1873,  and  165,145  tons  as  compared  with 
1872.  Notwithstanding  this  decrease,  the  pro- 
duction in  1874  was  much  larger  than  was  gen- 
erally anticipated — much  larger  even  than 
partial  returns  made  to  the  Association  at  the 
close  of  1874  indicated.  This  unexpected  re- 
sult is,  however,  susceptible  of  a  satisfactory 
explanation.  As  preliminary  to  this  explana- 
tion we  give  the  following  statistical  resume  :■ 


«w      • 

• 

«W   -I-3 

02 

03 

o 
o 

03 

a 

o  a 

o.  of  furnace 
built     durin 
the  year. 

otal  number  o 
furnaces  Dec 
31st. 

a> 
Q 

02 

03 

3 

=4-1   -|j 
O    02 

+^  ^ 

0  CO 

Q 

roduction     o 
pig  iron  in  ne 
tons. 

{H 

fc 

H 

b* 

O 

1— 1 

P-. 

1872. . 

574* 

41 

615 

1151 

500 

2,854,558 

1873.. 

615 

50 

665 

252 

413 

2,868,278 

1874. . 

665+ 

38         701    336     365 

2,689,413 

*  Including  3  spiegeleisen  furnaces  in  New 
Jersey, 
f  Two  furnaces  were  abandoned  in  1874. 
1[  Estimated. 


KAIL  WAY  NOTES. 


185 


On  the  1st  of  February,  1874,  of  701  com- 
pleted furnace  stacks  in  the  country,  there 
were  in  blast  303  stacks  and  out  of  blast  398 
stacks.  Sixty-two  furnaces  were  blown  out  in 
January.  These  figures  indicate  the  lowest  de- 
gree of  depression  reached  since  the  panic  up 
to  that  date.  Since  February  1st  the  number 
of  furnaces  out  of  blast  has  been  slightly  in- 
creased. 

The  number  of  new  furnaces  completed  in 
1874  was  38,  against  50  in  1873  and  41  in  1872. 
The  astonishing  number  of  46  stacks  is  reported 
to  us  as  being  in  course  of  erection  in  1875, 
while  other  new  furnaces  are  projected. 

The  following  States  made  more  iron  in 
1874  than  in  1873  :  Maine,  Vermont,  Mass- 
achusetts, New  York,  Virginia,  Georgia,  Ala- 
bama, Texas,  West  Virginia,  Tennessee,  Ohio, 
and  Michigan.  The  following  States  made  less 
iron  in  1874  than  in  1873  :  Connecticut,  New 
Jersey,  Pennsylvania,  Maryland,  North  Caro- 
lina, Kentucky,  Indiana,  Illinois,  Wisconsin, 
and  Missouri.  The  district  showing  the  great- 
est increase  during  1874  was  the  Miscellaneous 
bituminous  coal  and  coke  district  in  Ohio. 
The  district  showing  the  greatest  decrease 
during  1874  was  the  Lehigh  anthracite  district 
in  Pennsylvania. 

Utah  Territory  made  her  first  pig  iron  in 
1874 — 200  tons  of  charcoal.  After  a  long  rest 
Oregon,  with  one  furnace,  made  2,500  tons  of 
charcoal  iron  in  1874.  Texas  made  1,012  tons 
of  charcoal  iron  in  1874.  South  Carolina,  with 
eight  furnaces,  and  Minnesota,  with  one  fur- 
nace, made  no  iron  in  that  year. 

The  production  of  charcoal  pig  iron  in  1874 
was  within  1,903  net  tons  as  large  as  that  of 
1873,  being  572,817  net  tons  in  1874  against 
574,720  tons  in  1873. 

The  total  imports  of  pig  iron  into  the  United 
States  in  1874  were  61,165  net  tons,  against 
154,708  net  tons  in  1873,  295,967  net  tons  in 
1872,  and  245,535  net  tons  in  1871. 

The  total  exports  of  pig  iron  from  the  United 
States  to  all  countries  in  1874  were  16,039  net 
tons,  against  10,104  net  tons  in  1873,  and  1,477 
net  tons  in  1872. — Abstract  from  the  Bulletin. 


RAILWAY  NOTES. 

Enormous  Engines. — An  engine  has  recently 
been  placed  on  the  Pennsylvania  Railroad 
which  weighs  seven  tons  heavier  than  the  pon- 
derous Modoc,  whose  drawing  capacity  is 
almost  twice  that  of  an  ordinary  locomotive. 
The  Modoc  is  capable  of  taking  eighty  loaded 
cars  from  Harrisburg  to  Columbia,  while  other 
engines  are  put  to  a  severe  test  when  they  pull 
fifty  cars  on  that  portion  of  the  road.  The 
new  locomotive  when  fully  initiated  is  ex- 
pected to  get  away  with  a  hundred  cars.  The 
only  argument  that  can  be  used  against  large 
engines  is  that  they  are  hard  on  tracks,  but  as 
the  Pennsylvania  Railroad  Company  has 
adopted  steel  rails — able  to  withstand  a  far 
greater  pressure  than  iron  rails — the  wear  will 
not  be  material.  The  introduction  of  these 
mammoth  engines  is  considered  a  very  econ- 
omical measure  by  the  railroad  company. — 
Iron  World. 


The  total  length  of  railways  thrown  open  to 
traffic  in  Russia  during  1874,  may  be  taken 
as  1160  English  miles.  The  total  railway  mile- 
age of  Russia,  including  Finland,  represented 
11,576  English  miles  on  the  1st  of  January, 
1875,  which  length  very  nearly  coincided  with 
the  French  railway  mileage  on  the  1st  of  Janu- 
ary, 1874,  France  showing  then  a  total  corres- 
ponding mileage  of  18,565  kilometres,  or  11,- 
510  English  miles.  At  the  present  time  Russia 
is  engaged  upon  the  fourth  section  of  the 
Losowaja-Seevastopol  railway,  the  Rostow- 
Wladikawkas  line,  the  Kornescty-Pruhtbridge 
line,  the  Fastow-Snamenka  line,  the  Orenburg 
Railway,  the_Ural  line,  and  the  Vistula  Rail- 
way. 

Three  years'  experience  on  the  Denver  and 
Rio  Grande  3ft.  6in.  road  has  determined 
the  fact  that  much  wider  cars  can  be  run  with 
safety  than  was  at  first  supposed  possible  on  so 
narrow  a  gauge.  They  are  now  building  pass- 
enger and  freight  cars  8ft.  wide.  The  superin- 
tendent, Mr.  W.  Borst,  says  that,  were  he  to 
begin  anew,  he  would  make  all  the  passenger 
cars  8ft.  3in.  wide,  outside  measurement,  giv- 
ing room,  with  a  narrow  isle,  for  good  double 
seats  on  each  side,  as  in  wide  gauge  cars.  By 
placing  the  sills  of  the  narrow-gauge  car  so 
much  nearer  the  rail,  an  angle  of  safety  is  se- 
cured amply  sufficient  to  prevent  overturning, 
even  at  high  speed;  this  also  greatly  diminishes 
the  oscillation  of  the  car,  an  important  point 
for  the  comfort  of  passengers.  A  Denver 
editor  gives  it  as  his  experience  that  he  can 
write  on  a  narrow-gauge  with  less  difficulty 
than  on  any  wide-gauge  car,  not  even  except- 
ing the  Pullman  palace. — Engineering. 

INCRUSTATION  IN  LOCOMOTIVES. — Mr.  F. 
Kupka,  an  engineer  at  Vienna,  writes  to 
the  German  Organ  for  Railroad  Progress  of 
some  experiments  made  by  Mr.  A.  Feldbacher, 
engineer  of  the  Austrian  State  Railroad  Com- 
pany, on  lining  locomotive  boilers  with  sheet 
copper  to  prevent  accumulations  of  incrustation. 
Of  the  three  plates  forming  the  bottom  of  a 
locomotive  boiler,  the  two  at  the  ends  were 
covered  with  sheet  copper  one  millimetre 
(1.25in.)  thick,  the  middle  one  being  left  bare. 
This  engine  was  run  two  years,  making  about 
14,000  miles  in  switching  service  in  the  Vienna 
yard,  where  the  water  is  the  worst  on  the  line. 
On  removing  the  boiler  tubes,  a  layer  of  incrus- 
tation was  found  10  millimetres  thick  on  the 
iron  surfaces  and  two  to  three  millimetres  on 
the  copper  ;  the  iron  exhibited  corrosions  11- 
millimetre  deep  ;  the  copper  maintained  a  per- 
fectly smooth  surface,  while  the  iron  under 
the  copper  had  the  appearance  of  new  plate. 
The  structure  of  the  incrustation  was  coarser 
grained  on  the  iron  than  on  the  copper.  The 
cost  per  boiler  is  given  as  50  dols.  to  150  dols. 
Mr.  Kupka  summarises  the  advantages  of  this 
practice  as  follows  : — (1)  The  life  of  the  boiler 
is  increased  two  or  three  times,  and  extraordi- 
nary security  against  explosions  is  obtained. 
(2)  There  is  considerably  less  incrustation  on 
the  smooth  surface  of  the  Copper,  than  on  the 
porous  and  somewhat  oxidised  iron  and  steel, 
and  therefore  a  better  generation  of  steam  and 
utilisation  of  fuel.     (3)  The  boiler  plates  may 


186 


VAN  NOSTRAND'S   ENGINEERING   MAGAZINE. 


be  thinner  without  danger,  in  consequence  of 
the  favorable  action  of  the  copper  in  prevent- 
ing corrosion,  and  consequently  the  weight  of 
the  boiler  may  be  less.  (4)  The  joints  of  the 
plates  are  made  perfectly  tight  by  doubling  the 
thin  copper  sheets  over  the  iron  plates  and 
riveting  them  in.  (5)  There  is  a  considerable 
saving  in  boiler  repairs. — Engineering. 

Railway  Accidents  in  Great  Britain. — 
The  Pall  Mall  Gazette  says  :  The  returns 
relating  to  railway  accidents  for  the  last  year 
has  just  been  issued.  From  these  returns  it 
seems  that  the  total  number  of  persons  re- 
ported as  killed  to  the  Board  of  Trade  in  1875 
for  the  United  Kingdom  was  2425,  and  injured, 
5050.  Of  the  killed,  England  contributed 
1175  ;  Scotland,  211  ;  and  Ireland,  39.  Of  the 
injured,  the  numbers  for  England  are  4468  ; 
Scotland,  496  ;  and  Ireland,  86.  It  further 
appears  that  there  were  last  year  in  the  United 
Kingdom,  to  account  for  all  this  killing  and 
wounding,  fifty-five  collisions  between  passen- 
ger trains  or  parts  of  passenger  trains  ;  183 
collisions  between  passenger  trains  and  goods 
or  mineral  trains,  engines,  and  vehicles  stand- 
ing foul  of  the  line  ;  75  collisions  between 
goods  trains  or  parts  of  goods  trains  ;  six  col- 
lisions between  two  engines,  ninety-seven  ac- 
cidents from  passenger  trains  or  parts  of  pass- 
enger trains  leaving  the  rails  ;  seventy-four 
from  goods  trains  or  parts  of  goods  trains,  en- 
gines, &c,  performing  the  same  feat  ;  forty 
from  trains  or  engines  traveling  in  the  wrong 
direction  through  points  ;  twenty-one  from 
trains  running  into  stations  or  sidings  at  too 
high  a  speed  ;  195  from  trains  running  over 
cattle  or  other  obstructions  on  the  line  ;  fifty 
two  from  trains  running  through  gates  at  level 
crossing;  six  from  the  bursting  of  boilers,  &c, 
of  engines  ;  eight  from  the  failure  of  machin- 
ery, springs,  &c. ,  of  engines  ;  from  failure  of 
tires,  55  ;  ditto  of  wheels,  13  ;  of  axles,  229  ; 
of  brake  apparatus,  1  ;  of  couplings,  23  ;  of 
ropes  used  in  working  inclines,  3  ;  of  tunnels, 
bridges,  &c,  4  ;  493  are  charged  to  broken 
rails  ;  10  to  blocking  of  portions  of  permanent 
way  ;  8  to  slips  in  cutting  of  embankments  ; 
28  to  fire  in  trains  ;  12  to  fire  at  stations  or  in- 
volving injury  to  bridges  or  viaducts  ;  11  are 
returned  as  other  accidents.  Directors  hanged 
for  manslaughter,  0. 


ENGINEERING  STRUCTURES. 

Iron  Arched  Bridges. — At  the  last  Sessional 
meeting  of  the  Edinburgh  and  Leith  En- 
gineers1 Society,  the  President,  Professor 
Fleeming  Jenkin,  read  a  paper  on  metal 
arches.  He  began  by  explaining  the  stresses 
which  occurred  in  the  common  masonry  arch, 
illustrating  the  subject  by  means  of  a  wooden 
model  of  novel  description,  having  each  vous- 
soir  curved  so  as  to  render  the  arch  flexible. 
It  was  explained  that  in  papers  by  Professor 
Clerk  Maxwell,  Mr.  Bell,  and  Professor  Fuller, 
of  Belfast,  methods  were  given  by  which  the 
maximum  intensity  of  stress  on  each  part  of  a 
metal  rib  could  now  be  determined  with  as 
great  accuracy  as  the  stress  on  the  ordinary 
girders;    and  Professor  Jenkin  expressed    a 


strong  opinion  that  the  great  bridges  of  the 
future  would  be  metal  arches,  which  for  great 
spans  were  essentially  more  economical  than 
beams,  while  they  also  were  more  beautiful. 
In  illustration,  the  Bridge  of  St.  Louis,  at  Cin- 
cinnati, was  referred  to,  with  a  central  arch  of 
520  feet  in  span.  There  was  no  reason  why 
arches  of  700  or  800  feet  span  should  not  be 
erected,  and  in  some  situations  even  these 
great  spans  would  be  economical  in  compari- 
son with  a  number  of  smaller  openings  involv- 
ing expensive  foundations. 

The  Improvement  op  the  Tiber. — The  sur- 
veys of  the  deviation  of  the  Tiber,  as  pro- 
posed by  General  Garibaldi,  have  just  been 
completed  by  the  Government  engineers,  and 
show  clearly  the  great  difficulties  in  a  financial 
point  of  view  which  would  have  to  be   en- 
countered in   carrying  out    such    a    project, 
whether  on  the  right  bank  or  on  the  left.     The 
deviation  on  the  left  bank — which  would  be 
the  most  favorable — would  not  cost  less  than 
135  millions  of  francs,  or  £5,400,000  ;  whilst 
that  on  the  right,  which  would  entail  a  certain 
length    of    cutting    from    seventy    to    eighty 
metres  in  depth,  is  estimated  at  200  millions  of 
francs,    or    eight    millions    sterling.     In    our 
opinion  the  most  feasible  scheme  so  far  is  that 
presented  some  time  ago  by  a  well-known  en- 
gineer, Signor  Anderloni,  who  proposed  recti- 
fying the  river  in  its  course  through  the  city, 
giving  it  a  clear  waterway  of  100  metres,  and 
removing  all   obstacles — such  as    the    Ponte 
San'Angelo — which  in  heavy  floods  dam  back 
the  waters,  and  cause  them  to  overflow  the 
banks  and  inundate  the  city.     In  the  flood  of 
1870  the  water  stood  at  1.50  above  the  soffit  of 
the  arches  of  that  bridge .     Such  a  work,  in- 
cluding a  handsome  boulevard  on  each  side  of 
the  river,  with  earth  embankments  for  a  con- 
siderable distance  above  and  below  the  city, 
would  not  probably  cost  more  than  fifty  mil- 
lions of  francs,  or  two  millions  sterling,  and 
would,  no  doubt,  effectually  prevent  the  re- 
currence of  such  floods  as  that  of  1870,  when, 
according  to  Signor  Possenti,  the  President  of 
the  Commission  for  the  Tiber,  the  discharge  at 
Rome  reached  2800  cubic  metres  per  second. 
The  removal  of  the  obstacles  and  the  rectifica- 
tion of  the  river  would  produce  a  lowering  of 
the  levels  of  the  water  in  such  a  flood  as  that 
of  1870  of  3.22  metres  at  Ponte  Molle,  about 
4  kilos,  above  Rome;  of  4. 02 metres  atRipetta, 
where  the  river  enters  the  city  ;  1.78  metres  at 
Ripa  Grande,  where  it  leaves  Rome  ;  and  1.18 
metres  at  the  railway  bridge,  about  1£  kilos, 
lower  still,  or  6  kilos,  below  Ripetta.     In  this 
manner  the  flood  level  would  be  reduced  at 
the  Ripetta  from  17.29  metres  above  the  sea  to 
13.26  metres,  or  within  the  limits  of  safety.   It 
would  be  necessary  to  construct  intercepting 
sewers  along  the  embankment  to  carry  the 
drainage  of  the  town  some  distance  down  the 
river,  and  in  this  manner  there  would  be  no 
danger  of  those  parts  of  the  city  which  are 
only  12  metres  above  the  sea  being  flooded. 

Public  Works  in  Jamaica. — From  an  official 
document  just  issued  with  regard  to  this 
subject  we  glean  some  information  of  interest 
to  our  readers.     One  of  the  most  important 


ORDNANCE  AND   NAVAL. 


187 


works  being  carried  out  in  Jamaica  is  the  con- 
struction of  new  waterworks  for  the  improve- 
ment of  the  water  supply  of  Kingston.  In  the 
carrying  out  of  these  works,  a  dam  across  the 
Hope  River  has  been  constructed  for  the  pur- 
pose of  increasing  the  quantity  of  water  flow- 
ing into  the  culvert.  Two  reservoirs,  at  the 
termination  of  the  culvert  near  the  city,  are  in 
course  of  construction.  They  will  contain 
5,000,000  gallons  of  water.  Two  filter  beds 
have  also  been  constructed.  From  the  reser- 
voirs the  water  will  flow  into  the  city  and  its 
suburbs  by  a  system  of  iron  pipes.  The  main 
pipe  is  21  inches  in  diameter.  The  main  and 
supply  pipes  have  been  laid  down.  Already 
the  works  have  cost  more  than  $50,000,  while 
it  is  thought  that  about  $5,000  more  will  be  re- 
quired for  their  completion.  It  has  also  been 
decided  to  build  new  gasworks  for  the  city  of 
Kingston,  and  a  design  was  submitted  by  a 
London  gas  engineer,  but  it  was  considered 
too  costly.  Accordingly  it  was  determined  to 
get  a  plan  of  a  less  expensive  character. 
Another  important  work  in  Jamaica  is  the 
carrying  out  of  the  Rio  Cobre  irrigation 
scheme.  In  reference  to  this  Sir  J.  P.  Grant 
expressed  the  hope  that  it  would  have  been 
finished  long  ere  now,  but  he  has  been  disap- 
pointed, that  is  to  say,  with  regard  to  the  head 
works  of  the  Rio  Cobre  Canal,  the  trunk  line, 
and  the  Caymanas  branch.  With  reference 
to  the  progress  of  the  works  so  far  it  appears 
that  the  foundations  of  the  annicut  or  dam 
across  the  river,  the  most  difficult  and  expen- 
sive portion  of  the  work  has  been  completed, 
and  the  dam  carried  to  a  height  of  10  feet 
above  the  foundation  in  all  parts,  and  in  some 
parts  much  higher.  When  finished  this 
structure  will  be  in  length  320  feet,  reaching 
all  across  the  river  when  dammed  up;  in 
height  it  will  be  48  feet  above  the  bed  of  the 
river,  and  in  breadth  or  thickness  it  will  be  26 
feet  at  the  base  and  13  feet  at  the  top.  It  will 
contain  about  238,000  cubic  feet  of  masonry, 
besides  a  mass  of  concrete.  The  dam  will 
have  suitable  sluices  and  a  water  cushion. 
Work  on  the  Trunk  Canal  and  the  Caymanas 
branch  has  made  fair  progress.  The  masonry 
work  on  the  line  consist  of  three  calingulates, 
or  waste  water  wiers,  twe  aqueducts,  one 
culvert,  twenty-three  bridges,  and  eighteen 
falls.  — Engineer. 

A  Notable  Railway  Bridge. — The  railway 
system  of  India  has  necessitated  some  re- 
markable engineering  works,  amongst  which 
may  be  mentioned  the  Bhore  Ghat  incline,  from 
Bombay  to  Central  India.  This  work,  15f 
miles  in  length,  cost,  with  tunneling,  bridges, 
and  embankments,  as  much  as  £68,000  per 
mile,  nearly  the  same  as  the  Semmering  Pass 
in  the  Noric  Alps,  joining  Vienna  and  Trieste. 
The  height  surmounted  in  the  Ghat  incline  is 
1,831  feet,  by  gradients  averaging  1  in  48,  but 
with  8  miles  of  1  in  40,  and  1\  miles  of  1  in 
37.  There  are  also  very  numerous  railway 
bridges  on  the  Indian  lines,  as  may  be  inferred 
from  the  fact  that  one  English  firm  alone, 
Messrs.  Westwood  &  Baillie,  of  London-yard, 
Poplar,  have  already  built  more  than  16,000 
iron  bridges  for  the  Bombay,   Baroda,   and 


Central  India  and  other  Indian  railways.  The 
firm  referred  to  have  just  completed  and  dis- 
patched the  last  section  of  the  longest  bridge 
they  have  ever  constructed,  probably  the  long- 
est bridge,  when  its  erection  has  been  com- 
pleted, then  in  existence.  It  is  to  cross  the 
river  Chenab  in  the  Punjaub,  and  will  form  a 
part  of  the  through  route  from  Calcutta  and 
Bombay  to  Lahore,  Peshawar,  and  Cabool. 
The  Chenab  is  a  tributary  of  the  Indus,  and 
has  wide  low-lying  banks,  liable  to  inundation, 
that  are  spanned  by  the  bridge.  The  sub- 
structure is  to  consist  of  piers  of  masonry  10 
feet  9  inches  thick.  The  superstructure  is  en- 
tirely of  iron,  and  on  the  Warren  girder  prin- 
ciple. The  total  length  between  the  abut- 
ments at  each  end  is  9,088  feet,  or  If  miles 
less  51  yards.  The  whole  work  has  been 
built  in  Messrs.  Westwood  &  Baillie's  yard, 
and  has  been  sent  out  in  sections,  every  sepa- 
rate part  marked,  so  as  to  fit  into  its  own 
place.  The  last  section,  of  about  100  yards  in 
length,  that  we  saw  in  the  yard  was  an  excel- 
lent example  of  exact  work,  each  end  respond- 
ing perfectly  to  the  test  of  a  wire  under  high 
strain  applied  to  it.  The  bridge  will  have 
sixty -four  spans,  of  a  clear  width  of  131  feet  3 
inches  each.  It  will  carry  a  single  line  of  the 
metric  gauge,  that  prevails  in  India,  of  3  feet  3 
inches.  The  width  over  all  is  18  feet,  2 
inches,  which  leaves  a  sufficiently  wide  clear 
space  for  a  footway  on  each  side.  The  main 
girders,  which  are  15  feet  9  inches  between 
centres,  are  10  feet  4  inches  deep,  with  flanges 
of  2  feet  6  inches.  The  cross  box  girders,"of 
which  there  are  1,792  in  the  structure,  are 
placed  at  5  feet  3f  inches  apart.  The  rivets 
used  in  the  work  have  been  1,590,592,  and 
have  been  of  f  inch,  f  inch,  and  1  inch  rods, 
according  to  their  situations  and  the  duty  re- 
quired of  them.  The  rods  used  for  these 
rivets  would  extend  to  upwards  of  100  miles 
lineal.  The  roadway  is  covered  with  buckle 
plates,  bent  by  the  firm  with  their  own  power- 
ful hydraulic  machinery.  The  weight  of  the 
iron  used  in  the  bridge  is  about  6,000  tons.  If 
all  the  pieces  of  iron  employed  in  the  struct- 
ure, girder  plates,  struts,  ties,  buckle  plates, 
etc. ,  exclusive  of  the  rivets,  and  irrespective  of 
the  width  of  the  pieces,  were  laid  end  to  end, 
they  would  extend  to  a  length  of  250  miles. 
The  whole  of  the  work  for  the  riveting  has 
been  drilled,  not  a  single  rivet-hole  having 
been  punched.  We  have  heard  that  the  Gov- 
ernment, or  official  authorities  in  the  Punjaub 
concerned  with  the  erection  of  the  bridge, 
have  expressed  their  satisfaction  with  the  ma- 
terials and  workmanship.  The  whole  was 
completed  in  London-yard  in  eighty-six  weeks. 
— Engineering. 


ORDNANCE  AND  NAVAL. 

The  "Bessemer." — Those  of  our  readers 
who  have  read  the  accounts  of  the  trial 
trip  given  in  the  daily  papers,  will  probably 
be  disposed  to  thus  summarize  what  they  have 
read  : —  The  swinging  saloon  does  not  yet 
swing,  the  "  Bessemer"  does  draw  more  than 
eight  feet  of  water,  her  speed  is  very  much 
less  than  twenty  miles  an  hour  even  in  fine 


188 


VAN  nostrand's  engineering  magazine. 


weather,  and  she  is  not  adapted  for  the  present 
French  harbors  because  of  her  great  length, 
and  consequent  liability  to  be  swung  round  by 
the  tide.  So  much,  apparently,  has  perform- 
ance fallen  below  promise,  that  some  of  our 
contemporaries  have  gone  so  far  as  to  say  that 
the  "Bessemer,"  whatever  else  she  majT  be 
adapted  for,  cannot  be  used  successfully  as  a 
passenger  boat  between,  Dover  and  Calais 
until  there  is  a  larger  and  better  harbor  made 
on  the  French  side.  We  are,  at  present,  far 
from  any  such  conclusion  as  this,  and  so  we 
think  will  our  readers  be  after  hearing  what 
can  fairly  be  said  on  the  other  side  of  the 
question. — Nautical  Gazette. 

Steamers  for  Haytt.  — Messrs.  Nefie  & 
Levy,  of  Philadelphia,  have  on  hand  two 
war  steamers  for  the  Haytian  Government. 
The  steamers  are  being  built  of  wood,  and  the 
contract  for  their  hulls  have  been  sub-let  to 
Messrs.  Birely,  Hillman  &  Streaker.  The 
larger  of  these  two  vessels  will  be  of  700  tons 
burthen,  and  she  will  be  190  feet  long  by  32 
feet  beam,  and  14  feet  depth  of  hold.  The 
vessel  will  be  fitted  with  direct-acting  horizon- 
tal engines  of  the  surface  condensing  type, 
with  cylinders  38  inches  in  diameter  and  24 
inches  stroke.  Both  engines  and  boilers  are 
to  be  completely  surrounded  by  coal  bunkers, 
as  a  protection  against  shot  and  shell  from  an 
enemy.  The  steamer's  armament  will  consist 
of  an  11-inch  Rodman  gun  amidships,  two  30- 
pounder  Parrott  rifles  at  either  end,  and  two 
broadside  32-pounder  smooth  bores.  The 
smaller  vessel  will  be  158  feet  long  by  29  feet 
beam  and  12  feet  depth  of  hold.  Her  engines 
will  be  of  the  same  type  as  those  of  the  other 
steamer ;  the  cylinders  will  be  32  inches  in 
diameter  by  20  inches  stroke. — Engineering. 

The  Borsenzeitung  says  that  it  is  to  be  decid- 
ed in  the  course  of  the  present  summer 
whether  the  two  gunboats  built  for  service  on 
the  Rhine  are  to  form  the  nucleus  of  a  gun- 
boat flotilla  to  be  permanently  established  on 
that  river.  The  gunboats  in  question,  together 
with  the  two  French  ones  which  were  cap- 
tured in  the  second  battle  of  Orleans,  will 
make  various  trial  trips  on  the  river  for  the 
purpose  of  ascertaining  whether  the  establish- 
ment of  such  a  flotilla  would  be  desirable.  It 
is  not  proposed  to  use  these  boats  for  any 
other  object  than  to  strengthen  the  defences 
on  the  Rhine,  and  if  the  creation  of  a  flotilla 
should  be  determined  upon  it  will  be  divided 
into  squadrons  to  be  attached  to  the  various 
fortresses.  The  reason  of  this  is  that  the  diffi- 
cult navigation  of  the  Upper  Rhine  and  the 
strong  currents  in  that  pa^t  of  the  river  would 
make  it  almost  impossible  to  send  the  boats  up 
the  stream.  On  the  Lower  Rhine,  however, 
between  Cologne  and  Coblenz,  a  single  squad- 
ron will  be  sufficient  to  provide  for  the  defence 
of  the  whole  of  that  section  of  the  river.  The 
French  gunboats  are  covered  with  plates  from 
five  to  eight  centimetres  thick,  and  have  en- 
gines of  forty  horse  power.  They  draw  from 
1.1  to  1.25  metres  of  water,  carry  a  sixteen  or 
twenty-four  centimetre  gun  and  a  light  field 
gun  or  mitrailleur,  and  have  crews  of  from 
twenty-six  to  forty-five  men.     The  armament 


of  the  new  German  gunboats  is  not  yet  de- 
cided on. — Engineer. 

WE  noticed  some  time  ago,  says  the  Pall  Mall 
Gazette,  the  force  and  originality  of  the 
views  which  Admiral  Porter  took  occasion  to 
impress  upon  his  countrymen  in  the  annual  re- 
port on  the  United  States'  Navy.  Those  of 
his  suggestions  which  referred  to  the  construc- 
tion of  a  single  small  but  efficient  ironclad 
squadron,  backed  by  a  few  swift  corvette 
cruisers,  to  supersede  the  present  antiquated 
and  almost  useless  vessels  on  the  list,  remain 
still  in  abeyance.  But  the  late  votes  of  Con- 
gress have  been  applied  partly  to  another,  the 
improvement  of  the  offensive  torpedo  service. 
Admiral  Porter  avowed  his  belief  that  tor- 
pedoes used  merely  passively  would  greatly 
disappoint  their  designers  ;  and  he  even  satir- 
ised the  late  experiments  made  by  projecting 
them  from  the  bows  of  slow,  worn-out  steam- 
ers. But  he  expects  great  things  from  a  bold 
use  of  these  weapons  offensively  by  properly 
constructed  vessels,  and  the  new  torpedo 
steamer,  the  Alarm,  lately  launched  at  Brook- 
lyn, is  the  first  attempt  to  give  practical  effect 
to  his  views.  As  in  the  case  of  the  Dantzic 
torpedo  boats  of  Germany,  speed  is  a  special 
object,,  and  the  lines  are  consequently  fine 
and  the  engines  powerful.  But  the  Alarm  is 
over  300  tons  measurement,  thus  many  times 
larger  than  the  similar  models  of  the  Baltic 
builder,  and  is  to  carry  one  very  heavy  gun  as 
a  reserve,  in  case  her  torpedo  boom  falls,  with 
Gatling  guns  for  her  own  protection  from  boat 
attacks.  As  she  is  built  with  a  wheelhouse, 
this,  as  well  as  her  size,  will  prevent  her  hav- 
ing the  comparative  invisibility  on  which  the 
German  inventors  much  rely  for  the  efficiency 
of  their  squadron.  But,  on  the  other  hand, 
the  Alarm  is  constructed  to  face  a  sea  in  which 
their  low  and  fragile  vessels  would  be  quite 
useless.  — Engineer. 

Lighthouses  and  Wreck-Signals. — Owing 
to  the  wreck  of  the  "  Schiller,"  and  to  the 
absence  of  any  means  of  making  it  known  to 
the  shore  by  the  men  in  charge  of  the  Bishop 
Rock  Lighthouse,  many  suggestions  have  been 
made,  amongst  others,  that  a  telegraphic  wire 
should  belaid  between  the  Bishop  Rock  Light- 
house and  the  land,  and  that  a  similar  arrange- 
ment should  be  made  in  the  case  of  all  other 
detached  lighthouses.  It  appears  to  us  that 
there  are  four  objections  to  this.  The  first  is, 
that  vessels  would  be  more  frequently  tempted 
to  approach  the  lighthouses  for  the  purpose  of 
reporting  themselves,  and  thus  actually  run 
into  proximity  to  danger.  The  second  is, 
that  a  telegraphic  cable  would,  in  such  a  posi- 
tion among  rocks  and  breakers,  be  speedily 
liable  to  damage  and  even  destruction,  and 
would,  at  the  best,  be  untrustworthy  ;  the 
third  is,  that  the  occasions  when  such  a  wire 
might  be  useful  would  be  so  extremely  rare 
(for  it  certainly  must  not  be  used  for  any  other 
purpose  than  as  a  distress  signal)  that  from 
disuse  the  keepers  would  have  difficulty  in 
remembering  how  to  work  it,  and  the  apparatus 
would  be  very  liable  to  get  out  of  order  ;  and 
the  fourth  is,  that  a  telegraph  wire  is  really 
unnecessary  for  the  purpose.      The  Marine 


BOOK    NOTICES. 


189 


Department  of  the  Board  of  Trade  have  had 
manufactured  for  them  by  the  War  Depart- 
ment a  new  sort  of  rocket,  which  the  depart- 
ment has  named  a  "  call"  rocket.  It  is  to  be 
used  only  when  a  ship  is  seen  to  be  in  distress, 
wanting  assistance  from  the  shore.  At  present 
the  "call"  rocket  has  been  supplied  to  light 
ships  only,  but  we  would  throw  it  out  as  a  sug- 
gestion whether  it  should  not  be  also  supplied 
to  outlying  lighthouses  like  the  Bishop  Rock. 
It  is  a  day  signal  as  well  as  a  night  signal,  and 
is  quite  distinctive.  No  one  can  possibly  mis- 
take it  for  any  other  rocket  or  signal.  It 
reaches  an  altitude  of  2,500  feet,  carries  up 
with  it  a  very  large  charge  of  powder,  which 
explodes  with  a  great  noise,  and  also  shows 
both  in  its  upward  and  downward  course  a 
very  powerful  magnesium  light. —  Nautical 
lazine. 


BOOK  NOTICES. 

The  Year  Book  of  Facts  in  Science  and 
Arts  for  1874.  Edited  by  C.  W.  Vin- 
cent, F.  C.  S.,  etc.  'London:  Ward,.  Lock,  & 
Tyler.  For  sale  by  Van  Nostrand.  Price,  $1.25. 
This  is  a  fresh  issue  in  a  new  cover  of  a 
very  old  and  well-known  annual.  Mr.  Timbs, 
its  originator,  has  unfortunately  departed,  but 
his  mantle  has  descended  upon  Mr.  Vincent, 
who  has  rehabilitated  and  thrown  fresh  vigor 
and  force  into  a  very  valuable  book.  There 
were  indications  in  the  recent  volume  that 
Mr.  Timbs'  sources  of  information  were  nar- 
row and  few,  but  Mr.  Vincent  has  gone  wider 
and  further  afield,  and  the  value  of  the  book 
is  enhanced  accordingly.  It  is  a  very  useful 
work  of  reference. — Telegraphic  Journal. 

Hand  Book  of  Land  and  Marine  Engines. 
By  Stephen  Roper,  Engineer.  Phila- 
delphia :  Claxton,  Remsen  &  Haffelfinger. 
Price,  $3.50. 

This  work  includes  the  moulding,  construc- 
tion, running  and  management  of  engines  and 
boilers.  It  is  a  compendium  in  convenient 
form  of  the  miscellaneous  information  re- 
quired by  the  engine  builder  or  engine  driver. 

Besides  descriptions  of  many  of  the  leading 
forms  of  engines,  there  are  minute  directions 
for  the  adjustments  of  those  parts  which  the 
young  engineer  needs  most  to  learn  at  once. 
There  is  no  attempt  to  be  philosophical  on  the 
part  of  the  author,  but  the  information  given 
is  straightforward  and  plain  talk  rather  brief. 

Practical  Hints  on  the  Selection  and 
Use  of  the  Microscope.  By  John  Phin, 
Editor  of  the  Technologist.  New  York :  In- 
dustrial Publishing  Co.  For  sale  by  Van  Nos- 
trand.     Price,  75  cts. 

The  use  of  the  Microscope  is  rapidly  extend- 
ing. Whether  used  for  popular  amusement  or 
popular  instruction  its  value  is  beyond  all  com- 
putation superior  to  that  of  the  telescope. 
Every  school  should  have  a  compound  micro- 
scope, and  every  pupil  old  enough  to  feel  in- 
terested in  natural  science  should  learn  to  use 
one. 

How  to  select  an  instrument,  and  how  to 
collect  and  observe  objects  is  exceedingly  well 
told  in  this  little  book.  We  recommed  it  to 
all  who  have  not  access  to  the  larger  manuals. 


Con- 

AR 


The  Young  Seaman's  Manual,  compiled 
from  various  authorities  for  the  use 
of  the  U.  S.  Training  Ships  and  the  Ma- 
rine Schools.  NewYork:  D.  Van  Nostrand. 
Priee,  $3.00 

The  title  of  this  book  explains  its  scope. 
The  minuteness  of  the  information  can  be 
judged  from  the  topics  treated  in  separate 
chapters  ;  they  are  as  follows,  viz  :  I.  The 
Compass  and  Lead  ;  II.  Knotting  and  Splic- 
ing ;  III.  The  Log;  IV  Rope;  V.  Blocks; 
VI.  Tackles  ;  VII.  The  Mast— The  Rudder  ; 
VIII.  Cutting  and  Fitting  Rigging  ;  IX.  Mast- 
ing; X.  Rigging  Ship;  XL  Sails;  XII.  Boats. 

The  book  is  eminently  fitted  for  the  purposes 
of  instruction.  The  typography  is  excellent, 
with  all  technical  terms  printed  in  heavier 
type  than  the  context,  and  the  whole  illus- 
trated by  350  good  cuts. 

The    Engineers,    Architects,    and   Co: 
tractors'  Pocket-Book  for  the  Ye^ 
1875.     London:  Lockwood  &  Co.    For  sale  by 
Van  Nostrand. 

This  has  been  long  known  as  "  Neale's  En- 
gineers' Pocket-Book,"  and  has  been  jointly 
prized  for  the  extent  and  accuracy  of  its  infor- 
mation. 

A  new  edition  appears  yearly,  but  the 
changes  in  the  more  valuable  portions  of  the 
volume  are  few  or  none.  The  calender  and 
lists  of  officers  of  scientific  societies,  of  course, 
are  changed  for  each  new  year. 

A  yearly  pocket-book  of  formulas  is  pre- 
sumably freer  from  typographical  errors  than 
other  similar  works  in  that  portion  of  the  book 
which  is  reprinted  year  by  year,  as  each  new 
edition  is  a  new  opportunity  for  correction. 
Such,  we  believe,  to  be  the  merit  of  this 
pocket-book. 

Prime  Cost  Keeping,  for  Engineers,  Iron- 
founders,  Boiler  and  Bridge  Makers, 
&c,  Practically  Explained,  with  the 
Method  of  arriving  at  all  the  General 
Averages  required.  By  John  Walker. 
Liverpool :    Dunsford  &  Son. 

Nothing  is  more  essential  to  the  prosperity 
of  an  engineering  establishment  than  the  em- 
ployment of  an  efficient  system  of  keeping  the 
prime  cost  accounts,  and  this  being  so  we  are 
glad  to  notice  the  publication  of  the  useful 
manual  now  before  us.  Mr.  Walker  ap- 
pears thoroughly  familiar  with  his  subject, 
and  he  treats  it  in  full  detail,  giving  sample 
pages  of  the  books  suitable  for  keeping  the 
accounts  of  the  different  departments  of  an 
engineering  works,  and  explaining  the  mode 
of  preparing  general  averages  and  ge:  ting  out 
the  total  costs  of  articles  involving  different 
classes  of  work.  Altogether  the  book  is  cal- 
culated to  be  very  useful  to  those  who  have 
not  an  efficient  system  of  prime  cost  keeping 
in  operation  at  their  establishments. — 
Engineering. 

Hints  to  Young  Architects.  By  George 
Wighwick,  Architect.  A  New  Edition, 
revised  and  considerably  enlarged,  by  G.Hus- 
kisson  Guillaume,  Architect,  London  : 
Lockwood  &  Co.  For  sale  by  Van  Nostrand. 
Price,  $1.40. 


190 


van  nostrand' s  engineering  magazine. 


An  examination  of  this  book  shows  that  it 
forms  a  material,  extension  of  the  work  upon 
which  it  is  founded.  Thus  Parts  IV.,  V.,  and 
VI.,  comprising  about  a  hundred  pages,  are 
entirely  new,  while  other  parts  of  the  book 
have  received  many  additions  and  revisions. 
The  three  first  parts  of  the  work  refer  respect- 
ively to  the  school  studies,  studies  abroad,  and 
early  practice  of  a  young  architect,  and  con- 
tain numerous  hints  and  suggestions  of  value. 
Then  come  the  three  new  parts  already  men- 
tioned— these  dealing  with  the  principles  of 
construction,  sanitary  construction,  and  de- 
sign— and  lastly,  we  have  a  model  specifica- 
tion, which  appears  to  have  been  well  revised 
in  accordance  with  modern  practice.  The  book 
is  one  well  calculated  to  be  of  service  to  the 
class  for  whom  it  has  been  written. — Engineer- 
ing. 

European  Light  House  Systems.  By  Maj. 
Jj  Geo.  H.  Elliot.  New  York :  D.  Van 
Nostrand.     Price,  $5.00.   ■ 

This  report  is  the  result  of  observations 
made  during  a  tour  of  inspection  in  1873  un- 
der the  direction  of  the  Light  House  Board. 
The  writer  seems  to  have  been  exceedingly 
well  qualified  both  for  the  inspection  and  for 
the  report  of  it,  and  the  result  is  a  work  inter- 
esting to  an  exceptional  degree. 

Fifty-one  engraving's  and  thirty-one  wood 
cuts  illustrate  the  work;  all  are  well  executed. 

In  summarizing  his  preliminary  report  which 
forms  a  preface  to  the  complete  work,  the 
author  says  ;  "  While  the  British  and  French 
systems  are  necessarily  very  much  like  our 
own,  I  saw  many  details  of  construction  and 
administration  which  we  can  adopt  to  advan- 
tage, while  there  are  many  in  which  we  excel. 
Our  shore  fog-signals,  particularly,  are  vastly 
superior  both  in  number  and  power.  They 
are  in  advance  of  us  in  using  both  the  gas  and 
electric  lights  in  positions  of  special  import- 
ance ;  in  the  use  of  horizontal  condensing 
prisms  for  certain  localities  ;  in  the  character 
of  their  lamps  ;  in  the  use  of  fog-signals  in 
light-ships  ;  in  their  light-ships  with  revolving 
lights,  and  more  than  all,  in  their  character  of 
their  keepers,  who  are  in  service  during  good 
behavior  until  death  or  superannuation,  who 
are  promoted  for  merit,  and  whose  lives  are  in- 
sured by  the  government  for  the  benefit  of 
their  families." 

The  report  has  already  been  widely  com- 
mended. 

hydrology  of  south  africa;  or,  details 
of  the  Former  Hydrographic  condition 
of  the  Cape  of  Good  Hope  and  of  Causes 
of  its  Present  Aridity.  By  John  Croum- 
bie  Brown,  LL.D.  Kirkaldy:  John  Crawford. 

This  work  offers  testimony  bearing  on  a 
question  of  great  interest,  viz.  —  possible 
changes  in  the  moisture  of  the  climate  of  a 
section  of  country  and  the  probable  causes  of 
the  change. 

The  work  is  divided  into  three  distinct 
parts,  which  are  not  divided  in  chapters  and 
sections.    The  "  parts  "  treat  respectively  of — 

I.  Former  Hydrographic  Condition  of  South 
Africa. 


II.  Cause  or  Occasion  of  the  Desiccation  of 
South  Africa. 

III.  Aridity  and  "Water  Supply  of  South 
Africa. 

In  conclusion  the  author  holds  that  corre- 
sponding accounts  might  be  given  of  the  hy- 
drology of  other  lands,  and  that  appropriate 
remedies  are  the  erection  of  dams  to  prevent 
the  escape  of  a  portion  of  the  rainfall  to  the 
sea;  the  restriction  of  the  burning  of  the  veldt; 
the  consummation  and  extension  of  existing 
forests;  and  the  adoption  of  measures  similar 
to  the  reboisement  and  gazonnement  carried  out 
in  France  with  a  view  to  prevent  the  formation 
of  torrents,  and  the  destruction  of  property 
occasioned  by  them. 

A  large  portion  of  the  work  is  compiled 
from  standard  writers  on  physical  geography. 

A  Treatise  on  Railway  Signals  and  Acci- 
dents .  By  Archibald  D.  Dawnay,  As- 
soc. Inst.  C.  E.  London:  E.  &  F.  N.  Spon. 
Price,  80  cts .    For  sale  by  Van  Nostrand. 

Mr.  Dawnay  has  chosen  for  this  treatise  a 
subject  on  which  little  has  been  written,  while 
that  little  is  to  be  found  chiefly  in  the  Trans- 
actions of  scientific  societies  which  are  not 
accessible  to  the  general  public.  The  popular 
description  of  railway  signaling  to  be  found 
in  the  volume  before  us  is,  therefore,  likely  to 
be  appreciated.  Commencing  with  an  account 
of  the  earlier  forms  of  signals  or  semaphores 
used  for  communicating  intelligence,  Mr. 
Dawnay  proceeds  to  describes  the  numerous 
varieties  of  signals  now  in  use  on  the  railways 
of  this  country,  his  explanations  being  illus- 
trated by  numerous  engravings.  The  second 
part  of  the  work  is  similarly  devoted  to  de- 
scriptions of  the  various  forms  of  locking 
gear  and  systems  of  electric  signaling,  while 
in  the  third  the  author  treats  of  railway  acci- 
dents due  to  defective  signaling,  his  record 
being  a  very  interesting  one. 

The  fourth  part  of  Mr.  Dawnay's  treatise 
deals  with  the  defects  of  signaling  arrange- 
ments as  frequently  carried  out,  and  contains 
suggestions  for  improvements.  These  latter  are 
of  a  practical  kind,  and  have  apparently  been 
well  considered.  The  author  is  evidently  well 
acquainted  with  his  subject,  and  he  enters  into 
its  details  carefully,  and  without  showing  any 
prejudice  in  favor  of  particular  schemes. 
With  his  remarks  on  the  habitually  loose 
working  of  the  block  system  on  many  lines 
we  thoroughly  agree,  and  we  have  on  numer- 
ous occasions  condemned  the  policywhich  ren- 
ders such  working  possible  and  even  neces- 
sary. Altogether  Mr.  Dawnay  has  produced 
a  very  interesting  and  useful  treatise,  which 
we  have  pleasure  in  recommending  to  all  in. 
terested  in  railway  signaling. — Engineering. 

A  Practical  Treatise  on  the  Science  of 
Steam.  By  N.  P.  Burgh.  Part  I.  Lon- 
don: N.  P.  Burgh.  For  sale  by  Van  Nostrand. 
Mr.  Burgh  is  adding  another  to  the  long  list 
of  his  "practical  treatises."  "We  have  now 
before  us  the  first  part,  containing  two  excel- 
lent plates — the  best  feature  all  our  author's 
works — and  eight  pages  of  letterpress.  "We 
regret  that  Mr.  Burgh  does  not  pay  a  little 
more  attention  to  correct  modes  of  expression, 


MISCELLANEOUS. 


m 


exactness  of  language  being  absolutely  essen- 
tial in  scientific  literature.  Old  and  hack- 
neyed theories,  however,  are  wholly  discarded, 
and  even  Galileo  and  Tyndall  are  left  behind 
by  our  author,  who  explains  latent  heat  thus : — 
"  Electricity  is  at  the  bottom  of  it  all,  but  to 
what  extent  and  how  that  property  is  upheld 
and  mantained  by  the  Great  Creator  is  beyond 
our  wisdom."  The  wonderful  effects  of  heat 
are  thus  described  : — "  Heat  also  is  a  most 
powerful  agent,  as  for  example,  it  will  reduce 
solids  to  ashes,  and  also  form  liquids,  and 
cause  the  latter  to  evaporate  as  a  vapor  with  a 
small  sediment  behind.  In  fact,  heat  is  the 
reverse  of  cold,  while  both  are  governed  by 
the  same  law."  Perhaps  the  most  remarkable 
statement  in  the  part  is  an  explanation  of  the 
generation  of  steam  in  iron  boilers.  In  some 
cases,  it  appears  ' '  tlw  flaine  passes  through  ilie 
•plate  in  a  filtered  form,  and  forms  steam  with 
the  water."  The  explanation  of  this  fact — 
which  our  author  does  well  to  express  in  italics 
— is,  that  "there  is  a  space  filled  with  vapor- 
ised water  between  the  top  surface  of  the 
plate  and  the  bottom  of  the  water.  The  flame 
then  ignites  this  vaporised  water,  and  it  be- 
coming lighter  than  the  volume  above,  ascends 
and  heats  the  surrounding  currents  it  passes 
through."  Mr.  Burgh  has  only  to  fully  cor- 
roborate this  to  establish  his  claim  to  be  con- 
sidered one  of  the  most  remarkable  discoverers 
of  our  century  ! — Iron. 


MISCELLANEOUS. 


Casting  Metals.  —  Messrs.  Farnsworth  & 
Sanson,  of  Mansfield,  has  patented  some 
improvements  in  apparatus  used  in  forming 
moulds  for  the  casting  of  metals.  According 
to  the  invention,  the  moulding  table  is  formed 
with  a  true  surface,  and  is  fitted  to  receive  the 
moulding  boxes  and  the  mould  plate.  The 
moulding  boxes  used  are  fitted  with  pins  on 
one  half  and  holes  in  the  other,  and  are  all  in 
duplicate.  The  patterns  are  secured  to  a  pat- 
tern plate,  and  are  capable  of  sliding  through 
the  mould  plate,  the  forms  of  the  one  being 
exactly  the  counterpart  of  the  other,  so  that 
the  sand  is  prevented  from  being  pulled  down 
in  the  withdrawal  of  the  pattern.  The  pattern 
plate  is  capable  of  being  slid  up  and  down  in 
the  framing,  and  is  operated  for  this  purpose 
by  a  pinion  acting  on  a  rack  to  the  table,  such 
pinion  being  actuated  by  ordinary  gear  and 
hand  wheel  or  other  means. 

Hand  Pumps.— Mr.  J.  Davison,  of  South 
Shields,  engineer,  has  patented  an  inven- 
tion which  relates  to  the  removal  of  dead  cen- 
tres in  crank  shafts,  and  is  effected  by  keying 
on  to  a  straight  longitudinal  shaft,  supported 
in  journals,  a  hollow  barrel  with  solid  ends. 
This  barrel  is  divided  diagonally  and  spirally 
into  two  portions,  and  so  set  apart  from  each, 
other  as  to  permit  a  pin  to  travel  to  and  fro  on 
the  shaft  and  between  and  along  the  divided 
edges  of  the  two  portions.  Connected  to  the 
external  end  of  the  pin  is  an  upright  arm  fixed 
to  the  cross-head  that  works  on  a  centre  below 
the  barrel.     When  the  pin  is  driven  to  and  fro 


along  the  shaft  by  the  revolution  of  the  barrel, 
the  pin  carries  with  it  the  upright  arm  of  the 
cross-head,  causing  the  sum  to  oscillate,  and  by 
that  means  giving  motion  to  the  pump  rods  at- 
tached to  the  two  horizontal  arms  of  the  cross- 
head. 

The  Revue  d'Ar  tiller  ie,  published  by  order 
of  the  Minister  of  War  in  France,  con- 
tains the  report  of  Major  Bobillier,  of  the 
artillery,  on  the  experiments  made  last  year  at 
Creusot  in  steel,  for  the  construction  of  can- 
non. The  object  of  M.  Schneider  was,  of 
course,  to  produce  a  metal  that  should  be  free 
from  the  faults  of  both  cast  iron  and  bronze, 
and,  according  to  the  report,  this  object  has 
been  obtained;  for,  in  the  words  of  a  commu- 
nication made  by  General  Morin  to  the  Paris 
Academy  of  Sciences,  on  the  last  day  of 
August — "  On  the  one  hand  accidents  like 
those  which  caused  the  Russian  Government 
to  reject  a  whole  material  of  artillery  from  the 
famous  establishment  of  Essen  are  not  to  be 
feared  with  the  soft  steel  tried  at  Creusot; 
and,  on  the  other,  the  three  pieces  of  78  m.  6 
m. — 31Q  in. — experimented  on,  supported  with- 
out reaching  the  limit  of  their  power  of  resist- 
ance, and  without  being  deformed,  nearly  as 
much  as  bronze  would  have  done  under  the 
same  circumstances,  the  most  severe  trials, 
and  to  which  guns  of  the  calibre  are  never 
submitted  in  ordinary  service."  The  experi- 
ments are  still  being  pursued,  but  General 
Morin  told  the  Academy  that  it  might  be 
safely  asserted  that  the  establishment  at  Creu- 
sot possessed  the  necessary  elements  for  the 
production  of  cannon  in  steel,  with  all  the 
qualities  demanded  for  artillery,  namely,  re- 
sistance against  fracture  and  deformation. 


T 


wo  very  curious  articles  have  been  published 


Bwei-Pao,  protesting  against  the  construction 
of  railroads  in  the  Chinese  Empire.  The 
Hicei-Pao  is  of  opinion  that  the  existence  of 
railroads  in  Europe  is  too  recent  to  admit  of  a 
judgment  being  formed  as  to  their  practical 
utility,  and,  moreover,  that  there  is  not  suffi- 
cient business  in  China  to  render  them  profit- 
able. The  Chinese  journal  goes  on  to  say  that 
"tea  and  silk  are  the  principal  objects  of 
commerce,  and  these  have  hitherto  been  for- 
warded to  the  treaty  ports  by  river  steamboats. 
A  substitution  of  railroads  for  steamboats 
would  not  effect  any  saving  in  point  of  time, 
and  could  not,  therefore,  even  from  the  point 
of  view  tgken  by  the  foreigners  themselves,  be 
of  any  service  to  China.  Admitting  that  a 
little  time  was  gained,  the  Chinese  would  not 
be  benefitted,  for  the  goods  would  not  be  ex- 
ported more  rapidly.  Thus  the  railroads  would 
only  lead  to  an  accumulation  in  the  ports  of 
vast  quantities  of  goods  which,  as  they  would 
not  be  shipped  off  all  at  once,  would  fall  con- 
siderably in  price."  The  Hicei-Pao  also  says  : 
"  The  accidents  on  the  railroad  lines  are  very 
numerous,  caused  by  collisions,  by  the  engines 
or  tenders  taking  fire,  by  the  trains  running 
off  the  lines,  or  by  bridges  giving  way  and 
the  trains  being  precipitated  into  the  rivers 
below.  In  other  cases  the  carriages  are  in- 
jured by  the  great  speed  at  which  they  are  car- 


192 


VAN   NOSTRAND's   ENGINEERING  MAGAZINE. 


ried  along,  and  the  accidents  are  so  numerous 
that  it  is  often  impossible  to  ascertain  the  ex- 
act number  of  dead  and  wounded.  All  the 
foreign  journals  are  full  of  details  concerning 
these  accidents.  But  admitting  that  most  of 
these  casualties  are  preventible,  and  that  the 
trains  follow  their  regular  course,  they  travel 
quicker  than  the  thoroughbred  horse,  and  the 
people  walking  on  the  lines  would  have  no 
time  to  get  off  their  way.  From  this  cause 
alone  the  number  of  fatal  accidents  would  be 
enormous.  In  all  countries  where  railroads 
exist  they  are  considered  a  very  dangerous 
mode  of  locomotion,  and  beyond  those  who 
have  very  urgent  business  to  transact,  no  one 
thinks  of  using  them." 

The  Horse-Power  op  the  World. — Dr. 
Engel,  director  of  the  Prussian  Statisti- 
cal Bureau,  has  been  making  estimates  on  such 
statistical  data  as  are  available  of  the  total 
horse-power  of  steam  engines  in  the  world,  as 
every  country  has  tolerably  correct  railroad 
statistics.  Dr.  Engel  thinks  that  the  following 
returns  with  reference  to  locomotives  are  not 
far  from  right : 

Year.        Number. 


United  States 1873 

Great  Britain 1872 

Zolverein . . . . ...1871 

Russia 1873 

Austria 1873 

Hungary 1869 

France 1869 

East  Indies 1872 

Italy 1872 

Holland 1872 

Belgium 1870 

Switzerland 1868 

Egypt 1870 

Sweden 1872 

Denmark  1865 

Norway 1871 


14,223 

10,933 

5,927 

2,684 

2,369 

506 

4,933 

1,323 

1,172 

331 

371 

225 

212 

185 

39 

34 


Total 45,467 

It  may  be  assumed  that  there  are  still  four  or 
five  thousand  additional  locomotives  in  coun- 
tries from  which  no  statistics  have  been  re- 
ceived, so  that  something  like  fifty  thousand 
engines  of  that  description,  of  an  aggregate  of 
10,000,000-horse  power,  all  now  in  use.  Dr. 
Engel  estimates  all  the  engines  in  use,  locomo- 
tive, marine  and  stationary,  at  about  14,400,000- 
horse  power. 

Rotary  Puddling  Furnaces.  -Messrs .  Jones, 
of  Middlesborough,  have  patented  some 
improvements  in  rotary  puddling  furnaces. 
The  invention  consists — 1.  In  admitting  water 
intermittently  to  the  space  between  the  casings 
of  the  furnace  (when  the  furnace  is  composed 
of  2  casings)  by  various  modes  or  contrivances, 
one  mode  being  by  means  of  valves  or  cocks; 
another  method  is  by  means  of  scoops  or  bent 
pipes,  or  in  some  cases  by  a  coil  of  pipes  or 
annular  space  or  duct  formed  round  outside 
of  the  revolving  furnace;  and  another  plan  by 
means  of  buckets  arranged  at  intervals  around 
and  attached  to  the  outside  of  the  outer  cas- 
ing.— 2.  In  effecting  the  egress  of  the  water 
from  the  water  space  of  the  rotary  furnace  by 


means  of  pipes,  channels,  or  ducts,  one  or 
more  of  which  are  coiled  round  the  outside  of 
the  outer  casing,  and  communicate  at  one  end 
with  the  water  space. — 3.  In  forming  the  rings 
which  are  secured  round  the  ends  of  the  fur- 
nace (and  which  are  divided  into  two  or  more 
segments)  with  recesses  on  their  outer  faces 
respectively,  which  recesses  fit  over  corre- 
sponding projections  on  the  outer  faces  of  the 
rings  against  which  the  furnace  rings  revolve, 
and  serve  to  maintain  a  tight  joint  and  to  pre- 
vent the  waste  of  cinder  and  iron  thereat;  also 
in  connecting  the  water-pipes  (which  are  cast 
in  the  bodies  of  the  rings)  at  their  external 
ends  outside  the  furnace  with  the  water  space 
between  the  casings  by  means  of  branch  pipes 
or  connecting  pipes. — 4.  In  constructing  the 
cast  iron  or  steel  end  of  a  single-cased  rotary 
furnace  in  two  or  more  pieces  or  segments 
which  are  respectively  attached  to  the  circular 
flanged  end  of  the  furnace  by  bolts,  and  to 
each  other  by  internal  or  external  flanges  and 
bolts. 

Dimensions  of  the  Earth. — Two  German 
scientific  men,  Messrs.  Behum  and  Wag- 
ner, have  recently  published  the  results  of 
some  very  accurate  measurements  that  they 
have  made  respecting  the  dimensions  of  the 
earth.  From  these  it  appears  that  the  length 
of  the  polar  axis  is  12,712,136  metres,  that  of 
the  minimum  equatorial  diameter,  which  is 
situated  103  deg.  14  min.  east  of  the  meridian 
of  Paris,  or  76  deg.  46  min.  west,  is  12,752,701 
metres,  whilst  the  maximum  diameter  at  13 
deg.  14  min.  east,  and  166  deg.  46  min.  west, 
is  12,756,588  metres.  They  estimate  the  total 
surface  of  the  globe  at  509,940,000  square  kilo- 
metres, whilst  its  volume  is  equal  to  1,082,860,- 
000,000  cubic  kilometres.  The  circumference 
of  the  globe  on  its  shortest  meridian  is  40,000,- 
098  metres.whilst  that  of  the  longest  is  40,069,- 
903  metres.  The  oceans  and  glaciers  occupy 
375,127,950  square  kilometres.  The  total  num- 
ber of  inhabitants  of  the  earth  is  estimated  at 
1,391,000,000— viz.,  300,530,000  in  Europe,  798,- 
000,000  in  Asia,  203,300,009  in  Africa,  whilst 
the  population  of  America  is  84,542,000  and 
that  of  Oceana  4,438,000.  The  population  of 
the  towns  and  cities  exceeding  50,000  inhab- 
itants is  69,378,500,  or  about  one-twentieth 
part  of  the  total  population  of  the  globe,  leav- 
ing nineteen-twentieths  of  the  inhabitants  for 
the  villages  and  smaller  towns. 

The  change  of  proprietorship  of  the  Evening 
Star  and  the  issue  of  the  paper  from  the 
office  of  the  Glasgow  JSews  were  announced  by 
1,025,000  little  hand-bills,  which  were  printed 
in  the  incredibly  small  space  of  half  an  hour. 
Such  a  feat  of  rapid  printing,  we  believe,  has 
never  before  been  performed,  and  it  would 
have  been  impossible  to  perform  it  but  for  the 
Walter  Press.  The  process  was  interesting. 
The  small  hand  bill,  measuring  three  inches  by 
two,  was  reproduced  by  stereotyping  to  the 
extent  of  336  times,  and  by  4,000  revolutions 
of  the  Walter  Press  the  million  bills  were 
printed.  It  occupied  ten  hours  to  cut  them  up 
with  a  steam  guillotine  machine,  and  they  were 
distributed  throughout  the  town  from  the  win- 
dows of  two  carriages. 


VAN     NOSTRAND'S 


ECLECTIC 


ENGINEERING    MAGAZINE. 


NO.  LXXXI -SEPTEMBER,  1875.-V0L.  XIII. 


ELEMENTARY    DISCUSSION    OF    STRENGTH    OF    BEAMS 
UNDER    TRANSVERSE    LOADS. 

By  Prof.  W.  ALLAN. 
Written  for  Van  Nostband's  Engineering  Magazine. 

II. 

Case  IV. 


Let  the   load  be   equally  distributed 
over  the  beam  (Fig.  32).    In  this  case  the 


reaction  of  each  abutment =£  the  load,  or 

(36) 


R,=T=R> 


Take  any  section  E  F  whose  distance 
from  A=x.  Then  the  external  forces 
acting  between  A  and  E  F  are,  R:  and 


the  resultant  of  all  the  little  weights 
from  A  to  E  (=wx).  This  last  force 
acts  at  its  centre  of  gravity  (Fig.  33), 


A* 


!£ 


I 

i 

Fig.  33. 


Vol.  XIII.— No.  3—13 


194 


VAN"   NOSTKAND'S   ENGIlNrEETCING   MAGAZINE. 


whicl^  is  half    way   from  A   to  E.     Its  !  The  shearing  force  at  E  F  is 

x 
level-  arm  is  therefore  =  -.      Hence  the 


equation  of  moments  will  be 

wl  wx*     1 •'    ,  ■  _     , . 

— .  x =  -  Sod  =M 

2  2       6 


or 


xox 


(37) 


(l-x) 


SbcP=M 


2      N         '         6 
This  is  a  maximum  at  the  centre  where 
M=i.wP  (38) 


T= wx 

o 


(39) 


This  is  greatest  at  the  abutments  where 
x=l,  or  0 

.■•T.=i?  (40) 

At  the  centre         T=0 

Geometrically.     The  values  of   M   in 
eq.  (3*7)  may  be  represented  by  a  para- 


bola with  vertex  at  L,  the  ordinates  G  L  I  ing  force  is  represented  by  the  two  tri- 
(Fig.  34)  being  taken  =M0.     The  shear- 1  angles  AP  G  and  G  Q  C  (Fig.  35). 


Fig.  35. 


The  maximum  moment  exists  at  the 
point  (G)  when  the  shearing  force  is 
zero. 


O)  q  o>    @   a 


Corollary.  When  the  uniform  load 
extends  only  over  a  certain  distance 
from  one  of  the  supports,  as  in  (Fig.  36) 


I 


Fig.  36. 


letAD=loaded  segment=?w.     The  re- 
actions of  the  abutments  are: 


At  A,  R=wm( — j—  1 

At  C,  ^=wmy~f 


(41) 


Then  for  any  section  in  A  D  the  mo- 
ments of  the  external  forces  will  be  as 
in  the  case  just  discussed, 


(^-m) 


W  X 


And  the  equation  of  moments  in  A  D 
will  be : 


m 


x_w^=}_Sbd,=.M  (42) 


For  any  section  in  D  C  the  whole  load 
(torn)    is   to   be    considered    as    acting 


STRENGTH   OF   BEAMS   UNDER   TRANSVERSE   LOADS. 


J  95 


through  its  centre  of  gravity  (G),  and 
the  equation  of  moments  is  : 


Wm\-J-) 

Reducing 


x — vmi  (x — fyn)  =  -  S  bcV = M 
6 


!^(/_a;)=Is5^=M 
The  shearing  force  in  A  D  is 


(«) 


(44) 


1  z=W  Til.  1   -j I  —W 

In  DC,  T=:wOT.(^)-w; 
T  is  a  maximum  at  A,  or 


Geometrically.     Eq.   (42)  corresponds 
to  the  parabola  ALK  (Fig.  37),  which 


cuts  AC  at  A  and  K  (whose  distance 
from  A=  —  (I—  %m) )  and  whose  axis  is 

v 

vertical.  Eq.  (43)  corresponds  to  the 
straight  line  H  C.  We  only  use  the  part 
ALH  of  the  parabola,  the  moments  in 
D  C  being  represented  by  the  triangle 
DHC.  The  maximum  moment  is  at  N 
corresponding  to  the  vertex  L  of  the 
parabola.     The  value  of  this  moment  is : 

M_w(^i»y       (45) 


which  is  obtained  from  eq.  (42)  by  sub- 
stituting for  x  the  value  AN  (=•£  A K)  — 

7)1 

-j-{l—%  m).    This  M0  is  always  less  than 

the  maximum  moment  that  exists  when 
the  load  extends  all  over  the  beam  as 
will  appear  by  making  m  to  vary  in  eq. 
(45)  and  applying  the  tests  for  a  maxi- 
mum to  it. 

The  shearing  stress  for  the  loaded 
segment  is  represented  by  the  triangles 
APK  andKP'D  (Fig.  38),  and  fo/the 


Fig.  38. 


other  segment  by  the  rectangle  D II. 
The  point  K,  where  the  stress  is  zero,  is 
found  by  making  in  eq.  (44) 

m  il—h  m\ 

and  finding  the  value  of  x. 


This  point  corresponds  to  the  maximum 
moment.  It  may  also  be  found  graph- 
ically by  constructing  Fig.  38,  and,  as 
before,  affords  the  easiest  method  of  de- 
termining the  point  of  the  beam  where 
the  maximum  moment  exists  and  where 
consequently  there  is  greatest  danger  of 
rupture. 


196 


VAN  nostrand's  engineering  magazine. 


EXAMPLES. 

1.  Let  1=20  ft.   ?c=500  lbs.    per   ft. 
m=15  ft.  and  let  there  be  a  weight  in 

A 


r__ 


Fig.  39. 

addition.  W  =  5  tons  at  a  point  18  ft. 
distant  from  A.  Required  the  maxi- 
mum moment. 


loaded  with  a  uniform  load,  io=l  ton 


Fig.  40. 


per  foot,  and  the  other  half  with  a  uni- 
form load  of  «/=£  ton  per  foot.  Re- 
quired the  moments. 

Case  V. 
A  single  moving  load.    When  a  single 
moving  load  passes  over  a  beam,  as  in 
2.  Let  one-half  of  the  above  beam  be|  (Fig.  41),  the  maximum  moment  at  each 


Fig.  41. 


instant  (as  appears  from  Case  III.) 
takes  effect  at  the  section  just  under  the 
weight.  To  determine  the  law  of  vari- 
ation of  these  maxima  as  the  weight 
travels  over  the  beam:  Let  cc=the  dis- 
tance at  any  instant  from  A,  and  then 
the  reaction  of  A  at  that  instant  (=the 

part  of  W  transmitted  to  it)=W  — y^ 

v 

Multiplying  this  by  the  lever  arm  x  we 
have  for  the  moment  under  the  weight: 


W  r  1 


:M 


(46) 


This  is  a  maximum  at  the  centre,  where 

M=iWl  (47) 

Eq.  (46)  corresponds  to  a  parabola 
(Fig.  41)  with  vertex  at  L,  the  ordinate 
G  L  being=^  W  I.  The  shearing  force 
for  each  segment  into  which  W  (Fig. 
42)  at  any  instant  divides  the  beam  is 
equal  to  the  reaction  of  the  abutment 
corresponding  to  that  segment.     Thus, 


if  W  is  at  a  distance  x  from  A  the  re- 

l— x 
action  of  A  is— W— - —  and  of  C  it  is= 


I 


W 


If  W  has  the  position  marked  2  in 
(Fig.  42),  then  the  shearing  stress  in  the 
left  segment  is  shown  by  the  rectangle 
ANN'W  and  in  the  right  segment  by 
the  rectangle  W  N"  1ST'  C.  The  dia- 
gram shows  in  a  similar  way  the  stress 
at  other  points.  If  the  third  position  of 
W  in  the  figure  is  at  the  centre  of  the 
beam  then  evidently  the  greatest  shear- 
ing stress  to  be  provided  for  in  the  left 
half  of  the  beam  will  be  represented  by 
the  locus  of  the  points  like  L,  N',  P',  and 
for  the  right  half  it  will  be  the  locus  of 
the  points  P",  Q",  L',  etc. 

These  loci  are  given  by  the  equations: 

T=^  (l-x)=eq.  of  LC 

W  i 

T=—  x         =eq.  ofAL' 


STRENGTH   OF   BEAMS   UNDER   TRANSVERSE   LOADS. 


197 


Fig.  42. 


Turn  the  triangle  AL'C  down  for  con- 
venience, as  in  (Fig.  43),  and  then  the 
shearing  stress   to  be   provided   for    is 


given  by  the  figure  ALPL'C.     In  this 

W 
figure  A  L=C  L'= W  and  D  P=  — . 

6  2 


Fig.  43. 


Case  VI. 
A  distributed  moving  load.     When  a 
moving  load  gradually  covers  a  beam, 


(Fig.  44),  moving  on  from  one  end  as  a 
long  train  of  cars,  the  maximum  mo- 
ments produced  is  that  due  to  the*  load 


1 


I 
I 


Fig.  44. 


when  it  covers  the  entire  length  of  the 
beam,  and  consequently  this  case  is  pro- 
vided for  in  Case  IV. 

But  with  the  shearing  stress  it  is  dif- 
ferent. Here,  as  in  Case  V,  we  need 
the  locus  of  the  greatest  shearing  stresses 
that  can  be  brought  upon  the  beam. 
This  maximum  at  any  section  D  occurs 
when  the  longer  segment  into  which  D 
divides   the    beam   is   loaded,   and  the 


other  is  not.  In  that  case  the  shearing 
force  at  D  (=the  reaction  of  the  abut- 
ment C)  is 

T==£  m 

This     equation     gives    the     parabola 
ANP'  (Fig.  45)  with  vertex  at  A,  where 

CP'  =  — .     When  the  load  comes  from 
2 


198 


VAN  nostkand's  engineering  magazine. 


Fig.  45. 


the  other  end  of  the  beam  we  get  the 
parabola  C  N  P.  Hence  the  figure 
APNP'C  gives  the  maximum  shearing 
stress  to  be  provided  for. 

It  is  easy  to  see  that  the  shearing 
stresses  thus  obtained  are  greater  than 
those  which  exist  when  the  load  covers 
the  entire  beam.  In  the  latter  case  the 
forces  are  represented  by  the  triangles 
APG  and  GP'C  (Fig.  45), the  shearing 
stress  at  D  being  given  by  eq.  (39) 

T=wx-— =DH 

2 

In  the  case  of  the  passing  load  we  have 
just  seen  that 

wx? 


T: 


21 


=DK 


The  value  of  D II  is  always  less  than  that 

of  DK  when  x> - ;  for  if  2x  be  a  cer- 

tain  quantity,  then  the  product  of 
the  halves  of  that  quantity  (=^2)  is 
greater  than  the  product  of  any  other 
two  parts  (such  as  I  and  [2x—t]  )  into 
which  it  can  be  separated. 

That  is 


x°>l(2x-l) 
wx3     wl  (2x  —  l) 


or 


>?0  x- 


21 
wl 


(50) 


J 


In  the  expressions  for  the  moment  of 
resistance  M=-  S  b  d3  the  quantity  de- 
noted by  S  (=  the  stress  on  the  outside 
fibres)  varies  directly  as  M.  Hence,  all 
the  geometrical  illustrations  we  have 
given  of  the  moments  may  apply  equally 
well  to  the  values  of  S.  The  maximum 
moments  give  the  maximum  stress  on 
the  fibres,  and  indicate  the  points  of  rup- 
ture when  the  beam  is  loaded  with  its 
breaking  weight. 


ULTIMATE    VALUES    OF    S. 


If  beams  are  loaded  transversely 
until  fracture  takes  place,  the  value 
of  S  or  the  stress  on  the  outside  fibre 
which  exists  at  the  moment  of  frac- 
ture, gives  us  a  value  for  the  tensile  or 
compressive  strength  of  the  material  ac- 
cording to  the  manner  of  rupture.  If 
the  beam  yields  by  tearing,  S  gives  us 
the  tensile  strength,  if  by  crushing  S 
gives  the  compressive  strength.  We 
readily  obtain  the  value  of  S  answering 
to  the  ultimate  strength  from  any  of  the 
formulas  under  "Transverse  Stress,"  by 
substituting  given  values  for  I,  b,  and  d 
and  the  actual  breaking  weight  for  W. 

But  the  tensile  and  compressive 
strengths  of  materials  are  also  obtained 
by  direct  tension  and  compression,  the 
force  being  applied  in  the  direction  of 
the  length  of  the  bars  until  rupture  takes 
place. 

If  our  theory  were  perfect  the  values 
of  tensile  and  compressive  strength  thus 
deduced  would  agree  with  the  ultimate 
values  of  S  found  in  transverse  stress  ; 
but  they  do  not. 

The  difference  is  very  wide  sometimes. 
Thus  in  cast-iron,  S  (in  this  case  it  repre- 
sents the  tensile  strength)  derived  from 
breaking  rectangular  beams  by  a  trans- 
verse load  is  nearly  20  tons  per  square 
inch,  while  the  tensile  strength  obtained 
directly  is  only  about  8  tons.  This  dis- 
crepancy has  been  accounted  for  in  two 
ways. 

1.  That  the  neutral  axis  moves  towards 
the  compressed  side,  and  that  therefore 
a  larger  portion  of  the  beam  is  subject- 
ed to  tension  than  the  formula  supposes. 

2.  That  the  neutral  axis  always  remain- 
ing at  the  centre  of  gravity  of  the  beam, 
the  additional  strength  is  due  to  the 
adhesion  of  the  fibres  which  is  developed 
by  the  unequal  lengthening,  and  short- 
ening of  them  as  we  go  from  the  neutral 


STRENGTH   OF   BEAMS    UNDER   TRANSVERSE   LOADS. 


199 


axis  towards  the  surfaces.  In  favor  of 
this  view  is  the  fact  that  we  know  such 
adhesion  to  be  an  element  of  strength; 
for  the  compression  or  extension  due  to 
a  given  force  is  not  so  great  in  a  trans- 
versely loaded  beam  as  in  one  directly 
compressed  or  extended. 

The  action  of  this  adhesive  force  may 
be  illustrated  as  follows  : 


•w 


Qa  w 


Fig.  46. 


In  the  beam  AB  (Fig.  46),  strained  by 
the  weight  W,  all  the  fibres  are  equally 
elongated,  and  they  only  resist  by  their 
direct  tenacity.  But  in  the  beam  A'  C 
to  the  one-half  of  which  is  appended  the 
weight,  while  the  other  half,  E  C,  is  less 
strained  or  altogether  prevented  from 
extending,  evidently  W  will  have  to 
overcome  not  merely  the  tenacity  of  the 
fibres  in  A'  B'  but  the  adhesive  force  of 
the  fibres  along  the  plane  E  F,  where  the 
two  parts  of  the  beam  join  ;  for  this 
force  will  tend  to  prevent  the  stretching 
of  the  fibres  in  A'  B',  and  consequently 
increases  the  strength  of  A'B'.  This 
kind  of  force  exists  between  every  two 
layers  of  horizontal  fibres  in  a  beam 
under  transverse  loading,  and  is  called 
the  longitudinal  shearing  stress.  It  is 
neglected  in  the  formulae  we  have  given. 

From  the  variation  between  the  ulti- 
mate valves  of  S  (called  moduli  of  rup- 
ture) and  the  values  for  strength  obtain- 
ed by  direct  tension  and  compression,  it 
results  that  the  values  should  be  deter- 
mined in  be  th  ways,  and  that  the  values 
gotten  by  one  method  should  not  be  used 
in  calculations  involving  the  other  kind 
of  stress. 


BEAMS    OF   UNIFORM    STRENGTH. 

As  already  stated,  in  solid  rectangular 
beams,  S  has  different  values  for  the  va- 
rious points  in  the  length  of  the  beam. 
There  is  always  a  point  of  maximum 
stress  where  the  beam,  if  loaded  suffi- 
ciently, will  break.  Now  at  all  other 
points  there  is  an  excess  of  material 
which  is  useless  and  injurious  from  its 
own  weight.  To  secure  the  requisite 
strength  with  the  least  material  is  an  ob- 
ject usually  desirable,  and  this  can  be 
readily  accomplished  in  certain  materials 
(as  cast-iron),  by  giving  the  beam  such  a 
shape  as  will  make  S,  the  stress  on  the 
outside  fibre,  constant  throughout  its 
length.  In  wood  the  injury  resulting 
from  the  cross  cutting  of  the  fibres  fre- 
quently prevents  the  putting  of  the 
theory  into  practice. 

The  application  of  the  theory  of  uni- 
form strength  to  beams  of  rectangular 
cross  section  may  be  most  simply  explain- 
ed by  taking  up  the  cases  we  have  dis- 
cussed in  detail. 

In  Case  I.  from  eq.  (5)  the  maximum 
stress  in  the  outside  fibre  is, 


S= 


6WI 


bd* 


(51) 


This  stress  only  occurs  at  A,  where  the 
beam  will  ultimately  break,  and  it  is 
evidently  possible  to  take  away  some 
of  the  material  between  that  point  and 


Fig.  47. 

C  without  diminishing  the  strength.  If 
this  be  so  done  that  at  every  point  be- 
tween A  and  C  there  shall  exist  on  the 
outside  fibre  a  stress  equal  to  that  at  A, 
the  beam  will  be  one  of  uniform  strength, 
and  we  shall  have  attained  the  greatest 
economy  of  material.  Let  us  suppose, 
the  use  we  have  for  the  beam  requires 
the  depth  to  be  uniform.  What  must  be 
its  plan  in  order  that  S  shall  be  constant 
in  value,  or  the  beam  be  as  liable  to 
break  at  any  other  point  as  at  A6. 


200 


VAN   NOSTRAND'S   ENGINEERING   MAGAZINE. 


In  eq.  (4)  S: 


6  Wx 


if  we  assume  S  to 


be  constant,  the  other  side  of  the  equa- 
tion must  be  constant  also,  and  since 
6  W  is  constant,  and  we  have  made  d 
constant  by  assuming   the  depth  to  be 


uniform,  the  whole   expression    can    be 
constant  only  when  b  varies  as  x. 

bzox  whence  b=cx  (where 
c=some  constant  factor).  This  equation 
which  is  that  of  a  straight  line  shows 
that  the  breadth  must  vary  directly  as 


Fig.  48. 


the  length.     Hence  the  plan  should  be  a 
triangle  with  vertex  at  C  (Fig.  48.) 

On  the  other  hand,  if  we  suppose  the 
breadth  to  be  uniform  and  wish  to  have 

S  constant,  in  the  eq.  S=-  -,   „  ,  x  must 


vary  as  d',  or 


bd* 


di=cx 


This  corresponds  to  a  parabola,  and 
the  beam,  if  the  top  be  straight  will 
have  the  elevation  shown  in  (Fig.  49). 

Suppose  that  b  varies  as  d,  then  d=nb 
(n  being  a  constant)  and 


S= 


6W* 


?i*b* 


Fig.  49. 


To  render  S  constant  we  must  have, 
b*  y>x    .*.  b'=cx    and     d*=nicx. 

These  are  the  equations  of  a  cubic  para- 
bola.    Hence  the  horizontal  section  (Fig. 


Fig.  50. 

50),  and  the  vertical   section  (Fig.   51), 
should   be  curves   of   that  kind.      The 


A 

L  „ 

ElMfatiofV  ^v 

v 

Fig.  51. 

cross  section  is  rectangular  as  in  (Fig. 
52). 
In  Case  II.  we  have 


S= 


3W*' 


bd* 


(55) 


STRENGTH   OF   BEAMS   UNDER  TRANSVERSE   LOADS. 


201 


Hence,  if  we  make  suppositions  simi- 
lar to  those  above  we  shall  have,  when 
the  depth  is  uniform  (or  d=  a  constant) 
x2  varying  as  b,  or 

b=cx> 
Hence  the  plan  (Fig.  53)  should  con- 


Fig.  53. 


sist  of  parabolas  with  vertices  at  C.     If 
b  be  constant  then 

d1 = c  x*     or     d—  /\/e~x 
This  is  the  equation  of  a  straight  line, 
and  gives  for  the  elevation  the  triangle 
(Fig.  54). 


Fig.  54. 

In  Case  III.  the  analysis  gives  results 

similar  to  those  in  Case  I. 

6  W  n 
Thus   from   equation   (21)    S  =  — - — . 

x        TT        6Ww.  _  {,    , 

^—z..     Here  — = —  is  constant,  and  if  d 
bd  I 

be  constant  also,  b  must  vary  as  x. 

.'.     b=cx. 

This  gives  the  triangle  AGH  (Fig. 
55).  We  obtain  similarly  the  triangle 
G  C  H  for  the  other  end  of  the  beam. 


Fig.  55. 


If  the  breadth  be  constant  we  have, 

d*=cx 

which  gives  a  parabola  AK  (Fig.  56)  with 


vertex  at  A.  So,  for  the  right  hand  end 
of  the  beam  the  proper  elevation  is  the 
parabola  CK(Fig.  56).  The  elevation 
(Fig.  56)  assumes  that  the  top  of  the 
beam  needs  to  be  horizontal. 


Fig.  56. 


202 


VAN  nostrand's  engineering  magazine. 


In     Case    IV.,    equation     (37)    gives 

0      3  w  x  il—x)       u         . ,   ,  , 

»= =-^z :     Here,  if  a  be  constant 

bd 

in  order  to  render  S  constant  we  have 
b=cx  {l—x). 


This  may  be  represented  by  parabolas 
with  vertices  at  G  and  H  (Fig.  5*7)  op- 
posite the  middle  of  the  beam.  If  b  is 
constant,  then, 

d*=cx  U—x) 


which  is  the  equation  of  an  ellipse,  and 
the  beam  (if  it  is  required  to  be  hori- 
zontal on  top)  may  be  made  as  in  (Fig. 
58). 


In  these  cases  of  beams  of  uniform 
strength,  we  have  so  far  only  considered 
the  moments  of  the  weights  or  the  bend- 
ing moments  as  they  are  called.     But  the 


Fig.  58. 


results  are  to  be  modified  by  the  trans- 
verse shearing  stress.  In  ordinary  rec- 
tangular beams  this  shearing  stress  is  so 
small  compared  with  the  bending  mo- 
ment, that  it  may  be  left  out  of  consid- 
eration.      But    in    beams    of     uniform 


strength  the  ends  must  not  taper  to  a 
point,  but  must  always  be  left  large 
enough  to  bear  the  shearing  stress.  In 
the  case  represented  in  (Fig.  57)  the  beam 
should  have,  near  the  ends,  the  shape 
shown  in  (Fig.  59). 


Fig.  59. 


USE    OF   COIGNET   BETON    "  EN    MASSE. 


203 


ON  THE  USE  OF  COIGNET  BETON  "EN  MASSE." 


Condensed  from  Chief  Engineer  CHAS.  K.  GRAHAM'S  Report  to  the  "  Department  of  Docks." 


The  Canal  Street  section  was  com- 
menced on  the  4th  of  May,  1874,  by 
driving  piles  for  new  Pier  <34,  the  present 
Pacific  Mail  Steamship  pier.  It  springs 
from  the  bulkhead  wall,  almost  in  a 
direct  westerly  line  from  the  small  pier 
formerly  known  as  42^. 

The  bulkhead  wall  on  this  section,  110 
feet  of  which  has  been  finished,  founda- 
tion tip  to  stone  facing  for  a  distance  of 
80  feet  built,  and  pile  work  for  60  feet 
more  ready  for  concreting,  is  a  subject 
on  which  I  will  have  to  dwell  at  some 
length,  as  the  method  of  constructing  it 
differs  materially  from  that  used  at  the 
Battery  and  Christopher  Street  sections. 
At  the  latter  works  the  system  was — to 
drive  piles,  cut  them  off  at  a  fixed  dis- 
tance from  mean  low  water,  and  upon 
them  to  place  prepared  beton  blocks  by 
means  of  100-ton  derrick  and  divers. 

On  this  section,  as  well  as  the  King 
Street  section,  the  piles  are  punched 
down,  and  loose  concrete  laid  en  masse 
in  a  false  work  of  timber,  which  is  sub- 
sequently removed. 

That  eminent  authority,  Mr.  Thomas 
Stevenson,  in  his  work  on  the  "  Design 
and  Construction  of  Harbors,"  at  page 
201,  says:  "Sir  John  Hawkshaw  has 
passed  concrete  through  50  feet  of  water 
with  perfect  success.  As  far  as  his  ex- 
perience went,  the  concrete  set  quite  as 
well  under  these  circumstances,  as  when 
it  was  deposited  in  the  open  air.  He 
has  done  this  both  in  salt  and  fresh 
water.  In  passing  concrete  through 
water,  he  used  a  box  containing  almost 
2  cubic  yards;  when  it  reached  bottom, 
a  bolt  was  withdrawn,  and  the  concrete 
dropped  out." 

The  same  authority,  on  page  202  of 
the  same  work,  also  says :  "  Mr.  W. 
Parkes  put  in  the  foundation  of  the  iron 
light-house  in  the  Red  Sea  by  means  of 
a  caisson  into  which  the  fluid  concrete 
in  bags  was  deposited."  He  thus  de- 
scribes the  method  of  construction: 
"During  this  time  some  progress  was 
made  at  the  light-house  works.  The 
caisson  of  iron-plates  to  enclose  the  con- 
crete base  had  been  deposited  upon  the 


reef,  where  it  was  exposed  to  a  wash 
sufficient  to  remove  some  of  its  clayey 
particles,  without  carrying  it  out  of 
reach.  As  soon  as  a  sufficient  quantity 
of  gravel  was  accumulated,  the  process 
of  depositing  the  concrete  was  com- 
menced. As  circumstances  did  not  admit 
of  the  usual  plan  of  depositing  the  con- 
crete in  the  water  in  large  masses  from 
boxes,  the  following  plan  was  substi- 
tuted :  Sheets  of  tarred  canvas  were 
prepared  of  such  sizes  as  would  fill  up 
the  spaces  between  the  piles,  and  allow 
2  feet  round  each  side,  to  be  turned  up, 
so  as  to  form  large  shallow  bags.  The 
edges  of  the  tarpaulin  were  then  lashed 
to  the  wooden  rods,  which  were  slung 
to  the  piles,  so  as  to  allow  the  tarpaulin 
bag  to  float  slackly  on  the  surface  of  the 
water.  Two  or  three  hours  below  low 
water  the  work  was  commenced.  The 
concrete  was  mixed  in  the  lighters 
moored  alongside  the  caisson — 6  meas- 
ures of  gravel  being  used  with  one 
measure  of  cement,  and  a  suitable  quan- 
tity of  water.  The  materials  were 
thrown  into  the  centre  of  the  canvas 
bag, which  gradually  sunk  to  the  bottom 
(generally  from  1  to  2  feet  under  water), 
and  the  bag  was  spread  out  evenly  over 
the  whole  area  as  it  became  filled.  This 
was  continued  until  the  tide  rose  nearly 
to  the  level  of  the  top  of  the  deposited 
concrete,  when  the  sides  of  the  tarpaulin 
were  drawn  close  over  the  soft  mass, 
and  lashed  tight.  In  this  way  blocks  of 
from  6  to  14  tons  were  deposited  with- 
out the  material  having  been  subjected, 
in  small  quantities,  to  the  action  of  the 
water.  The  blocks  were  generally  hard 
enough  on  the  following  day  to  allow  of 
the  exposed  parts  of  the  tarpaulin  being 
cut  away;  and  so  complete  was  the  set. 
that  casts  of  the  cords  and  the  edges  of 
the  tarpaulin  were  often  sharply  im- 
pressed upon  the  face  of  the  concrete." 

At  the  Canal  Street  section,  the  joints 
of  the  caisson  were  so  close,  as  to  admit 
of  scarcely  any  wash,  and  being  in  a  slip 
with  block  and  bridge  piers  on  either 
side,  the  current  was  scarcely  percepti- 
ble, consequently  when  the  concrete  was 


204 


VAN   NOSTRAND  S    ENGINEERING    MAGAZINE. 


deposited,  little  more  "laitance"  or  milk- 
iness  was  visible  than  would  have  been 
occasioned  if  fresh  made  beton  blocks 
prepared  on  land  had  been  immersed  in 
water.  That  eminent  marine  engineer, 
Sir  Charles  Hartley,  in  his  valuable  re- 
port on  the  "  Delta  of  the  Danube,"  at 
page  39,  says:  *  *  *  "and  the  ab- 
sence of  divers  to  execute  the  work, 
induced  the  author,  at  first,  to  adopt  the 
plan  of  building  the  wall  on  a  roughly 
leveled  foundation,  by  carefully  lower- 
ing down  masses  of  unset  concrete  within 
movable  timber  dams,  fitted  in  lengths 
of  from  15  to  30  feet,  to  the  framework 
of  the  piers.  This  plan  was  not  adopted 
on  a  large  scale,  until  it  had  been  found, 
by  repeated  exjDeriments,  that  the  con- 
crete, when  made  with  a  sufficient  quan- 
tity of  Portland  cement,  set  perfectly 
hard  on  a  rocky  foundation  in  a  seaway, 
although  lowered  through  the  water  in  a 
semi-liquid  state." 

In  passing  the  cement  through  the 
water  at  Canal  Street,  two  separate  one- 
yard  tubs  were  used,  and  the  concrete 
mixed  was  comparatively  dry  and  far 
from  a  semi-liquid  state. 

At  page  41  Sir  Charles  further  says: 
"  The  spaces  between  the  beton  blocks 
used  were  filled  up  with  newly  made 
concrete,  which,  searching  its  way  under 
the  adjacent  blocks,  and  filling  in  the 
grooves,  moulded  in  their  sides  expressly 
to  this  end,  caused  the  whole  mass  to 
become  ultimately  as  solid  as  if  it  con- 
sisted of  but  a  single  stone." 

As  to  the  strength  of  the  Portland 
cement  used,  Sir  John  Coode,  in  his  re- 
marks from  Hartley's  description  of  the 
"Delta  of  the  Danube," at  page  74,  says: 

"  The  cement  was  tested  by  Grant's 
machine  to  resist  a  tensile  strain  of  350 
pounds  per  square  inch,  after  being  im- 
mersed in  water  7  days.  He  had  made 
large  quantities  of  cement  in  mass  under 
water  and  at  a  considerable  depth,  with 
the  proportions  of  1  of  cement  to  5  of 
gravel;  he  had  executed  a  large  amount 
of  such  work  for  some  years  past,  and 
had'?built  a  substantial  sea  wall  to  the 
height  of  40  feet  upon  it." 

The  proportions  used  at  Canal  and 
King^Streets  are  almost  identical — 1  of 
cement,  2  of  sand,  and  5  of  broken  stone. 
At  page  76,  same  work,  Mr.  Coode  says: 
"  He  had  lately  put  down  some  founda- 
tions for  a  heavy  sea  work  on  a  rough, 


rocky  surface,  where,  if  he  had  not  de- 
posited the  concrete  in  mass  upon  the 
rock,  the  expense  of  preparing  the  bot- 
tom to  receive  the  blocks  would  have 
been  somewhere  about  twice  or  three 
times  as  great,  and  the  time  occupied 
would  have  been  three  or  four  times  as 
long  as  was  required  to  execute  the 
works  by  means  of  concrete  deposited 
'in  situ'  upon  the  bottom  in  16  feet  of 
water  at  the  lowest  spring  tides." 

I  further  give  some  excerpts  taken 
from  the  reports  of  the  Institute  of  Civil 
Engineers,  London,  Vol.  1862-3,  a  paper 
by  Daniel  Miller,  C.  E.,  entitled  "Struct- 
ures in  the  Sea  without  Coffer  Dams:" 

"  The  system  of  building  under  water 
by  means  of  diving-bells  and  diving- 
dresses  has  been  practised  to  a  consider- 
able extent;  and  the  improved  appa- 
ratus, now  used,  gives  great  facilities 
for  this  kind  of  work;  but  it  is  only  ap- 
plicable under  particular  circumstances, 
and  it  is  also  costly,  besides  being  liable 
to  cause  delay  in  the  progress  of  the 
work." 

"  There  are  three  modes  in  which  con- 
crete may  be  aj^plied  for  constructive 
purposes  —  building  it  in  mass  and 
allowing  it  to  set  before  water  has 
access  to  the  work,  as  has  been  adopted 
in  the  construction  of  the  walls  of  the 
Victoria  Docks  by  Mr.  Bidder,  and  in 
those  of  the  London  Docks  by  the  late 
Mr.  Rendel — preparing  it  first  in  blocks 
and  allowing  it  to  harden  before  being 
used,  as  employed  by  the  late  Mr. 
Walker,  at  the  Dover  Breakwater,  and 
by  Mr.  Hawkshaw  for  the  new  sea  forts 
for  protecting  the  arsenals  of  Plymouth 
and  Portsmouth — and  depositing  it  in  a 
liquid  state,  and  allowing  it  to  set  under 
water,  as  practised  upon  a  gigantic  scale 
by  Mr.  Noel  in  the  construction  of  the 
large  Government  Graving  Docks,  at 
Toulon.  In  the  latter  case,  hydraulic 
concrete  has  been  deposited  in  a  liquid 
state  in  the  sea  water  at  a  depth  of 
about  40  feet,  forming  a  vast  rectangular 
trough  of  beton  about  100  feet  wide,  of 
the  length  of  each  dock  respectively, 
and  with  walls  and  bottom  about  16  feet 
thick." 

Speaking  of  the  various  kinds  of  hy- 
draulic limes,  Mr.  Miller  says:  "It  may 
be  useful  to  mention,  for  comparison, 
the  proportions  of  some  of  the  concretes 
made   from    these   various   limes.     The 


USE   OF   COIGNET   BETON    "EN   MASSE. 


205 


Arden  lime  concrete  employed  by  Messrs. 
Bell  &  Miller  for  the  foundations  of  the 
large  Graving  Docks  at  Glasgow  was 
composed  of  1  part  of  ground  Arden 
lime,  1  part  of  iron  mine  dust,  and  4J 
parts  of  gravel  and  quarry  chips.  The 
lias  concrete  used  at  the  recent  extension 
of  the  London  Docks  by  Mr.  Rendel 
consisted  of — 1  part  of  blue  lias  lime  to 
6  parts  of  gravel  and  sand.  The  propor- 
tions adopted  for  the  blocks  of  the  Mole 
at  Marseilles  were  2  parts  of  broken 
stone  to  1  of  mortar,  the  latter  being 
composed  of  3  parts  of  Tiel  lime  to  5  of 
sand."  *  *  *  •*  *  "The  Portland 
cement  used  at  the  new  Westminster 
Bridge  is  harder  and  more  compact  than 
the  greater  number  of  building  stones, 
even  where  put  down  in  the  bed  of  the 
Thames,  and  where  it  is  exposed  to  the 
running  stream."  *  *  *  "The  author 
had  lately  an  opportunity  of  examining 
at  Genoa  the  extension  of  one  of  the 
Moles  of  the  harbor,  the  inner  side  of 
which  has  a  vertical  wall." 

"  The  latter  was  in  process  of  being 
constructed  under  vmter  entirely  of  poz- 
zuolana  concrete,  simply  thrown  into 
the  sea  from  baskets,  carried  on  men's 
heads,  a  boarding  confining  it  to  the 
shape  of  the  wall.  In  a  short  period  it 
set  quite  hard,  so  as  to  enable  the  upper 
part  of  the  wall,  which  is  of  stone,  to  be 
built  on  it."  ******  Though 
the  depth  of  the  quay  wall  was  not 
great,  this  shows  the  confidence  which 
the  Italian  engineers  have  in  concrete 
applied  under  water  in  a  soft  state.  The 
piers  of  the  new  basin  constructed  by 
the  Austrian  Government  at  Pola,  in 
Istria,  are  also  formed  in  a  similar  man- 
ner, of  concrete,  confined  between  rows 
of  timber  piling.  But  perhaps  the  most 
striking  application  on  a  large  scale  of 
pozzuolana  concrete,  is  in  the  great  Mole 
which  protects  the  port  of  Algiers.  To 
form  the  Mole,  blocks  of  beton  of  im- 
mense size,  so  as  to  be  immovable  by 
the  force  of  the  sea,  were  employed, 
some  of  these  formed  '  in  situ,''  by  pour- 
ing the  concrete  into  large  timber  cases 
without  bottoms,  sunk  in  the  sea  in  the 
line  of  the  Mole." 

"Hydraulic  concrete,  to  be  effective, 
requires  great  care  and  attention  hi  its 
manipulation  and  in  the  regulations  of 
the  proper  proportions  of  its  mate- 
rials." 


"  Any  failures  must  have  arisen  from 
inattention  to  these  or  similar  points,  as 
there  is  ample  experience  to  show,  that 
when  properly  made,  every  confidence 
may  be  placed  in  the  strength  and  dura- 
bility." 

In  the  construction  of  the  Albert  Har- 
bor, Greenock,  the  following  occurs, 
same  authority  :  "  The  mode  in  which 
the  work  was  designed  was  to  form  the 
walls  under  low  water,  of  a  combination 
of  cast-iron  guide  piles  in  front,  with  a 
continuous  stone  facing,  slid  down  over 
and  inclosing  these,  and  of  concrete 
backing  deposited  in  a  soft  state,  all  of  ■ 
which  could  be  easily  accomplished  from 
above  the  water  line."  *  *  *  * 
This  plan  was  felt  to  be  so  novel,  par- 
ticularly as  regards  the  concrete,  that, 
though  the  trustees  as  a  body  had  the 
greatest  confidence  in  the  engineers 
(Messrs.  Bell  &  Smith),  they  considered 
it  to  be  their  duty,  before  proceeding 
with  the  work,  to  fortify  themselves  by 
having  the  opinion  of  another  engineer; 
accordingly  Mr.  Thomas  Page,  M.  Inst. 
C.  TO.,  was  consulted,  who  fully  satisfied 
them  as  to  the  efficiency  of  hydraulic 
concrete  applied  in  the  manner  proposed, 
and  otherwise  confirmed  the  soundness 
of  the  principles  upon  which  the  works 
were  designed. 

Again,  same  authority  :  "  Immediately 
after  being  mixed,  and  when  brought  to 
a  proper  consistency  with  water,  it  is 
conveyed  to  where  it  is  to  be  used,  is  let 
down  under  water  in  the  discharge  boxes, 
and  in  a  short  time  sets  very  hard.  *  *  * 
This  mode  of  constructing  walls  in  deep 
water,  without  coffer  dams,  has  proved 
very  successful,  and  a  sea  pier  of  great 
solidity  and  durability  has  been  formed 
at  a  comparatively  moderate  cost."  *  *  * 

"Temporary  sheet  piling  or  boarding, 
instead  of  loose  stone,  may  be  employed 
to  keep  the  concrete  in  its-  place  until  it 
has  set." 

General  H.  G.  Wright,  of  the  United 
States  Engineers  Corps,  an  officer  of 
great  experience,  in  a  letter  addressed  to 
Major-General  Hamilton,  late  Superin- 
tendent in  Charge  of  Yards,  on  the  sub- 
ject of  Rosendale  cement,  among  other 
things,  says  :  "  Of  this  cement  I  used 
some  50,000  bbls.  in  the  fort  at  the  Tor- 
tugas,  a  large  part  of  which  was  for 
foundations  and  walls  under  water  ;  the 
particular   blocks   to   which   I    referred 


206 


VAN"   NO  STRAND  S   ENGINEERING   MAGAZINE. 


were  laid  to  test  the  icorkings  of  the 
tremie.  *  *  *  *  They  were  laid  in 
1848,  I  think  ;  and  when  I  left  in  185(3, 
they  were  in  as  good  condition  as  when 
laid,  the  surfaces  being  apparently  as 
perfect.  The  concrete  was  made  with 
sea  water,  no  fresh  water  having  been 
used." 

In  a  subsequent  statement,  more  par- 
ticularly on  the  working  of  the  tremie 
system,  made  lately,  that  eminent  officer 
said  :  "  The  success  attending  (the 
above)  induced  him  to  construct  the 
foundation  of  several  of  the  forts  in 
Southern  waters  in  a  similar  manner,  and 
with  like  success." 

Forts  Jefferson  and  Carroll  he  cited  as 
prominent  examples.  "*  *  *  * 
Should  not  hesitate  to  construct  founda- 
tions under  water,  by  depositing  liquid 
concrete  in  mass,  if  care  was  taken  in 
its  manipulation." 

Besides  the  valuable  experience  of 
General  Wright,  as  above  detailed,  to  my 
own  knowledge  mass  concrete  has  been 
used  in  this  country  in  the  construction 
of  foundations  below  water  for  a  period 
of  twenty -five  years  at  least. 

While  Engineer  of  the  Brooklyn  Navy 
Yard  I  constructed  a  wall  en  masse, 
which  is  a  standing  witness  to-day  of 
the  success  of  the  system.  My  prede- 
cessor in  office  there  used  somewhat 
similar  means.  Mr.  McElroy's  wall  at 
the  Wallabout  would  have  proved  a  suc- 
cess if  attention  had  been  given  to  the 
placing  of  more  piles  in  the  foundation, 
and  had  the  Rosendale  cement  used,  re- 
tained its  previoixsly  high  character,  and 
not  deteriorated  in  its  tensile  strength. 

I  will  now  briefly  describe  the  method 
of  placing  this  mass  concrete  in  situ  on 
the  works  in  question. 

The  wall,  up  to  within  2'  2tV'  (two  feet 
two  and  seven-sixteenth  inches)  of  mean 
low  water,  is  made  of  a  huge  monolith 
of  concrete  en  masse  manufactured  on 
the  spot  and  deposited  in  situ. 

The  site  for  the  wall  was  first  thor- 
oughly dredged  to  a  mean  depth  of  20 
feet  below  mean  low  water  ;  piles  were 
then  driven,  8  in  a  cross  section  of  IV 
feet  6  inches,  and  of  an  average  distance 
of  2  feet  6  inches  from  centres,  except 
the  two  front  rows,  which  are  centred 
two  feet  ;  longitudinally  the  outer  and 
inner  rows  were  driven  as  close  as  could 
be  done  without  interference  ;  they  were 


punched  to  about  a  mean  distance  of  13 
feet  below  mean  low  water,  by  means  of 
a  heavy  oak  follower  26  feet  in  length 
and  12  inches  in  section,  armed  at  the 
bottom  with  an  iron  pintle  and  banded 
with  iron  to  strengthen  against  fracture; 
this  punching  obviated  the  cutting  off  of 
any  other  than  the  westerly  row,  and 
those  only  for  a  distance  of  1 80  feet ; 
this  uneven  punching  afforded  a  good 
grasp  to  the  concrete  around  their 
heads.  Broken  stone,  measuring  about 
4  cubic  inches,  was  then  filled  in  between 
the  piles  and  allowed  to  take  a  bearing. 
The  false  work  for  receiving  the  con- 
crete was  then  erected.  Yellow  pine 
square  piles,  12  inches  by  12  inches  in 
section,  and  of  an  average  length  of  40 
feet,  were  driven  in  front  of  the  westerly 
row  of  punched  piles  at  a  batter  of  If 
inches  to  the  foot,  and  on  the  back  at  a 
batter  of  \  inch  to  the  foot,  centred 
longitudinally  8  feet  ;  to  the  inside  of 
these  square  piles,  previous  to  their 
being  driven,  battens  of  4  inches  by 
2.J  inches  spruce  were  nailed  on  firmly, 
and  on  these  further  pieces  of  spruce,  12 
inches  by  2  inches,  were  fastened,  form- 
ing grooves  for  receiving  constructed 
wooden  shutters  or  gates  which  were 
slid  into  place  after  the  pile  alignment 
was  perfected.  These  piles  were  then 
capped  crosswise  by  square  12-inch  tim- 
ber, braced  laterally  by  waling  pieces 
12'x6",  and  on  these  cross  caps  string- 
ers were  laid,  on  which  were  placed 
rails  of  flat  iron  to  receive  the  wheels  of 
a  movable  platform  car,  bearing  on  it  a 
10  horse-power  engine  for  the  lowering 
of  the  concrete  into  the  caisson.  This 
platform  car  had  erected  on  it  a  gallows 
frame  holding  traverse  wheels  with  pen- 
dant bales  of  iron,  from  which  were  sus- 
pended double  block  purchases  for  the 
lowering  and  hoisting  of  two  separate 
1-yard  buckets,  each  working  from  a 
separate  drum  independent  of  the  other, 
so  that  one  bucket  could  be  lowered 
while  the  other  was  filled. 

The  concrete  was  mixed  on  a  platform 
in  the  rear,  constructed  on  the  stay  piles 
driven  in  the  rear  of  the  wall,  wheeled 
to  the  car,  dumped  into  the  buckets  or 
tubes,  and  then  lowered  into  the  caisson. 
The  door  of  the  bucket  being  opened 
from  above  by  a  trap  rope,  did  away 
with  the  necessity  of  employing  divers, 
and  the  only  occasion  when  divers  were 


USE   OF   COIGTNET   BETON    "  EN   MASSE." 


207 


used  at  all  was  when  Mr.  McDonald, 
foreman  of  masons,  himself  a  practical 
driver,  leveled  off  the  top  layer  of  con- 
crete to  receive  the  granite  facing.  The 
buckets  could  be  shifted  from  above  in 
such  a  manner  as  to  command  any  por- 
tion of  the  bottom. 

The  proportions  of  the  concrete  varied 
occasionally,  but  the  usual  proportions 
were,  as  before  stated,  1,  2,  and  5,  or  1 
part  cement  (Portland),  2  of  sharp  sand, 
and  5  of  small  broken  stone. 

Concreting  was  commenced  on  the 
24th  of  December  last  and  continued 
until  the  6th  of  January,  1875,  a  layer 
of  two  feet  being  spread  over  the  bot- 
tom, soaking  into  the  broken  stones  at 
the  bottom,  and  binding  the  pile  heads 
firmly  together.  The  quantity  of  ice  by 
this  time  proving  very  troublesome,  con- 
creting was  suspended  until  the  middle 
of  March  (though  further  piling  for  the 
wall  was  continued  throughout  the  win- 
ter, with  scarcely  any  intermission),  and 
vigorously  prosecuted  until  the  end  of 
April,  when  the  whole  mass  necessary 
was  placed.  In  the  hearting  of  the 
caisson,  one-fifth  of  granite  spawls,  from 
the  Departmental  Stone  Yard,  were 
placed  and  thoroughly  grouted,  preserv- 
ing the  stability  of  the  wall  and  lessen- 
ing the  expense. 

In  placing  the  concrete  in  water,  chill- 
ed sometimes  to  3°  colder  than  the  freez- 
ing point  of  fresh  water,  some  means 
had  to  be  adopted  to  counteract  its  chilli- 
ness. That  eminent  and  versatile  en- 
gineer, Mr.  Chanute,  in  his  report  on  the 
Kansas  City  Bridge,  says  : 

"  Both  masonry  and  beton  were  laid 
in  extremely  cold  weather,  the  use  of 
hot  sand  and  water  being  found  to  make 
this  practicable.  The  sand  was  heated 
in  large  sheet  iron  braziers,  and  the 
water  warmed  in  cast-iron  kettles,  one 
of  each  being  found  sufficient  to  supply 
the  force  working  on  a  pier.  The  heat 
which  was  thus  artificially  given  to  the 
mortar  hastened  its  setting,  causing  this 
to  take  place  before  the  mass  had  cooled 
enough  to  make  freezing  possible." 

Mr.  T.  C.  Clarke,  in  his  able  and  ex- 
haustive report  on  the  Quincy  Bridge, 
says  : 

"During  this  time  the  glass  fell  as  low 
as  16°  Fahr.  A  shanty  was  built  on  a 
flat,  and  in  this  a  kettle  was  placed  on  a 
stove,  and  the  cement   mixed  with  hot 


water.  During  the  coldest  days  each 
stone  was,  before  being  set,  held  over  a 
brazier  of  charcoal  to  draw  out  the  frost. 
The  mortar  was  examined  carefully  in 
the  spring,  and  found  to  be  as  hard  and 
perfect  as  any  on  the  work.  Much  of 
the  masonry  of  this  bridge  was  con- 
structed during  winter,  although  none  in 
as  cold  weather  as  this  pier,  and  there  is 
apparently  no  difference  in  the  quality  of 
the  mortar  whether  built  in  vrlnter  or 
summer." 

As  the  quantity  of  cement  used  by 
these  gentlemen  was  very  small  in  com- 
parison with  that  which  would  have  to 
be  used  in  the  bulkhead  wall  in  question, 
some  means  had  to  be  taken  of  a  more 
extensive  nature.  For  heating  the  water, 
the  following  simple  apparatus  was  used. 
A  cask  capable  of  containing  60  gallons 
of  water,  holding  a  coil  pipe,  was  placed 
on  the  movable  car,  and  through  this 
coil  the  steam  from  the  boiler  of  the  en- 
gine was  passed  at  will ;  thjs  heating- 
was  done  very  rapidly  and  efficiently,  it 
only  taking  from  4  to  8  minutes  to  heat 
the  whole  60  gallons  from  32°  to  100° 
Fahr.,  the  water  thus  heated  being  car- 
ried to  the  mixing  platform  by  india- 
rubber  tubing.  To  heat  the  sand  and 
broken  stone,  heaters  made  of  iron,  simi- 
lar to  those  used  in  street  paving,  were 
constructed  by  Mr.  Joseph  Edwards,  414 
Water  Street,  New  York,  each  capable 
of  heating  a  cubic  yard  of  material,  the 
fuel  used  being  old  barrel  staves,  etc. 
They  did  their  work  thoroughly,  and  by 
this  means  work  was  carried  on,  on  one 
occasion  when  the  temperature  of  the 
air  was  11°  Fahr.  and  that  of  the  water 
32°,  the  concrete  becoming  as  hard  as  if 
made  during  the  hotter  summer  months, 
thus  practically  substantiating  the  opin- 
ions of  Messrs.  Chanute  and  Clarke. 

In  laying  the  backing  to  the  granite 
facing  1  have  introduced  a  change  from 
that  at  Christopher  Street  section,  which 
has  materially  lessened  the  expense, 
while  preserving  the  stability  of  the 
wall.  Blocks  of  about  three  cubic  yards 
capacity  were  made  at  the  Seventeenth 
Street  yard  out  of  old  granite  spawls 
and  Portland  cement;  when  sufficiently 
compact  they  were  transported  to  Canal 
Street,  and  placed  in  position  with  great 
rapidity,  over  70  lineal  feet  being  laid 
during  one  tide.  The  success  attending 
the  use  of  these  rubble  blocks  has  been 


208 


VAN   NOSTRAND'S   ENGINEERING   MAGAZINE. 


such  that  I  have  recommended  to  the 
Board  in  my  report  on  the  "Develop- 
ment of  the  Harlem  River  and  Spuyten 
Duyvil  Creek  for  Commercial  Purposes," 
that  the  bulkhead  wall  when  constructed 
should  be  composed  of  beton  placed  en 
masse  with  a  rubble  masonry  facing  sur- 
mounted by  a  granite  cope. 

On  the  removal  of  the  shutters  and 
square  piles — the  false  work  of  the  cais- 
son— which  had  been  down  nearly  three 
months,  Mr.  McDonald  carefully  exam- 
ined the  sides  of  the  monolith  and  re- 
ported that  he  found  it  as  smooth  and 
compact  in  appearance  as  any  blocks  he 
had  ever  seen  which  were  manufactured 
on  land — and  no  sign  of  honey-comb. 
This  assertion  was  verified  by  my  assist- 
ants, who  passed  a  boat  hook  all  along 
the  sides  both  front  and  rear,  and  found 
it  as  smooth  as  the  Gansevoort  Street 
manufactured  blocks  ;  the  edges  of  the 
"  berme,"  too,  6  inches  in  width  where 
the  stone  facing  springs  from  the  mono- 
lith of  concrete,  was  as  distinctly  defined 
as  that  of  a  well  cut  piece  of  granite. 
A  great  saving  has  been  effected  by  this 
system  of  construction,  over  that  of  the 
block  system,  including  coping  not  as 
yet  required  on  this  section  (the  wall 
constructed  being  in  the  wake  of  the 
pier);  the  saving  amounts  to  $6*7.77  per 
foot  run,  or  over  $350,000  per  mile,  the 
cost  per  foot  run  being  $311.67. 

By  having  a  long  stretch  of  work,  a 
judicious  use  of  labor,  and  using  made 
rubble  blocks  surmounted  by  granite 
scope,  instead  of  cut  facing,  I  am  of 
the  opinion  that  the  cost  can  be  reduced 
at  least  20  per  cent 

%  *  ^j  H^  *  * 

Since  this  report  was  written,  the  Ca- 
nal Street  section  has  been  extended 
about  200  feet,  the  short  section  at  the 
foot  of  King  Street  completed,  and  a 
new  section  commenced  at  the  foot 
Clarkson  Street.  The  plan  of  construc- 
tion being  in  every  case  precisely  simi- 
lar except  on  the  Clarkson  Street  section, 
where  it  has  been  deemed  advisable,  in 
consequence  of  the  great  depth  and  soft- 
ness of  the  mud,  to  drive  the  two  front 
rows  of  piles  with  a  batir  of  If  inches, 
instead  of  perpendicularly,  as  on  the 
other  sections;  the  object  of  the  change 
being  to  oppose  still  greater  resistance 
on  the  part  of  the  foundation  to  lateral 
pressure,  and  to  enable  the  mould  boards 


to  be  slid  down  further,  so  that  the  con- 
crete may  bind  the  pile  heads  to  a  great- 
er depth. 

The  advantages  of  the  beton  "en 
masse  "  system  are : 

1st.  As  many  sections  as  the  Depart- 
ment deem  advisable  can  be  in  course 
of  construction  at  any  one  time — the 
distance  between  the  old  piers  enabling 
the  work  to  be  prosecuted  in  the  slips 
without  any  serious  hindrance  to  com- 
merce. 

2d.  The  work,  by  the  adoption  of  the 
heating  process,  as  applied  to  water, 
sand,  and  stone,  may  be  prosecuted  at 
least  during  nine  months  out  of  the 
twelve. 

3d.  Unskilled  labor  can  replace  to  a 
very  great  extent  the  skilled  labor  re- 
quired under  the  block  system. 

4th.  The  new  piers  being  differently 
spaced  fiom  the  old,  these  new  piers 
may  be  projected  from  the  new  bulk- 
head wall  and  completed  in  a  great 
many  instances  before  it  becomes  neces- 
sary to  remove  the  old  ones. 

5th.  The  rapidity  with  which  the  work 
may  be  prosecuted  and  the  immense 
saving  in  its  cost. 


The  Drainage  of  the  Thames  Val- 
ley. The  City  Solicitor  announced  to 
the  Hampton  Wick  Local  Board  that  a 
letter  had  been  received  from  an  inspec- 
tor of  the  Local  Government  Board, 
stating,  in  reference  to  the  subject  of  a 
combination  of  sanitary  authorities  in 
the  Thames  Valley  for  the  purpose  of 
carrying  out  a  joint  scheme  of  sewerage, 
that  it  was  proposed  to  hold  a  conference 
in  London,  and  asking  that  two  or  three 
members  of  the  board  might  be  named 
as  delegates.  Messrs.  Frere  &  Co.,  of 
Lincoln's  Inn  Fields,  had  also  written, 
stating  that  they  were  instructed  to  take 
proceedings  against  the  Local  Board  of 
Hampton  Wick  for  a  disregard  of  the 
notice  to  discontinue  the  flow  of  sewage 
into  the  river  Thames.  Mr.  Nelson 
thought  this  letter  from  Messrs.  Frere 
could  not  have  come  at  a  more  inoppor- 
tune moment,  and  suggested  they  should 
be  informed  that  a  commission  was  is- 
sued by  the  Government,  and  that  under 
the  circumstances  the  Conservators  had 
better  abstain  from  any  proceedings, 
which  the  board  were  prepared  to  meet. 


NEW   MATERIALS   AND   INVENTIONS   FOR   BUILDING. 


209 


NEW  MATERIALS   AND   RECENT  INVENTIONS   CONNECTED 

WITH  BUILDING.* 


From  "The  Architect." 


The  subject  I  have  the  honor  of  intro- 
ducing to  your  notice  is  necessarily  full 
of  details,  and  when  once  we  have  plung- 
ed into  these  it  is  not  likely  we  shall  be 
able  to  quit  them  for  generalities.  I 
therefore  ask  you  to  permit  me  to  lay 
befoi-e  you  such  general  considerations 
as  seem  to  belong  to  it  now  at  the  out- 
set, rather  than  to  reserve  them  till  the 
close  of  the  paper. 

The  first  remark  that  will  occur  to 
most  observant  men  is,  that  the  building 
art,  as  conducted  in  England  at  the  pres- 
ent day,  presents  fewer  novelties  than 
almost  any  others  of  the  leading  technic 
processes.  Steam,  electricity,  and  the 
progress  of  mechanical  inventions  and 
chemical  research  have  revolutionized 
most  of  the  great  divisions  of  human  in- 
dustry. Sometimes  it  is  a  new  method 
of  manufacture  which  has  supplanted  an 
old  one — the  material  remaining  un- 
changed. Sometimes  the  old  material 
has  given  way  to  a  new  one,  and  not  un- 
f requently  both  material  and  method  are 
alike  revolutionized  by  discoveries  made 
through  that  restless  and  eager  spirit  of 
inquiry  and  invention  which  is  perhaps 
the  chief  glory  of  the  present  century. 

For  examples  of  new  methods  of  em- 
ploying old  materials,  we  may  turn  to 
the  principal  fabrics  used  in  clothing. 
Wool,  flax,  cotton  and  silk,  are  what 
they  always  were ;  but  spinning,  weaving, 
dyeing  and  ornamenting,  which  once 
were  handicrafts,  are  now  mechanical 
processes  carried  on  by  steam  machinery 
in  vast  factories.  Printing  is  another 
example  of  the  same  change  ;  paper, 
ink  and  type  are  still  employed,  but  the 
contrast  between  the  handpress — which 
within  the  recollection  of  many  of  us 
was  the  only  method  in  use — and  one  of 
Mr.  Hoe's  magnificent  steam  machines 
is  enormous. 

Of  new  materials  which  have  sup- 
planted or  supplemented  old  ones,  a  very 
long  list  could  be  made  out.  One  or 
two  will  suffice  for  the  purposes  of  an 
illustration.     Various  grasses  and  other 


*  From  a  paper  read  before  the  Royal  Institute  of  Brit- 
ish Architects,  by  Mr.  T.  Roger  Smith. 

Vol.  XIII.— No.  3—14 


substances  have  now  come  into  use  either 
along  with  linen  rags  or  as  a  substitute 
for  them  in  the  manufacture  of  paper. 
Stearine  and  various  similar  products 
have  almost  displaced  wax,  spermaceti, 
and  even  tallow  as  material  for  candles. 
Mineral  oil  has  largely  displaced  fish  oil. 
We  are  using  stamped  and  printed  paper 
for  window  curtains,  and  printed  cloth 
for  embroideries,  German  silver  instead 
of  plate,  and  papier  mache  in  place  of 
wood  ;  and  in  a  hundred  other  instances 
the  craftsman  has  a  constantly  increas- 
ing series  of  new  substances  placed  with- 
in his  reach  by  the  scientific  discoverer. 

The  most  remarkable  cases  of  all  are, 
of  course,  those  where  material  and 
method  are  both  alike  new,  having  either 
been  called  into  being  to  supply  some 
new  want,  or  else  presenting  themselves 
with  such  capacities  for  being  useful  or 
pleasant  inherent  in  them,  that  a  want 
has  sprung  up,  after  the  power  of  sup- 
plying it  was  acquired.  All  the  applica- 
tions of  photography,  0f  the  electric 
telegraph,  of  the  spectroscope,  and  of 
our  amazingly  enlarged  chemical  knowl- 
edge, seem  to  belong  to  this  head.  Till 
we  knew  we  could  have  them  our  wildest 
dreams  never  led  us  to  desire  such  things 
as  photographs  of  our  friends,  or  tele- 
graphs from  them  when  at  the  antipodes ; 
and  such  contrivances  as  the  sewing  ma- 
chine, such  materials  as  gutta  percha, 
or  such  inventions  as  the  locomotive, 
have  brought  into  existence  a  whole 
range  of  new  requirements,  which  the 
world  had  never  dreamed  of  till  the 
power  of  supplying  them  was  called  into 
existence. 

Building,  compared  with  such  matters 
as  locomotion,  the  manufacture  of  cloth- 
ing, or  the  transmission  of  intelligence, 
is  an  art  which  has  changed  wonderfully 
little,  so  little  indeed  that  I  am  some- 
times tempted  to  believe  that  there  still 
remains  open  to  some  inventive  genius 
among  ourselves,  the  possibility  of  ef- 
fecting something  like  the  revolution 
which  Arkwright  commenced  for  textile 
fabrics,  when  he  applied  steam  power  to 
spinning.     It  is,  of  course,  natural  to  say 


210 


VAN   NOSTRAND'S   ENGINEERING  MAGAZINE. 


that  it  cannot  be  done  ;  bnt  the  same 
thing  might  have  been  said  beforehand 
of  all  the  great  steps  which  handicrafts 
have  taken,  and  we  might,  I  believe,  do 
worse  than  entertain  very  seriously  in- 
deed the  possibility  of  adapting  machin- 
ery, mechanical  processes,  and  novel 
combinations  of  material  to  building,  on 
such  a  scale  and  in  such  a  way  as  to 
cheapen  the  cost  of  simple  plain  struc- 
tures to  a  great  extent.  This  subject 
would  land  us  at  once  in  a  region  of 
speculations  which  might  prove  of  prac- 
tical advantage,  and  to  us  I  confess  the 
subject  is  tempting  in  the  extreme,  but  I 
have  not  any  intention  of  inviting  you 
to  pursue  it.  If,  however,  a  wholesale 
transformatian,  such  for  example  as 
would  be  effected  were  we  prepared  to 
abandon  brickwork  for  concrete,  and 
slates  for  felt,  is  not  within  our  reach, 
there  are  available  for  use  no  small 
number  of  inventions,  in  which  the  pro- 
gress of  contrivances  and  discovery  has 
told  upon  the  resources  at  the  builder's 
disposal ;  and  it  is  some  of  these  which 
we  are  to  consider. 

Granted,  then,  that  there  exist  a  cer- 
tain number  of  novelties,  my  second 
preliminary  observations  must  be  direct- 
ed to  the  position  which  the  architect 
ought  to  take  with  regard  to  them. 
This  is  a  question  which  has  two  sides.  It 
may  be  said  that  the  architect  as  the 
skilled,  cultivated,  and  trained  director 
of  the  work,  is  bound  to  know  what  is 
going  on,  to  make  himself  familiar  with 
the  latest  improvements,  and  to  give  his 
clients  the  benefit  of  his  knowledge ;  in 
short,  he  is  to  be  abreast  of  the  building 
art  in  his  own  day,  and  is  to  show  that 
he  is  solely  making  himself  acquainted 
with  each  capital  invention  as  it  comes 
out,  and  to  embrace  every  opportunity 
of  using  it.  This  is  a  position  which 
has  much  to  be  said  in  its  favor.  And  if 
men  expect  their  doctors  to  know  the 
latest  medicines,  and  their  lawyer  to  be 
acquainted  with  the  most  recent  legisla- 
tion, they  may  be  excused'  if  they  ask 
that  their  architect  shall  be  equally  well 
posted.  If,  however,  you  ask  your  medi- 
cal man  whether  if  some  new  remedy  of 
which  you  have  heard  is  not  said  to  suit 
your  symptoms,  he  will  probably  reply  : 
"  Yes,  but  I  doubt  whether  it  would  suit 
your  constitution  ;  the  reports  of  its 
actions  are  by  no  means  uniform  or  com- 


plete, and  if  you  take  it  you  will  be 
trying  an  experiment."  Your  solicitor 
when  you  ask  him  to  take  proceedings 
under  some  new  Act  will,  if  he  be  pru- 
dent and  honest,  reply  :  "  True,  the  lan- 
guage of  the  Act  seems  to  fit  the  case, 
but  it  has  not  yet  been  tested  before  the 
Courts,  and  your  case  will  be  the  one  to 
fix  the  interpretation  upon  the  language 
if  you  proceed  under  this  Act ;  better 
be  cautious." 

In  both  instances  the  professional  man, 
if  he  had  no  duties  to  his  client,  would 
be  delighted  at  the  opportunity  of  con- 
tributing to  the  fabric  of  professional 
experience  an  item  possibly  of  much  im- 
portance ;  the  expense  or  distress  of  the 
process  being  borne  by  the  vile  body — 
or  purse — of  his  client.  But  if  he  is 
true  to  that  maxim  of  professional  con- 
duct— which  I  take  to  be  a  sound  one, 
so  long  as  it  does  not  carry  a  man  be- 
yond the  limits  of  honor  and  good  faith 
— "  do  the  best  you  can  for  your  client  " 
— the  experiment  is  left  for  some  one 
else  to  try,  while  better  known  and  safer 
methods,  supposing  such  to  exist,  are 
adopted,  even  if  they  be  less  brilliant. 
This  I  hold  illustrates  an  architect's  true 
position  in  regard  to  new  inventions.  He 
ought  to  make  himself  familiar  with 
them  all;  he  ought  to  neglect  no  advant- 
age offered  by  them;  but  he  has  no  busi- 
ness to  try  experiments  at  a  client's  ex- 
pense. If  this  be  true  there  are  only 
three  conditions  under  which  an  architect 
is  at  liberty  to  adopt  a  novelty.  First — 
If  it  has  been  in  some  way  put  beyond 
doubt  that  the  novelty  will  succeed ; 
Second — If  it  is  certain  that  received 
methods  will  not  succeed,  and  the  novelty 
offers  a  better  chance  ;  Thirdly — If  the 
client,  knowing  that  there  is  the  possi- 
bility of  failure,  decides  that  the  novelty 
shall  be  tried. 

It  may  be  said  that  these  conditions 
very  much  limit  the  adoption  of  new  in- 
ventions, and  no  doubt  they  do  so  ;  but 
I  hold  that  our  first  duty  as  architects  is 
to  secure  that  our  buildings  shall  answer 
their  purpose,  and  that  trying  experi- 
ments in  them  is  not  justifiable  except 
under  conditions  which  either  render 
failure  impossible,  or  at  least  shift  the 
entire  responsibility  on  to  other  shoul- 
ders. 

It  now  only  remains  to  guard  you  and 
the   readers  of   this  paper   against  any 


NEW   MATERIALS   AND   INVENTIONS   FOR  BUILDING. 


211 


misconception  as  to  its  nature  and  scope. 
I  do  not  claim  to  have  hunted  up  and 
named  all  the  inventions  worth  notice 
brought  forward  during  the  past  few 
years.  Still  less  do  I  claim  to  have  se- 
lected the  best.  I  shall  not  attempt  to 
do  more  than  to  point  out  the  directions 
in  which  invention  has  been  chiefly  ex- 
ercised, and  to  give  under  each  head  a 
few  specimens,  selected  not  as  the  best 
but  as  the  most  convenient  illustrations. 
The  subject,  thus  looked  at,  seems  to 
divide  itself  into  (1)  new  materials,  (2) 
new  methods,  (3)  new  structures,  and  (4) 
new  appliances.  New  materials  may  in- 
clude revived  ones,  and  applications  of 
known  materials  to  new  purposes.  New 
methods  refer  to  new  modes  of  working, 
chiefly  to  the  substitution  of  machinery 
for  manual  labor.  New  structures,  hard- 
ly perhaps,  need  explanation,  but  must, 
of  course,  be  understood  as  applying  to 
structures  of  hitherto  unknown  sorts, 
and  which  "from  their  novel  nature  are 
essentially  new  inventions;  or  new  intro- 
ductions. New  contrivances  will  em- 
brace those  appliances  which  forms  por- 
tions of  our  buildings,  such  as  lifts,  bells, 
or  cooking  apparatus  ;  and  also  will  in- 
clude some  few  new  combinations  of 
building  materials  for  special  purposes. 

New  or  Hevived  Materials. — of  these 
the  most  important  by  far  are  iron  and 
glass.  The  modern  application  of  both  to 
building  has  been  well  known  to  us  now 
for  a  quarter  of  a  century  ;  in  fact  ever 
since  the  Exhibition  of  1851  showed  how 
rapidly  and  cheaply  vast  structures  of 
iron  and  glass  (the  iron  work  being  chiefly 
cast)  could  be  erected,  and  how  great  a 
charm  they  possessed  ;  and  the  applica- 
tions of  these  materials  have  been  nu- 
merous and  varied.  The  leading  princi- 
ple upon  which  that  building  depended, 
and  to  which  it  owed  both  its  architectural 
quality  and  its  constructional  success  was 
the  continued  repetition  of  a  small  num- 
ber of  well-considered  forms.  Every 
pane  of  glass  was  of  one  size,  and  so  up- 
wards as  far  as  possible.  Every  column 
was  of  the  same  length,  and  every  girder 
was  of  the  same  span.  This  principle  was 
adhered  to  in  the  design  of  the  Sydenham 
Crystal  palace,  but  it  has  been  in  some 
other  instances  over-looked. 

An  iron  and  glass  building  is  no  doubt 
not  a  very  durable  one,  nor  very  weather- 


tight,  and  the  expense  of  its  maintenance 
will  be  considerable  ;  but  nothing  is  in 
first  cost  so  cheap,  and  for  the  purpose* 
of  large  gatherings  of  people,  nothing  so 
appropriate. 

Treated  in  a  different  way,  iron  ribs, 
carrying  some  light  filling  in,  which  may 
be  glass  or  wood,  have  enabled  us,  when 
we  enclose  enormous  spaces  in  a  more  per- 
manent manner,  to  roof  them  over.  The 
great  railway  sheds,  and  such  buildings 
as  the  Agricultural  Hall,  the  British 
Museum  reading-room,  and  the  Albert 
Hall  are  examples  of  buildings  having 
iron  roofs  of  prodigious  span.  These  are 
buildings  such  as,  from  time  to  time, 
come  within  the  ordinary  scope  of  an 
architect's  practice.  It  is  very  desirable 
for  us  to  obtain  a  familiarity  with  the 
principles  upon  which  these  roofs  are 
constructed,  as  although  it  may  be  very 
wise  to  obtain  upon  them  the  assistance  of 
an  engineer,  whose  whole  time  is  spent  in 
working  out  the  details  of  iron  work,  the 
architect  will  find  that  he  is  at  a  great 
advantage  if  he  can  design  their  general 
forms  himself.  All  these  applications  of 
iron  as  a  building  material  seem,  how- 
ever, to  shrink  into  insignificance  before 
Mr.  Scott  Russell's  Vienna  cone  ;  but 
this  has  been  so  recently  described  here 
by  the  inventor  himself  that  I  need  not 
do  more  than  refer  to  it. 

Other  applications  of  iron  to  construc- 
tion are  so  familiar  that  I  shall  hardly  be 
justified  in  referring  to  many  of  them 
among  new  inventions.  I  may,  however, 
allude  to  Phillips's  girders,  as  a  contri- 
vance which  is  still  tolerably  new.  These 
are  built  up,  as  you  are  aware,  by  bolt- 
ing two  rolled  iron  joists  together,  and 
sometimes  four  such  joists  are  combined 
with  plates  in  addition  to  their  own 
flanges,  into  one  large  beam.  It  is  not 
easy  to  see  the  scientific  ground  upon 
which  this  combination  (which  places  a 
very  large  amount  of  material  compar- 
atively near  the  neutral  axis  of  the  beam) 
can  be  advocated,  but  there  is  obviously 
a  good  deal  of  simplicity  and  handiness 
in  the  combination,  and  it  is  said  to  have 
good  practical  qualities. 

Messrs.  Moreland  &  Son,  who  are  well 
known  as  skilled  in  the  application  of 
iron  to  building  purposes,  have  contrived 
a  description  of  fire-proof  construction, 
in  which  they  imbed  a  kind  of  slight  bow 
string  truss  in  the  concrete,  which  they 


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van  nostrand's  engineering  magazine. 


fill  in  between  large  girders.  This  con- 
stuction  is  so  far  different  from  ordinary 
fire-proofing  as  to  deserve  to  be  mention- 
ed. It  was  employed  at  the  St.  Pancras 
Hotel,  and  appeared  to  me,  when  1  saAV 
it  being  fixed  there,  to  offer  considerable 
advantages. 

The  next  material  which  I  propose  to 
notice  is  one  which  has  but  resently  been 
introduced,  and  may  fairly,  on  that  ac- 
count, lay  claim  to  the  title  of  a  perfect- 
ly new  invention.  I  refer  to  selenitic 
mortar,  the  invention  of  General  Scott. 

This  mixture  I  shall,  I  believe,  correct- 
ly describe  if  I  say  that  it  consists  of  the 
ordinary  ingredients  of  mortar — namely, 
lime  and  sand,  though  the  sand  is  in 
larger  proportions  than  usual,  with  the 
additions  of  a  small  quantity  of  gypsum 
(sulphate  of  lime),  intimately  mixed  with 
the  lime.  This  mortar  requires  to  be 
mixed  in  a  pug-mill  very  thoroughly,  and 
when  carefully  prepared,  will  be  found 
to  have  acquired,  to  some  extent,  the 
properties  of  a  cement,  for  it  sets  rapidly, 
and  when  set  it  is  extremely  hard  and 
tenacious.  It  is  to  the  admixture  of  the 
gypsum  that  the  rapid  setting  is  due, 
but  perhaps  some  of  the  general  excel- 
lence of  the  material  may  be  owing  to 
its  having  been  better  mixed  than  usual. 
The  Albert  Hall  was  the  first  large 
building  in  which  this  material  was  em- 
ployed; and  while  that  hall  was  in 
course  of  erection  I  had  repeated  oppor- 
tunities of  noticing  its  admirable  behav- 
iour. The  London  School  Board  have 
latterly  adopted  it  throughout  their  new 
buildings,  and  probably  their  architects 
may  have  met  with  varying  results,  con- 
sidering the  various  builders  who  have 
worked  for  them;  but  there  can,  I  think, 
be  no  doubt  that,  on  a  building  of  any 
magnitude  and  under  proper  supervision, 
selenitic  mortar  will  be  found  to  be  a 
trustworthy  auxiliary  to  the  architect. 
Of  the  use  of  the  same  material  for 
plastering  I  cannot  speak  so  fully. 

The  adaptation  of  concrete  to  building 
walls,  floors,  and  roofs,  as  well  as  the 
foundations,  may  fairly  claim  a  moment's 
notice.  Tall  and  Drake  are  two  names 
best  known  in  connection  with  it.  As 
far  as  I  am  aware  the  use  of  lime  con- 
crete, which  involves  walls,  etc.,  of  con- 
siderable thickness,  has  not  been  much 
pushed.  Portland  cement  concrete,  a 
stronger  material,  capable  of  being  used 


on  thin  walls,  and  haAdng  the  property 
of  hardening  very  rapidly,  is  more  com- 
monly employed.  The  different  patents 
have  for  their  object,  when  walls  are  to 
be  built,  the  construction  of  troughs  by 
the  help  of  frames  and  movable  boards 
or  shutters.  These  troughs  are  the  ex- 
act size  of  the  wall,  and  the  concrete  is 
filled  into  them.  When  the  material 
has  set  the  trough  is  taken  to  pieces,  re- 
fixed  at  a  higher  level,  and  the  process 
is  repeated.  I  am  not  disposed  to  believe 
that  much  economy  results  from  building 
in  concrete,  except  where  the  work  is 
very  plain  and  straightforward,  and  when 
little  is  spent  on  subsequent  finish;  but 
there  can  be  no  doubt  that  a  wonderfully 
strong  and  tenacious  material  is  ob- 
tained; and  probably  where  the  founda- 
tion is  unquestionable,  the  materials 
good,  and  the  supervision  during  the 
progress  of  the  work  thorough,  a  strong- 
er building  is  erected — and  one  more 
proof  against  the  attacks  of  weather 
than  if  brick  were  employed — and  at  a 
not  greater  expense. 

Allied  to  concrete  is  artificial  stone, 
and  this,  with  the  various  panacea  for 
arresting  the  decay  of  building  stones, 
has  of  late  retreated  to  some  extent 
from  the  public  view.  It  is  happily 
very  difficult  indeed  to  make  bad  stone 
into  good,  and  consequently  most  of  the 
solutions  and  washes  which  have  that 
for  their  object  have  proved  unsuccess- 
ful. Not  that  there  are  not  many  of 
them  which  have  a  sound  scientific  basis, 
but  the  difference  is  very  great  between 
treating  a  specimen  of  stone  in  the 
course  of  a  well  -  arranged  laboratory 
experiment,  and  treating  similar  stone, 
built  into  a  wall,  perhaps  saturated  with 
wet,  and  exposed  to  all  vicissitudes  of 
weather,  in  the  rough  way  in  which,  on 
a  scaffold,  even  careful  workmen  will 
apply, what  they  call  chemical  stuff;  and 
we  cannot  wonder  that  solutions,  which 
are  theoretically  excellent,  have  often 
in  practice  failed  to  protect  masonry. 
The  artificial  stone  of  Mr.  Ransome  is, 
I  think,  the  only  material  called  artificial 
stone  which  has  held  its  ground;  and  I 
believe  that  under  his  more  recent 
patents  an  excellent  and  durable  sub- 
stance has  been  produced,  but  in  many 
cases,  not  at  such  a  price  as  has  enabled 
it  to  displace  natural  stone  for  plain 
work.     Where   elaborate   work,  such  as 


NEW   MATERIALS   AND   INVENTIONS   FOR   BUILDING. 


213 


would  admit  of  being  produced  in  a 
mould,  has  been  required,  this  material 
has,  I  am  informed,  proved  both  econom- 
ical and  satisfactory. 

Another  material  which  (while  it  is 
incorrect  to  call  it  a  substitute  for 
stone)  can  often  be  adopted  as  an  alter- 
native material,  is  that  very  old  form  of 
brick,  known  as  terra  cotta,  the  use  of 
which  has  revived  to  such  an  extent  as 
to  stimulate  the  manufacture.  Although 
terra  cotta  is  not  a  new  material  in  one 
sense,  it  is  so  in  another,  for  it  is  only 
very  recently  that  it  has  become  possi- 
ble to  obtain  it  in  such  quantities,  and 
of  such  varied  quality,  that  it  could  be 
readily  adopted  by  the  English  archi- 
tect. He  who  would  employ  terra  cotta 
must  submit  to  a  certain  amount  of  lim- 
itation; he  cannot  deal  with  it  as  freely 
as  he  can  with  masonry.  He  must  de- 
sign his  ornament  long  befoi-ehand;  he 
must,  if  possible,  arrange  for  a  large 
amount  of  repetition;  he  must  so  design 
his  work  that,  if  slightly  warped  in 
burning,  the  effect  shall  not  be  entirely 
spoilt ;  he  must  prepare  for  delay  and 
trouble,  and  he,  or  some  one  for  him, 
must  draw  out  all  profiles,  etc.,  to  a 
sufficient  scale  to  allow  for  their  shrink- 
age. But  subject  to  these  and  other 
minor  conditions  terra  cotta  is  an  ad- 
mirable material.  When  used  in  large 
quantities  it  is  cheap ;  it  is  very  durable ; 
it  can  be  obtained  of  beautiful  color  and 
texture;  it  is  the  most  appropriate  mate- 
rial to  employ  along  with  brick,  and  it 
admits  of  the  introduction  of  great 
richness,  and  of  the  indefinite  multipli- 
cation of  a  few  pieces  of  artistically 
modeled  work.  It  is  to  be  hoped  that 
the  Natural  History  Museum,  where 
Mr.  Waterhouse  is  employing  it  on  an 
extensive  scale,  will  give  a  great  stimu- 
lus to  its  use.  In  the  various  buildings 
of  the  department  at  South  Kensington 
and  in  the  Albert  Hall,  terra  cotta  has 
been  extensively  employed;  and  Mr. 
Barry's  Dulwich  College,  and  Mr.  Chris- 
tian's Insurance  Office  in  Bridge  Street, 
may  be  pointed  to  as  other  examples  of 
its  use. 

Bricks  themselves,  and  tiles  have  not 
furnished  of  late  years  many  really  new 
inventions.  The  damp  courses,  air 
bricks,  shaped  facing  bricks,  and  roof- 
ing tiles  of  the  ingenious  Mr.  John  Tay- 
lor are,  I  have  no  doubt,  known  to  all 


present.  I  do  not  recollect  any  other 
varieties  of  brick  requiring  mention  here 
till  we  come  to  Pether's  ornamental 
bricks,  a  variety  available  for  use  in  sur- 
face decoration.  These  bricks  have  a 
pattern  impressed  on  them,  and  being 
made  of  fine  clay  and  well  executed, 
have  been  often  introduced  lately  into 
decorative  work,  and  might  with  great 
advantage  be  more  generally  employed, 
as  architects  could  readily  design  orna- 
ment appropriate  to  them. 

The  various  sorts  of  flooring  and  en- 
caustic tiles  are  no  longer  new,  indeed 
they  present  one  of  the  best  possible 
examples  of  a  new  building  material  be- 
coming generally  so  adopted  as  in  a  few 
years  to  grow  perfectly  familiar.  A  tile 
of  German  manufacture  was,  however, 
introduced  into  this  country  a  short  time 
ago  which  has  not  yet  become  very  gen- 
erally known  ;  it  is  in  large  slabs,  and 
rather  delicate  tones  of  color  seem  pre- 
ferred, though  very  elaborate  decora- 
tions have  been  executed  in  it. 

A  comparatively  new  mode  of  employ- 
ing tiles  for  the  lining  of  rooms  have 
been  introduced  by  Messrs.  Simpson, 
who  have  decorated  the  interior,of  many 
parts  of  Messrs.  Spiers  &  Pond's  "Crite- 
rion," in  this  manner.  The  tiles  are 
placed  together  in  their  unglazed  state, 
and  a  picture  is  painted  upon  them  in 
suitable  colors  for  firing.  They  are  then 
taken  asunder  and  put  into  the  furnace, 
and  then  subjected  to  great  heat  and 
glazed.  If  this  is  successfully  accom- 
plished, the  tiles  can  now  be  fixed 
against  the  wall  of  the  room  and  present 
an  absolutely  indestructible  decoration, 
which  can  be  washed  as  often  as  it  is 
needed,  though  from  its  high  glaze  it  is 
not  easily  apt  to  catch  dirt. 

Mosaic — the  most  ancient  of  all  the 
arts  of  decoration — has  a  claim  to  be 
named  among  the  revived  processes  if 
not  admissible  as  a  new  one.  I  shall 
not  attempt  to  describe  Salviati's  most 
praiseworthy  revival  of  glass  mosaic, 
which  has  placed  hi  the  hands  of  our 
architects  a  method  of  executing  surface 
decoration  which,  ancient  though  it  be, 
is,  I  think,  really  knew  to  Great  Britain 
in  its  application  to  vaults  such  as  the 
Wolsey  Chapel,  at  Windsor,  or  the  vault 
of  the  Albert  Memorial. 

Other  descriptions  of  mosaic,  however, 
especially  tile  mosaics,  if  less  surnptu- 


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ous,  are  less  out  of  reach,  on  the  score  of 
cost,  and  deserve  our  notice  as  affording 
a  means  of  executing  original  decorative 
work  at  a  distance  from  the  eye  as  well 
as  near.  The  ornamental  frieze  round 
the  galleries  of  the  Albert  Hall,  executed 
in  tessera?  of  about  an  inch  square,  is  a 
good  example.  Here  only  two  or  three 
tints  of  color  were  employed,  and  the 
mosaics  were  rapidly  made,  after  the  full 
size  cartoon  had  once  been  completed, 
by  placing  the  tessera?  on  a  tracing  to  a 
portion  of  the  cartoon  till  a  space  of  a 
certain  size  had  been  covered  (about  six 
superficial  feet,  I  think)  and  then  upon 
the  back  of  the  tessera?  Portland  cement 
was  applied  till  a  stout  slab  was  formed 
which  admitted  of  being  handled  readily 
and  could  be  hoisted  up  and  fixed  in 
place. 

Another  description  of  work  approach- 
ing mosaic  has  been  lately  introduced  to 
London,  and  is  obtainable  of  Mr.  Burke, 
of  Regent  Street — I  allude  to  marble 
mosaic.  This  work  is  executed  to  a 
large  extent  out  of  smallish  irregrdarly- 
shaped  fragments  of  the  material,  of  two 
or  three  tints,  so  laid  as  to  produce  the 
general  appearance  of  a  mottled  ground, 
which  gives  relief  to  a  few  portions  of 
brighter  colors  executed  in  more  valu- 
able marbles.  When  well  done  this  sort 
of  mosaic  is  very  effective  ;  it  can  be 
obtained  at  a  very  moderate  price,  and 
it  may  be  expected  to  prove  extremely 
durable. 

We  will  now  proceed  to  consider  for 
a  few  moments  the  second  head — new 
methods — not  because  the  list  of  materi- 
als is  exhausted,  far  from  it;  but  because 
enough  has  been  said  to  carry  out  my 
promise  that  I  would  name  a  few  as 
specimens  of  the  whole,  in  the  hope  that 
in  the  discussion  your  own  sources  of 
information  will  enable  you  to  enlarge 
my  list. 

New  methods  need  not  detain  us  long. 
The  building  trade  has  not  been  revolu- 
tionized by  the  introduction  of  machin- 
ery as  other  trades  have  been,  and  it  is 
really  only  in  one  or  two  of  its  branches 
that  anything  approaching  to  innova- 
tion awaits  us.  A  remarkable  attempt 
to  introduce  machinery  into  this  produc- 
tion of  high  art  work  was  made  when 
the  machines  by  which  the  woodwork  of 
the  Houses  of  Parliament  was  roughed 
out  were   designed.     These,   I   believe, 


are  now  in  the  possession  of  Messrs.  Cox 
&  Son,  and  are  still  worked  by  them; 
but  from  various  circumstances  they  do 
not  seem  to  have  become  generally 
known  or  copied. 

Machinery  for  dressing  stone  has  been 
again  and  again  attempted,  and  has  been 
employed  with  considerable  success. 
The  contractor  for  St.  Thomas's  Hospi- 
tal had  a  series  of  machines  at  work, 
partly  employed  in  sawing  up  the  stone 
and  partly  in  dressing  it ;  and  one  or  two 
stone,  dressing  yards  exist,  or  did  lately 
exist,  where  plain  descriptions  of  work 
are  performed  by  mechanical  means. 
The  action  of  such  machines  is,  gener- 
ally speaking,  that  they  bring  a  series  of 
chisels,  or  tools  answering  to  chisels, 
forcibly  down  upon  the  stone  so  as  to 
imitate  the  action  of  a  mason  at  many 
points  at  the  same  time.  Usually  the 
chisels  are  carried  on  the  periphery  of  a 
wheel,  though  different  arrangements  are 
adapted  by  different  inventors.  Pro- 
bably sawing  can  be  done  better  by  ma- 
chinery than  by  hand,  as  well  as  cheaper. 
The  plain  dressing  of  surfaces,  and  even 
the  moulding  of  them,  is  within  the 
reach  of  machinery,  but  it  is  doubtful  if 
it  will  be  so  well  executed  as  a  good 
mason  would  do  it,  especially  if  the  stone 
operated  upon  were  of  uneven  or  unequal 
texture,  and  the  more  elaborate  the  work 
or  the  fewer  the  repetitions,  the  less  ad- 
vantage, generally  speaking,  can  be  ex- 
pected from  the  machine. 

Joiners'  work  admits  of  the  applica- 
tion of  machinery  to  a  larger  extent  than 
masons'  work,  chiefly,  if  not  solely,  be- 
cause it  includes  so  much  more  repeti- 
tion. In  a  first-class  joiner's  shop  you 
now  find  a  very  interesting  and  complete 
series  of  machines,  which  render  it  pos- 
sible to  diminish  the  labor  on  j ornery 
very  largely.  It  is  hardly  necessary  to 
describe  these  inventions  at  length;  they 
may  be  seen  at  work  in  the  establish- 
ments of  our  large  builders,  and  no  one 
who  has  watched  their  operation  can 
doubt  their  efficiency  hi  all  ordinary 
work. 

Here,  perhaps,  I  may  most  appropri- 
ately introduce  a  reference  to  the  contri- 
vances for  testing  materials,  which  sup- 
ply us  with  information  as  to  their 
strength  and  behaviour  under  different 
kinds  of  strain.  We  have  now  in  Mr. 
Kirkaldy's  large  and  accurate  machine  a 


NEW   MATERIALS   AND   INVENTIONS   FOE   BUILDING. 


215 


testing  engine  of  a  power  practically  un- 
limited, and  accurate  to  the  extent  of 
making  single  pounds  of  pressure,  while 
it  will  admit  specimens  as  large  as  forty- 
feet  in  length.  Here,  then,  we  have  a 
means  of  investigating  the  strength  of 
building  materials  such  as  has  not  been 
previously  at  our  disposal,  and  we  have 
only  ourselves  to  thank  if  our  knowledge 
is  not  extended  thereby. 

Our  third  head  need  not  detain  us  long. 
New  structures  are  not  so  often  met  with 
as  that  the  enumeration  of  them  should 
fill  much  space;  and  were  we  to  attempt 
more  than  an  enumeration,  a  single  nov- 
elty would  claim  the  whole  time  at  our 
disposal.  A  railway  station,  a  Crystal 
Palace,  a  modern  hospital  on  the  pavil- 
ion plan,  a  cottage  hospital,  a  monster 
hotel,  an  aquarium,  a  winter  garden,  a 
model  prison,  a  workhouse,  a  block  of 
model  dwellings,  a  board  school — each  of 
these  is  a  new  structure,  each  embodies 
very  modern  ideas,  and  each  of  them  re- 
quires to  be  studied  with  some  care  be- 
fore it  can  be  safe  for  an  architect  to 
venture  upon  it,  and  each  is  in  fact  a 
new  structure.  And  first,  every  such 
modern  building  as  a  market,  a  town 
hall,  an  exchange,  or  a  court  of  law, 
built  to  serve  the  same  purposes  as  an- 
cient structures,  must  in  the  present  day 
be  much  more  perfect  and  much  more 
elaborate  than  was  formerly  necessary, 
and  is  in  effect  an  almost  new  contri- 
vance. 

A  year  or  two  back  we  were  threat- 
ened with  an  importation  of  Swedish  or 
Norwegian  buildings, which,  so  far  as  their 
employment  in  this  country  is  concerned, 
would  be  new  buildings.  I  refer  to  timber 
dwelling-houses.  The  publicity  given 
to  Mr.  Vicary's  importation  of  a  timber 
house,  which  he  erected  in  Devonshire, 
turned  attention  to  the  possibility  of 
building  very  roomy  structures  of  wood 
at  a  low  cost.  I  have  no  means  of 
knowing  how  far  this  house  has  been 
copied,  but  it  does  not  seem  to  have  led  to 
many  such  experiments,  or  some  of  them 
would  have  been  pretty  sure  to  become 
generally  known.  It  is  not  easy  to  see 
why  this  build  of  house  should  not  be 
followed  hi  sheltered  situations  in  this 
country.  No  doubt  careful  examination 
would  show  that  it  has  drawbacks,  but 
for  use  as  a  country  resort,  a  shooting 
lodge,  or  a  hunting  box,  a  timber  house 


properly  constructed  ought  to  be  fairly 
comfortable  and  cheap. 

This  leads  us  to  another  attempt  at 
importation,  this  time  from  our  own 
colonies,  and  due  to  the  ingenuity  of  Mr. 
John  Taylor,  whom  I  have  already  had 
occasion  to  name,  as  a  building  inventor. 
I  allude  to  the  bungalows  which  that 
gentleman  has  erected  near  Westgate, 
and  at  Birchington  in  the  Isle  of  Thanet. 
I  have  had  the  opportunity  of  seeing 
these  houses,  and  of  examining  one  of 
them  in  course  of  construction.  They 
are  very  simple  in  shape,  mostly,  but  not 
always,  one  story  high,  spanned  by  a 
simple  low-pitched  roof,  portions  of  which 
are  prolonged  in  the  true  Anglo-Indian 
style  to  form  a  verandah.  These  build- 
ings seem  thoroughly  well  adapted  to 
the  purpose  for  which  they  are  erected — 
that  of  summer  sea-side  dwelling  houses; 
they  can  be  worked  and  kept  clean  with 
a  very  small  amount  of  labor,  as  many 
contrivances  to  diminish  servants'  work 
have  been  introduced,  and  they  are  evi- 
dently cheap  to  build,  though  tasteful 
both  outside  and  in.  For  the  purpose 
of  these  buildings  Mr.  Taylor  has  in- 
vented what  may  perhaps  be  called  a 
water-proof  wall.  This  invention  has 
been  patented  by  Mr.  Taylor,  who  is 
willing  to  grant  licences  to  those  who 
desire  to  use  it. 

Other  new  buildings  are  to  be  found 
now  about  watering  places  where  a  pub- 
lic room,  more  or  less  resembling  the 
etablissement  of  a  French  sea-side  town; 
is  often  now  to  be  found,  and  where  also 
an  aquarium  or  winter  garden,  and  a 
pier  with  a  pavilion  at  its  head  is  now 
de  rigeur.  As,  however,  the  Committee 
on  Sessional  Papers  will,  without  doubt, 
see  fit  to  obtain  a  descriptive  account  of 
some,  if  not  all  these  structures,  they 
need  not  detain  us  at  the  present  mo- 
ment ;  and  the  same  remark  applies  to 
that  strikingly  new  construction  which 
the  Safe  Deposit  Company  have  engaged 
our  Fellow,  Mr.  Whichcord,  to  erect  op- 
posite the  Mansion  House. 

In  conclusion  Mr.  Smith  enumerated 
various  new  building  appliances,  and  re- 
gretted that  he  had  been  prevented  by 
want  of  time  from  procuring  a  larger 
number  of  specimens  for  exhibition.  Be- 
fore an  architect  used  any  new  invention 
he  would  naturally  first  inquire — How  it 
would  go  wrong  ;    secondly,  if  it  went 


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VAN   NOSTRAND'S   ENGINEERING   MAGAZINE. 


wrong  what  would  be  the  worst  conse- 
quences ;  and,  thirdly,  whether  failure 
was  preventable  ?  Upon  the  question  of 
repairs,  he  pointed  out  that  it  would  not 
be  a  fatal  objection  to  the  use  of  iron 
shutters  if  the  manufacturer's  works 
were  100  yards  off  ;  but  it  would  be  in- 
tolerable if  they  had  to  be  sent  100  miles 
when  they  got  out  of  repair.  The  posi- 
tion of  the  architect  with  regard  to  the 
use  of  novelties  was  a  very  responsible 
one,  and  Mr.  Smith  explained  that  his 
review  of  a  very  large  subject  had  nec- 
essarily been  very  partial  and  incom- 
plete. 

Mr.  Hebb  said  that  he  had  been  asked 
to  call  the  attention  of  the  meeting  to 
some  specimens  on  the  walls,  and  would 
apologise  for  not  doing  so,  because  the 
indiscriminate  introduction  of  inventions 
was  perhaps  not  desirable.  In  the  pres- 
ent instance  the  exhibitor  was  not  mere- 
ly the  owner  but  also  the  producer  of 
the  invention.  The  inventor,  who  lived 
in  London,  was  a  man  of  some  artistic 
ability,  and  the  process,  which  was  called 
xylography,  was  somewhat  similar  to 
that  called  xylatechnigraphy,  described 
in  a  paper  recently  read  before  the  Insti- 
tute by  Mr.  G.  T.  Robinson.  By  means 
of  the  peculiar  nature  of  the  ink  em- 
ployed the  inventor  obtained  a  cheaper 
impression  than  had  hitherto  been  pro- 
duced in  wood. 

Professor  Kerb,  in  rising  to  propose  a 
vote  of  thanks  to  Mr.  Smith,  said  that 
the  subject  selected  was  one  upon  which 
he  thought  it  would  be  well  if  an  annual 
paper  were  read.  The  public  complained 
of  the  backwardness  of  architects  in  the 
introduction  of  new  inventions,  and  he 
thought  it  would  be  good  policy  to  meet 
such  an  objection  in  the  mode  suggested, 
as  the  difficulty  he  was  convinced  would 
not  lie  in  finding  material  for  discussion, 
but  rather  in  confining  the  material 
within  reasonable  limits.  The  paper  was 
very  suggestive,  and,  like  all  that  Mr. 
Smith  undertook,  was  modest  and  unam- 
bitious :  he  knew  where  to  stop.  One 
thing,  Professor  Kerr  said,  he  could  not 
help  observing — that  although  Mr.  Smith 
began  by  saying,  in  effect,  that  building 
was  making  no  progress  at  all  as  com- 
pared with  the  progress  made  in  various 
other  arts,  yet  in  the  course  of  his  dis- 
quisition he  proved  that  building  was 
making    very    great     progress    indeed. 


This  was  sufficiently  apparent  to  anyone 
who  looked  back  twenty  or  thirty  years, 
and  still  more  so  to  those  whose  memory 
could  carry  them  back  to  a  remoter 
period.  Mr.  Smith  had  referred  to  the 
use  of  iron  and  glass  for  structural  pur- 
poses ;  and  the  extent  to  which  those 
materials  had  developed  in  various  de- 
partments was  remarkable.  At  the  same 
time,  the  crystal  palaces  built  in  various 
parts  of  the  country,  although  works  of 
great  magnificence,  could  not,  structur- 
ally speaking,  be  regarded  as  a  great 
success.  Great  effects  were  no  doubt 
accomplished,  yet  he  did  not  think  that 
architecture  had,  constructively  speak- 
ing, very  materially  advanced  by  that 
invention.  One  matter  well  worthy  of 
consideration  was  whether  steam  might 
not  be  rendered  subservient  to  building 
processes.  In  his  (Professor  Kerr's)  opin- 
ion the  Vienna  dome  or  Vienna  cone)  as 
it  ought  properly  to  be  designated)  was 
one  of  the  most  remarkable  inventions 
of  modern  times — its  marvellous  simplic- 
ity was  extremely  interesting,  and  he 
would  repeat  what  he  had  said  before, 
that  students  of  construction  would  be 
well  repaid  by  mastering  the  principles 
involved  in  its  construction.  With  re- 
gard to  Phillips'  girders  he  thought  the 
invention  was  meritorious,  and  scarcely 
deserved  to  be  passed  over  with  the  as- 
sertion that  it  consisted  mainly  in  the 
accumulation  of  material  at  the  neutral 
axis,  because  the  simplicity  of  the  gird- 
ers, and  the  absence  of  riveting  were 
most  important  features  and  worthy  of 
careful  study.  As  to  the  selenitic  mortar, 
of  which  Mr.  Smith  spoke  with  much 
approval,  it  was  rather  a  pecubar  thing, 
and  he  believed  that  although  General 
Scott  was  credited  with  its  discovery, 
selenitic  mortar  was,  in  fact,  based  upon 
an  invention  of  Mr.  Westnacott  —  the 
only  difference  being  that,  for  the  pur- 
pose of  expelling  the  carbonic  acid  from 
the  stone,  gypsum  was  substituted  by 
General  Scott  for  ground  chalk.  Upon 
the  question  of  concrete  he  maintained 
that  a  concrete  wall,  as  compared  with 
stone  or  brick,  was  the  only  perfect  wall 
we  had  ;  the  only  difficulties  were  in  the 
successful  manipulation  of  the  concrete, 
and  in  making  it  air-tight.  The  wet 
might,  he  believed,  be  excluded  from  a 
concrete  wall  by  the  application  of  ce- 
ment :   and  concrete   should  not  be  re- 


MAGNETIC   IRON    ORES   OF   NEW   JERSEY. 


217 


garded  as  a  substitute  for  brick  and 
stone,  but  as  something  entirely  distinct. 
Upon  the  interesting  subject  of  artificial 
stone,  the  Professor  said  that  he  was 
glad  to  hear  Mr.  Smith  touch.  Ran- 
some's  artificial  stone  would  probably 
have  been  much  more  extensively  used 
if  it  had  not  been  brought  out  at  too 
high  a  price  to  admit  of  its  competing 
with  natural  stone.  The  material  was 
used  extensively  in  America,  but  only  to 
a  very  limited  extent  in  England.  The 
question  of  terra  cotta  had  been  dealt 
with  very  properly,  but  not  exhaustively, 


by  Mr.  Smith.  He  (Prof.  Kerr)  thought 
that  in  designing  terra  cotta  they  should 
endeavor  to  accommodate  it  to  the 
roughness  of  the  materials  with  which  it 
was  associated,  and  he  objected  alto- 
gether to  the  principle  of  the  indefinite 
of  the  reproduction  of  the  same  kind  of 
forms. 

Why  should  not  terra  cotta  in- 
stead of  being  treated  for  the  sake  of 
obtaining  an  infinite  reproduction  of  the 
same  feature  be  handled  with  the  tool  in 
such  a  way  as  to  procure  much  greater 
variety  ? 


THE  MAGNETIC  IRON  ORES  OF  NEW  JERSEY— THEIR 

GEOGRAPHICAL    DISTRIBUTION    AND 

GEOLOGICAL   OCCURRENCE. 

By  Professor  J.  C.  SMOCK,  New  Brunswick,  New  Jersey. 
Transactions  of  American  Institute  of  Mining  Engineers. 


The  magnetic  iron  ores  of  New  Jer- 
sey are  found  in  the  northern  part  of  the 
State,  in  the  Highland  Mountain  range, 
which  runs  from  the  New  York  line  on 
the  northeast,  to  the  Delaware  River, 
near  Easton,  at  the  southwest.  The 
same  range  continues  across  Orange 
County  to  the  Hudson  River,  and  towards 
the  southwest  it  is  known  in  Pennsyl- 
vania as  the  South  Mountain.  It  is  more 
properly  an  elevated  table-land,  quite 
deeply  furrowed  by  several  narrow, 
longitudinal  valleys,  and  shorter  cross- 
valleys  or  gaps.  The  ridges  or  lines  of 
elevation,  as  well  as  the  lower  valleys, 
conform  in  their  general  direction  very 
closely  to  the  general  trend  of  the  whole 
belt  or  table-land,  that  is,  from  north- 
east to  southwest.  This  also  agrees 
with  the  prevailing  strike  of  the  rocks. 
This  great  uniformity  in  the  altitudes  of 
the  hills  and  ridges,  and  the  direction  of 
the  lines  of  depression  corresponding  to 
the  strike  of  the  strata,  point  to  an  orig- 
inal table-land,  which,  through  the  long 
action  of  denuding  agents,  has  been 
quite  deeply  eroded,  giving  rise  to  the 
present  surface  configuration,  so  that 
some  of  the  former  and  uniform  features 
have  been  partially  obliterated.  The  very 
few  cross-valleys  or*  depressions  are 
much  more  irregular  in  their  course,  and 


serve  as  outlets  through  which  the  drain- 
age is  carried  either  into  the  Kittatinny 
Valley  on  the  northwest,  or  to  the 
broad,  red  shale  and  sandstone  plane 
bounding  the  highlands  on  the  south- 
east. The  area  of  this  highland  region 
in  New  Jersey  is  about  nine  hundred 
square  miles.  Its  average  elevation 
above  the  ocean  is  about  one  thousand 
feet. 

Except  the  valleys  towards  the  north- 
western border,  as  the  Wallkill,  Mus- 
conetcong,  Pohatcong,  and  German, 
which  contain  magnesian  limestone  and 
Hudson  River  slate,  this  whole  range 
consists  of  crystalline  rocks,  mainly 
gneiss,  granite,  syenite,  and  limestone, 
covered  in  many  places  by  drift  and 
alluvial  beds.  These  rocks  resemble 
closely  those  of  the  Laurentian  forma- 
tion of  Canada,  both  in  their  structure 
and  mineralogical  characters.  Stratifica- 
tion is  nearly  everywhere  plain,  indicat- 
ing a  sedimentary  origin  and  subsequent 
metamorphism.  In  the  Geological  Sur- 
vey reports  of  the  State  they  have  been 
described  as  belonging  to  the  "  Azoic 
Formation." 

It  is  in  this  series  of  crystalline,  meta- 
morphic  rocks,  that  the  magnetic  iron 
ores  occur.  The  extent  of  this  outcrop 
and   the   iron   mines   and    localities    at 


218 


VAN  nostkand's  engineeking  magazine. 


which  ore  in  workable  amounts  has  been 
obtained,  are  both  indicated  upon  the 
geological  maps  of  the  State  survey,  one 
of  which  has  just  been  published.  This 
map  shows  the  mines  as  in  lines  nearly 
parallel  to  one  another,  and  having  the 
same  direction  as  that  of  the  whole  belt 
or  range.  In  some  instances  they  are 
so  close  as  almost  to  form  a  continuous 
line,  as  the  Mount  Hope,  Allen,  Baker, 
Richards,  Mount  Pleasant,  and  others, 
near  Dover,  in  Morris  county.  Others 
appear  in  a  sort  of  en  echelon  arrange- 
ment. 

This  occurrence  in  lines,  or  what  may 
be  more  properly  termed  ranges,  is  so 
well  known  that  miners  and  those  search- 
ing for  ore  speak  of  veins  continuing  for 
miles,  and  of  certain  mines  belonging  to 
certain  veins.  Large  and  productive 
mines,  as  the  Hibernia,  Mount  Hope, 
TDickerson,  Ogden,  and  Kishpaugh,  with 
others,  give  names  to  such  lines.  The 
complete  breaks  in  veins  worked,  and 
the  absence  of  any  indications  of  con- 
tinuity, show  that  these  popular  theories 
are  not  yet  substantiated  by  the  facts, 
although,  if  by  the  terms  lines  or  veins, 
or,  better,  ranges,  series  of  ore-beds 
whose  several  lines  of  strike  or  axes  run 
closely  parallel  to  one  another,  are 
meant,  then  they  have  a  foundation  in 
truth.  In  the  "Geology  of  New  Jer- 
sey," published  in  1S68,  the  mines  then 
opened  were  grouped  in  such  lines,  and 
these  were  called  ranges.  The  map  ac- 
companying that  report,  as  well  as  the 
one  just  issued  issued  by  the  State  Sur- 
vey, shows  these  lines  and  the  interven- 
ing belts.  A  comparison  of  these  two 
maps  confirms  in  some  degree  this  theory 
of  ranges,  or  what  would  be  better 
termed,  ore-belts,  inasmuch  as  the  hun- 
dred or  more  new  mines  and  ore  out- 
crops opened  since  1868,  and  repre- 
sented on  the  latter  map,  are  nearly  all 
either  on  old  and  well-known  lines  or 
what  must  be  considered  as  new  ones. 
These  discoveries  have  shortened  the  gaps 
and  widened  the  ranges.  Thus  the  new 
mines  near  Chester,  and  those  along  the 
eastern  base  of  Copperas  Mountain,  all 
in  Morris  County,  have  tilled  in  wide 
blanks,  and  greatly  extended  what  were 
but  very  faintly  indicated  as  ranges  or 
belts  of  ore.  The  numerous  openings 
quite  recently  made  on  Marble,  Scotts, 
and  Jenny  Jump  Mountains,  in  Warren 


Countjf,  constitute  a  new  and  marked 
line.  In  this  the  manganiferous  charac- 
ter of  the  ore  throughout  its  whole 
length  seems  to  give  additional  evidence 
in  proof  of  such  a  relation.  An  order  of 
arrangement  or  division  into  such  lines 
or  belts,  based  upon  lithological  and 
mineralogical  characters,  has  not  been 
possible,  but  it  is  hoped  that  further 
studies  will  develop  the  existence  of 
such  characteristic  features  which  will 
confirm  the  indications  from  the  geo- 
graphical distribution. 

The  last  map  also  shows  groups  of 
mines,  between  which  very  little  ore  has 
been  found.  One  of  the  best  known 
and  largest  of  these  groups  is  near 
Dover,  Morris  County,  and  a  map  of 
this  district  was  published  in  1868. 
Northeast  of  this  there  is  an  interval  of 
several  miles,  extending  almost  to  Ring- 
wood,  in  which  there  are  no  working 
mines,  and  comparatively  but  few  local- 
ities where  ore  is  known  to  exist.  But 
the  newly  opened  Board,  Ward,  Green 
Pond,  Pardee,  and  Splitrock  mines, 
show  that  the  lines  of  ore  are  beginning 
to  be  traced  into  this  hitherto  barren 
district,  and  point  to  future  discoveries 
which  will  connect  the  Ringwood  and 
Sterling  groups  with  the  Morris  County 
lines.  A  lack  of  cheap  and  ready  trans- 
portation has  prevented  the  thorough 
examination  of  this  part  of  the  State,  or 
the  development  of  any  localities  which 
were  promising. 

The  extended  workings  in  the  older 
mines  are  also  doing  much  to  prove  the 
great  length,  and  probably  continuity, 
of  some  of  these  veins.  Thus  the  long 
run  from  Mount  Hope  to  the  Dickerson 
mine,  a  distance  of  seven  miles,  has 
been  so  opened  as  to  show  an  almost 
uninterrupted  bed  or  vein  of  ore,  or  a 
series  of  veins  parallel  to  each  other, 
and  all  within  a  very  narrow  belt;  and 
all  of  the  facts  of  geographical  distribu- 
tion, as  well  as  the  arguments  which 
could  be  drawn  from  the  probable  mode 
of  origin  of  this  ore,  tend  to  support  this 
theory  of  lines  or  ranges,  or  better,  per- 
haps, belts  of  ore. 

Magnetite,  as  a  mineral,  is  very  com- 
mon in  the  crystalline  rocks  of  the  High- 
lands, occurring  more  frequently  than 
any  other  mineral,  excepting  the  ordinary 
constituents  of  ttie  gneissic  rocks,  viz., 
quartz,  feldspar,  mica,  and  hornblende, 


MAGNETIC   IRON   ORES   OF   NEW   JERSEY. 


219 


And  so  widely  is  it  distributed  that  it  is 
impossible  to  find  many  strata  in  succes- 
sion where  it  is  entirely  wanting.  It 
appears  as  one  of  the  constituent  miner- 
als of  these  beds,  either  wholly  or  in 
part  replacing  their  more  common  com- 
ponents, or  it  is  added  to  these,  and  in 
each  case  occurs  in  thin  layers  or  laminae 
alternating  with  them,  or  it  is  irregularly 
distributed  through  the  rock  mass.  The 
unstratified  granitic  and  syenitic  rocks, 
as  well  as  the  bedded  gneisses,  also  often 
contain  magnetite.  In  these,  however, 
it  occurs  in  larger  and  more  irregular 
crystalline  masses  or  bunches,  and  does 
not  appear  to  be  so  properly  a  constitu- 
ent of  the  whole,  but  rather  as  foreign 
to  it.  The  same  mode  of  replacement  is 
sometimes  seen  in  these  as  in  the  strati- 
fied rocks.  In  both  these  classes  it 
enters  into  the  composition  in  all  propor- 
tions, increasing  in  amount  until  the 
whole  is  sufficiently  rich  to  be  considered 
as  an  ore  of  iron.  Between  rock  entirely 
free  from  magnetite  and  the  richest  ore 
there  is  an  endless  gradation,  making  it 
impossible  to  fix  any  other  line  of  de- 
marcation between  them  other  than 
that  of  the  minimum  percentage  for  the 
profitable  extraction  of  the  iron.  Three 
modes  of  occurrence  have  been  assigned 
to  this  mineral,  two  of  which  are  in  the 
rock,  as  one  of  its  constituents  either  in 
irregular  bunches  or  in  a  granular  form, 
and  the  third  in  seams  or  strata,  when  it 
is  called  ore.  But  these  distinctions  are 
not  fixed,  and  therefore  it  is  better  to 
consider  it  as  one  of  the  more  common 
minerals  of  these  gneissic  and  granite 
rocks,  and  in  places  forming  the  whole 
mass,  or  else  so  much  of  it  as  to  be 
workable,  and  then  to  be  called  an  ore. 
Rock  containing  from  twenty  to  forty  per 
cent,  of  metallic  iron,  the  most  of  which 
is  in  the  form  of  magnetite,  has  been 
found  in  many  places,  and  some  of  these 
have  been  explored  to  a  considerable 
extent  in  searching  for  richer  ores.  The 
granitic  and  syenitic  rocks  containing 
magnetite  are  generally  found  to  cut  the 
beds  of  gneiss,  and  are,  geologically, 
huge  ore  -  bearing  dykes.  The  most 
common  mineral  aggregation  is  feldspar, 
quartz,  magnetite,  and  hornblende,  or 
mica,  although  in  some  cases  both  the 
latter  enter  into  the  composition.  Such 
rock  is  worked  at  a  few  points,  but  these 
operations   are   not   yet   worthy  of  the 


designation  of  mines.  And,  in  fact,  the 
great  irregularity  and  the  varying  per- 
centage of  iron  in  it  does  not  make  it  a 
desirable  ore.  Gneiss  containing  mag- 
netite in  quantity  sufficient  to  render  it 
workable,  has  been  opened  and  mined  at 
several  localities.  Perhaps  it  should  be 
called  lean  ore.  One  of  the  most  exten- 
sive outcrops  of  such  ore  is  near  the 
Pequest  mine,  in  what  is  known  as  the 
Henry  tunnel,  about  two  miles  north  of 
Oxford  Furnace.  Here  there  is  a  breadth 
of  twelve  feet  or  more,  in  which  the 
beds  are  highly  impregnated  with  mag- 
netite, while  those  on  each  side  are  free 
from  it.  Extensive  drifting  and  sinking 
have  exposed  several  hundred  feet  of 
these  beds  on  the  line  of  strike,  and 
shown  an  increase  in  the  percentage  of 
iron  going  from  the  surface  to  the  lowest 
levels.  Near  Hackettstown,  in  Warren 
County,  there  are  several  localities  of 
such  ore-bearing  rock,  but  nearly  all  of 
them  are  failures  as  mines.  The  Scrub 
Oak  mine,  near  Dover,  the  Combs  mine, 
near  Walnut  Grove,  the  Swedes  and 
Beach  Glenn  mines,  also  in  Morris  Coun- 
ty, have  large  portions  of  their  veins  so 
mixed  with  rock  that  they  may  be  class- 
ed with  the  above  localities  of  ore-bear- 
ing gneiss.  And  all  the  lean  ores  of  the 
State  may  be  considered  as  gradations 
in  the  series  from  rock  to  what  is  con- 
ventionally termed  ore. 

While  it  is  impossible  to  separate  these 
lean  ores  from  the  rock  upon  any  decis- 
ive or  marked  distinctions  or  differences, 
the  richer  ores  are  to  be  considered  as  a 
distinct  mode  of  occurrence,  as  these 
differ  from  the  lean  ores  and  rock  in 
their  simplicity  of  composition,  being 
made  up  of  fewer  elements,  and  these 
predominating  to  the  exclusion  of  all 
others. 

Assuming  this  as  another  mode  in 
which  the  magnetite  occurs,  the  geologi- 
cal features  of  these  seams  or  strata  may 
claim  our  attention. 

They  are  often  called  veins  because  of 
their  highly  inclined  or  almost  vertical 
position,  and  hence  resemblance  to  true 
veins.  Their  irregular  form  has  helped 
to  strengthen  this  opinion  of  them.  But 
as  they  show  well-marked  planes  of 
stratification  and  also  lamination,  both 
parallel  to  the  beds  of  gneiss  which  in- 
close them  on  the  sides,  and  have  strike, 
dip,  and  pitch,  and  are  folded,  bent,  con- 


220 


VAN   NOSTRAND'S   ENGINEERING   MAGAZINE. 


torted,  and  broken,  just  as  stratified  rock, 
they  must  be  called  beds,  and  be  classed 
among  the  sedimentary  rocks.  The  ir- 
regularities in  their  extent,  thickness, 
and  the  presence  of  included  masses  of 
rock,  known  as  horses,  are  phenomena 
common  to  the  gneiss  and  them,  and 
therefore  these  cannot  serve  as  an  argu- 
ment for  calling  them  veins.  Lenticular 
masses  of  micaceo-hornblendic  gneiss, 
lying  in  feldspathic  and  quartzose  beds, 
or  the  converse,  are  quite  common,  nor 
do  the  strata  of  these  rocks  run  on  un- 
changed in  character.  But  tbey  thin  out 
or  grow  thicker,  or  change  in  mineral 
composition  just  as  these  veins  are  seen 
to  pinch  out  or  swell  into  thick  shoots,  or 
be  replaced  more  or  less  gradually  by 
rock.  The  similarity  in  these  respects 
between  these  ore  masses  and  the  sur- 
rounding stratified  rocks  proves  them  to 
be  beds  and  of  contemporaneous  origin. 
Imbedded  in  the  gneissic  strata  of  this 
highland  belt  or  region,  these  iron-ore 
beds  or  veins  (so  called)  have  the  same 
general  strike  or  dip  in  common  with 
them.  The  prevailing  direction  of  the 
first  is  towards  the  northeast,  varying, 
however,  within  the  quadrant  from  north 
to  east.  In  most  cases  it  is  between  the 
north  and  northeast.  From  these  there 
are  several  exceptions,  as  at  Oxford  Fur- 
nace, where  the  veins  run  north  25°  west; 
the  Connet  mine,  a  few  miles  west  of 
Morristown,  where  it  is  also  northwest 
and  southeast.  While  these  lines  of 
strike  have  a  general  straight  bearing, 
they  exhibit  short  irregularities  and  de- 
flections, often  varying  from  side  to  side, 
or  zigzagged  by  faults  or  offsets.  The 
rocks  of  this  formation,  as  observed  in 
hundreds  of  places,  show  the  same  pre- 
vailing straight  lines  as  are  seen  in  the 
longer  openings  for  ore.  Bends  or  fold- 
ings are  very  rare.  One  of  the  most  re- 
markable of  these  is  on  Mine  Hill,  Frank- 
lin, Sussex  County,  although  this  ^occurs 
in  a  zinc  vein  or  bed,  and  not  in  iron  ore. 
Here  there  is  a  quite  sudden  bend,  so 
that  the  vein  returns  almost  to  its  origi- 
nal course — which  is  the  usual  northeast 
and  southwest  one.  In  the  iron  mines  of 
the  State,  the  Waterloo  or  Brookfield 
mine,  about  five  miles  north  of  Hacketts- 
town,  in  Warren  County,  shows  a  curv- 
ing strike — turning  from  northeast  and 
southwest  to  north  and  south.  Further 
opening  may  find   as  complete  a  bend 


here  as  is  to  be  seen  on  Mine  Hill.  But 
the  best  example  of  such  folding  is  at 
Durham,  Pa.,  where  the  iron-ore  vein,  as 
followed  in  the  mining  operations,  coin- 
cides in  its  course  very  nearly  with  the 
contour  line  of  the  Mine  Hill,  running 
around  in  a  semicircle  on  the  western 
side  of  this  elevation. 

The  dip  of  these  ore-beds  being  at 
right  angles  to  the  line  of  strike  has,  of 
course,  the  same  degree  of  uniformity 
in  direction,  and  that  is  towards  the 
southeast ;  or  more  generally  towards 
the  east-southeast.  In  some  localities 
the  strata  are  in  a  vertical  position  or 
inclined  towards  the  northwest,  and  the 
dip  is  in  that  direction.  But  this  has 
been  observed  in  a  few  mines  only,  and 
in  some  of  these,  deeper  working  has 
found  the  vein  below  assuming  the  pre- 
vailing southeast  dip,  indicating  the  ex- 
istence of  a  fold,  of  which  the  vein 
opened  is  a  segment,  or  a  bending  over 
near  the  surface  caused  by  some  power- 
ful force  acting  subsequently  to  the  ele- 
vating and  folding  agents.  The  Beach 
Glenn  and  Davenports'  mines,  in  Morris 
County,  offer  illustrations  of  northwest 
dips.  The  rock  outcrops  show  a  number 
of  such  directions,  but  they  are  compara- 
tively few  in  number,  when  the  thousand 
or  more  observed  southeast  dips  are  con- 
sidered. In  the  Connet  mine  (mentioned 
above)  the  dip  is  towards  the  southwest. 
At  Durham  it  is  radiating  towards  a 
central  axial  line  of  what  is  considered 
as  a  fold,  and  in,  towards  the  centre  of 
the  hill.  In  the  Hurd  mine,  as  also  at 
the  zinc  mine,  Franklin,  the  two  legs  of 
the  synclinals  show  dips  at  different 
angles  towards  the  southeast,  one  of 
those  at  Hurdtown,  being  almost  verti- 
cal, while  the  other  is  quite  steep.  In 
the  large  openings  of  the  Ford  and  Sco- 
field  mines  there  is  no  dip,  the  beds 
standing  vertical. 

The  term  pitch  is  used  to  designate 
the  descent  or  inclination  of  the  ore-bed 
or  shoots  of  ore  towards  the  northeast — 
or  in  the  line  of  strike.  If  we  should 
conceive  of  the  line  of  strike  as  broken 
and  depressed  so  as  to  descend  towards 
the  northeast,  we  should  get  a  good  ex- 
ample of  this  pitch  of  shoots.  This  in- 
clination has  been  observed  in  the  rock 
as  well  as  in  the  ore.  It  is  so  commonly 
observed  in  mining  these  magnetic  ores 
as  to  be  expected  everywhere,  and  min- 


MAGNETIC   IKON  ORES   OP  NEW  JERSEY. 


221 


ers  speak  of  the  ore  pitching  or  shooting, 
and  their  working  has  constant  reference 
to  such  a  structure  in  both  ore  and  the 
inclosing  rocks.  In  nearly  all  cases  the 
.  pitch  is  towards  the  northeast.  It  is 
beautifully  exhibited  in  the  Cannon 
mine,  at  Ringwood,  where  it  amounts  to 
45°  inclination  from  a  hoi'izontal  line. 
The  long  slope  of  the  Hurd  mine,  in 
Morris  County,  and  the  thick  swells  al- 
ternating with  intervening  pinches,  or 
barren  ground,  at  Mount  Hope,  show 
this  same  structural  phenomenon. 

These  shoots  of  ore,  however  named, 
are  best  described  as  "  irregular,  lenticu- 
lar masses  of  ore  imbedded  in  the  gneiss, 
their  longest  diameters  coinciding  with 
the  strike  and  pitch  of  the  rock,"  which 
in  nearly  all  cases  is  towards  the  north- 
east, and  their  dip  conforming  to  that  of 
the  same  surrounding  rocky  case,  and 
generally  at  a  high  angle  towards  the 
southeast.  They  vary  greatly  in  their 
dimensions,  sometimes  thinning  out  or 
pinching,  when  followed  on  the  line  of 
the  strike,  or  on  that  of  the  dip,  to  a 
thin  sheet  or  seam  of  ore  and  occasion- 
ally ending  wedge-like  in  rock.  Some- 
times they  split  up  into  several  small 
veins  or  fingers  which  are  dovetailed,  as 
it  were,  in  with  the  rock,  and  so  gradually 
pinch  out.  Quite  often  there  is  a  sort  of 
flattened  kernel  or  core  of  rock  inclosed 
in  the  shoots  of  ore,  but  generally  these 
horses,  or  what  are  called  such,  are  in- 
terpenetrating masses  of  rock  from  the 
outside  country  rock.  Extensive  mining 
operations  and  explorations  have  shown 
some  of  these  shoots  to  be  connected  with 
others,  forming  a  series  of  these  lenticu- 
lar masses,  or  if  not  actually  united  by 
ore,  associated  and  arranged  on  closely 
parallel  planes,  if  not  in  the  same  axial 
plane.  Following  the  plane  of  the  dip 
downwards,  the  pinches  between  the 
shoyts  are  nearly  everywhere  continuous 
sheets  of  ore,  and  these  are  not  often 
greater  in  breadth  than  the  shoots. 
That  is,  the  distance  from  shoot  to  shoot 
measured  across  the  pinch  is  not  often 
greater  than  the  breadth  of  the  former. 
But  quite  frequently  these  shoots  are  en- 
tirely separate  from  one  another,  rock 
intervening  in  the  same  plane,  or  they 
are  in  different  planes  or  geological  hori- 
zons. Nearly  all  of  our  New  Jersey 
mines  work  on  more  than  one  shoot, 
since  the  extraction  of  the  ore  from  near 


the  surface  is  easier  and  more  economi- 
cal than  following  a  single  shoot  down- 
wards. Their  length  is  unknown.  In 
the  Hurd  mine  the  slope  is  nearly  900 
feet  long  descending  on  the  bottom  rock 
and  there  are  no  signs  of  exhaustion.  In 
the  Weldon  mine  (near  the  Hurd  mine) 
there  are  two  shoots  side  by  side,  but 
not  exactly  parallel,  nearing  each  other 
as  they  pitch  down,  and  now  separated 
by  about  twelve  feet  of  gneiss  rock. 
These  may  come  together  and  prove  to 
be  leaders  from  one  large  shoot. 

In  most  of  our  iron  mines  the  ore  is 
bounded  by  well  defined  walls  or  strata 
of  rock  from  which  the  ore  comes  off 
clean  in  mining,  but  very  frequently 
there  are  no  such  plain  boundaries  or 
sudden  transitions  from  magnetite  to 
gneiss,  but  a  very  gentle  gradation  of 
ore  into  rock,  and  in  these  cases  the  min- 
ing goes  only  so  far  as  the  richness  of 
the  beds  in  iron  makes  it  profitable  to 
remove  them.  Following  the  shoots 
downward,  the  same  gradual  replace- 
ment has  been  observed  until  the  whole 
was  too  lean  to  work,  or  altogether  free 
from  ore  ;  but  this  feature  is  not  so  com- 
mon as  that  of  the  gradation  or  replace- 
ment towards  the  sides  of  the  shoots  or 
the  walls.  Occasionally  the  shoot  is  said 
to  run  out,  that  is,  there  is  a  sudden 
change  from  ore  to  rock  ;  some  of  these, 
however,  may  be  faults  rather  than 
shoots  changed  in  mineral  composition. 

The  thinning  out  of  the  shoots  towards 
the  edges,  or  at  right  angles  to  the  line 
of  pitch,  or  towards  what  may  be  called 
the  lines  of  pinch,  which  run  parallel  to 
the  lines  of  swell  or  axes  of  these  shoots, 
has  originated  the  terms  cap-rock  and 
bottom  rock.  The  former  makes  the 
arched  or  double-pitched  roof  of  the 
mine,  while  the  latter  constitutes  the 
trough-like  floor  or  bottom.  These  pecu- 
liar features  are  very  finely  exhibited  in 
the  Hurd  mine,  Hurdtown,  Morris 
County,  where  the  extraction  of  the  ore, 
following  the  conformation  of  the  shoot, 
has  left  the  cap-rock  overhead  and  the 
bottom  rock  below,  on  which  the  long 
slope  runs  down  to  the  bottom  of  the 
mine. 

In  the  Cannon  mine,  at  Ringwood, 
the  same  capping  rock  appears  in  the 
heading  or  northeast  side  of  the  large 
opening,  and  the  track  runs  down  on  the 
bottom    rock     towards    the    northeast. 


222 


VAN  nostrand's  engineering  magazine. 


Here  the  pitch  is  nearly  twice  as  great 
as  in  the  Hurd  mine  and  the  shoot  as 
worked  is  much  broader  being  nearly 
of  the  same  size  both  ways.  And  here 
there  may  be  said  to  be  four  walls  that 
surround  the  ore.  Sometimes  miners 
speak  of  these  top  and  bottom  rocks  as 
walls.  But  generally  there  is  a  narrow 
vein  or  sheet  of  ore  left  both  at  the  top 
and  in  the  bottom  ;  and  these  may  gra- 
dually run  out  entirely,  or  they  may  con- 
nect with  other  shoots  of  ore  lying  in 
the  same  plane  of  dip  as  that  of  the 
shoot  worked.  And  this  is  true  in  near- 
ly every  case  ;  the  exceptions  being  con- 
sidered as  not  yet  fully  demonstrated  as 
such,  since  the  mining  operations  gener- 
ally cease  when  the  vein  pinches  up  so 
as  to  become  unprofitable  for  the  remov- 
al of  its  ore. 

The  extent  of  these  shoots  of  ore  is 
exceedingly  varying,  and  our  mines  are 
not  yet  deep  enough  to  show  their  maxi- 
mum length.  The  width  and  thickness, 
or  the  lateral  dimensions,  are  soon  ascer- 
tained, the  former  scarcely  ever  exceed- 
ing one  hundred  feet,  from  cap  to  bottom 
rock,  or  from  pinch  to  pinch  ;  and  the 
latter  varying  from  an  inch  to  eighty 
feet  ;  but  more  often  less  than  thirty 
feet — they  may  average  five  to  twenty 
feet.  These  figures  always  include  some 
rock,  or  horses.  The  oldest  and  deepest 
of  our  mines,  as  the  Blue  mine,  at  Ring- 
wood,  the  Mount  Hope,  Swedes,  Dicker- 
son,  and  Hurd  mines,  are  all  steadily 
going  down,  increasing  the  length  of 
their  slopes,  and  they  are  apparently  as 
inexhaustible  as  ever,  and  promise  to 
continue  so,  at  least  as  far  as  our  present 
appliances  for  hoisting  ore  and  water  can 
allow  of  the  economical  extraction  of 
ore  from  them.  Such  are  some  of  the 
more  general  and  essential  features  that 
characterize  the  iron-ore  beds  of  the 
State. 

Lying  imbedded  in,  and  being  con- 
temporaneous in  origin  with,  the  gneis- 
soid  rocks  of  this  Azoic  formation,  these 
ore  beds  or  veins  have  been  subject  to 
the  same  disturbing  forces  which  have 
elevated,  folded,  wrinkled,  and  broken 
all  the  strata  belonging  to  it,  and  which 
have  given  to  it  its  present  structure. 
These  forces,  so  manifold  and  acting 
through  so  long  a  period  of  time,  and 
probably  at  wide  intervals,  have  so  des- 
troyed any  degree  of  uniformity  which 


once  may  have  existed,  that  it  is  often 
difficult,  and  sometimes  impossible,  to 
recognize  amidst  this  chaos  any  order  of 
structure  whatever.  The  beds  of  ore 
and  rock  have  been  squeezed  into  close 
folds,  so  that  they  now  stand  on  edge, 
and  through  these  agencies  have  come 
the  strike  and  dip.  Other  forces  acting 
on  lines  traversing  the  veins  at  all  angles, 
have  variously  dislocated  and  further  dis- 
turbed the  strata,  giving  rise  to  frequent 
faults  or  offsets,  and  what  are  called 
cross-slides — phenomena  seen  in  both  the 
veins  and  in  the  rock  strata  of  this  for- 
mation. In  some  instances  the  veins 
have  been  displaced  one  hundred  feet, 
while  in  others  the  ore-mass  has  been 
broken  apart,  but  not  pushed  aside,  so  as 
to  interrupt  its  course.  The  planes  of 
these  dislocations  traversing  the  veins  in 
all  directions,  the  dip  and  strike  are 
sometimes  both  altered.  These  faults 
are  common,  and  can  be  seen  in  nearly 
all  of  the  mines  ;  sometimes  so  frequent 
as  to  cut  the  vein  into  short  segments, 
giving  it  a  zigzag  course.  The  most  re- 
markable faults  or  offsets  are  seen  in 
the  Mount  Hope  mines,  where  five  veins 
are  all  displaced  over  a  hundred  feet ;  in 
the  Hurd  mine,  where  the  displacement 
has  been  in  a  vertical  plane  and  the  or- 
iginal long  and  continuous  shoot  appears 
as  two  distinct  masses,  the  upper  of 
which  has  been  worked  out.  Other  ex- 
amples are  in  the  Byram  and  the  Mount 
Pleasant  mines,  near  Dover.  Generally 
a  thin  seam  of  ore  mixed  with  rock  con- 
nects the  vein  on  corresponding  sides  of 
the  fault,  and  this  serves  often  as  a 
gtfide  to  find  the  vein  beyond  the  break 
or  offset.  Miners  have  several  so-called 
rules  about  offsets,  but  these  are  not  uni- 
versal, and  there  is  no  general  law  in 
the  direction  of  the  throw  or  displace- 
ment. Occasionally  one  fault  is  crossed 
by  another — increasing  the  irregularity 
in  the  course  of  the  vein. 

From  these  numerous  faultings,  dis- 
covered in  mining  operations,  we  learn 
something  of  the  extent  to  which  these 
strata  have  been  disturbed  since  their 
original  deposition,  and  probably  all 
subsequent  to  their  elevation  and  com- 
pression into  folds.  More  thorough  sur- 
veys of  the  surface  and  more  extended 
mining  may  yet  enable  the  geologist  and 
miner  to  trace  out  these  lines  of  frac- 
ture, and  learn  how  much  they,  together 


VENTILATION  BY  VERTICAL  SHAFTS. 


223 


with  the  general  effects  of  elevation  and 
folding  of  the  whole  formation,  have 
contributed  towards  the  grouping  of  the 
iron-ore  as  we  find  it,  and  this  knowledge 
may  direct  both  our  mining  and  our 
searches  for  ore.  The  facts  already  ob- 
tained point  to  a  system,  and  the  suc- 
cessful pursuit  of  the  ore  in  its  crooked 
and  broken  course  in  some  of  the  largest 


mines  is  the  best  evidence  of  the  accu- 
racy of  the  laws  of  structure  as  now  un- 
derstood. 

They  also  show  most  forcibly,  and 
illustrate  most  beautifully,  the  inti- 
mate and  necessary  relations  of  mining 
and  the  principles  of  geology,  and  show 
that  the  two  ought  never  to  be  disso- 
ciated. 


VENTILATION  BY  VERTICAL  SHAFTS. 


Prom  "  The  Architect." 


The  Times  has  published  a  long  article 
upon  a  discovery  by  a  Mr.  Tobin,of  Leeds, 
of  a  method  of  ventilation  which,  it  is 
affirmed,  renders  the  atmosphere  of  any 
chamber   as  pure   as   that   outside    the 
building,  without  improper  lowering  of 
temperature,  and  without  the  production 
of  draught.     Mr.  Tobin's  own  account 
of  the  matter  is  that  he  was  once  watch- 
ing a  current  of  water  which  flowed  into 
a  still  pond.    He  observed  that  the  mov- 
ing water  kept  together,  and  held   its 
own,  until  its  course  was  arrested  by  the 
opposite  bank,  when  it  curved   gently 
round  on  either  side,  and  was  lost  insen- 
sibly in  the  general  body,  which  had  its 
outlet  for  overflow  at  one  side.     He  re- 
flected that  a  current  of  air  introduced 
into  a  room  would  act  precisely  in  the 
same  manner,  keeping  together  until  it 
encountered  an  obstacle,  then  mixing  in- 
sensibly with  the  air  around  it,  and  com- 
pelling an  overflow  wherever  there  was 
an  opening  available.     He  saw  that,  if 
this  were  so,  it  would  only  be  necessary 
to  give  the  entering  current  an  ascending 
direction,  so  that  it  would  reach  the  ceil- 
ing without  impinging  on  any  person,  in 
order  to  solve  the  whole  problem  of  do- 
mestic ventilation.     Experiments  at  his 
own  house  confirmed  his  anticipation,  and 
led  him  to  contrive  methods,  which  he  has 
patented,  of  carrying  his  principle  into 
practice. 

At  that  time  the  state  of  the  Borough 
Police  Court  at  Leeds  was,  as,  indeed,  it 
had  been  for  some  time  previously,  a 
source  of  great  perplexity  to  the  Town 
Council.  The  Justices  were  often  com- 
pelled to  make  their  escape  before  the 
business  of  the  day  was  concluded;  and 


the  Council  had  expended  between 
£1,400  and  £1,500  on  successive  venti- 
lation doctors,  each  of  whom  had  left 
matters  as  bad  as,  if  not  worse  than, 
they  were  before. 

Mr.  Tobin  suggested  that  the  Council 
should  pay  him  a  nominal  royalty  for 
the  use  of  his  patent,  and  that  they 
should  pay  the  few  pounds  required  for 
doing  the  work,  leaving  his  own  remuner- 
ation to  their  discretion  when  they  saw 
the  effect.  These  terms  having  been  ac- 
cepted, he  placed  under  the  floor  of  the 
Court  three  horizontal  shafts  which  com- 
municated with  the  open  air  through  a 
cellar  grating.  From  these  were  brought 
eight  vertical  shafts  through  the  floor  at 
different  points.  The  shafts  rise  about 
four  feet  above  the  floor,  and  are  each 
five  inches  in  diameter.  They  have  open 
mouths,  and  are  placed  out  of  the  way 
in  corners,  or  against  the  partitions  of 
the  Court.  From  each  shaft  there  as- 
cends to  the  ceiling  an  unbroken  current 
of  the  outer  air,  like  a  fountain,  or  like  a 
column  of  smoke  when  the  barometer  is 
high.  The  current  will  support  feathers, 
or  wool,  and  other  light  substances,  and 
has  so  little  tendency  to  spread  laterally 
that  it  can  be  made  to  influence  half  the 
flame  of  a  candle,  while  the  other  half 
remains  undisturbed.  A  person  resting 
his  cheek  against  the  margin  of  one  of 
the  tubes  feels  no  draught,  and  the  hand 
feels  none  Tintil  it  is  inclined  over  the 
orifice.  The  effect  was  instantly  to  ren- 
der the  Court  as  fresh  and  sweet  as  the 
external  air  of  the  building,  as  the  pro- 
ducts of  respiration  was  forced  out 
through  the  skylight. 

After  three  months'  trial,  and  after  all 


224 


VAN   NOSTRAND'S   ENGINEERING   MAGAZINE. 


the  magistrates  for  the  borough  had 
joined  in  a  report,  which  expressed  their 
entire  and  unmixed  satisfaction,  the  Cor- 
poration voted  Mr.  Tobin  an  honorarium 
of  £250,  to  express  their  sense  of  the 
benefit  which  he  had  conferred  upon  the 
town.  They  also  applied  his  system  to 
the  Council  Chamber;  and  their  example 
was  followed  by  some  of  the  leading 
bankers  and  merchants,  by  the  church- 
wardens of  St.  George's  Church,  and  by 
the  proprietors  of  the  Leeds  Mercury. 

The  system  of  vertical  tubes  is  neces- 
sary for  rooms  which  have  no  side  win- 
dows, or  which  have  only  a  small  window 
surface  in  proportion  to  their  cubic  con- 
tents. But  Mr.  Tobin  at  the  same  time 
contrived  a  cheap  and  simple  method,  by 
which  vertically  ascending  air  currents  can 
be  introduced  through  common  window 
sashes;  and  this  method  will  suffice  for  all 
ordinary  living  or  sleeping  apartments. 
Each  of  the  openings  made  for  this  pur- 
pose is  provided  with  a  cover  by  which 
it  can  be  closed  at  will;  and  they  admit 
of  a  method  of  securing  the  sashes  which 
affords  almost  entire  security  against 
burglars.  A  very  competent  authority 
has  communicated  to  the  Times  his  ex- 
perience for  eight  weeks  of  a  room  con- 
taining 2,500  cubic  feet,  ventilated,  under 
Mr.  Tobin's  direction,  by  four  window 
openings  which  have  an  aggregate  area 
of  30  square  inches,  but  which  are  filled 
by  layers  of  cotton  wool  to  filter  the  en- 
tering air  from  dirt  and  moisture.  The 
currents  ascend  in  absolute  contact  with 
the  glass,  keeping  so  close  to  it  that  they 
do  not  not  affect  the  flame  of  a  taper 
which  is  held  vertically  in  contact  with 
the  sash  bar  ;  although,  as  soon  as  the 
taper  is  inclined  towards  the  pane  its 
flame  is  strongly  fluttered.  In  this  way 
the  air  ascends  to  the  top  of  the  window, 
where  it  is  directed  to  the  ceiling  and 
lost  as  a  current,  being  no  longer  trace- 
able by  taper,  hand,  or  fragments  of 
down,  although  closing  the  window  open- 
ings diminishes  in  a  marked  manner  the 
draught  up  the  chimney.  Each  opening, 
as  already  described,  has  an  independent 
cover,  and,  without  the  wool,  the  four 
would,  in  cold  weather,  be  too  much  for 
a  room  of  the  size  specified.  With  the 
wool  they  do  not  perceptibly  diminish 
the  temperature,  but  they  give  a  feeling 
of  absolute  out-of-  door  freshness,  which 
must  be  experienced  in  order  to  be  appre- 


ciated. There  is  no  draught  anywhere, 
and  the  openings  are  not  visible  unless 
sought  for,  so  that  curious  inquirers 
who  have  remarked  on  the  result  have 
been  unable  to  find  the  inlets.  Arranged 
as  described,  the  openings  are  sufficient 
to  feed  a  large  argand  table  gas  burner, 
and  to  sweep  away  entirely  the 
products  of  its  combustion;  so  that, 
when  the  room  is  shut  up,  with  the  gas 
lighted  and  with  a  good  fire,  for  three 
or  four  hours,  persons  entering  it  from 
the  open  air  are  not  able  to  discover,  ex- 
cept by  the  greater  warmth,  any  change 
of  atmosphere.  A  bed-room  ventilated 
in  a  similar  manner  is  as  fresh  when  the 
door  is  opened  in  the  morning  as  when 
it  was  closed  at  night. 

Mr.  Tobin's  experiments  early  led  him 
to  the  conclusion  that  the  prevailing  no- 
tions about  the  necessity  for  carefully 
planned  outlets  were  fallacious,  and 
that,  if  proper  inlets  are  provided,  the 
outlets  may  generally  be  left  to  take 
care  of  themselves.  In  order  to  test 
this,  he  fitted  two  vertical  tubes  into  a 
small  room  which  had  a  fire-place  and  a 
three-fight  gas  pendant.  He  closed  the 
opening  of  the  fire  -  place,  and  every 
other  opening  into  the  room,  except  the 
tubes,  hermetically,  and  shutting  himself 
within,  pasted  slips  of  paper  all  round 
the  door.  He  found  that  there  was  then  no 
entrance  current  by  the  tubes.  The  room 
had  no  outlet;  it  was  full  of  air,  which 
his  respiration  had  not  had  time  to  con- 
sume in  any  appreciable  quantity,  and 
no  more  could  get  in.  He  next  lighted 
the  three  gas  burners, .  and  a  steady 
entrance  current  immediately  set  in 
through  the  tubes,  and  continued  as  long 
as  the  gas  was  burning.  He  waited 
nearly  an  hour  without  any  deterioration 
of  the  atmosphere  becoming  perceptible 
to  his  senses,  and  with  the  currents 
steadily  coming  in  and  ascending  in  their 
customary  manner.  He  then  cut  through 
the  paper  which  secured  the  door,  and 
left  the  room,  shutting  the  door  behind 
him.  Returning  half  an  hour  later,  he 
found  the  atmosphere  still  fresh.  He 
next  extinguished  the  gas,  and  the  cur- 
rents gradually  died  away,  the  original 
state  of  equilibrium  or  fulness  being  re- 
stored. This  experiment,  which  has  been 
several  times  repeated,  seems  to  show 
that  the  external  air  will  enter  just  in 
proportion  as  room  is  made  for  it  by 


VENTILATION   BY   VERTICAL   SHAFTS. 


225 


combustion  or  respiration,  and  that  the 
rate  of  supply  is  essentially  governed  by 
the  rate  of  destruction  or  demand. 

In  order  to  obtain  an  absolutely  per- 
fect result  it  is  necessary  to  bear  in  mind 
that  the  behavior  of  the  entering  current 
will  be  precisely  like  that  of  the  vertical 
column  of  water  sent  up  by  a  fountain, 
except  that,  as  the  ascending  air  is  re- 
ceived in  a  fluid  of  only  little  less  density 
than  its  own,  it  will  mingle  with  that 
fluid  gradually  when  the  propulsive 
force  is  exhausted,  instead  of  falling 
almost  vertically  by  the  action  of  gravi- 
ty. But  just  as  a  fountain,  if  it  encoun- 
tered an  obstacle  while  its  column  was 
still  compact,  would  rebound  from  that 
obstacle  with  considerable  violence,  so 
the  entering  current  of  air,  if  it  meet 
with  an  impediment  prematurely,  will  be 
reflected  as  a  draught.  To  prevent  such 
an  occurrence,  it  is  necesssary  to  make 
the  inlets  so  low  down  that,  under  all 
ordinary  circumstances,  the  force  of  the 
stream  will  be  expended  before  the  ceil- 
ing is  reached ;  and  when,  from  any  cir- 
cumstances, this  cannot  be  done,  the 
current  may  be  broken  by  strainers  of 
wire  gauze  or  other  suitable  material. 
In  this,  as  in  most  other  matters,  some 
special  adaptation  of  means  to  ends  is 
required;  and  the  arrangements  for  any 
given  room  must  be  planned  by  some 
one  who  has  practical  knowledge  of  the 
subject. 

Within  the  last  two  or  three  weeks 
Mr.  Tobin  has  adapted  his  system  to  the 
Liverpool  Police  Court,  and  there,  as 
well  as  at  Leeds,  he  has  entirely  suc- 
ceeded in  attaining  his  object,  and  the 
satisfaction  given  to  the  local  authorities 
has  been  such  that  it  has  been  deter- 
mined that  all  the  other  courts  in  the 
Town-hall  shall  at  once  be  ventilated  in 
a  similar  manner.  In  London  the  method 
of  ventilation  by  vertical  tubes  has  been 
applied  to  one  of  the* wards  of  St. 
George's  Hospital,  and  that  by  window 
openings  to  the  Council  Chamber  of  the 
Society  of  Arts  and  to  a  few  private 
houses,  everywhere  with  the  same  excel- 
lent results. 

The  discovery  that  the  pressure  of  the 
atmosphere  can  thus  be  utilized  as  a  per- 
petual source  of  air  supply,  without  the 
aid  of  fans  or  other  mechanical  con- 
trivances; the  discovery  that  all  draughts 
can  be  obviated  by  the  employment  of 
Vol.  XIII.— No.  &— 15 


vertical  entrance  channels,  provided  only 
that  their-  mouths  are  not  too  near  the 
ceiling,  and  the  discovery  that  improper 
lowering  of  temperature  is  prevented  by 
the  circumstance  that  the  rate  of  en- 
trance of  air  is  governed  by  the  demand, 
are  truly  comparable  in  their  simplicity 
to  the  balancing  of  the  egg  by  Colum- 
bus. Simple  as  they  are,  they  are  none 
the  less  calculated  to  add  greatly  to  the 
public  health  and  comfort. 

Captain  Douglas  Galton,  commenting 
on  the  invention,  says : — The  principle  of 
ventilation  by  utilizing  the  pressure  of 
the  atmosphere  is  not  new.  It  has  been 
applied  in  a  number  of  ways  in  various 
public  and  private  buildings;  notablv  in 
the  method  of  barrack  ventilation  adopt- 
ed in  1857  by  the  Barrack  and  Hospital 
Commission  under  Lord  Herbert's  au- 
spices. Nor  is  there  any  novelty  in  the 
method  of  introducing  fresh  air  into  a 
room  by  means  of  vertical  shafts  deliv- 
ering the  air  into  the  room  at  a  few  feet 
from  the  ground.  I  iised  it  in  1S61  in 
the  wards  of  the  Herbert  Hospital  at 
Woolwich,  and  in  other  hospitals,  but  I 
utilized  the  fire-place  for  the  purpose, 
placing  it  in  the  centre  of  the  ward,  with 
its  flue  carried  under  the  floor,  in  order 
that  in  cold  weather  the  fresh  air  should 
be  tempered  by  the  spare  heat  from  the 
fire.  Plenty  of  other  instances  might  be 
cited. 

The  principles  of  ventilation  are  well 
known.  It  is  the  application  of  those 
principles  in  special  cases  which  causes 
the  difficulty.  The  amount  of  current 
of  inflowing  air  into  a  room  will  depend 
upon  the  facilities  or  arrangements  for 
outflow,  and  vice  versa.  Therefore,  for 
perfect  ventilation,  the  proportions  and 
position  of  both  outlet  and  inlet  must  be 
considered;  neither  can  be  neglected; 
and  if  in  the  room  on  which  Mr.  Tobin 
experimented  the  air  remained  pure,  it 
was  because  there  was,  in  addition  to 
the  inflow,  some  means  for  an  outflow  of 
a  sufficient  quantity  of  air  to  remove  the 
impurities  given  out  from  the  lungs  in 
breathing  and  from  the  gas  in  combus- 
tion. In  English  rooms  of  ordinary  con- 
struction the  open  fireplace  creates  the 
difficulty  in  the  introduction  of  fresh 
air.  It  is  the  cause  of  draughts,  because 
the  chimney  with  a  fire  in  the  grate  is  a 
strong  engine  for  removing  the  air  from 
a  room,  and  it  draws  in  through  every 


226 


VAN  nostrand's  engineering  magazine. 


means  of  ingress  air  to  supply  the  place 
of  that  removed.  If  this  air  comes  in 
cold  draughts  are  felt,  whatever  be  the 
position  or  manner  in  which  the  air  is 
delivered.  The  hotter  the  fire  the 
stronger  the  current  up  the  chimney, 
and  the  greater  the  draught.  For  this 
reason,  if  a  room  with  an  open  fire  is  to 
be  really  comfortable  it  should  be  pro- 
vided with  a  continuous  supply  of  fresh 
warmed  air,  and  if  the  inlet  be  from  6 
to  9  feet  above  the  floor  the  inflow  will 
not  be  felt  by  the  occupants.  The  waste 
heat  from  the  fire  affords  the  most  econ- 


omical method  of  warming  the  fresh  air. 
When  the  principles  of  ventilation, 
which  are  perfecly  well  known,  are  care- 
fully attended  to,  and  where  the  inlets 
for  fresh  air  and  the  outlets  are  duly 
proportioned  to  each  other  and  placed 
in  proper  positions,  and  the  fresh  air  ad- 
equately warmed  and  cooled  as  required, 
there  will  be  no  failure  in  ventilation. 
Where  failure  does  occur  it  is  either  be- 
cause of  a  misapplication  of  principles, 
or  of  a  disinclination  to  incur  the  neces- 
sary expense  for  carrying  the  principles 
into  effect. 


THE  STABILITY  OF  AKCHES. 

By  E.  SHERMAN  GOULD,  C.  E. 
Written  for  Van  Nostrand's  Magazine. 


It  is  customary,  in  discussing  the  con- 
ditions of  stability  of  an  arch,  to  con- 
sider the  arch-ring  as  sustaining,  besides 
its  own  weight,  that  of  the  entire  super- 
structure raised  over  it,  and  receiving  at 
the  key-stone  the  whole  horizontal  thrust 
of  the  combined  mass. 

That  this  view  is  an  erroneous  one,  is 
clearly  evidenced  by  the  perfect  stabil- 
ity of  many  light  arches  standing  under 
high  spandril  walls  ;  a  stability  which 
could  never  exist  were  the  actual  condi- 
tions of  pressure  such  as  would  be  com- 
monly assumed  in  calculating  the  proper 
dimensions  for  the  arch-ring. 

Such  a  pressure  from  the  surcharge  is 
only  found  in  the  case  of  a  liquid  mass, 
and  then  the  direction  of  the  pressure 
upon  each  voussoir  is  toward  the  centre 
of  the  arch,  and  not  vertically  downward 
as  in  the  case  of  a  coherent  mass,  bond- 
ed in  with  the  extrados  of  the  arch-ring. 

Suppose,  in  the  case  of  a  spandril  wall, 
such  as  is  shown  in  half  elevation  in 
Fig.  1,  that  the  arch-ring  were  removed. 
What  would  be  the  result  ?  If  the  com- 
mon assumption  were  true,  the  entire 
wall  within  the  span,  would  fall  bodily 
to  the  ground.  Now  we  know  that  this 
would  not  really  occur,  but  that  an  ir- 
regular mass  A,  varying  in  size  accord- 
ing to  the  span  and  character  of  the  wall, 
would  detach  itself  and  come  down,  not 
probably  in  a  body,  but  by  piecemeal. 


In  general  terms,  we  may  say  that  the 
office  of  the  arch-ring  is  to  sustain  that 


Fig.  1. 

portion  of  the  surcharge  which  is  not 
self  supporting.  Moreover,  the  arch 
and  wall  thus  sustained,  form  together 
an  arched  girder,  and  the  horizontal 
thrust  of  the  combined  mass  is  resisted 
by  the  entire  section  from  the  soffit  to 
the  top  of  the  wall.  So  that,  in  point 
of  fact  the  higher  the  wall  the  greater 
the  safety  to  the  arch  -  ring.  In- 
deed, one  would  feel  instinctively,  that 
he  could  knock  a  hole  through  the  foot 
of  a  high  brick  wall  with  greater  impun- 
ity than  through  a  low  one,  particularly 
if  there  were  a  heavy  surcharge  resting 
on  the  top. 

In  this  connection  I  may  be  pardoned 
for  offering  what  I  consider  a  much  sim  - 


THE   STABILITY    OF   ARCHES. 


227 


plified  method  of  determining  the  line  of 
pressure  in  an  arch-ring.  The  plan,  in- 
troduced by  Mons.  Mery,  and  I  believe 
at  present  almost  universally  adapted, 
at  least  in  principle,  is  to  ascertain  the 
weight  of  arch  including  surcharge,  as- 
certain its  centre  of  gravity,  derive  the 
horizontal  thrust,  apply  this  latter  to 
some  point  in  the  vertical  section  of  the 
crown,  and,  combining  it  with  the  weight 
of  successive  portions  of  the  arch,  work 
the  resultant  down  to  skew-back.  The 
consideration  of  certain  facts  in  relation 
to  a  loaded  arch  lead  us,  I  think,  to  a 
preferable  method  of  procedure.     What- 


ever may  be  the  conditions  of  loading, 
and  whatever  direction  the  line  of  pres- 
sure may  consequently  follow,  we  know 
that  each  abutment  must  sustain  one* 
half  of  the  weight  of  the  arch  and  load, 
and  that  this  weight  on  the  abutment 
must  have  a  resultant  at  right  angles  to 
the  skew-back.  "We  have  then  here  a 
positive  basis  to  start  from,  and  by  com- 
bining this  resultant  with  the  weights  of 
the  successive  voussoirs  and  their  respec- 
tive loads,  we  can  trace  the  path  of  the 
line  of  pressure  through  the  arch-ring. 

Thus,  suppose  Fig.  2  to  represent  an 
arch,  60  feet  in  span,  with  a  rise  of  15 


Fig.  2. 


feet,  the  intrados  being  the  arc  of  a 
circle,  struck  with  a  radius  of  37.5  feet. 
Let  us  suppose  the  weight  of  voussoirs 
and  corresponding  loads,  commencing 
next  to  the  skew-back,  to  be  represented 
by  the  numbers  3.5;  2;  1.25;  1.25;  1  and  1 
respectively.  This  gives  a  weight,  rep- 
resented by  10,  resting  on  the  abutment. 
The  reaction  of  this  weight,  acting  verti- 
cally upward,  and  the  horizontal  thrust, 
have  a  resultant,  as  we  have  seen,  named 
to  the  skew-back,  represented  by  12.6, 
the  horizontal  thrust  being  represented 
by  7.7.  Transferring  this  triangle  of 
forces  to  the  centre  of  gravity  of  the 
first  voussoir,  and  combining  the  weights 
in  and  on  each  voussoir  successively,  we 
carry  the  line  of  pressure  through  the 
arch-ring,  and  recover  the  horizontal 
thrust  of  7.7  in  the  resultant  at  the 
crown.  (This  procedure  will  somewhat 
remind  the  railroad  engineer  of  the 
method  of  locating  a  curve  by  chord  de- 
flections.) The  shorter  the  voussoirs, 
the  nearer  the  differential  will  approach 
to  the  arcs,  the  nearer  the  broken  line 
will  approach  to  a  true  curve,  and  the 
nearer  will  the  first  centre  of    gravity 


approach  to  the  skew-back,  and  the  last 
to  the  mid  section  of  the  crown. 

This  process  demonstrates  itself,  and  is 
moreover  merely  an  application  of  the 
well-known  principle  of  the  suspended 
chain,  but  it  will  be  satisfactory  to  apply 
it  to  some  known  curve  of  equilibrium, 
and  see  how  they  agree.  Of  all  external 
pressures  which  we  encounter  in  con- 
struction, hydrostatic  pressure  is  the  one 
about  the  action  and  direction  of  which 
we  are  most  certain,  and  therefore,  of  all 
curves  of  equilibrium,  the  hydrostatic 
curve  is  the  least  ambiguous.  Let  us 
take  the  example  of  this  curve,  given  by 
Professor  Allan,  page  387  of  the  tenth 
volume  of  this  Magazine.  With  a  span 
of  50  feet  and  a  depth  of  load  at  the 
crown  of  16  feet,  the  Professor  gives  as 
the  radii,  at  crown  and  springing,  of  32.5 
feet  and  14.1  feet  respectively.     He  also 

y  p 

gives  as  the  formula   S=*       ° 


y 


for   the 


radius  at  any  point,  situated  at  a  depth 
y  below  the  water  line.  The  curve  is 
now  to  be  found  by  approximation. 
Start  at  the  crown  with  the  radius  32.5 
and  strike  a  short  arc.     From  the  end 


228 


VAN  nostrand's  engineering  magazine. 


away  from  the  crown,  measure  the  verti- 
cal distance  y  to  the  water  line,  and  di- 
viding the  constant  yapa=5.20  by  this 
distance  you  obtain  the  next  radius. 
Proceed  thus  to  the  end  of  the  arch, 
when  you  will  find  that  you  have  over- 
run the  span  by  a  distance  less  or  more, 
according  as  the  divisions  have  been 
more  or  less  numerous.  Now,  begin  at 
the  sp ringing,  with  the  radius  14.1  feet, 
and  work  back  toward  the  crown.  You 
will  find  this  new  curve  gradually  ap- 
proach the  first  one  for  a  certain  dis- 
tance, and  then  begin  to  leave  it.     Stop 


here.  You  have  now  two  curves,  be- 
tween which  the  true  curve  lies,  and 
with  one  of  which  it  coincides  at  the 
crown  and  springing.  The  margin  will 
be  less,  the  greater  the  number  of  small 
arcs  you  have  taken.  Sketch  the  true 
curve  in  by  haiid,  and  selecting,  by 
trial,  a  few  centres,  strike  in  a  clean 
curve  coinciding  with  the  hand-made 
one.  It  will  be  well  to  test  these  centres, 
and  the  corresponding  radii,  by  the  for- 
mula p=y0p0,  measuring  p  and  y  on  the 
y  drawing.  Now  (Fig.  3),  take  the  area 
a,  b,  c,  d,  say  in  square  feet,  which  will 


Fig.  3. 


represent  the  weight  resting  on  each 
abutment  for  a  foot's  length  of  arch. 
We  have  for  this,  the  number  508. 
Then  divide  the  curve  into  a  certain 
number  of  equal  parts,  8  in  the  figure, 
and  multiply  their  common  length  by 
the  distance  from  their  centres  of  grav- 
ity to  the  water  line.  This  gives  the 
pressure  on  each  of  the  equal  arcs  in 
terms  of  the  weight'  on  abutment,  which 
pressure  is  directed  toward  the  centre  of 
the  circle  of  the  same  radius  as  the  arc. 
Draw  lines  from  the  centre  of  the  arcs, 
properly  directed,  and  make  them  of  a 
length  representing  by  scale  the  amount 
of  pressure  on  the  arcs  to  which  they 
belong.  Then,  from  the  first  centre  of 
gravity,  next  the  springing,  draw  the 
vertical  508,  and  from  its  upper  extrem- 
ity draw  a  line,  parallel  to  the  direction 


of  the  pressure  on  that  centre  of  grav- 
ity, and  equal,  by  scale,  to  its  amount. 
This  gives  us  the  triangle  of  forces,  b,  e, 
f.  Produce  f,  e,  making  h,  g,  equal  to 
f,  e,  and  proceed  thus  through  to  the 
crown.  It  will  be  found  that  the  curve 
thus  obtained  coincides  with  the  hydros- 
tatic curve  located  by  the  formula,  and 
the  resultants  equal  T=H=V,  as  they 
should. 

No  account  has  been  here  taken  of  the 
weight  of  the  voussoirs,  which,  as  they 
act  vertically,  would  somewhat  modify 
the  curve 

In  closing,  I  may  add  that  I  do  not 
recollect  seeing  in  any  work  in  English, 
Dejardin's  excellent  and  simple  method 
of  tracing  the  extrados  of  an  arch  in 
equilibrium,  when  the  intrados  is  given. 
It  is  shown,  in  its  mo.°t  simple  applica- 


TESTS   OF   STEEL. 


229 


tion  in  Fig.  4,  which  represents  part  of 
an  arch  with  arc  intrados  following   a 


Fig.  4. 

circular  arc.  The  method  is  based  on 
the  principle,  that,  as  the  horizontal 
thrust  is  constant  throughout  the  arch, 
the  vertical  projection  of  each  joint  a  b, 
ef,  etc.,  should  be  equal  to  the  depth  d, 
at  the  crown.  This  is  secured  by  draw- 
ing a  horizontal  line  at  a  distance  0  0'=c? 
above  the  centre  of  the  circle  to  which 
the  intrados  is  struck,  and  making  the 
distances  a  a',  e  e',  etc,  on  the  radii  pro- 
duced, =  radius. 

This  method  is  general.  In  the  case 
of  an  intrados  struck  from  several  centres 
(Fig.  5),  let 

r  =  radius  at  the  crown. 
r'=  radius  at  any  joint,  making  an  angle 
d  with  the  vertical. 


e  =  depth  of  arch-ring  at  crown. 


Fig.  5. 


Then,  e'  =  —  x 


,  sufficiently  near 


r'     Cos.  d 
in  practice. 

On  the  vertical  OA=r,  take  OB=e, 
and  draw  the  horizontal  line  BD.  To 
obtain  the  length  e'  of  a  joint  making  an 
angle  d  with  the  vertical,  through  O, 
draw  O  K  parallel  to  the  joint  e',  and 
=r'.  Through  the  point  I,  where  O  K 
meets  B  D,  draw  I L  parallel  to  A  K. 
Then  O  L  will  be  the  length  e'  required. 
For,  A  O  K,  L  O I  being  similar  tringles, 


OL= 


OAx  01 


OK 


r         e 
~'r'XCo~s~d 


TESTS  OF  STEEL.* 

By  A.  L.  H0LLEY,  C.  E. 


The  intention  of  this  paper  is  not  to 
discuss  this  important  subject  in  all  its 
bearings,  but  merely  to  point  out  why 
mechanical  tests  of  steel,  as  ordinarily 
made,  are  not,  alone,  of  any  special  value 
to  engineers — certainly  not  to  general 
mechanical  engineers. 

The  agents  of  the  Barrow  Hasniatite 
Steel  Company,  one  of  the  largest  and 
most  successful  Bessemer  establishments 
in  England,  have,  recently  distributed 
a  report,  made  by  Sir  William  Fairbairn, 
on  the  transverse,  tensile  and  compres- 
sive resistances  of  certain  bars  of   this 

*  A  paper  read  before  the  American  Institute  of  Mining 
Engineers. 


steel.  The  number  of  tests  is  very 
large  ;  they  seem  to  be  careful  and 
minute  ;  and  the  modulus  of  elasticity, 
the  work  up  to  the  limit  of  elasticity, 
and  the  limit  of  working  strength,  are 
fully  tabulated  according  to  the  latest 
formula. 

This  is  very  well — indeed  it  is  indis- 
pensable, as  far  as  it  goes  ;  but  it  goes 
no  further  than  to  inform  the  ordinary 
engineer  that  there  is  an  unknown  sub- 
stance which  possesses  these  physical 
properties.  As  to  what  the  substance  is, 
the  report  gives  him  no  working  knowl- 
edge, for  not  a  single  analysis  is  given 
of  anv  of   the  bars   tested.     The  most 


230 


VAN   NOSTRAND'S   ENGINEERING   MAGAZINE. 


that  is  said  of  some  of  them  is  that  they 
are  either  "hard"  or  "soft,"  which  is 
sufficiently  evident  from  the  experiments. 
"  A  bar  of  steel "  is,  in  the  present  state 
of  the  art,  a  vastly  less  definite  expres- 
sion than  "  a  piece  of  chalk."  To  the 
engineer  who  wants  steel  for  a  specific 
purpose,  it  gives  only  the  faintest  clue, 
to  say  that  steel  is  hard  or  soft.  There 
are  a  dozen  grades  of  both  hard  and 
soft  steel,  adapted  to  different  purposes. 
Rail  steel  is  soft,  and  boiler-plate  steel  is 
soft,  as  compared  with  many  structural 
steels,  and  with  the  whole  range  of  spring 
and  tool  steels  ;  but  the  one  perfectly 
adapted  to  rails  would  be  useless  for 
boilers. 

In  order  that  engineers  may  know 
what  to  specify,  and  that  manufacturers 
may  know  not  only  what  to  make,  but 
how  to  compound  and  temper  it,  the 
leading  ingredients  of  each  grade  of 
steel  must  be  known.  Pure  iron  would 
be  unfit  for  nearly  all  structural  purposes. 
Upon  the  substances  associated  with  it 
depend  its  hardness,  malleability,  stiff- 
ness, toughness,  elasticity,  tempering 
qualities,  and  adaptations  to  various 
structural  uses.  These  ingredients  are 
indeed  impurities,  but  the  term  "  impur- 
ity" unfortunately  implies  a  defect, 
whereas  the  thing  may  really  impart  the 
essential  quality.  All  the  usual  ingre- 
dients give  what  is  called  "body"  to 
steel.  Carbon,  within  specific  limits,  as 
is  well  known,  gives  hardness,  elasticity, 
resistance  to  statical  strains,  and  temper- 
ing qualities.  Under  certain  conditions 
of  composition  it  even  gives  resistance 
to  sudden  strains.  Manganese  (and  this 
fact,  by  the  way,  is  not  so  generally 
known)  gives,  in  the  proportion  of  f  to 
1  per  cent.,  hardness,  toughness,  malle- 
ability, and  elasticity.  Chromium  im- 
parts similar  qualities,  but  to  what  pre- 
cise extent  we  do  not  know,  in  default  of 
a  proper  comparison  of  chemical  and 
mechanical  tests.  Silicon,  although  con- 
sidered a  bane  by  steel-makers  generally, 
and,  singularly  enough,  advertised  as  the 
great  panacea  for  the  weaknesses  of 
steel  by  certain  modern  inventors,  has 
probably,  in  proper  proportions,  a 
healthful  influence  on  the  physical  pro- 
perties of  steel.  Even  phosphorus,  the 
arch-enemy  of  the  Bessemer  and  open- 
hearth  manufacturers,  may  in  some  de- 
gree be  a  valuable  ingredient. 


Whether  or  not  certain  foreign  sub- 
stances, which  separately  added,  pro- 
duce similar  results,  would  produce  a 
better  result  if  combined  in  certain  pro- 
portions— for  instance,  whether  carbon 
alone  in  any  degree,  or  silicon  alone  in 
any  degree,  would  make  as  good  a  steel 
for  certain  uses  as  carbon  and  silicon 
combined,  it  is,  in  default  of  proper  ex- 
periments, impossible  to  state.  The  pro- 
bability is,  that  there  is  a  proportion  of 
carbon  and  manganese  which  would  give 
the  highest  possible  value  to  all  struc- 
tural steels.  "We  formerly  added  spiege- 
leisen  to  decarburized  Bessemer  metal 
solely  to  impart  manganese  to  the  oxy- 
gen of  the  oxyde  of  iron  formed  in  the 
Bessemer  process.  We  now  add  a  larger 
proportion  of  spiegeleisen,  not  only  to 
remove  the  oxygen,  but  also  to  mix 
manganese  with  the  steel.  And  we 
think  we  find  that  if  the  proportions  of 
silicon  and  phosphorus  are  sufficiently 
low,  and  carbon  does  not  exceed  a  third 
of  one  per  cent.,  manganese  to  the 
amount  of  three-quarters  per  cent,  to 
one  per  cent,  gives  the  resulting  product 
a  high  degree  of  toughness  and  hardness 
combined — a  degree  of  suitableness  for 
rails,  which  no  proportion  of  either  car- 
bon or  manganese,  not  associated,  can 
impart. 

When  we  consider  that  two  and  three- 
tenths  of  one  per  cent.,  and  in  some  cases 
a  fraction  of  a  tenth  of  one  per  cent,  of 
foreign  metals,  will  change  the  character 
of  steel  in  a  high  degree  ;  and  when  we 
farther  consider  that  the  physical  results 
of  these  combinations  have  never  been 
tested  or  analyzed  in  any  thorough  and 
comprehensive  manner,  we  may  well  re- 
iterate the  common  expression,  that  the 
iron  and  steel  manufacture  is  in  its  in- 
fancy. 

But  it  is  not  necessarily  in  its  infancy. 
We  simply  do  not  develop  it.  The  gen- 
eral complaint  of  engineers  and  machin- 
ists is,  that  they  occasionally  get,  but  can 
never  get  regularly,  the  precise  quality 
of  steel  they  require  ;  and  yet  it  is  pro- 
bable that  thousands  of  tons  of  steel 
have  been  made  which  are  suitable  for 
each  of  these  purposes,  but  have  been 
used  for  others,  and  that  the  precise 
grade  required  in  every  case  could  be 
reproduced  by  the  ten  thousand  tons. 
The  trouble  is  that  neither  the  user  nor 
the  maker  knows  what  the  material  is. 


TESTS   OF   STEEL. 


231 


They  have  put  no  mark  on  it  by  which 
they  can  recognize  it;  they  have  kept  no 
recipe.  All  they  can  do  is  to  use  in- 
gredients of  the  same  name,  and  ap- 
proximately the  same  quality,  and  to 
guess  at  the  physical  properties  of  the 
product,  aided  by  such  crude  tests  as  can 
be  made  during  manufacture.  Mr.  Wil- 
liam H.  Barlow,  in  a  late  address  on 
modern  steel  before  the  British  Associa- 
tion, says  that  one  reason  why  steel  is 
not  more  used  for  structural  purposes  is, 
that  the  metal  is  of  various  qualities, 
"  and  we  do  not  possess  the  means,  with- 
out elaborate  testing,  of  knowing  wheth- 
er the  article  presented  to  us  is  of  the 
required  quality."  But  neither  Mr.  Bar- 
low, nor  any  of  his  associates  in  govern- 
ment experiments,  proposes  the  true  solu- 
tion of  the  difficulty.  It  is  no  more  ne- 
cessary to  test  one  or  two  of  each  lot  of 
bars  to  destruction,  in  order  to  find  out 
the  quality  of  the  rest,  than  it  is  to  burn 
up  a  Chinese  village  to  get  roast  pig. 

If  the  user  would  analyze  not  one,  but 
twenty  samples  of  the  steel  that  meets 
a  particular  want,  and  then  base  his 
order  on  an  analysis  that  should  come 
within  the  highest  and  lowest  limits  of 
the  samples,  he  would  get  substantially 
the  same  metal  every  time.  The  prob- 
lem is  a  more  difficult  one  for  the  steel- 
maker, since  he  must  analyze  the  many 
materials  that  go  into  his  product  ;  but 
if  he  imposes  the  same  restrictions  on 
the  makers  of  these  materials — in  short, 
if  from  the  ore  and  limestone  and  coal, 
up  to  the  finished  bar,  each  user  buys  by 
analysis,  and  pays  in  proportion  to  uni- 
formity, the  production  of  steel  of  the 
most  multiform  grades  and  qualities, 
each  homogeneous  and  uniform  to  any 
extent  of  production,  becomes  a  possible, 
if  not  a  comparatively  easy,  matter. 

What  are  Sir  William  Fairbairn,  and 
Mr.  Barlow,  and  Mr.  Kirkaldy,  and  the 
other  great  experimenters  in  the  physi- 
cal properties  of  steel — in  its  adaptation 
to  certain  specific  uses — what  are  they 
doing  to  relieve  the  engineering  world 
from  these  uncertainties  ?  They  are 
simply  discovering  the  vast  number  of 
qualities  which  steel  may  be  made  to 
possess,  without  giving  more  than  a  clue 
to  the  method  by  which  these  qualities 
may  be  predetermined  and  reproduced. 
They  are  going  to  avast  expense  of* time 
and  material  to  inform  us,  not  that  a  cer- 


tain combination  of  metals,  but  that  a 
bar  of  steel,  has  such  resistance  and 
elasticity.  This  sort  of  experimenting 
has  much  the  same  value  as  the  steam- 
engine  tests  of  a  late  chief  engineer  in 
the  navy,  of  whom  it  is  said,  that  in  a 
coal-consumption  test  he  would  calculate 
the  ashes  to  ten  places  of  decimals,  and 
guess  at  the  coal  put  into  the  furnaces. 

Moreover,  Sir  William  Fairbairn  may 
be  doing  injustice  to  other  steel-makers, 
to  Brown,  Cammell,  and  Bessemer,  bare 
of  whose  steel  he  has  also  similarly  test- 
ed, and  found  not  quite  so  suitable  for 
certain  purposes  as  the  Barrow  bars  are. 
But  he  neglects  to  make  it  clear  that  the 
disparaged  bars  may  be  better  than 
these  particular  Barrow  bars  for  other 
purposes.  He  makes  the  mistake  which 
we  should  suppose  Sir  William,  of  all 
men,  would  not  make,  of  being  absurdly 
general  and  random  in  one  element  of 
his  conclusions,  while  he  is  fractionally 
accurate  in  others — of  cramming  the 
whole  matter  of  chemical  ingredients 
into  the  terms  "  hard  "  and  "  soft." 

The  first  and  easiest  step  in  the  de- 
sired direction  is  to  find  out  what  AT  is. 
It  is  not  necessarily  a  bar  of  steel  made 
by  Turton  &  Sons,which  one  tool-maker 
will  swear  by,  and  another  will  swear 
at;  nor  is  it  necessarily  a  boiler-plate 
steel  which  Park  Bros,  made  once,  and 
Firth  got  at  twice,  and  Singer,  Nimick, 
&  Co.  hit  two  or  three  times.  It  is  a 
steel  which  Turton,  and  Firth,  and  Park, 
and  Singer,  can,  either  of  them,  make 
by  the  ten  thousand  tons,  if  you  will 
only  tell  them  what  it  is  made  of,  as 
well  as  what  its  physical  qualities  are. 
In  the  various  uses  to  which  engineers 
have  applied  steel,  there  are  a  vast  num- 
ber of  specimens  which  have  long  ful- 
filled all  the  requirements.  When  more 
steel  of  the  same  sort  is  wanted,  the 
usual  method  is  either  to  apply  to  the 
same  maker,  who  kept  no  complete 
record,  and  does  not  know  what  is 
wanted;  or  to  get  bids  based  on  a  stere- 
otyped and  very  inadequate  physical 
test,  for  instance,  that  the  bar  must 
stand  such  and  such  a  blow  from  a 
drop.  The  lot  of  steel  is  made,  and  is, 
as  well  it  may  be,  very  heterogeneous 
in  physical  character,  although  it  may 
be  in  accordance  with  the  one  test.  The 
result  is  that,  under  wear,  some  of  it 
fails,  or,  under  load,  an  excessive  margin 


232 


VAN   NOSTRAND  S   ENGINEERING   MAGAZINE. 


of  safety  must  be  allowed.  The  obvi- 
ously rational  way  to  reproduce  a  lot  of 
steel  which  is  proved  suitable  for  any 
purpose,  is  to  analyze  many  samples  of 
it — at  least  for  carbon,  manganese,  sili- 
con, phosphorus,  and  any  element  which 
exceeds  a  tenth  of  one  per  cent.,  and 
thus  to  give  the  steel- maker  a  recipe  for 
making  it. 

It  may  be  suggested  that  this  chemi- 
cal synthesis  of  steel  will  be  ruinously 
costly.  For  certain  exact  purposes, 
such  as  the  members  of  a  long-span 
bridge;  or  for  certain  fine  purposes, 
such  as  gun-barrels,  the  cost  of  analyses, 
or  any  loss  in  applying  to  other  uses  the 
lots  of  steel  that  were  not  up  to  the 
mark,  would  be  very  small  compared 
with  the  extraordinary  margin  of 
strength  that  must  be  given  to  an 
uncertain  metal,  and  compared  with  the 
cost  of  occasional  failures  under  final 
test.  And  this  cost,  whatever  it  is,  the 
user — that  is  to  say,  the  public,  snould 
and  must  bear. 

But  steel-makers  will  find  that  work- 
ing by  analysis  is  not  so  very  formidable 
after  all.  The  color-test  of  carbon  is 
already  applied  to  all  charges  of  all 
Bessemer  and  open-hearth  makers,  and 
it  is  one  of  the  most  important.  There 
is  another  view  ■  of  the  case.  After  a 
certain  experience  in  comparing  mechan- 
ical tests,  which  are  comparatively  easily 
made,  with  the  more  costly  determina- 
tions of  manganese,  phosphorus,  etc., 
the  expert  will  not  need  to  analyze 
every  charge.  He  will  learn  to  read 
manganese,  approximately,  in  an  elastic 
limit  test,  just  as  the  expert  blacksmith 
can  now  read  carbon  quite  accurately  by 
the  water-hardening  test.  Herein  will 
lie  one  of  the  values  of  the  combined 
mechanical  and  chemical  tests,  that 
they  will  supplement  and  prove  each 
other. 

When  the  proper  amounts  of  carbon, 
manganese,  silicon,  etc.,  for  certain  uses 
are  known,  it  will  not  be  impossible  to 
approximate  to  them,  in  the  Bessemer 
process,  to  a  very  helpful  degree,  and  in 
the  open-hearth  and  crucible  process,  to 
a  reasonably  accurate  degree.  Of  course, 
the  character  of  the  ingredients  must  be 
much  more  definitely  known  than  at 
present,  and  numerous  batches  of  nomi- 
nally the  same  ingredient,  such  as  pig- 
iron,  blooms,   or  puddle-balls,  must  be 


mixed,  so  as  to  largely  dilute  any  high 
degree  of  impurity  which  any  one  batch 
may  contain. 

The  thing  first  in  order  is,  of  course, 
to  ascertain  the  mechanical  properties  of 
all  grades  of  steel — not  merely  the  indi- 
vidual resistances  to  destructive  strains, 
which  are  but  the  stones  that  compose 
the  mosaic,  but  the  resistance  within 
the  elastic  limit,  which  is  the  finished 
picture.  To  this  end  experiments  like 
those  of  Sir  William  Fairbairn  are  indis- 
pensable, but  to  these  must  be  added 
analyses  of  every  grade  of  steel  that 
can  be  produced,  or  the  character  of 
the  metal  is  but  half  known. 

In  the  present  state  of  constructive 
and  metallurgical  art,  it  thus  seems  not 
only  vitally  important,  but  highly  feasi- 
ble, to  increase  in  a  large  degree  the 
uniformity  of  all  grades  of  steel,  and  to 
make  grades  adapted  to  all  special  uses, 
instead  of  following  the  hit-or-miss  and 
large-margin  system,  or  want  of  system, 
that  now  obtains.  Of  course,  the  change 
must  come  slowly,  and  its  early  stages 
will  be  attended  with  difficulty  and  ex- 
pense; but  there  can  be  no  question  as 
to  its  ultimate  success  and  its  immense 
advantage  in  constructive  and  manu- 
facturing engineering  and  art. 

What  probable  expense  of  experiment- 
ing is  to  be  considered  when  it  will  in- 
crease, possibly  double,  the  resistance  of 
metals  to  specific  stresses,  and  decrease 
the  present  enormous  margin  of  safety  ? 
It  seems  unaccountable  that  government 
commissioners  have  so  long  neglected 
the  chemical  half  of  the  problem— have 
so  long  neglected  to  complete  the  cir- 
cuit,  so  that  the  metal  will  tell  us  its  own 
story. 

New  Method  of  Developing-  Mag- 
netism.— Tommasi  has  recently  stated 
in  a  paper  communicated  to  the  French 
Academy  of  Sciences,  that  when  a  cur- 
rent of  steam  under  a  pressure  of  five  or 
six  atmospheres  is  driven  through  a  cop- 
per tube  one-eighth  to  one-quarter  of  an 
inch  in  diameter,  wound  in  the  form  of  a 
helix,  a  bar  of  iron  placed  in  the  axis  of 
this  helix,  becomes  so  strongly  magnet- 
ized that  a  needle  placed  several  centi- 
metres distant  from  this  steam-magnet, 
is  decidedly  attracted.  The  magnetism 
remains  in  the  bar  so  long  as  the  current 
of  steam  continues. 


WATER   SUPPLY   AND   DRAINAGE. 


233 


WATER  SUPPLY  AND  DRAINAGE.* 

By  W.  A.  CORFIELD,  Esq.,  M.A.,  M.D. 

II. 

COLLECTION   AND    DISTRIBUTION    OF   WATER. 


Having  found  a  sufficient  supply  of  good 
water,  or  a  sufficient  supply  of  water 
that  can  be  purified  on  a  large  scale  by 
filtration — a  subject  which  we  shall  con- 
sider further  on — or  by  means  of  Clarks' 
process,  which  I  have  described  to  you, 
or  by  both  combined,  we  come  to  the 
modes  of  collection  and  distribution, 
which  vary  very  much  as  to  the  site, 
sources,  &c.  One  of  the  oldest  plans, 
and  for  all  that  one  of  the  best,  is  the 
eastern  or  Roman  plan,  if  you  like  so  to 
call  it,  which  is  that  of  tapping  natural 
springs  at'  their  sources,  or  lakes,  above 
the  places  to  be  supplied,  and  conduct- 
ing the  water  by  channels  or  aqueducts 
above  or  below  ground,  or  alternately 
above  and  below,  as  occasion  may  re- 
quire ;  collecting  it  in  large  cisterns,  al- 
lowing the  sediment  to  settle,  and  then 
distributing  by  means  of  gravitation. 

In  later  times  we  can  adopt  the  same 
plan,  and  distribute  either  by  gravitation 
or  by  steam  power  as  we  choose.  Per- 
manent springs  at  a  distance  may  be  con- 
veyed by  the  Roman  plan  through  chan- 
nels across  the  country,  covered  the 
whole  way  right  up  to  the  distributing 
reservoirs  or  tanks.  The  conduits  may 
be  built  of  masonry  and  cement,  like  the 
Roman  aqueducts,  embedded  in  puddle, 
or  they  may  be  earthenware  pipes,  in 
which  case  they  must  be  laid  in  water- 
tight trenches,  and  jointed  securely,  or 
the  water  may  be  contaminated  in  vari- 
ous ways,  and  much  of  it  may  be  lost, 
or  the  pipes  may  be  of  cast-iron,  and 
this  should  be  the  case  where  deep  val- 
leys have  to  be  crossed  by  means  of  in- 
verted syphons. 

Earthenware  pipes  are  not  strong 
enough  to  be  used  as  inverted  syphons. 
The  rule  is,  that  if  the  fall  is  greater 
than  1  in  300,  then  cast-iron  pipes  should 
be  used.  The  fall  of  these  conduits 
should  be  5  feet  in  a  mile,  if  they  are  of 
something  like  2  feet  in  diameter,  which 
is  of  a  small  size.     If  larger,  it  may  be 

*  Abstract  of  lectures  delivered  before  the  School  of 
Military  Engineering  at  Chatham. 


less,  down  to  1  in  10,000,  or  6  inches  in 
the  mile.  That  is  the  fall  of  the  New 
River  conduit  that  supplies  part  of  the 
north  of  London  with  water. 

The  velocity  of  the  water  should  not 
be  less  than  one  foot  in  the  second,  so 
that  it  may  move  at  a  sufficient  rate,  nor 
greater  than  four  feet  in  a  second,  for 
fear  it  should  wear  away  the  course  by 
carrying  down  stones,  etc.  As  an  opin- 
ion about  this  plan,  which  I  am  going  to 
describe  to  you  at  greater  length,  I  may 
mention  that  Mr.  Rawlinson  stated,  in  a 
discussion  on  the  water  supply  of  Mel- 
bourne, which  you  will  find  reported  in 
Vol.  IS  of  the  proceedings  of  the  Insti- 
tution of  Civil  Engineers,  that  "  he 
thought  the  plan  of  gathering  spring 
water  in  Great  Britain,  by  means  of 
earthenware  pipes  to  some  common 
storage  reservoir,  was  one  that  might  be 
favorably  looked  at;  the  modern  means 
of  making  earthenware  pipes  offered 
many  facilities;  and  where  springs  were 
at  a  sufficient  elevation  and  tolerably 
permanent,  the  water  might  be  collected 
and  brought  into  a  covered  reservoir  on 
the  Eastern  plan.  There  were  situations 
where  that  plan  might  be  preferable  to 
making  an  impounding  reservoir." 

Now,  I  should  like  to  give  you  a  short 
account  of  some  of  the  points  which  are 
to  be  observed  in  the  Roman  aqueducts 
at  Rome  ;  and  afterwards  I  propose  to 
give  you  an  account  of  some  extremely 
remarkable  Roman  aqueducts  which  are 
very  little  known,  and  which  have  been 
very  seldom  described,  to  wit,  the  aque- 
ducts with  which  the  town  of  Lugudu- 
num,  now  called  Lyons,  was  supplied, 
which  aqueducts  have  some  very  inter- 
esting and  instructive  points  about 
them,  as  3rou  will  see  directly. 

As  I  think  I  told  you  before,  Rome 
Avas  supplied  by  nine  aqueducts.  The 
first  two  were  built  entirely  underground 
for  their  whole  length,  because  the  water 
supply  might  otherwise  have  been  cut* 
oft'  in  case  of  invasion.  The  more  an- 
cient of  these  two,  the  oldest  of  all  the 


234 


VAN   NOSTRAND'S   ENGINEERING   MAGAZINE. 


nine  aqueducts,  ran  for  a  distance 
of  about  11  miles.  I  need  not  say  any- 
thing more  about  that  one.  When  the 
Romans  built  the  third  aqueduct  they 
were,  it  appears,  no  longer  afraid  of  its 
being  destroyed  by  enemies,  and  so  they 
built  it  partly  above  ground,  and  partly 
underneath  the  ground.  By  the  direct 
road  to  the  place  from  which  they  took 
the  water  was  39  miles  from  Rome. 
Three  thousand  men  were  set  to  work 
at  it  under  the  Praetor  Marcius,  and  so 
it  has  been  called  the  Marcian  aqueduct. 
This  aqueduct  was  made  so  strong  that 
the  two  succeeding  ones  were  built 
on  the  top  of  it,  so  that  you  have  the 
three  channels  one  above  another.  The 
size  of  the  channel  of  the  Marcian  aque- 
duct was  about  5  Roman  feet  high  by 
2|  wide.*  The  thickness  of  each  of  the 
sides  was  a  foot.  You  can  see  this  aque- 
duct outside  one  of  the  gates  of  Rome 
at  the  present  day. 

On  these  aqueducts  there  were  venti- 
lating shafts.  There  were  also  what  are 
known  as  piscina?,  or  small  settling  res- 
ervoirs. These  piscinae  I  shall  describe 
to  you  a  little  further  on.  Then  the 
base  of  the  channel  was  broken  up  by 
inequalities,  partly  to  help  to  break  the 
very  considerable  fall,  and  likewise  to 
aerate  the  water  by  agitation. 

I  may  now  say  a  word  or  two  about  the 
water  supply  of  the  Roman  town  of  Lug- 
udunum,  in  Gaul.  In  the  first  place,  I 
must  remind  you  that  those  aqueducts 
which  supplied  Rome  with  water  were 
carried  across  no  deep  valleys,  they  had, 
it  is  true,  often  to  be  supported  on  high 
arches,because  they  pass  over  low  ground, 
and  the  Romans  have  over  and  over  again 
been  blamed  for  not  using  syphons  ;  it 
has  been  said  that  the  Romans  were  not 
acquainted  with  the  properties  of  water, 
in  that  they  did  not  use  syphons  in  these 
aqueducts.  We  shall  see  directly  wheth- 
er that  is  true  or  not. 

The  town  of  Lugudunum  (Lyons)  was 
supplied  by  water  by  means  of  three 
aqueducts.  The  first  of  them  was  built 
in  the  first  century  before  Christ,  and 
here  is  the  description  of  it  in  a  few 
words.  It  had  two  branches,  which  unit- 
ed at  a  particular  place.  It  passed  over 
a  large  plateau  in  a  straight  line  ;  then 
went  underground.     Emerging  from  be- 

*  The  Roman  foot  was  equal  to  about  11.65  English 
inches. 


neath  the  ground,  it  descended,  by  means 
of  inverted  syphons,  into  a  deep  valley, 
and  was  received  at  the  bottom  of  that 
valley  on  a  supporting  bridge  of  arches. 
It  was  thus  carried  across  the  valley,  and 
ascended  the  other  side  into  a  reservoir. 
So  you  see  in  the  course  of  this  aque- 
duct, which  was  built  in  the  first  century 
before  Christ,  there  was  a  large  and 
deep  valley  crossed  by  means  of  invert- 
ed syphons,  by  the  very  method  which 
we  employ  now ;  and  this  shows  you 
that  the  Romans  then  certainly  under- 
stood and  perfectly  well  appreciated  the 
properties  of  the  syphon. 

I  will  now  give  you  a  description  of 
the  second  aqueduct  by  means  of  which 
Lugudunum   was  supplied  with   water. 

It  was  under  ground  the  whole  way, 
and  it  carried  the  water  to  a  greater 
height  than  the  other.  The  reason  that 
it  was  constructed  at  all  was,  because 
the  water  was  required  to  be  carried  to 
a  greater  height  than  the  former  aque- 
duct brought  it.  It  was  very  nearly  the 
size  of  the  Marcian  aqueduct.  It  was 
built  of  cubical  stones  placed  together, 
as  I  may  tell  you  a  great  many  of  these 
aqueducts  were  built.  The  stones  were 
placed  together  without  cement,  and 
they  fitted  so  accurately  that  some  aque- 
ducts built  in  this  way  are  not  even  lined 
with  cement.  This  aqueduct  is  in  all 
j>robability  intact  at  the  present  day  for 
three-fourths  of  its  length.  Now  we 
come  to  the  third,  which  is  the  most  im- 
portant of  the  three,  and  which  is,  per- 
haps, the  most  remarkable  Roman  aque- 
duct of  which  we  have  the  remains  any- 
where. The  two  former  ones  did  not 
bring  the  water  to  a  sufficient  height. 
There  is  at  Lyons  an  abrupt  hill  (Four- 
vieres),  on  which  several  Roman  palaces 
were  built,  and  it  was  necessary  to  bring 
water  to  these.  The  Emperor  Claudius, 
who  was  born  at  Lugudunum,  and  who 
lived  there,  determined  to  bring  water 
on  to  this  hill.  He  had  already  made  an 
aqueduct  for  Rome  (the  Claudiun  aque- 
duct), and  so  he  knew  something  about 
it. 

He  had  not  used  inverted  syphons 
however,  in  his  aqueduct  at  Rome,  and 
for  the  simple  reason,  as  you  will  pres- 
ently see,  that  it  was  practically  impos- 
sible ;  but  he  comes  and  orders  a  new 
aqueduct  to  be  built  for  the  city  of 
Lugudunum,  and  it  is  that  one  which  we 


WATER   SUPPLY   AND   DRAINAGE. 


235 


are  now  going  to  consider,  as  briefly  as 
possible. 

This  aqueduct  descended  in  the  first 
place  into  three  or  four  valleys  on  its 
way.  The  aqueduct  was  52  kilometres 
long,  including  the  syphons.  It  had  17 
or  18  bridges  of  arches  to  carry  it  over 
low  grounds,  and  four  bridges  to  carry 
the  syphons  across  the  valleys. 

And  now  I  may  tell  you  the  size  of 
the  two  more  important  of  these  valleys. 
The  valley  of  the  river  Garon,  which  is 
the  second  one  it  had  to  cross,  is  120 
metres   deep,    and    800    metres    broad. 

The  valley  of  Bonan  ,  which  is 

the  next,  and  which  is  the  place  at  which 
I  examined  the  aqueduct  very  carefully 
some  time  ago  ,  is  139  me- 
tres deep,  and  1,060  metres  across  be- 
tween the  two  reservoirs,  which  are 
placed  one  on  each  side  of  the  valley. 
So  you  see  these  are  two  very  consider- 
able valleys  that  had  to  be  crossed. 

And  now,  how  did  the  Romans  man- 
age to  effect  their  purpose?  Bridges 
were  out  of  the  question,  although  we 
know  that  they  built  splendid  aqueduct 
bridges,  where  possible,  in  such  situa- 
tions, as  witness  the  well-known  Pont 
du  Gard,  near  Nismes,  which  had  three 
rows  of  arches  one  above  another,  sup- 
porting the  channel,  and  which  is  even 
now  so  perfect  that  it  is  about  to  be 
utilized  for  the  purpose  for  which  it  was 
originally  built. 

They  used  inverted  syphons.  I  told 
you  that  earthenware  pipes  will  not  do 
for  syphons.  Cast  iron  pipes  need  to 
be  employed  for  large  syphons.  The 
Romans  could  only  work  iron  on  a 
small  scale  and  so  used  leaden  syphons. 
One  thing  they  did,  and  which  it  is  im- 
portant to  note  in  this:  the  water  was 
brought  up  along  the  single  channel  of 
the  aqueduct — the  specus,  as  it  was 
called — which  in  this  particular  one  is 
about  2  Roman  feet  broad  by  6  high, 
into  a  reservoir.  This  reservoir  had 
some  such  dimensions  as  5  yards  by 
nearly  2,  and  the  walls  were  about  a 
yard  thick;  there  was  an  opening  in 
the  roof  for  the  purpose  of  cleansing, 
and  on  the  front  side  of  the  reservoir 
(the  one  facing  down  the  valley),  there 
were  several  holes  into  which  the  leaden 
pipes  were  fixed.  Now  one  of  these 
valleys  had  8  leaden  syphons,  another 
9,   and  another  10;    and  the  object,  of 


course,  of  dividing  the  water  in  this 
way  was  that  they  might  get  pipes  that 
would  resist  the  enormous  pressure,  and 
if  a  pipe  burst  the  rest  might  remain 
sound,  so  that  only  part  of  the  water 
would  be  lost.  Delorme,  I  should  tell 
you,  has  calculated  that  this  single  aque- 
duct brought  11  millions  of  gallons  of 
water  into  the  place  in  24  hours.  It  is 
hardly  likely  that  it  brought  so  much  as 
that,  but  it  certainly  brought  a  consider- 
able amount. 

The  interior  of  the  channels  was  usual- 
ly constructed  of  very  small  stones  care- 
fully placed,  and  generally  laid  in  ce- 
ment. There  was  in  this  particular  one 
— and  probably  it  was  so  generally — a 
layer  of  cement  along  the  walls  of  the 
watercourse,  and  another  layer,  a  consid- 
erably thicker  one,  along  the  base  of  the 
channel.  The  arches  of  the  bridges 
were  built  of  enormous  rectangular 
blocks  of  stones,  and  the  pillars  broken 
at  certain  intervals  by  layers  of  brick- 
work buried  in  cement.  The  whole  of 
the  exterior  of  this  was  covered  over 
with  the  work  known  to  engineers  as  the 
"  opus  reticulatum,"  which  is  made  of 
cubical  pieces  of  stone,  fitted  carefully 
together  so  as  to  give  an  appearance 
such  as  that  indicated  in  the  drawing 
(like  a  chessboard  set  up  on  one  corner). 

There  is  another  curious  thing  to  ob- 
serve, and  that  is  that  the  syphons  were 
provided  with  little  tubes,  or  valves,  to 
let  out  any  air  that  might  be  carried 
down  from  the  height  by  the  water,  and 
which  might  otherwise  break  the  pipes. 
In  the  smaller  valleys  there  were  small 
leaden  tubes,  which  rose  up  from  the 
lowest  part  higher  than  the  reservoirs, 
and  in  the  larger  ones  weighted  valves 
were  used  for  the  same  purpose.  But 
what  I  want  you  to  see  in  this  is,  that 
by  the  time  the  Romans  constructed 
even  the  earliest  of  these  aqueducts  at 
Lugudunum,  they  knew  perfectly  well 
the  properties  of  water.  They  knew 
perfectly  well  they  could  make  it  travel 
up  to  the  top  of  a  hill  if  it  had  come 
down  a  slightly  higher  hill  on  the  other 
side  of  a  valley.  Now  I  just  wish  to 
give  you  the  height  of  the  reservoir  on 
the  one  side  of  the  valley  of  Bonan.  the 
deepest  of  them  all.  The  height  of  that 
reservoir  above  the  level  of  the  Saone  at 
Lyons,  is  151  metres,  or  something  over 
that.     At  the  other  side   of  the  valley 


236 


VAN   NOSTRAND'S   ENGINEERING   MAGAZINE. 


into  which  the  water  was  received  the 
reservoir  was  143  metres  above  same 
level,  that  is  to  say,  the  difference  in 
height  between  those  two  reservoirs  was 
only  eight  metres.  In  another  case,  it 
was  9  metres.  Not  only  then  did  they 
understand  these  matters  so  well  as  that, 
but  they  actually  lessened  this  amount 
by  causing  the  syphons  to  enter  nearest 
reservoir — the  one  nearest  the  place  to 
be  supplied — high  up  close  to  its  roof,  so 
that  they  actually  thus  diminished  the 
pressure  by  at  least  a  metre.  I  have 
given  you  this  description  at  such 
length,  because  it  shows  how  much  we 
have  to  learn  from  what  has  been  done  a 
very  long  time  before  our  own  age,  and 
also  because  there  are  so  few  descrip- 
tions of  these  splendid  aqueducts. 

We  now  come  to  the  next  plan,  that 
of  having  a  large  drainage  area,  and  of 
collecting  the  water  from  that  area  into 
an  impounding  reservoir.  Before  I  be- 
gin to  describe  this,  I  will  give  you  a 
brief  account  of  one  or  two  important 
impounding  reservoirs.  The  first  one 
will  be  that  of  the  Rivington  Pike  reser- 
voir, which  now  supplies  the  town  of 
Liverpool  with  most  of  its  water.  This 
Rivington  Pike  reservoir  is  calculated  to 
supply  21  millions  of  gallons  of  water 
per  day  to  Liverpool,  and  it  has  481 
million  cubic  feet  of  contents,  with  a 
drainage  area  of  16-j  square  miles  ;  its 
embankment  is  20  feet  high.  You  will 
see  from  that,  that  it  is  calculated  to 
contain  150  days'  supply. 

Then  there  is  a  reservoir  which  was 
made  to  supply  Melbourne  with  water, 
the  particulars  of  which  are  given  in 
the  volume  from  which  I  quoted  to  you 
before,  namely,  Vol.  18  of  the  Proceed- 
ings of  the  Institution  of  Civil  Engin- 
eers, in  a  paper  by  Mr.  Bullock  Jackson. 
It  is  called  the  Yan  Yean  reservoir.  The 
description  runs  thus  : 

"  The  Yan  Yean  reservoir  was  formed 
by  throwing  an  embankment  across  a 
valley  between  two  spurs  of  hills ;  thus 
retaining  the  rain-water  which  falls  on 
the  natural  basin,  as  well  as  the  flood- 
water  which  is  led.  into  it  in  winter  from 
the  Upper  Plenty  River;  the  river  itself 
and  the  artificial  watercourse  forming, 
in  the  latter  case,  a  vehicle  for  its  con- 
duction. The  area  of  this  reservoir, 
when  full,  is  1,303  acres  ;  the  greatest 
depth  is  25  feet  6  inches,  and  the  aA7er- 


age  depth  not  less  than  18  feet.  Its 
contents  measure  nearly  38,000,000  cubic 
yards,  or  upwards  of  6,400,000,000  gal- 
lons. The  area  of  the  natural  catchwater 
basin,  independent  of  the  reservoir,  is 
4,650  acres;  so  that,  including  the  area 
of  600  acres  drained  by  the  watercourse, 
there  is  a  direct  drainage  into  the  reser- 
voir of  5,250  acres.  .  .  .  The  origi- 
nal surface  of  the  ground  at  the  site  of 
the  Yan  Yean  reservoir  consisted  of  a 
stiff  retentive  clay  ;  the  site  was,  there- 
fore, admirably  adapted  for  a  reservoir. 
Prior  to  the  commencement  of  the 
works,  about  two-thirds  of  the  whole 
area  were  densely  timbered  with  large 
specimens  of  eucalyptus,  which  were 
taken  up  and  burnt.  The  sides  of  the 
reservoir,  excepting  in  two  parts,  rise  in 
a  steep  slope.  The  embankmeut  is  1,053 
yards  in  length  at  the  top,  and  30  feet  9 
inches  in  height  at  the  deepest  part;  the 
width  at  the  top  is  20  feet ;  the  inner 
slope  is  3  to  1,  and  the  outer  slope  2  to 
1.  The  inner  slope  is  pitched  with  rough 
stones  from  15  to  20  inches  deep.  Along 
the  centre  is  a  puddle  bank  and  puddle 
trench,  with  an  inner  apron  and  check 
trench.  The  puddle  trench  and  bank 
are  unusually  thick,  because,  in  the  first 
place,  almost  the  whole  of  the  material 
used  in  the  construction  of  the  bank  was 
clay,  so  that  it  entailed  little  extra  ex- 
pense; but  principally,  because  previous 
to  the  works  being  commenced,  the  site 
of  the  embankment  was  occupied  by 
trees  of  a  gigantic  size,  with  long  strag- 
gling roots,  which  were  all  grubbed  up, 
and  which  it  was  feared  might  leave 
clefts  in  the  soil." 

According  to  Mr.  Hawkesley,  the  con- 
siderations that  you  have  to  take  into  ac- 
count in  constructing  impounding  reser- 
voirs are  these:  In  the  first  place  you 
have  to  consider  the  extent  of  the  drain- 
age area.  In  the  second  place,  the 
amount  of  rainfall.  And  in  the  third 
place  the  quantity  of  rainfall  which  can 
be  collected  into  any  reservoir  which  it 
is  practical  to  make  in  the  district.  The 
size  of  these  reservoirs  must  be  propor- 
tioned to  the  population  to  be  supplied, 
their  area  often  requiring  to  be  -h  of  the 
area  of  the  water-shed.  Mr.  Hawkesley 
stated  in  a  discussion,  that  he  considered 
on  an  average  of  years  that  30  inches  of 
rainfall  out  of  a  rainfall  of  48  inches, 
could  be  collected  in  an  impounding  res- 


WATER   SUPPLY   AND   DRAINAGE. 


237 


ervoir.  It  is  usually  considered  that 
one-sixth  part  of  the  total  rainfall  must 
be  put  down  as  lost  every  year  by  floods 
that  you  cannot  store.  The  water  that 
you  cannot  collect  is,  of  course,  lost  by 
evaporation  from  the  surface  of  the 
ground,  absorption  by  plants,  and  so  on. 

Now  as  to  the  site  of  the  reservoir. 
In  the  first  place  steep-sided  valleys  are 
the  best  situations.  In  the  next  place, 
it  is  necessary,  of  course,  that  the  place 
for  collecting  and  storing  water  should 
be  sufficiently  high  above  the  place  to 
be  supplied,  so  as  to  enable  you  to  sup- 
ply water  by  gravitation,  and  necessary 
also,  that  it  shall  not  be  too  high  above 
it,  so  that  you  may  not  have  too  great 
a  rush  of  water. 

Then  besides  the  situation,  the  incline 
of  the  rocks  must  be  considered.  It  is 
especially  important  in  limestone  that 
the  dip  of  the  strata  shall  be  in  the 
direction  in  which  the  water  is  running, 
because  if  the  clip  is  against  it  you  very 
often  have  immense  quantities  of  water 
lost,  disappearing  between  the  strata 
and  running  away  in  another  direction. 
Stiff  impervious  clay  or  compact  rock 
affords  the  best  situation.  Trial  shafts 
or  borings  require  to  be  made  at  various 
places,  it  being  better  to  make  shafts 
than  borings,  to  see  if  you  have  a  suffi- 
ciently impervious  material  for  the  bed 
of  the  reservoir,  and  a  sufficient  depth 
of  it.  It  is  only  with  small  reservoirs, 
as  a  rule,  that  you  can  safely  puddle  the 
whole  of  the  bottom,  or  that  it  is  done, 
and  for  this  reason  in  small  reservoirs 
the  site  is  of  less  importance,  as  you  can 
puddle  the  whole  of  the  bottom,  and 
carry  it  under  the  embankment  of  the 
puddle  wall. 

The  embankment  should  have  con- 
structed what  is  called  a  puddle  wall 
down  the  centre  of  it.  I  shall  do  well 
to  give  you  some  rules  about  this.  Mr. 
Rawlinson  lays  it  down,  that  the  puddle 
wall  is  to  be  a  foot  thick  at  the  surface 
of  the  ground  for  every  three  feet  in 
height  of  the  embankment,  that  is  to 
say,  that  in  an  embankment  100  feet 
high,  the  puddle  wall  should  be  about 
33^  feet  thick  at  the  base.  Then  it 
slopes  up  to  the  top  so  as  to  be  about 
four  feet  broad  at  the  top.  Having  de- 
cided the  thickness  that  you  are  going 
to  make  the  puddle  wall  by  the  height 
that  you  are  going  to  make  the  embank- 


ment, according  to  that  rule,  you  have 
then  to  dig  what  is  called  a  puddle 
trench.  This  is  dug  down  to  a  con- 
siderable depth  into  the  impervious  bed 
that  willbe  the  bottom  of  the  reser- 
voir. The  trench  is  usually  sunk  with 
sides  sloping  towards  one  another, 
though  this  is  considered  by  some 
authorities  to  be  an  insecure  plan.  It 
would  involve  a  considerable  amount  of 
extra  work,  which  would  to  a  great  ex- 
tent be  unnecessary,  to  sink  the  puddle 
trench  with  sides  diverging  from  one 
another,  as  you  would  expect  it  ought  to 
be,  and  so  it  is  sometimes  recommended 
to  sink  the  puddle  trench  with  perpen- 
dicular sides.  If  it  is  very  wet  at  the 
bottom  of  a  puddle  trench,  it  is  usual  to 
begin  filling  it  with  Portland  cement 
concrete,  and  then  to  go  on  with  the 
puddling.  For  puddling  only  the  stiffer 
kinds  of  clay  are  used.  On  each  side  of 
the  puddle  wall  a  masonry  wall  is  built, 
about  equal  to  it  in  thickness.  The  ex- 
ample I  gave  you  was  one  in  which  the 
embankment  slope  on  each  side  of  this 
puddle  wall  was  pretty  correct,  namely, 
three  to  one  inside,  and  two  to  one  out- 
side. This  embankment  is  made  of  such 
materials  as  can  be  obtained  in  the 
neighborhood,  and  the  whole  embank- 
ment must  be  made  in  very  thin  layers, 
and  should  be  trampled  in  as  much  as 
possible.  The  inner  slope  of  the  em- 
bankment is  shingled  up  to  a  little  short 
of  the  water-mark,  and  from  that  point 
it  is  pitched  with  blocks  of  stones.  It  is 
sometimes  necessary  to  make  minor  em- 
bankments across  valleys  that  may  join 
with  the  one  you  are  going  to  make  into 
a  reservoir.  Now  a  reservoir  requires  a 
waste  weir  for  the  storm  waters.  This 
is  generally  made  round  the  end  of  the 
embankment,  or  cut  into  the  hillside. 
The  water  is  carried  from  this  point 
down  to  the  old  stream-course,  and  the 
channel  is  puddled  until  you  are  well 
clear  of  the  embankment. 

I  have  one  or  two  words  to  say  about 
the  reason  for  the  existence  of  these  im- 
pounding reservoirs,  and  also  about  the 
size  which  it  is  necessary  to  make  them, 
and  the  rules  that  are  laid  down  for  the 
amount  of  water  that  they  should  hold. 
In  the  first  place,  they  are  necessary 
where  a  sufficiently  copious  and  perma- 
nent supply  cannot  be  got  from  a  river 
or  large  stream,  or  from    artesian  wells. 


238 


VAN"   NOSTRAND  S   ENGINEERING  MAGAZINE. 


in  order  to  secure  a  constant  supply  of 
water  throughout  the  year,  and  they  do 
this  by  storing  the  extra  supply  of  water 
during  floods,  so  that  it  may  be  saved 
for  use  in  times  of  drought;  secondly, 
they  allow  a  settling  to  take  place;  and, 
in  third  place,  they  are  necessary  to  pre- 
vent damage  to  the  lower  lands  by 
floods,  for  great  damage  is  occasionally 
done  by  the  floods,  even  of  such  rivers 
as  the  Thames  and  the  Severn,  and,  of 
course,  great  quantities  of  water  are 
wasted. 

The  size  must  depend  upon  the 
amount  of  water  required,  and  upon  the 
permanence  of  the  supply  ;  we  have 
reckoned  the  requisite  supply  at  thirty 
gallons  per  head  per  day.  Impounding 
reservoirs  should,  according  to  the  opin- 
ion of  many  engineers,  hold  a  six  months 
demand.  You  can  tell  how  much  that 
is,  if  you  will  lay  down  the  amount  of 
gallons  which  you  intend  to  supply  per 
head,  and  the  population  to  be  supplied. 
If  possible,  the  gathering-ground,  that 
supplies  these  reservoirs  should  be  so 
large  that  the  least  available  annual 
rainfall  is  sufficient  for  the  supply;  and 
then  the  reservoir  should  contain  an  ex- 
cess of  six  months  demand  over  six 
months  least  possible  supply;  that  is  to 
say,  supposing  the  least  possible  supply 
at  any  time  during  the  year  is  zero,  then 
the  reservoir  must  contain  six  months 
demand.  The  reservoir  must  be  (to  put 
it  in  Mr.  Hawkesley's  words)  "  suffi- 
ciently large  to  equalize  all  the  droughts 
and  floods  to  which  the  country  was 
subject.  Occasionally,  but  not  very  fre- 
quently, there  might  be  a  great  excess 
of  downfall,  resulting  in  floods  as  large 
as  three  or  four  hundred  times  the  mini- 
mum volume."  Now  the  minimum  vol- 
ume is  only  about  an  18th  or  20th  part 
of  the  mean  volume,  so  it  follows,  that 
the  floods  are  only  15  or  20  times  the 
mean  volume. 

Now  with  regard  to  compensation. 
It  is  necessary  in  many  instances  to 
compensate  owners,  mill  -  owners,  and 
others,  people  who  are  interested  in  the 
streams  that  you  are  going  to  impound, 
and,  on  an  average,  it  is  found  that  in 
England  one-third  of  the  amount  of 
water  requires  to  be  given  as  compensa- 
tion to  these  people,  and,  therefore, 
two-thirds  remain  for  the  use  of  the 
town.     This    compensation,    of    course, 


must  be  considered  in  determining  the 
size  of  the  reservoir.  Sometimes  it  has 
been  arranged  that  the  amount  given  to 
the  owners  on  the  banks  should  be  the 
average  summer  discharge,  minus  the 
floods,  and  sometimes  special  compensa- 
tion reservoirs  have  been  built  to  collect 
the  water  from  a  certain  portion  of  the 
drainage  area,  these  compensation  reser- 
voirs being  entirely  under  the  control  of 
the  persons  who  are  to  be  compensated. 
However,  you  may  take  it  as  an  aver- 
age, that  about  one-third  in  England 
generally  goes  to  them. 

The  culverts  have  been  commonly 
built  through  the  embankment  in  the 
made  earth.  This  is  stated  to  be  a  bad 
plan.  Mr.  Rawlinson  says  they  should 
always  be  built  in  the  rock  or  in  the 
solid  ground,  and  not  in  the  made  earth. 
The  water  tower  is  generally  built  just 
inside  of  the  embankment,  and  the  dis- 
charge or  outlet  pipes  open  into  it  with 
valves,  which  valves  ought  to  be  inside 
the  embankment,  and  not  outside  of  it. 
What  are  called  "  separating  weirs " 
have  been  constructed  in  some  reser- 
voirs. They  are  ingenious  contrivances 
by  which  the  water,  when  at  its  ordinary 
height,  flows  over  the  weir  into  the  cul- 
vert to  be  taken  away  to  the  town. 
When  it  is  in  flood,  the  force  with  which 
it  comes  enables  it  to  pass  over  the 
opening  leading  to  the  culvert,  and  to 
get  away  into  the  old  watercourse. 
"  Feeders "  for  diverting  streams  into 
the  reservoir  are  also  sometimes  necessa- 
ry. It  is  often  found  to  be  necessary  to 
cut  a  new  course  for  the  stream  that 
runs  down  the  valley,  especially  if  it  be 
a  very  large  stream,  or  if  it  be  a  stream 
that  is  liable  to  floods. 

I  see  that  I  forgot  to  mention  one 
point,  which  I  should  have  stated  at  the 
beginning  of  the  lecture,  with  regard  to 
the  situation  of  these  reservoirs.  The  site 
must  not  be  too  low,  for  if  it  is,  the  res- 
ervoir is  necessarily  too  shallow,  and 
shallow  reservoirs  are  very  bad,  in  that 
the  water  cannot  possibly  be  kept  pure, 
it  being  perfectly  impossible  to  store  it 
and  keep  it  pure  in  shallow  reservoirs. 
If  the  ground  is  too  high,  and  no  other 
suitable  place  can  be  got,  then  it  is  nec- 
essary to  make  what  are  called  "balanc- 
ing reservoirs,"  so  that  the  force  of  the 
water  may  be  broken  by  its  being  kept 
in  a  series  of  reservoirs  at  different  levels. 


WATER   SUPPLY   AND   DRAINAGE. 


239 


I  do  not  profess  to  have  given  you  the 
engineering  details,  as  you  will  plainly 
see.  All  I  have  tried  to  do  is  to  give 
you  some  of  the  most  important  points, 
according  to  the  best  authorities  that  I 
have  been  able  to  find. 

The  channels  are  generally  made  of 
masonry  or  brickwork.  The  water-way 
is,  according  to  Rankine,  best  semi-cir- 
cular, or  a  half  squai'e,  or  a  half  hexa- 
gon. These  channels  are  usually  made 
cylindrical  ;  they  require  ventilating 
shafts  after  the  custom  of  the  Romans. 
Occasionally  they  are  made  with  an 
egg-shaped  section,  like  large  sewers. 

Channels  require  to  be  curved  at  their 
junctions,  or  at  any  rate,  they  require  to 
be  joined  at  very  acute  angles. 

With  regard  to  aqueducts,  Mr.  Raw- 
linson  tells  us  that  "  aqueducts  of  iron 
will  probably  be  cheaper  than  masonry 
or  brickwork  constructions."  They  have 
been  made  self-supporting  by  Mr.  Simp- 
son, by  constructing  them  in  the  form 
of  tubular  iron-girders. 

Now,  with  regard  to  the  fall  of  these 
■channels,  I  gave  you  one  or  two  points 
before,  when  considering  the  pipes  con- 
veying the  streams.  In  the  discussion 
on  the  water  supply  of  Paris,  in  the 
25th  Volume  of  the  Proceedings  of  the 
Institute  of  Civil  Engineers,  Mr.  Bate- 
man  gave  the  following  example  with 
reference  to  the  Loch  Katrine  aqueduct 
of  the  Glasgow  Water  Works:  "The 
fall  was  10  inches  to  the  mile  through- 
out, except  where  the  water  was  carried 
by  syphon  pipes  across  deep  valleys, 
which,  in  one  instance  of  a  hollow  of 
250  feet,  was  done  for  a  distance  of  3^ 
miles,  and  in  these  cases  there  was  a  fall 
of  5  feet  per  mile,  to  economize  the  size 
of  the  pipes." 

This  aqueduct,  I  believe,  is  about  the 
largest  that  has  been  constructed.  The 
channel  is  cylindrical,  and  about  8  feet 
in  diameter.  Mr.  Rawlinson  said  in  the 
same  discussion,  that  "the  fall  of  an 
aqueduct  must  be  in  proportion  to  the 
depth  and  volume  of  water  which  it  had 
to  deliver.  The  fall  of  the  New  River 
in  London  was  1  in  10,000,  or  6  inches 
to  the  mile,  but  with  so  large  a  volume, 
and  an  unpaved  channel,  it  was  necessary 
to  form  a  weir,  and  give  the  water  a 
vertical  fall  of  a  few  inches  at  certain 
points  of  its  course.  He  found  that 
plan  was  adopted  in  the  East.   In  laying 


out  a  line  of  aqueduct  two  principles 
were  involved.  If  it  were  graded,  as 
the  Romans  graded  some  of  theirs,  from 
5  to  15  feet  per  mile,  there  would  be 
difficulty  in  stopping  the  water  at  any 
point.  It  was  practicable,  however,  to 
grade  an  aqueduct  having  a  fall  of  15 
feet  or  20  feet  per. mile,  if  vertical  falls 
were  introduced  at  intervals,  alternately 
with  level  or  nearly  level  lengths.  This 
mode  enabled  an  engineer  to  fix  the 
velocity,  so  as  to  prevent  undue  wash- 
ing. The  vertical  falls  tended  to  aerate 
the  water,  and  this  in  itself  constituted 
an  additional  advantage.  All  covered 
aqueduct  conduits  should  be  abundantly 
ventilated,  and  there  should  be  side  en- 
trances, stop  gates,  overflows,  and  wash- 
out valves."  Sometimes  in  aqueduct 
bridges,  the  sectional  area  of  the  channel 
is  diminished,  and  the  gradient  made 
steeper.  This,  of  course,  gives  greater 
velocity  to  the  water,  and  a  smaller 
amount  of  material  is  required,  and  so 
less  expense  incurred  in  constructing  the 
bridges.     So  much  as  to  the  masonry. 

Now  as  to  pipes.  Earthenware  pipes 
are  made  up  to  about  3  feet  in  diameter. 
If  they  are  of  compact  glazed  earthen- 
ware, they  are  very  tough  and  strong, 
but  they  will  not  bear  shocks,  either  the 
shocks  of  water  or  anything  else,  and 
they  cannot  be  jointed  so  as  to  resist  a 
great  pressure,  and  so  are  not  suitable 
for  syphons.  We  will  not  say  anything 
more  about  lead  pipes,  because  they  are 
not  now  used  for  this  purpose.  Cast 
iron  pipes,  Rankine  says,  should  be  of  a 
uniform  thickness ;  and  he  lays  down  the 
following  rule  for  the  minimum  thick- 
ness: "  The  thickness  of  a  cast  iron  pipe 
is  never  to  be  less  than  a  mean  propor- 
tioned between  its  internal  diameter  and 
one  forty-eighth  of  an  inch."  But,  he 
adds,  "  it  is  very  seldom  indeed,  that  a 
less  thickness  than  f  of  an  inch  is  used 
for  any  pipe  how  small  soever."  Large 
cast  iron  pipes  are  liable  to  burst,  and 
there  are  some  instances  on  record  of  it; 
one  in  the  water  works  for  the  supply 
of  Melbourne,  which  I  have  already 
mentioned  once  or  twice,  in  which  case 
the  pipe  was  33  inches  in  width,  was 
laid  through  the  embankment  of  the  res- 
ervoir and  burst.  Now  this  is  what  Mr. 
Hawkesley  said  in  a  discussion  on  the 
subject  at  the  Institution  of  Civil  En- 
gineers, about  the  bursting  of  east  iron 


240 


VAN   NOSTKAND'S   ENGINEETCING   MAGAZINE. 


pipes:  "Cast  iron  in  the  shape  of  a 
pipe  would  stand  little  unequal  pressure 
externally,  although  such  a  pipe  would 
bear  an  enormous  pressure  when  equally 
distributed,  whether  applied  externally 
or  internally,  and  most  in  the  former 
case,  as  the  metal  then  would  be  under 
compression,"  and  he  went  on  to  say, 
that  at  "  the  Rivington  Pike  reservoir 
of  the  Liverpool  water  works  two  lines 
of  pipes  were  carried  through  an  em- 
bankment 20  feet  high,  at  a  distance  of 
16  feet  from  the  top  of  it.  They  were 
cast  iron  pipes,  each  pipe  being  made  in 
10  or  12  pieces,  and  they  are  the  largest 
pipes  that  have  been  laid,  each  pipe 
being  44  inches  in  diameter.  Now,  out 
of  these  two  lines  of  pipes,  fully  one- 
third  of  the  pipes  so  placed,  which  were 
excellent  castings, were  broken,  although 
they  borne  a  pressure  of  300  feet  in- 
ternally. The  fractures  invariably  oc- 
curred at  the  top  and  bottom,  and  not  at 
the  two  sides  as  might  have  been  expect- 
ed. The  pipes  being  flattened  and  dis- 
torted by  the  pressure  of  the  earth,  were 
subjected  to  a  strain  at  the  top  and  bot- 
tom greater  than  at  the  sides,  and  were 
undoubtedly  broken  by  compression. 
This  fact  convinced  him,  that  pipes  in 
that  position  were  very  insecure.  Com- 
monly, in  similar  cases,  there  was  a 
pressure  of  water  on  the  inside,  and  a 
pressure  of  earth  on  the  outside;  and  it 
was  a  usual  arrangement  for  the  valve 
which  shut  off  the  water  to  be  placed 
under  the  embankment,"  (that  is  a  point 
I  have  referred  to  as  one  of  considerable 
importance),  "so  that  if  a  pipe  became 
ruptured  when  in  use  the  water  would 
escape  into  the  embankment,  and  if  it 
found  its  way  to  the  back  of  the  puddle, 
the  embankment  would  be  torn  down, 
and  the  whole  of  the  water  in  the  reser- 
voir set  free.  It  was  not,  therefore,  de- 
sirable that  large  pipes  should  be  laid 
under  an  embankment, where  they  would 
be  subject  to  a  considerable  pressure  of 
earth." 

When  a  pipe  of  that  magnitude  breaks 
it  usually  does  great  damage.  In  one  of 
these  pipes  that  I  have  just  mentioned 
to  you,  sixteen  million  gallons  of  water 
were  capable  of  being  discharged  daily, 
and  if  an  accident  occurred,  there  would 
be  a  column  of  44  inches  in  diameter, 
acting  with  perhaps  200  or  300  feet  of 
pressure   to   be   dealt   with.       Another 


thing  about  these  large  pipes  is,  that 
there  is  a  considerable  difficulty  in  re- 
pairing them.  One  length  of  these 
weighs  about  4  tons,  so  that  they  cannot 
easily  be  dragged  about  or  taken  up. 
Now,  cast  iron  pipes  are  said  often  to 
break  from  the  pressure  of  the  air. 
Whenever  air  gets  driven  in  along  with 
the  water,  and  especially  so  in  syphons 
where  valleys  are  crossed,  these  pipes 
are  broken  (it  is  said)  by  the  collection 
of  compressed  air. 

Mr.  Hawkesley  tells  us,  that  he  con- 
siders that  they  are  broken  when  the  air 
is  let  out;  that  it  is  the  shock  caused  by 
the  running  together  of  the  two  sepa- 
rated parts  of  the  water  that  causes  the 
breakage  of  these  pipes,  when  the  com- 
pressed air  that  is  collected  in  them  is 
let  out  too  suddenly;  and  he  recom- 
mends, and  has  practised  in  the  case  of 
those  large  mains  at  the  Liverpool  water 
works,  the  adoption  of  valves  with  an 
aperture  of  only  f  of  an  inch;  through 
the.se  the  air  rushes  out,  but  they  do  not 
permit  the  columns  of  water  to  come 
together  very  suddenly;  there  should  be 
one  of  these  at  each  place  throughout 
the  channel  where  the  pipe  is  higher 
than  the  theoretical  line,  or  than  the 
line  of  the  fall.  At  each  one  of  these 
places  air  is  liable  to  accumulate  and  to 
become  compressed,  and,  perhaps,  to 
burst  the  pipe.  At  each  one  of  these 
places,  therefore,  there  should  be  means 
of  letting  out  the  compressed  air,  and 
even  with  regard  to  this  precaution  we 
were,  as  I  showed  you  before,  forestalled 
in  the  aqueducts  of  the  ancients. 

Pipes  are  also  sometimes  burst  by  the 
pressure  of  the  water  when  a  valve  on 
the  main  is  closed;  this  difficulty  has 
been  overcome  by  a  plan  mentioned  by 
Mr.  H.  Maudslay  at  the  Institute'  of 
Civil  Engineers:  "In  some  instances 
there  had  been  a  small  valve  and  pipe, 
so  placed  at  the  side  of  the  large  main 
as  to  join  the  main  both  before  and  be- 
yond the  large  valve,  in  order  that  the 
whole  body  of  water  might  not  act  like 
a  water-ram  on  the  closing  of  the  large 
valve.  This  plan  has  been  adopted  in 
the  Neptune  fountain  at  Versailles,  and 
also,  he  believed,  in  the  mains  supplying 
the  fountains  at  the  Crystal  Palace.  On 
shutting  the  large  valve,  the  main  flow 
was  stopped,  but  the  small  pipe  permit- 
ted  a   continuous   flow   of   the    smaller 


WATER  SUPPLY   AND   DRAINAGE. 


241 


quantity,  and  thus  the  danger  of  burst- 
ing was  avoided.  The  second  valve  was 
afterwards  closed  gradually.  He  thought 
that  this  was  the  most  simple  plan  that 
could  be  adopted,  and  perhaps  the  least 
costly,  while  it  was  certainly  very  effect- 
ive." Another  plan  is  that  described  by 
Mr.  Hawkesley,  as  follows:  "The  value 
upon  the  main  at  Liverpool  was  divided 
into  three  openings,  each  of  which  was 
provided  with  a  separate  screen,  so  that 
by  raising  or  lowering  each  of  these 
slowly  in  succession  the  water  was  either 
admitted  or  turned  off  very  gradually. 
The  object  of  dividing  the  valve  into 
three  apertures  was  to  enable  a  work- 
man to  operate  with  facility  on  any  one 
of  the  screws.  In  large  pipes,  where  the 
pressure  was  great,  it  was  necessary,  in 
order  that  the  brass  pieces,  upon  which 
the  valve  acted,  might  not  be  abraded, 
that  only  a  certain  amount  of  pressure 
should  be  put  upon  them,  and  that  the 
friction  under  that  pressure  should  not 
be  greater  than  a  man  could  overcome, 
by  simply  turning  a  handle,  without 
stripping  the  thread  of  the  screw.  As  a 
further  provision  the  centre  valve  was 
made  very  narrow;  the  side  valves  were 
first  closed  and  then  the  centre  one,  so 
that  concussion  was  prevented.  In  ad- 
dition there  were  branches  at  various 
points,  upon  which  eepiilibrium  valves, 
with  a  piston  underneath,  were  placed, 
and  others  had  double  beat  valves.  But 
as  these  valves  required  to  be  heavily 
weighted,  the  inertia  of  the  weight 
would,  if  other  means  were  not  taken, 
prevent  the  valve  from  rising  so  rapidly 
as  was  desirable.  Therefore,  between 
the  weight  and  the  valve  there  was  a 
spring,  the  action  of  which  was  inde- 
pendent either  of  the  valve,  or  of  the 
weight,  so  that  instead  of  the  valve 
waiting  for  the  large  weight  to  rise,  the 
spring  immediately  yielded  under  it  and 
the  water  was  discharged  instantaneous- 
ly. When  these  valves  were  used  not 
the  slightest  shock  was  experienced.  If 
there  had  been,  the  pipe  would  undoubt- 
edly have  been  ruptured,  for  the  length 
of  the  column,  and  the  velocity,  upon 
which  the  force  of  concussion  was  de- 
pendent, were  both  very  great.  That 
was  another  reason  he  preferred  a  small- 
er pipe.  There  were  still,  however,  other 
precautions.  Powerful  disc-valves,  made 
by  Sir  W.  Armstrong  &  Co.,  and  which 
Vol.  XIII.— No.  3—16 


acted  in  a  similar  way  to  the  cataract 
apparatus  if  a  small  power  steam-engine 
were  placed  upon  the  main.  They  were 
made  to  close  slowly,  being  let  go  by  a 
trigger.  As  a  hundred  million  gallons 
might  pass  through  the  main  in  twenty- 
four  hours,  if  a  pipe  burst,  without  any 
provision  being  made  to  stop  the  flow,  a 
great  deal  of  mischief  would  ensue. 
Supposing,  however,  a  fracture  to  occur 
when  the  disc-valve  was  open,  then  the 
valve  would  gently  close  in  about 
two  minutes,  and  arrest  the  discharge. 
These  valves  cost  £300  each.  He  had 
found  them  to  act,  on  various  occasions, 
extremely  well,  and  but  for  them  the 
country  would  have  been  flooded  on 
several  occasions." 

Now,  we  have  considered  the  Roman 
plan  and  also  the  plan  of  collecting 
water  by  drainage  areas  into  large  im- 
pounding reservoirs  and  conveying  it  by 
channels  to  the  place  that  wants  it,  the 
place  where  it  is  to  be  distributed. 
When  it  comes  there,  it  is  collected  in 
what  are  called  service  reservoirs.  The 
most  ancient  examples  of  these  service  res- 
ervoirs are  those  very  piscina?,  upon  the 
Roman  aqueducts,  which  I  have  spoken 
of,  and  you  can  see  examples  of  them  in 
Rome  at  the  present  day.  The  best  I 
ever  saw  was  at  a  place  called  Bona  in 
Algeria,  where  is  to  be  seen  a  set  of  the 
most  magnificent  service  reservoirs.  The 
plan  was  to  have  four  compartments. 
The  water  was  first  let  into  one  of  the 
two  upper  ones;  it  then  fell  from  that 
into  one  below,  possibly  over  a  waste- 
pipe.  The  water  then  passed,  possibly 
through  strainers,  into  another  compart- 
ment on  the  same  level,  and  it  then  rose 
through  the  roof  of  that  compart- 
ment into  a  third  at  the  level  of 
the  first  one,  out  of  which  it  went 
onwards,  and  a  considerable  settling 
took  place.  Now,  there  were  means 
of  scouring  out  these  two  lower 
compartments,  which  could  be  shut  off 
from  the  upper  ones  so  that  the  mud 
might  be  got  out  of  them.  The  water, 
when  it  is  brought  to  these  reservoirs  by 
either  of  these  two  methods,  or  when  it 
is  got  into  them,  as  it  very  often  is  now 
for  the  supply  of  large  towns,  directly 
out  of  the  river,  very  often  requires  To 
be  filtered,  as  mere  settling  is  not  enough 
for  it.  We  have  then  to  consider  what 
materials  are  used  for  filtering;  the  water. 


242 


TAN  Ts'OSTRANDS   ENGINEERING    MAGAZINE. 


what  size  the  filter  beds  require  to  be, 
and  what  effect  is  produced  on  water  by 
filtration. 

Xow,  hi  the  first  place,  the  materials 
that  are  commonly  used  for  filtration  are 
sand  and  gravel.  The  different  merits 
of  sand  and  gravel  and  also  of  charcoal 
I  shall  have  to  consider  in  the  next 
lecture,  but  I  must  conclude  this  lecture 
by  telling  you  that  the  effect  of  filtration 
of  water,  even  by  sand  and  gravel,  is  not 
merely  the  mechanical  effect  of  remov- 
ing the  suspended  substances  that  the 
water  may  contain,  but  that,  at  the 
same  time,  there  is  a  chemical  action 
going  on.  This  is  on  account  of  the  air 
that  is  contained  between  the  little  par- 
ticles of  sand,  which  air  is  so  brought 
into  contact  with  the  finely  divided 
water  that  any  substances  in  the  water 
that  are  capable  of  oxydation  do  become 
oxydized,  and  a  considerable  amount  of 
the  organic  matters  in  the  water  are  thus 
oxydized,  and  transformed  into  inocuous 
matters.  That  is  the  first  important  point 
to  understand  about  filters,  whether  in 
filtering  water  for  drinking  purposes,  or 
with  regard  to  a  filter  about  which  we 
shall  have  to  say  more  after  a  while — a 
filter  to  purify  sewer  water. 

I  have  shown  you  that  it  was  a  fallacy 
to  suppose  that  the  Romans  did  not 
understand  the  principle  of  the  syphon, 
but  that  they  constructed  most  admir- 
able ones  on  the  aqueducts  that  brought 
water  to  Lyons.  It  so  happens,  by  a 
curious  chance,  that  I  have,  recently, 
seen  some  plans  and  sections  of  the 
Roman  aqueducts  which  supplied  Jerus- 
alem with  water,  and  on  one  of  those  I 
find  a  syphon,  not  made  with  lead  pipes, 
but  a  syphon  made  of  stone.  It  is  made 
of  blocks  of  stone  with  a  hole  through 
each;  the  blocks  are  put  together  so  as 
to  form  a  continuous  pipe.  Each  piece 
is  cut  at  the  end  so  that  around  the  pipe 
itself,  the  aperture  in  the  stone,  there  is 
a  ring  left  projecting  on  the  face  of  the 
stone,  and  that  ring  fits  into  a  groove  on 
the  next  stone.  That  made  a  sufficiently 
tight  syphon  to  convey  the  water,  with- 
out any  great  amount  of  leakage,  to  a 
considerable  vertical  depth  and  up  again. 
The  depth,  as  far  as  I  can  judge  from 
the  plans,  is  about  100  feet  from  the 
highest  point  to  the  lowest.  Well,  now, 
we  get  up  to  the  point  where  the  water 
has  reached  the  town,  and  there  I  told 


you  it  is  almost  necessary,  certainly 
usual,  to  construct  a  service  reservoir. 
The  Romans  constructed  them  under  the 
name  of  Piscina3;  and  I  told  you,  I 
think,  in  two  words,  how  those  were 
made;  I  now  want  to  give  you  a  rather 
longer  account  of  their  construction. 
The  water  that  was  brought  by  one  of 
the  aqueducts  to  Rome  was  taken  direct 
from  the  river  Anio,  and  .the  result  of 
taking  the  water  direct  from  the  river 
was  that  after  the  heavy  rains  it  was 
charged  with  mud,  and  though  large 
cisterns  were  provided,  in  which,  by  an 
ingenious  arrangement,  much  of  the 
sediment  was  caught,  still  it  was  not 
considered  satisfactory  by  Frontinus, 
who  was  the  engineer  and  who,  there- 
fore, under  his  patron  the  Emperor 
Nerva,  altered  the  source.  Still  the 
water  that  came  to  Rome  required  to 
have  settling  tanks,  as  described  by  Mr. 
Parker  in  a  paper  I  quoted  before,  and 
from  which  I  again  quote: 

"  The  building  consisted  of  four  cham- 
bers—two beneath  and  two  above.  Sup- 
posing, for  the  sake  of  illustration  and 
in  the  absence  of  a  diagram,  the  letters 

A  B 

„       represent  the  four  chambers.     The 

channel  of  the  aqueduct  coming  from 
the  east,  at  a  tolerably  high  level  enters 
the  chamber  B.  Thence  the  water 
passed  (possibly  over  a  large  waste  pipe) 
into  the  chamber  beneath,  D.  Between 
D  and  C  there  were  communications 
through  the  wall  (possibly  provided 
with  fine  grating).  Through  the  roof 
of  C  there  was  a  hole,  and  the  water 
passed  upwards,  of  course,  finding  the 
same  level  in  A  as  in  B,  whence  it  was 
carried  off  into  another  stream.  By  the 
aid  of  sluice  gates  the  water  could  be 
transferred  direct  from  chamber  B  to 
chamber  A,  and  access  was  obtained  by 
an  opening  to  the  chambers  beneath, 
and  the  mud  was  from  time  to  time 
cleared  out." 

Just  the  same  thing  was  the  case  at 
Lugdunum  (Lyons).  Large  settling  tanks 
have  been  found  on  the  hill  of  Four- 
vieres,  consisting  of  two  reservoirs  with 
vaulted  roofs,  thus  described:  One  of 
them  was  48  feet  long  by  44  feet  broad, 
and  20  feet  high,  with  two  conduits  to 
admit  the  water,  and  several  round  holes 
in  the  roof  from  which  it  could  be 
drawn.     The  walls  were   3   feet   thick, 


WATER   SUPPLY   AND   DRAINAGE. 


243 


lined  with  very  hard  cement.  A  second 
was  100  feet  long,  12  feet  broad,  and  15 
feet  high,  divided  by  a  wall  into  two 
chambers.  A  third  was  a  large  one, 
of  which  five  of  the  supporting  arches 
remain,  and  the  discharge  conduit,  lj 
feet  broad,  which  distributed  the  water, 
by  means  of  leaden  pipes  (of  which  a 
specimen  has  been  found)  to  the  palaces, 
gardens,  etc.  In  some  cases  similar  con- 
structions formed  public  reservoirs  from 
which  the  people  drew  the  water.  In  Rome 
"there  were  591  open  reservoirs  (lacus) 
for  the  service  of  all  comers.  *  *  * 
These  reservoirs  were  what  we  usually 
speak  of  as  fountains;  and  some  hun- 
dreds are  in  use  to  this  day,  many  proba- 
bly on  the  site  of  the  older  ones.  There 
were  very  stringent  laws  respecting 
their  use.  Heavy  penalties  were  inflicted 
upon  any  one  dipping  a  dirty  bucket  or 
vessel  into  the  reservoir.  There  were 
also  laws  respecting  the  '  overflow,'  as 
the  fountains,  of  course,  were  constantly 
running;  these  were  the  most  important 
to  keep  in  order,  as  all  the  poorer  classes 
depended  entirely  upon  them  for  their 
supply  of  water." 

Now  let  us  consider  the  Service  Res- 
ervoirs as  they  are  made  now.  Service 
reservoirs  must  either  be  placed  at  a 
low  level,  so  that  the  water  has  to  be 
pumped  from  them,  or  high  up,  which  is 
better,  so  that  the  water,  if  not  brought 
to  them  at  that  level,  is  piimped  into 
them,  as  at  Lyons,  on  the  Rhone,  where 
the  water  is  brought  to  them  at  the 
highest  point.  They  are  made  to  con- 
tain a  few  days'  supply.  In  the  first 
jjlace,  they  must  always  be  covered; 
even  the  Roman  ones  were.  The  reason 
of  there  being  covered  is  that,  if  not 
covered,  the  water  becomes  impure,  for 
the  impurities  of  the  air  dissolve  in  the 
water  and  the  growth  of  confervse  is 
also,  of  course,  very  much  aided  by 
light.  If  they  are  at  the  level  of  the 
ground,  they  are  built  of  masonry. 

Mr.  Rawlinson  says,  "  The  ground  ex- 
cavated for  the  foundation  of  a  tank 
should  be  made  perfectly  water-tight. 
The  bottom  may  be  covered  with  clay 
puddle  and  the  side  walls  be  backed  or 
lined  with  clay  puddle.  The  thickness 
of  the  puddle  should  not  be  less  than  12 
inches.  If  the  site  selected  for  a  tank  is 
sand,  gravel,  or  open  jointed  rock,  great 
care  must  be  taken  to  give  the  puddle  a 


full  and  even  bearing  over  the  whole 
surface  area  ;  open  joints  in  rock  must 
be  cleaned  out  and  then  filled  up  with 
concrete.  In  gravel,  large  stones  must 
be  removed  and  the  entire  surface 
brought  to  a  level,  smooth,  and  even 
plain.  Clay  puddle  will  only  resist  the 
pressure  of  water  when  it  rests  solidly 
on  an  even  bed,  so  as  to  prevent  the 
water  forcing  holes  through  it,  which 
will  be  the  case  if  there  is  a  rough 
uneven  surface  and  open  space  beneath." 
{Suggestions  as  to  the  preparation  of 
plans  as  to  Main  Sevierage  and  Drain- 
age and  as  to  Water  Supply.) 

The  roof  is  supported  on  piers  with 
arches  between  them,  and  across  some- 
times iron  columns  are  placed  in  rows 
supporting  the  girders  which  carry  the 
arches.  The  supply  pipe  has  one  or 
more  exits,  a  waste  and  a  wash-out, 
which  may  be  connected  by  valves  so 
that  the  supply  can  be  directly  connect- 
ed with  the  exit  independently  of  the 
tank. 

[Drawing  exhibited.]  That  gives  a 
general  idea.  The  water  is  received  in 
a  sort  of  well  or  tower  through  which  it 
passes  into  the  tank,  and  after  settling 
has  taken  place  it  passes  out  through  a 
valve  into  the  exit  pipe.  When  the 
sujjply  is  too  great  it  is  carried  off  by  an 
overflow  to  which  the  wash-out  pipe 
may  be  jointed. 

Well  now,  I  should  like  to  give  you  a 
more  detailed  description  of  such  reser- 
voirs, and  I  take  as  an  instance,  and 
that  for  several  reasons,  the  description 
of  some  reservoirs  with  supply  tanks: 

"  The  reservoir  of  Passy  is  intended 
to  receive  the  waters  pumped  from  the 
Seine  at  Chaillot,  and.  those  furnished 
by  the  Artesian  well  of  Passy  when 
disposable;  it  is  composed  of  three  com- 
partments, two  of  which  are  covered  by 
a  second  range  of  arches,  the  third,  in- 
tended as  a  reserve  in  case  of  fire,  being- 
deeper  than  the  rest,  and  only  of  one 
story;  the  two  upper  ranges  of  arches, 
also,  are  to  be  made  to  hold  a  supply  of 
water,  one  of  them  being  covered  and 
the  other  not.  The  united  capacity  of 
these  various  compartments  is  9,22  7,097 
gallons,  and  their  levels  above  the  Seine 
are  respectively  arranged  at  150  feet, 
and  163  feet,  above  zero  of  the  scale  of 
the  bridge  of  la  Tournelle.  The  capacity 
of  the  separate  reservoirs  is,  for  those 


244 


VAN   NOSTRAND'S   ENGINEERING   MAGAZIN] 


nearest  to  the  ground,  respectively 
2,232,800  and  2,344,984  gallons;  these 
are  covered  with  reservoirs  of  the  ca- 
pacity of  1,282,792  and  1,495,729  gal- 
lons; and  the  uncovered  side  portions 
of  the  reservoir  are  devoted  to  the  re- 
maining 870,792  gallons.  These  build- 
ings are  formed  on  the  '  tuf  du  calcaire 
lacustre,'  which  afforded  a  hard,  resist- 
ing foundation,  and  did  not  require  any 
particular  precautions  to  prevent  the 
subsidence  of  the  piers,  or  to  secure  the 
water  tightness,  or  the  impermeability 
of  the  bottom.  The  external  walls  have 
been  in  consequence  carried  down  to  the 
depth  of  8  ft.  4  in.  and  have  a  width  of 
8  ft.  8  in.  all  around.  The  floors  are  of 
masonry,  1  foot  thick  in  meuliere  and 
cement,  covered  with  a  rendering  coat  of 
1^  inches  of  the  same  cement  worked  to 
a  fine  face.  This  is  covered  with  a 
range  of  cylindrical  vaults  of  10  feet 
opening,  springing  from  pillars  2  ft.  8 
in.  square  upon  the  top,  gradually  en- 
larging to  5  ft.  at  the  bottom.  It  is  cal- 
culated that  in  no  case  does  the  weight 
brought  upon  a  square  inch  of  this 
masonry  exceed  152  lbs.  The  thickness 
of  the  arch  forming  the  roof  of  the  first  | 
tier,  and  the  floor  of  the  second  division, 
is  about  1  ft.  2  in.  on  the  crown;  that  of 
the  roof  of  the  upper  division  is  only  4^ 
inches,  executed  in  two  courses  of  tiles 
bedded  in  cement,  and  'rendered'  with  a 
coating  of  that  material  and  covered 
with  concrete. 

"  The  reservoirs  of  Menilmontant  are 
considerably  larger  than  those  of  Passy, 
and  being  founded  upon  the  upper  mem- 
bers of  the  Paris  Basin,  special  precau- 
tions were  required  to  insure  that  the 
ground  should  not  yield  under  the  com- 
bined pressure  of  the  masonry,  and  the 
29^  million  gallons  of  water  intended  to 
be  stored.  The  marls  covering  the  gyp- 
sum of  which  the  mountain  of  Menil- 
montant is  composed,  were  not  consid- 
ered to  be  able  to  withstand  that  weight. 
The  foundations  of  the  piers  were  there- 
fore carried  lower  down,  and  thence 
built  in  a  description  of  rough  rubble  of 
menliere  set  in  hydraulic  lime.  The 
bottom  floor  of  the  reservoir  is  arched 
over  these  piers,  and  the  upper  tier  of 
arches  rests  upon  this  floor." 

It  is  only  fair  to  tell  you  that  some 
engineers,  and  among  others,  Mr.  Raw- 
linson,  considered  the  plan  of  building 


two-storied  reservoirs  as  a  bad  one,  and 
not  to  be  imitated  ;  but  it  necessary  to 
know  that  there  is  such  a  plan,  and  the 
description  applies,  to  a  great  extent,  to 
all  reservoirs. 

To  take  an  example  nearer  us,  there  is 
Mr.  Simpson's  elevated  reservoir  on  Put- 
ney Heath;  that  contains  ten  millions  of 
gallons  altogether.  There  is  there  a 
double  covered  reservoir  to  contain 
filtered  water  for  domestic  use,  and  a 
smaller  open  one  to  contain  unfiltered 
water  for  the  streets,  and  to  supply  the 
Serpentime,  and  so  on.  So  that  you  see 
it  is  usual  in  these  cases  to  build  several 
reservoirs  together.  This  covered  reser- 
voir that  has  to  contain  water  for  do- 
mestic purposes,  is  double,  or  constructed 
in  two  halves.  Each  part  has  an  area  of 
310  feet  by  160  feet,  and  a  depth  of  20 
feet.  The  sides  all  round  have  a  slope 
of  one  to  one.  This  gives  a  mean  area 
of  290  feet  by  140  feet,  and  a  capacity 
of  about  5,075,000  gallons  for  each  res- 
ervoir, exclusive  of  the  space  occupied 
by  the  piers.  "  Hence  the  whole  ca- 
pacity may  be  taken  "  as  stated  by  Mr. 
Simpson  in  his  evidence,  "at  10,000,000 
gallons.  The  sides  of  the  reservoir  are 
cut  out  in  the  form  of  steps,  which  are 
filled  up  with  concrete  to  a  uniform 
slope  of  one  to  one  ;  and  a  bed  of  con- 
crete one  foot  in  thickness  is  also  laid 
over  the  whole  bottom;  each  half  of  the 
reservoir  is  covered  with  eight  brick 
arches,  averaging  rather  less  than  20 
feet  span,  the  arches  being  each  20  feet 
span,  and  the  others  18  ft.  8  in.  Two 
piers  supporting  these  arches  are  built 
lengthways,  and  are  each  310  feet  long 
at  the  top,  and  270  feet  at  the  base. 
The  arches  are  each  one  brick  in  thick- 
ness; and  are  covered  over  with  a  layer 
of  puddle,  the  haunches  being  filled  up 
with  concrete.  The  piers  are  carried 
out  14  inches  thick;  but  the  division 
wall  between  the  two  parts  of  the  reser- 
voir is  rather  more  than  four  feet  thick,, 
with  a  concrete  slope  of  one  and  a  half 
to  one  on  each  side.  The  14-inch  piers 
supporting  the  arch  are  built  with  large 
circular  hollows  17-J  feet  diameter.  The 
centres  of  these  circular  hollows  are  40 
feet  apart,  so  that  solid  brickwork  23 
feet  long  is  left  between  the  circular 
hollows,  supposing  a  horizontal  section 
taken  through  the  centres  of  the  hollows. 
Each  of  the  23  feet  spaces  has  a  14-inch 


WATER   SUPPLY   AND    DRAINAGE. 


245 


counterfort  carried  out  at  right  angles. 
These  counterforts  occur  at  intervals  of 
26  feet  and  13  feet  alternately,  and  pro- 
ject 6  feet  wide  at  the  base,  on  each  side 
of  the  pier,  and  run  out  to  nothing  at 
the  top,  or  springing  of  the  arches." 
"  The  versed  sine  or  rise  of  the  arches  is 
4  ft.  3  in.,  or  rather  more  than  one-fifth 
of  the  span.  Each  arch  is  provided 
with  two  openings  in  the  centre,  com- 
municating with  a  line  of.  12-inch  earth- 
enware tubular  pipe,  which  passes 
through  the  spandrils  and  communicates 
with  perforated  iron  tops  in  the  division 
wall  between  the  two  parts  of  the  reser- 
voir. By  this  contrivance  the  space 
above  the  water  in  the  covered  reser- 
voirs is  effectually  ventilated.  The  sup- 
ply pipe  from  Thames  Ditton  is  30  in.  in 
diameter  and  comes  into  each  part  of 
the  reservoir  at  the  level  of  top-water, 
which  is  a  few  inches  below  the  spring- 
ing of  the  arches.  At  this  level  a  waste 
weir,  or  overflow,  is  fixed  to  prevent  the 
reservoir  being  filled  too  full.  The  exit 
-mains  to  London  consist  of  two  24-inch 
pipes,  and  they  pass  from  the  bottom  of 
the  reservoir,  which  has  an  inclination 
in  one  direction  of  1  in  20,  and  a  fall 
across  of  six  inches."  (  Hughes  on 
"Waterworks:"  Weale's  Series.) 

Now  a  great  reason  for  the  existence 
of  these  service  reservoirs  is,  that  the 
hourly  demand  during  the  day  varies 
very  much  from  the  mean.  It  is  some- 
times so  much  as  three  times  the  mean 
demand,  during  certain  hours,  so  that  by 
this  means  it  is  not  necessary  for  the 
mains  to  be  made  inordinately  large. 
But  otherwise  the  mains  would  have  to 
be  made  large  enough  to  give  the  great- 
est demand,  instead  of  being  only  suffi- 
cient for  the  mean  demand.  And  this  is 
the  case  if  the  reservoir  is  only  large 
enough  to  contain  half  the  daily  demand. 
In  that  case  the  distributing  pipes  need 
only  to  be  calculated  to  give  the  greatest 
hourly  demand.  These  you  will  recol- 
lect are  under  ground  tanks.  Elevated 
tanks  are  sometimes  made  of  cast  iron, 
or  wrought  iron  plates  bolted  together, 
and  tied  by  wrought  iron  rods  at  the  bot- 
tom, to  one  another.  The  supply,  exit, 
and  overflow  pipes  ought  to  be  together 
in  a  corner  of  the  reservoir,  in  a  small 
separate  compartment.  This  separate 
compartment  is  connected  with  the  main 
reservoir   by  a  valve,  so  that   the  main 


reservoir  can  be  cleaned  out  and  the 
supply  go  on  independently  of  it.  Tims 
you  can  shut  out  the  supply,  stop  pump- 
ing, open  a  valve,  and  let  out  all  the 
water  from  the  large  reservoir  by  the 
supply  pipe  to  the  town.  Then  you  can 
close  the  valve  and  let  the  supply  go  on 
through  this  little  separate  reservoir, 
while  the  other  is  being  mended  or 
cleaned  out. 

The  overflow  pipe,  or  waste  pipe,  or 
whatever  you  like  to  call  it,  ought  to 
open  into  an  open  channel,  and  not  be 
connected,  as  is  very  frequently  the  case, 
with  the  nearest  drain  or  sewer.  It 
ought  to  open  above  ground,  because  as 
the  reservoir  is  covered,  if  it  does  not  do 
so,  the  foul  air  from  the  drain  will  come 
up  that  waste  pipe,  and  be  dissolved  by 
the  water  in  the  cistern,  and  so  you  will 
render  the  water  that  you  have  taken  so 
much  trouble  to  get  pure,  you  will  ren- 
der it  impure,  and  that  is  what  is  con- 
tinually done  in  all  towns,  and  in  houses, 
as  I  shall  tell  you  presently  when  speak- 
ing of  sewerage. 

For  distributing  basins  or  tanks,  Ran- 
kine  says,  that  "  the  most  efficient  pro- 
tection against  heat  and  frost  is  that 
given  by  a  vaulted  roof  of  masonry,  or 
brick,  covered  with  asphaltic-concrete,  to 
exclude  surface  water,  and  with  two  or 
three  feet  of  soil,  and  a  layer  of  turf." 
Mr.  Rawlinson  says,  that  "  brick  and 
masonry  tanks,  if  arched,  may  be  cover- 
ed in  with  sand,  or  fine  earth,  to  the 
depth  of  18  inches,  which  will  preserve 
.the  water  cool." 

Up  to  the  present  time  we  have  been 
describing  works  connected  with  im- 
pounding reservoirs  ;  now,  with  regard 
to  river  works.  With  river  works  you 
still  more  certainly  require  settling  res- 
ervoirs into  which  water  may  either  flow 
directly  through  culverts  from  the  river, 
as  it  does  at  Chelsea,  or  into  which  it 
may  be  pumped.  When  the  water  flows 
in  from  culverts,  you  require  almost  in- 
variably to  have  filter  beds,  which  we 
shall  describe  a  little  further  on.  Some- 
times for  river  works  it  is  necessary  to 
construct  a  weir  right  across  the  river, 
in  -order  to  keep  the  water  as  near  as 
may  be  at  constant  level.  The  engine 
power  employed  ought  to  be  consider- 
ably greater  than  that  which  is  actually 
wanted,  one-third  greater  at  any  rate, 
and  of  course  there  ought  always  to  be 


246 


VAN   NOSTEAND'S   ENGINEERING   MAGAZINE. 


a  reserve  engine.  At  the  Chelsea  works, 
to  which  I  have  before  referred,  the  de- 
positing reservoirs  are  made  in  London 
clay,  and  the  bottom  and  sides  are  mere- 
ly lined  with  cement  placed  upon  this 
clay.  From  this  the  water  passes  direct 
to  the  filter  beds. 

"With  regard  to  those  cases  in  which 
the  water  is  taken  from  rivers,  there  are 
certain  things  I  want  to  tell  yon.  I 
want  to  tell  you  something  about  the 
purification  of  river  water.  We  know 
that  into  rivers,  especially  in  thickly 
populated  countries,  an  enormous 
amount  of  refuse  matter  of  all  sorts  is 
thrown,  and  it  is  necessary  to  know 
whether  this  refuse  matter  is  destroyed 
in  its  passage  along  the  rivers,  that  is  to 
say,  whether  the  water,  after  running  a 
certain  distance,  becomes  sufficiently  pure 
to  be  used  for  drinking.  And  now  I 
must  quote  to  you  from  a  book  from 
which  I  shall  have  occasion  to  quote  a 
great  many  times  during  the  course  of 
the  remaining  lectures,  a  book  entitled 
"A  Digest  of  Facts  relating  to  the 
Treatment  and  Utilization  of  Sewage." 

"  The  evidence  collected  on  this  head 
by  the  Royal  Commission  on  Water 
Supply  was  very  various.  Dr.  Frank- 
land  says  : 

'  There  is  no  process  practicable  on  a 
large  scale  by  which  that  noxious  mate- 
rial (sewage  matter)  can  be  removed 
from  water  once  so  contaminated,  and 
therefore  I  am  of  opinion  that  water 
which  has  been  once  contaminated  by 
sewage  or  manure  matter  is  henceforth 
unsuitable  for  domestic  use.'  " 

Now  the  results  of  experiments  are 
found  to  give  the  following  facts  : — In 
the  first  place  it  appears  that  in  rivers 
that  are  well  known  to  be  polluted,  and 
the  water  of  which  has  a  temperature 
not  exceeding  64°  Fahrenheit,  a  flow  of 
between  eleven  and  thirteen  miles  "  pro- 
duces but  little  effect  upon  the  organic 
matter  dissolved  in  the  water."  To  re- 
move all  uncertainty  from  the  "varia- 
bility of  the  composition  of  the  river 
waters  at  different  times  of  the  day,"  ex- 
periments were  made  by  mxing  filtered 
London  sewage  with  water;  "it  was 
then  well  agitated  and  freely  exposed  to 
the  air  and  light  every  day,  by  being 
syphoned  in  a  slender  stream  from  one 
vessel  to  another,  falling  each  time 
through  three  feet  of  air."    The  mixture 


which  originally  contained,  in  100,000 
parts  .267  of  organic  carbon  and  .081  of 
organic  nitrogen  was  found  to  contain, 
after  96  hours,  .250  of  organic  carbon 
and  .058  of  organic  nitrogen  ;  and  after 
192  hours  ;  .2  of  organic  carbon  and 
.054  of  organic  nitrogen.  The  tempera- 
ture of  the  air  during  this  experiment 
was  about  20  deg.  cent.  (6S°  Fahrenheit). 
"These  results  indicate  approximately 
the  effect  which  would  be  produced  by 
the  flow  of  a  stream  containing  10  per 
cent,  of  sewage  for  96  and  192  miles 
respectively,  at  the  rate  of  one  mile  per 
hour."  They  show  then,  that  at  the 
above  temperature,  during  a  flow  of  96 
miles,  at  the  rate  of  one  mile  an  hour, 
the  amount  of  organic  carbon  was  re- 
duced 6.4  per  cent.,  that  of  organic 
nitrogen  28.4  per  cent.;  while  during  the 
flow  of  192  miles,  at  the  same  rate, 
the  amounts  of  these  two  substances 
were  only  reduced  25.1  and  83.3  per  cent, 
respectively.  It  is  shown  that  the  oxy- 
dation  of  this  organic  matter  is  chiefly 
affected  by  the  amount  of  atmospheric- 
oxygen  dissolved  in  the  water,  "  such 
dissolved  oxygen  being  well  known  to 
be  chemically  much  more  active  than  the 
gaseous  oxygen  of  the  air." 

It  was  found,  however,  that  the  action 
of  this  dissolved  oxygen  was  not  really 
anything  like  so  quick  or  so  perfect  as 
generally  supposed,  and  that  62  per  cent, 
of  the  sewage  was  the  maximum  quan- 
tity that  would  be  oxydized  during  168 
hours,  even  supposing  that  the  oxydation 
took  place  during  the  whole  time  at  the 
maximum  rate  observed,  which  was  cer- 
tainly not  the  case. 

"  It  is  thus  evident,  that  so  far  from 
sewage' mixed  with  20  times  its  volume 
of  water  being  oxydized  during  a  flow 
of  10  or  12  miles,  scarcely  two-thirds  of 
it  would  be  so  destroyed  in  a  flow  of  168 
miles  at  the  rate  of  one  mile  per  hour,  or 

after  the  lapse  of  a  week 

Thus,  whether  we  examine  the  organic 
pollution  of  a  river  at  different  points  of 
its  flow,  or  the  rate  of  disappearance  of 
the  organic  matter  of  sewage  when  the 
latter  is  mixed  with  fresh  water  and 
violently  agitated  in  contact  with  air,  or 
finally  the  rate  at  which  dissolved  oxygen 
disappears  in  water  polluted  with  5  per 
cent,  of  sewage,  we  are  led  in  each  case 
to  the  inevitable  conclusion  that  the 
oxydation  of  the  organic  matter  in  sew- 


WATEE   SUPPLY   AND   DRAINAGE. 


247 


age  proceeds  with  extreme  slowness, 
even  when  the  sewage  is  mixed  with  a 
large  volume  of  unpolluted  water,  and 
that  it  is  impossible  to  say  how  far  such 
water  must  flow  before  the  sewage  mat- 
ter becomes  thoroughly  oxydized.  It 
will  be  safe  to  infer,  however,  from  the 
above  results,  that  there  is  no  river  in 
the  United  Kingdom  long  enough  to  ef- 
fect the  destruction  of  sewage  by  oxy- 
dation. 

Now  there  were  several  scientific  men 
who  gave  evidence  of  another  sort,  and 
who  declared  that  practically  speaking 
water  was  sufficiently  pure  after  even  .a 
short  flow.  The  answer  to  that  state- 
ment is  found  if  we  just  go  into  a  few 
of  the  public  health  facts.  Here  is  one. 
This  is  gathered  from  Mr.  Simon's  re- 
port on  the  cholera  epidemics  of  London 
in  1848-49  and  1853-54.  "When  the 
Lambeth  Company  took  its  water  from 
the  Thames  near  Hungerford  Bridge, 
the  peojde  who  drank  that  water  died  at 
the  rate  of  12.5  per  thousand.  When 
the  source  of  supply  was  moved  to  the 
Thames  at  Thames  Ditton,  the  mortality 
was  only  3.7  per  thousand,  while  at  the 
same  time,  and  in  the  same  districts,  the 
mortality  among  the  people  who  were 
supplied  with  water  by  the  Southwark 
Conrpany  from  the  Thames  at  Battersea 
was  at  the  rate  of  13  per  thousand." 

I  could  give  you  any  number  of  facts 
of  that  sort  to  show  you  that  water  that 
has  been  polluted  is  dangerous  to  drink. 
I  may  just  mention  to  you  the  opinion 
which  Sir  Benjamin  Broclie,  the  late  Pro- 
fessor of  Chemistry  at  Oxford,  has 
given  ;  he  said  in  his  evidence  before 
the  Rivers'  Pollution  Commissioners  : — 
"I  believe  that  an  infinitesimaily  small 
quantity  of  decayed  matter  is  able  to 
produce  an  injurious  effect  upon  health. 
Therefore  if  a  large  proportion  of  or- 
ganic matter  was  removed  by  the  pro- 
cess of  oxydation  the  quantity  left 
might  be  quite  sufficient  to  be  injurious 
to  health.  With  regard  to  the  oxyda- 
tion we  know  that  to  destroy  organic, 
matter  the  most  powerful  oxydizing 
agents  are  required :  we  must  boil  it 
with  nitric  acid  and  chloric  acid,  and  the 
most  perfect  chemical  agents.  To  think 
to  get  rid  of  organic  matter  by  exposure 
to  the  air  for  a  short  time,  is  absurd." 

I  give  you  those  statements  in  order 
to  bring  you  to  the  conclusion  to  which 


I  wish  you  to  come,  namely,  that  we 
should  not  take  water  for  the  supply  of 
villages  and  towns,  from  a  river  that  has 
been  contaminated  at  all,  if  it  can  pos- 
sibly be  helped  ;  that  it  has  never  been 
proved  that  such  water  gets  really  pure 
again  ;  and  that  at  certain  times  there- 
fore very  considerable  danger  may  arise 
from  drinking  such  water  ;  in  fact  as 
Mr.  Simon  said  when  examined  before 
the.  Royal  Commission  on  water  supply 
"  it  ought  to  be  made  an  absolute  condi- 
tion for  a  public  water  supply  that  it 
should  be  uncontaminable  by  drainage." 

The  water  when  taken  from  the  river, 
or  even  if  it  is  taken  from  the  gentle 
slopes  of  cultivated  lands,  and  also  in 
some  other  instances,  requires  to  be  fil- 
tered as  well  as  allowed  to  settle  ;  de- 
position is  not  sufficient  of  itself.  It  is 
important,  also,  to  keep  out  inferior 
waters,  that  is  when  there  are  several 
sources  ;  and  with  this  condition,  you 
may  prevent  the  necessity  of  the  water 
all  requiring  to  be  filtered. 

Mr.  Parker  says  : — "  At  last  it  may  be 
interesting  to  know  what  Frontinus  did, 
or  rather,  what  he  says  with  becoming 
modesty,  his  patron,  the  Emperor  Xerva, 
accomplished  on  this  score  :  '  But  the 
water  of  the  Anio  ISTovus  often  spoilt  the 
rest,  for  since  it  was  the  highest  as  to 
level,  and  held  the  first  rank  as  to  abund- 
ance, it  was  most  often  made  use  of  to 
help  the  others  when  they  failed.  The 
stupidity,  however,  of  the  Aquarii  was 
such  that  they  had  introduced  this 
water  into  the  channels  of  several  others 
where  there  was  no  need,  and  spoilt 
water  which  was  flowing  in  abundance 
without  it.  This  was  the  case  especially 
as  regards  the  Claudian,  which  came  all 
the  way  for  many  miles  in  its  own  chan- 
nel perfectly  pure,  but  when  it  reached 
Rome  and  was  mixed  with  the  Anio  it 
lost  all  its  purity.  And  thus  it  happen- 
ed that  many  were  not  in  fact  helped  at 
all  by  the  addition  of  the  extra  water, 
through  the  want  of  care  on  the  part  of 
those  who  distributed  it.  For  instance, 
we  found  even  the  Marcian,  the  most 
pleasant  to  drink  on  account  of  its 
brightness  and  freshness,  in  use  hi  the 
baths,  and  by  the  cloth-fullers,  and  ac- 
cording to  all  accounts  employed  for  the 
most  base  services.  It  pleased,  there- 
fore, the  Emperor  to  have  all  these  sepa- 
rated, and  for  each  to  be   so   arranged 


248 


TAN   NOSTRAND'S   ENGINEERING   MAGAZINE. 


that  first  of  all  the  Marcian  should  be 
assigned  to  its  own  use,  so  that  the  Anio 
Vetus,  which  from  various  reasons  was 
found  to  be  less  wholesome,  as  well  as 
being  at  a  low  level,  should  be  employed 
for  the  watering  of  the  gardens  in  the 
suburbs,  and  in  the  city  itself,  for  viler 
purposes.' " 

So  you  see  they  had,  even  then,  found 
out  that  one  water  was  more  wholesome 
than  another,  and  when  they  had  got 
supplies  from  two  or  three  sources  they 
knew  it  was  better  to  keep  them  sepa- 
rate, and  so  use  the  best  one  for  drink- 
ing purposes  and  the  inferior  ones  for 
other  purposes. 

Now  when  water  containing  substances 
in  suspension  is  passed  through  a  medium 
provided  with  fine  pores,  it  is,  of  course, 
at  least  the  purer  by  virtue  of  the  re- 
moval of  all  such  matters  as  are  unable 
to  pass  through  the  pores.  If  that  were 
all  that  filtration  accomplished,  it  would 
be  only  a  fine  straining  process.  But 
that  is  not  all.  If  you  take  a  large 
quantity  of  porous  material,  for  instance, 
a  large  mass  of  sand,  or  gravel,  or  espe- 
cially charcoal, — almost  any  porous  ma- 
terial,— and  pass  water  through  it,  water 
containing  certain  substances  in  solution, 
and  certain  substances  in  suspension, 
those  in  suspension  will  remain  unless 
they  are  fine  enough  to  pass  through  the 
pores  of  the  material.  But  all  these 
porous  substances  contain  an  immense 
amount  of  air  between  their  pores,  and 
the  water  by  being  passed  through  them 
is  divided  into  an  infinite  number  of  ex- 
ceedingly small  rivulets,  exceedingly 
small  streams,  and  so  the  substances  in 
solution  in  the  water  are  brought  into 
the  closest  possible  contact  with  the 
oxygen  of  the  air  between  the  pores  of 
the  filtering  material,  and  so  when  you 
have  passed  the  water  through  a  filter, 
a  chemical  action  takes  place,  and  not 
merely  a  mechanical  action.  You  have 
a  mechanical  action  first,  and  then  you 
have  also  a  chemical  action.  That  chemi- 
cal action  consists  in  the  oxydation  of 
the  substances  held  in  solution  in  the 
water — that  is,  such  substances  as  are 
capable  of  oxydation,  and  these  are  the 
ammonia  and  the  putrescible  organic 
matters  which  are  so  dangerous  when 
left  in  drinking  waters. 

One  of  the  best  filtering  substances, 
that  is,  one  which  alters  the  substances 


contained  in  water  most  in  its  passage 
through  it,  is  animal  charcoal,  and  you 
will  find  in  the  26th  and  27th  Vols,  of 
the  Proceedings  of  the  Institution  of 
Civil  Engineers,  a  most  important  and 
interesting  discussion  on  this  property  of 
animal  charcoal,  and  other  substances — 
sand,  and  so  on — upon  the  power  of 
these  materials  to  cause  the  oxydation 
of  substances  in  water.  I  should  tell 
you  that  the  paper  itself  to  which  I  re- 
fer in  that  26th  vol.  is  not  worth  read- 
ing, but  the  discussion  afterwards  is  very 
well  worth  careful  study.  The  paper  is 
worthless,  because  it  came  to  an  entirely 
erroneous  conclusion  on  account  of  the 
experiments  being  performed  by  a  pro- 
cess which  is  practically  worthless. 

Here  I  must  give  you  an  example. 
Dr.  Frankland  tells  us  that  he  filtered 
New  River  water  through  animal  char- 
coal ;  that  before  filtration  it  contained 
in  solution  about  1 8  grains  in  a  gallon  of 
solid  matters,  that  after  filtration  it  con- 
tained 11.6.  Of  course  you  are  pre- 
pared for  a  less  amount  of  impurity  after 
filtration.  Now  the  organic  and  other 
volatile  matters  contained  in  the  water 
before  filtration  amounted  to  .37  of  a 
grain  in  a  gallon,  and  after  filtration  the 
amount  was  1 5 ;  that  is  to  say  that  more 
than  one  half  of  these  matters  were  re- 
moved by  filtration  through  animal  char- 
coal. After  a  month  this  charcoal  re- 
moved still  more  organic  matter,  and 
some  mineral  matters  as  well,  and  even 
a  few  months  afterwards  one  half  of  the 
organic  and  volatile  matters  only  re- 
mained after  filtration.  These  experi- 
ments show  a  very  important  thing, 
which  is  perfectly  true  of  a  sand  filter 
as  it  is  of  an  animal  charcoal  filter,  and 
that  is,  it  is  not  by  storing  up  these  mat- 
ters that  a  filter  works,  or  else  it  would 
be  of  no  use  whatever  to  make  a  filter. 
You  would  have  it  choked  up  in  a  very 
short  time,  and  it  would  continually  have 
to  be  renewed,  whether  made  of  sand,  of 
gravel,  of  charcoal,  or  what  not.  It  is 
by  oxydizing  the  substances  that  the 
advantage  is  obtained,  and  the  results  of 
oxydation  you  can  find  in  the  water 
afterwards,  and  these  results  of  the  oxy- 
dation are  nitrates  and  nitrites,  and  car- 
bonates. Of  course  these  are  hannless 
matters,  and  that  is  the  important  action 
which  a  filter  has.  Dr.  Frankland  stated 
that  he  had  passed  the  water  supplied  to 


WATER   SUPPLY   AND    DRAINAGE. 


249 


London  by  the  Grand  Junction  Company 
through  a  thickness  of  three  feet  of  ani- 
mal charcoal,  at  the  rate  of  41,000  gal- 
lons per  square  foot  per  day  of  twenty- 
four  hours,  under  a  head  of  water  of 
thirty  feet,  the  charcoal  being  in  granules 
like  coarse. sand,  and  that  at  that  rate — 
,a  tremendous  rate — more  than  one  half 
of  the  organic  matter  was  removed. 
He  thought  from  these  experiments  on 
animal  charcoal  that  persons  who  had  to 
supply  water  to  towns  ought  to  use  it,  as 
at  any  rate  one  of  the  media  in  the  filter 
beds.  I  must  not  pass  from  charcoal 
without  mentioning  that  vegetable  char- 
coal is  agreed  on  nearly  all  hands  to  be 
almost  entirely  useless  for  purposes  of 
filtration.  In  the  first  place  it  contains 
enormous  amounts  of  salts  which  are 
soluble  in  water,  so  that  the  water  be- 
comes very  much  harder  in  passing 
through  it  than  before,  and  then  it  does 
not  purify  water  in  the  way  that  animal 
charcoal  does. 

Well,  now  some  of  the  effects  of  sand 
filters,  as  employed  by  the  Water  Com- 
panies, Wanklyn  points  out.  He  says 
that  the  Thames  water  at  Hampton  con- 
tains fifteen  parts  of  albuminoid  am- 
monia, or  ammonia  derivable  from  or- 
ganic matter,  in  one  hundred  millions, 
that  is  to  say  .15  in  100,000,  which  is  the 
way  we  have  generally  reckoned  it,  and 
that  after  filtration  by  the  company  it 
only  contains  5  or  6  ;  so  that  you  see 
water  is  capable  of  being  purified — that 
is,  the  matters  in  solution  are  capable  of 
being  altered  in  drinking  water  on  an 
immense  scale. 

.  Now  what  sort  of  things  are  these 
filter  beds,  as  they  are  made,  because 
laboratory  experiments  are  all  very  well, 
but  you  have  practically,  to  do  it  on  a 
large  scale.  Mr.  Hawkesley  has  made 
some  large  waterworks,  as  you  are  most 
of  you  probably  aware,  at  Leicester,  and 
there,  there  is  a  reservoir  of  forty  acres 
in  extent.  There  are  also  four  filter 
beds,  each  ninety-nine  feet  long,  and 
sixty-six  feet  wide,  and  eight  feet  eight 
inches  deep  from  the  ground.  The  water 
comes  in  separate  channels  to  these  filter 
beds,  and  it  is  passed  downwards  through 
the  following  filtering  materials  : — Two 
feet  six  inches  of  sand,  and  then  two 
feet  six  inches  of  layers  of  gravel  of 
various  sizes  (from  the  size  of  beans  up 
to  eggs)  to  the  drains  below  and  thence 


by  pipes  into  an  octagonal  pure  water 
tank.  This  tank,  eight  feet  eight  inches 
deep,  holds  seven  feet  eight  Laches  of 
water,  and  is  sixty-six  feet  from  side  to 
side.     That  is  the  general  plan. 

The  supply  comes  to  the  filter  beds 
from  the  reservoir  at  various  points  ;  it 
passes  through  two  feet  six  inches  of 
coarse  sand — for,  it  must  be  observed, 
fine  sand  will  not  do,  as  it  gets  choked 
up  by  the  suspended  matters  in  the 
water — and  then  through  two  feet  six 
inches  of  gravel.  The  filtering  beds 
have  sloping  sides  and  are  made  of  sand, 
fine  gravel,  coarse  gravel,  then  very 
coarse  gravel,  with  a  drain  at  the  bot- 
tom. The  filtered  water  is  delivered 
into  an  upright  pipe  in  the  tank,  which 
comes  within  two  feet  of  the  top,  so 
that  the  pressure  of  the  water  on  the 
beds  from  above  can  never  be  greater 
than  that  due  to  a  height  of  two  feet. 
It  is  essential  that  the  pressure  on  the 
surface  of  the  beds  should  not  be  too 
great. 

Well  now  from  these  filters  six  hund- 
red or  seven  hundred  gallons  per  day 
per  square  yard  flow,  and  the  proper 
rate  of  vertical  descent  for  the  water,  as 
it  is  generally  considered,  is  six  inches 
per  hour,  not  more,  or  sevent-five  gal- 
lons per  square  foot  in  twenty-four 
hours,  and  that  you  see  is  about  the  rate 
at  which  it  passes  through  these  last 
named  works ;  now  the  effect  at  this 
particular  place  is  that  the  water  is  clari- 
fied, and  a  considerable  proportion  of 
the  organic  matters  in  solution  are  re- 
moved from  it.  The  sand  of  the  surface 
of  the  filter  beds  requires  scraping  from 
time  to  time  and  also  renewing. 

At  the  Gorbals  Filtration  Works  near 
Glasgow,  the  filtering  materials  are 
placed  in  vertical  compartments  with 
passages  between  them,  in  each  of  which 
the  water  rises  to-  nearly  its  original 
level  and  then  flows  over  into  the  next 
compartment  and  down  through  the 
filtering  material  in  it.  There  are  two 
other  plans  I  must  mention,  at  Black- 
burn, for  instance,  there  is  no  filtration. 
There  they  have  a  service  reservoir,  and 
they  take  the  water  out  of  it  from  the 
top  by  a  sort  of  process  of  decantation. 
They  let  it  settle,  and  then  take  only  the 
water  from  the  top.  Another  plan  is  in 
practice  at  St.  Petersburg.  There  the 
water  is  made  to  fall  down  a  series  of 


250 


VAX   XOSTKAXD  S   ENGINEERING-   MAGAZINE. 


steps,  and  then  through  wire  gauze,  and 
lastly  through  sand  filters,  and  by  these 
means  the  water  which  is  generally  very 
impure  is  rendered  tolerably  pure  and  a 
considerable  amount  of  putreseible  or- 
ganic matters  are  collected  from  this 
wire  gauze. 

Now  we  have  to  consider  briefly  the 
ways  in  which  water  may  be  distributed 
in  towns.  In  the  first  place,  as  to  the 
mains:  their  size  must  be  calculated  ac- 
cording to  the  supply  required. 

Mains  are  often  made  in  towns  on 
both  sides  of  the  streets  in  order  that 
the  supply  may  not  be  entirely  cut  off 
dining  repairs.  There  must  be  means 
provided  by  which  the  water  may  be 
stopped  in  a  main  in  order  that  it  may 
be  repaired.  The  bends  and  junctions 
shoidd  always  be  curved.  There  should 
be  no  junctions  made  at  right  angles, 
and  there  should  be  no  angular  junctions 
if  it  can  be  helped.  Mains  should  be 
made  of  cast  iron.  They '  should  be 
greater  than  3  inches  in  diameter.  The 
best  service  pipes  for  houses  are  §  in.,  or 
1  inch  wrought  iron  service  pipes  that 
screw  together.  They  are  better  than 
lead,  and  they  are  likewise  cheaper  than 
lead.  Wrought  iron  pipes  are  better 
than  lead  for  this  reason,  that  certain 
kinds  of  water  act  upon  lead.  Soft 
water  is  apt  to  act  upon  lead.  Fortu- 
nately, hard  waters,  containing  a  con- 
siderable amount  of  carbonic  acid,  act 
very  little  on  leaden  pipes,  and  so  it  is 
the  practice  very  frequently  to  have 
leaden  pipes  and  cisterns  made  of  lead, 
and  practically  very  little  harm  results. 
If  you  refer  to  the  25th  Yol.  of  the 
"  Proceedings  of  the  Institution  of  Civil 
Engineers,"  you  will  find  a  discussion  on 
water  supply,  and  there  you  will  see 
that  Mr.  Bateman  gave  it  as  his  opinion 
that  even  soft  water  acted  very  little 
indeed  on  leaden  pipes,  after  a  time. 
It  acts  on  them  at  first,  but  the  leaden 
pipe  or  cistern  soon  gets  covered  inside 
with  an  insoluble  coat  of  subcarbonate 
of  lead,  and  the  result  is  that  afterwards 
the  water  acts  very  little  on  it.  The 
water  of  Loch  Katrine,  which  is  supplied 
to  Glasgow,  acts  very  little  on  the  lead- 
en pipes  and  cisterns  used.  However, 
there  is  no  reason  for  having  lead  if  dan- 
ger be  apprehended  as  likely  to  result; 
wrought  iron  will  do  just  as  well  and  is 
cheaper. 


A  town  may  be  supplied  in  one  of 
two  ways.  These  two  ways  are  known 
as  the  Constant  and  Intermittent  sys- 
tems. First,  there  is  the  Constant  sys- 
tem, in  which,  of  course,  the  mains  are 
always  full  and  the  water  is  brought 
into  the  houses  by  pipes  from  the  mains, 
no  cisterns  being  needed,  as  the  water  is 
always  in  the  pipes,  and  you  have  only 
to  turn  a  tap  in  order  to  get  it.  Second- 
ly, there  is  the  Intermittent  system,  in 
which  the  water  is  only  supplied -for  a 
short  time  during  the  day,  and  in  this 
Intermittent  system  it  is  therefore  neces- 
sary to  have  cisterns  in  the  houses.  Now 
as  to  the  relative  advantages  and  disad- 
vantages. Professor  Eankine  says  : 
"  The  system  called  that  of  Constant  ser- 
vice according  to  which  all  distributing 
pipes  are  kept  charged  with  water  at  all 
times,  is  the  best,  not  only  for  the  con- 
venience of  the  inhabitants,  but  also  for 
the  durability  of  the  pipes  and  for  the 
purity  of  the  water  ;  for  pipes  when 
alternately  wet  and  dry  tend  to  rust,  and 
when  emptied  of  water  they  are  liable 
to  collect  rust,  dust,  coal  gas  and  the 
effluvia  of  neighboring  sewers,  which 
are  absorbed  by  the  water  on  its  re-ad- 
mission. In  order,  however,  that  the 
system  of  Constant  service  may  be  car- 
ried out  with  efficiency  and  economy,  it 
is  necessary  that  the  diameters  of  the 
pipes  should  be  carefully  adapted  to 
their  discharge  and  to  the  elevation  of 
the  district  which  they  are  to  supply, 
and  that  the  town  should  be  sufficiently 
provided  with  town  reservoirs.  When 
these  conditions  are  not  fulfilled,  it  may 
be  indispensable  to  practise  the  system 
of  Intermittent  service,  especially  as  re- 
gards elevated  districts,  that  is  to  say, 
to  supply  certain  districts  in  succession 
during  certain  hours  of  the  day."  You 
see,  therefore,  that  Professor  Rankine 
emphatically  condemns  the  system  of 
Intermittent  service  as  compared  with 
that  of  Constant  service. 

Now  the  great  objection  to  the  system 
of  Intermittent  service  is  the  necessity 
'  of    having  cisterns,  whatever   they   are 
!  made  of.     Water  becomes  impure  in  cis- 
!  terns,  dust  collects  in  them,  and  the  cis- 
i  terns  require  frequently  to  be  cleansed. 
J  If  this  is  not  done  the  water  may  even 
become  dangerous  to  drink.     Where  cis- 
terns   are   necessary,    slate   cisterns   are 
[  the  best.     They  require  to  be  made  with 


WATER   SUPPLY   AND   DRAINAGE. 


251 


good  cement,  or  they  are  apt  to  leak, 
and  then  you  are  liable  to  get  red  lead 
or  something  of  that  sort  used  to  fill  up 
the  joints,  and  so  you  get  the  water 
tainted.  Iron  rusts,  and  for  that  reason 
cast-iron  mains  require  to  be  varnished 
inside  and  out.  Zinc  has  been  used  for 
cisterns  and  also  for  pipes,  but  zinc  often 
contains  lead,  and  cases  have  been  known 
of  lead-poisoning  having  resulted  from 
the  use  of  zinc  pipes  or  cisterns.  There 
have  been  plenty  of  ways  proposed  for 
coating  lead  pipes  so  that  the  water  may 
not  act  upon  them.  Several  of  them  are 
absolutely  objectionable ;  one  of  the 
methods,  for  instance,  was  the  use  of  a 
varnish  containing  arsenic  ;  and  even 
other  varnishes  which  do  not  seem  to  be 
objectionable,  are  not  now  practically 
used. 

If  you  look  in  Vols.  12  and  25  of  the 
Proceedings  of  the  Institution  of  Civil 
Engineers,  you  will  see  a  great  many 
arguments  for  and  against  both  the 
"  Constant  "  and  "  Intermittent  "  sys- 
tems, and  one  argument  against  the 
"  Intermittent "  system  is  always  that 
the  amount  of  waste  is  enormous.  It  is 
stated  as  you  will  there  find,  that  at  that 
time  the  amount  of  water  wasted  in  Lon- 
don was  something  like  half  the  supply. 
You  find  it  alleged  that  there  is  great 
waste  also  on  the  Constant  system,  be- 
cause, it  is  said,  the  mains  are  always 
full  and  the  taps  are  apt  to  be  left 
running.  But  this  may  be  provided 
against  by  having  the  taps  placed  inside 
the  houses,  and  then  you  will  be  quite 
sure  there  is  not  much  waste.  Then,  the 
waste  that  has  been  observed  with  the 
Constant  system  has  been  mostly  caused 
where  .the  Intermittent  system  has  been 
changed  for  the  Constant  system,  and  in 
that  case  you  do  sustain  a  loss  of  water; 
a  loss  on  account  chiefly  of  faulty  pipes, 
and  leaky  fittings,  for  such  as  may  do 
very  well  under  the  Intermittent  system 
are  not  good  enough  to  be  employed  for 
the  Constant  system.  In  Liverpool,  at  a 
particular  date,  there  were  used  33,000,- 
000  gallons  of  water  a  week,  in  the  sup- 
ply of  which  only  1,000,000  gallons 
were  supplied  on  the  Constant  service, 
and  the  whole  of  the  remaining  32,000,- 
000  gallons  were  on  the  Intermittent  ser- 
vice. For  some  weeks,  as  an  experi- 
ment, three-sevenths  of  the  town  were 
put  on  the  Constant  service,  and  then 


the  amount  of  water  used  rose  from 
33,000,000  to  41,000,000  gallons  per 
week.  But  where  there  has  originally 
been  sufficient  attention  to  the  fittings. 
and  where  they  are  strong  enough  it  is 
otherwise.  For  instance,  in  the  case  of 
Wolverhampton,  at  the  same  period,  it 
is  stated  that  in  that  town  there  was  a 
saving  effected  by  changing  from  the 
Intermittent  to  the  Constant  system,  a 
saving  of  no  less  than  20  gallons  per 
head  per  day.     (Vol.  xii.,  p.  503.) 

A  disadvantage  of  the  Constant  sys- 
tem is  that  the  water  supply  sometimes 
runs  short  in  the  higher  parts  of  the 
town,  while  in  the  lower  parts  there  is  a 
sufficient  supply  ;  so  that  cisterns  would 
sometimes  need  to  be  provided,  even 
under  the  Constant  system,  in  these  high- 
er parts  of  the  town. 

As  a  summary  :  with  the  Constant 
system  the  waste  of  water  is  certainly 
less  than  with  the  other  if  the  fittings 
are  properly  attended  to,  and  if  the  fit- 
tings, jfipes,  &c,  have  been  originally 
arranged  for  the  Constant  system.  The 
water  in  the  case  of  the  Constant  ser- 
vice is  purer  and  fresher,  and  at  a  lower 
temperature  in  summer,  and  less  subject 
to  frost  in  winter.  The  water  is  purer 
because  it  escapes  the  impurities  which  I 
have  already  pointed  out,  as  collecting 
in  pipes,  and  it  also  escapes  those  im- 
purities which  the  water  gets  by  being 
stored  in  cisterns. 

The  inconvenience  from  interruption 
to  the  supply  during  repairs  is  never 
actually  experienced,  as  the  interruption 
need  only  be  for  a  few  hours.  On  the 
other  hand,  the  interruptions  and  the 
waste  caused  by  neglect  of  turncocks,  by 
the  limitation  of  the  quantity  of  water, 
by  leaky  taps  and  cisterns,  and  in  other 
ways — these  inconveniences  are  absent. 
Then  the  leakage  from  pipes  is  less.  In 
the  Constant  service  the  pipes  are  made 
stronger,  and  practically  there  is  niueh 
less  bursting.  Mr.  Hawkesley  states 
that  the  difference  between  the  systems 
is  a  question  of  pipes  and  fittings,  and 
that  when  the  supply  is  well  managed 
the  waste  under  the  Constant  system  is 
less. 

Then  the  water  supply  should  always 
be  to  the  top  of  the  house,  and  if  pos- 
sible, to  each  story  of  the  house.  If  cis- 
terns are  necessary  those  used  for  drink- 
ing water  should  always  be  separate  from 


252 


TAX   NOSTRAND  S   ENGINEERING   MAGAZINE. 


any  other  cistern  in  the  house,  If,  for 
instance,  there  is  a  cistern  for  the  water 
closet,  it  should  he  entirely  separate  from 
tbe  cistern  used  for  the  storage  of  drink- 
ing water  ;  there  should  be  two  separate 
cisterns.  Then  a  chief  point  to  attend 
to  with  regard  to  the  drinking  water 
system  is  that  it  should  he  covered. 
Secondly — That  it  should  he  easily  ac- 
cessible, so  as  to  be  readily  cleaned  out : 
and  thirdly — and  this  a  most  important 
point — that  the  waste  pipe  from  it  should 
empty  out  into  the  open  air  either  over 
the  surface  of  the  yard  or  over  a  roof 
or  into  a  rain  water  pipe,  which  itself 
does  not  go  down  into  a  drain.  The 
waste  pipe  should  on  no  consideration  be 
connected  with  any  water  closet  appa- 
ratus or  with  drains.  This  is  almost  in- 
variably done,  and  that  is  why  I  insist 
so  much  on  the  importance  of  this 
point. 

I  may  tell  you  that  one  of  the  most  fre- 
quent causes  of  typhoid  fever  in  London 
at  this  moment — of  this  I  have  not  the 
slightest  doubt — is  that  the  waste  pipes 
from  the  drinking  water  cisterns  are  con- 
nected with  some  part  of  the  sewerage 
apparatus,  and  very  often  directly  with 
the  sewers.  The  house  drain,  more  fre- 
quently than  not,  being  unv^ntilated,  the 
waste  pipe  of  the  drinking  water  cistern, 
becomes  the  ventilator  of  the  house 
drain,  and  the  foul  air  of  the  house  drain 
goes  up  into  the  space  between  the  sur- 
face of  the  water  and  the  lid  of  the  cis- 
tern and  is  absorbed,,  and  the  result,  in 
many  cases,  as  I  have  frequently  observ- 


ed, has  been  a  severe  attack  of  diarrhoea 

through  the  whole  household,  or  else  of 
typhoid  fever,  and  I  have  no  doubt  in 
some  cases  of  cholera  also. 

The  overflow  pipes  from  other  cisterns 
we  need  not  be  so  particular  about,  be- 
cause we  do  not  recmire  to  drink  the 
water  ;  but  it  is  just  as  well  that  they 
should  empty  in  a  similar  way  if  pos- 
sible. If  not,  they  may  be  made  to  end 
in  what  is  called  the  D  trap  of  the  water 
closet.  I  shall  explain  that,  however, 
more  fully  further  on. 

Now  we  have  brought  the  water  into 
the  house — either  into  the  cisterns,  or  it 
may  be,  merely  into  the  pipes,  which 
are  kept  constantly  full,  and  which  have 
taps  at  various  levels  inside  the  house. 
When  inside  the  house,  it  may  be  puri- 
fied still  further,  if  necessary,  by  house- 
hold charcoal  filters,  or  by  boiling  and 
then  being  left  to  stand  in  stone  vessels. 
That  is  an  excellent  plan,  and  I  must  tell 
you  here,  that  impure  water  may  be  puri- 
fied to  a  very  considerable  extent  by 
making  an  infusion  in  it  :  for  instance, 
an  infusion  of  tea.  This  is  very  import- 
ant for  you  to  know  when  you  may  have 
to  drink  water  in  marshy  countries.  A 
great  deal  of  mischief  is  sometimes 
done  by  drinking  water  in  marshy  coun- 
tries, and  this  mischief  may  be  prevented 
by  merely  boiling  it.  That  is  a  very 
good  thing,  but  still  it  is  better,  on  the 
whole,  to  make  a  weak  infusion  of  some- 
thing like  tea,  in  it,  and  that  is  the  sys- 
tem which  has  been  practised  for  a  thous- 
and years  in  China. 


MARITIME  ATTACK  BY  TORPEDOES. 


From  "The  Engineer." 


Nearly  at  the  close  of  the  Crimean 
War,  just  twenty  years  ago,  the  first  at- 
tempt at  ironclad  ships  of  war  appeared 
before  Kertch,  in  those  floating  iron 
boxes  the  Meteor  and  Thunder,  built  like 
the  corresponding  floating  batteries  of 
our  allies,  from  designs  suggested  by  the 
Emperor  of  the  French,  which  latter  were 
carried  out  under  his  naval  constructors. 
These  proved  themselves  invulnerable  to 
32  lb.  round  shot,  at  very  short  ranges  ; 
and  there  was  not  wanting  on  our  parts 
some  self-congratulation  that  our  great 


iron-making  country  must  derive  from 
the  discovery  a  new  lease  of  our  mari- 
time supremacy.  About  the  same  time 
the  first  real  achievements  in  the  way  of 
perfecting  a  system  of  heavy  rifled  artil- 
lery began  to  appear,  by  the  adoption  of 
ringed  structure  for  guns  in  wrought 
iron  or  steel,  and  with  these  the  predic- 
tion of  Robins,  that  the  nation  that  first 
produced  an  effective  system  of  rifled 
fire-arms  and  artillery  would — on  land, 
at  least,  and  for  a  time — out-distance  all 
competitors  in  warfare,  seemed  about  to 


MAEITIME  ATTACK  BY  TORPEDOES. 


253 


be  realized.  It  has  been  realized,  to  a 
vast  extent,  upon"  land,  and,  together 
with  the  railway  system,  has  perma- 
nently changed  the  former  methods, 
tactical  and  strategic,  of  European  war- 
fare. 

The  idea  of  stopping  a  cannon  shot 
by  an  iron  plate  probably  never  entered 
the  sagacious  brain  of  Robins — who 
lived  in  the  pre-iron  age  ;  nor  could  he 
have  had  any  conception  of  the  rapid 
and  powerful  progress  of  invention  and 
mechanical  power  which  characterize  our 
epoch.  From  1854  to  the  present  hour 
the  unforeseen  contest  of  gun  against 
plate  has  been  uninterrupted ;  though 
with  little  more  recondite  scientific  base 
for  the  contest  than  the  obvious  fact 
that  a  thicker  plate  could  still  be  pierced 
by  a  bigger  gun  than  before  ;  and  mil- 
lions have  been  expended,  and  to  a  large 
extent  wasted,  in  simply  repeating  upon 
a  larger  and  larger  scale  this  almost  self- 
evident  truth.  From  time  to  time  scien- 
tific artillerists,  engineers  and  naval  con- 
structors, have  speculated  upon  whether 
the  final  victory  would  rest  with  the  pon- 
derous armor-clad,  or  the  enormous  ar- 
tillery it  was  proposed  to  carry  ;  and, 
viewed  from  a  scientific  point  alone, 
those  were  most  nearly  right  who  de- 
clared that  the  gun  must  be  the  final 
victor,  by  its  almost  limitless  power  of 
penetration  or  dislocation — the  thickness 
of  possible  armor-plating  being  limited 
by  the  size  of  the  ship  to  carry  it  not  sur- 
passing that  which  should  be  manageable 
in  narrow  waters,  and  in  the  perils  of  sea 
and  weather.  The  stages  at  which  the 
duel  of  plate  and  gun  have  arrived  dur- 
ing the  last  few  years  have  brought,  in 
a  more  or  less  distinct  form,  before  the 
minds  of  men  regarding  the  subject  with 
a  larger  view  than  that  afforded  by  sci- 
ence only,  that  the  contest  at  last,  if  car- 
ried on  on  previous  principles,  must 
draw  near  its  close,  and  eventually  be 
decided,  not,  perhaps,  in  favor  of  either 
plate  or  gun,  but  by  the  correlative  con- 
ditions and  financial  or  economic  eventu- 
alities which  the  enormous  increase  in 
magnitude  of  both  must  give  rise  to. 

The  means  of  attack  and  of  defence 
as  they  have  been  enlarged  have  inevit- 
ably led  to  our  being  compelled  to  put 
"  too  many  eggs  into  one  basket."  We 
have  come  on  the  one  side  to  armor  of 
2  feet   thick,  and   costing   probably  for 


material  alone  in  place  £600  the  square 
fathom,  to  say  nothing  of  the  cost  of 
the  ship  to  carry  it,  so  that  the  destruc- 
tion of  a  single  iron-clad,  carrying  only 
a  few  ponderous  guns,  would  involve  a 
national  loss  in  war  material  exceeding 
the  value  of  many  a  naval  squadron 
deemed  powerful  in  Nelson's  day.  On 
the  other  hand  we  have  arrived  through 
the  gradual  stages  of  twelve,  eighteen, 
twenty-five  and  thirty-five  ton  guns,  at 
length  at  those  of  eighty  tons,  the  first 
of  which  is  now  in  progress  at  Woolwich. 
The  actual  outlay  for  the  production  of 
this  first  enormous  gun,  including  new 
forges  and  forty-ton  hammer,  steam  and 
hydraulic  cranes,  special  furnaces,  coil 
rolling  and  bending  machinery,  gigantic 
tongs  of  thirty  tons  weight,  and  a  mul- 
titude of  minor  paraphernalia,  will  proba- 
bly be  little  short  of  £100,000.  If  we  as- 
sume that  the  gun  itself  shall  ultimately 
prove  a  success — and  in  the  hands  of 
Colonel  Campbell  and  Mr.  Fraser  we 
see  no  great  reason  to  doubt  this — then 
it  would  be  unfair  to  charge  the  whole 
of  this  to  the  first  gun,  though  nobody 
can  predict  what  additional  expenses  in 
the  way  of  plant  the  experience  to  be 
obtained  hereafter  from  the  first  gun 
may  suggest,  or  necessitate.  The  esti- 
mated cost,  however,  for  wages  and  ma- 
terial alone  for  the  production,  as  stated 
on  authority,  of  this  first  gun  amounts 
to  £6,500;  and  bearing  in  mind  the  mar- 
gin which  experience  proves  always  ex- 
ists between  estimated  and  actual  costs 
in  all  new  and  arduous  engineering  tm- 
dertakings,  we  may .  safely  assign  f roni 
£10,000  to  £12,000  as  the  cost  of  this 
single  gun,  and  that  with  the  ship  that 
is  to  carry  it,  the  gun-carriage,  mechan- 
ical means  of  training  and  loading,  and 
the  many  other  paraphernalia  that  such 
a  piece  of  artillery  will  entail  before  it 
is  ready  to  be  discharged  against  an 
enemy,  the  entire  apparatus  will  stand 
in  our  national  ledger  at  from  £300,000 
to  perhaps  half  a  million.  Yet  the  very 
idea  inseparable  from  these  gigantic  con- 
ceptions is  that  the  chance  of  a  single 
successful  shot  from  either  the  attacking 
or  attacked  ship  must  in  all  probability 
disable  or  send  her  opponent  to  the  bot- 
tom. Such  is  the  swift  catastrophe  that 
seems  inevitably  attendant  upon  any  real 
conflict  at  sea  between  the  warships  of 
our  day.     While  we  are  at  peace  we  can 


254 


YAIST   NOSTEAND'S   ENGHSTEEEING   MAGAZINE. 


look  complacently  at  the  enormous  money 
stake  thus  set  afloat  in  every  iron-clad. 
We  are  amused  by  the  newspaper  ac- 
counts of  the  wonderful  doings  of  a  De- 
vastation or  some  other  terrible  monster 
which,  after  a  time,  passes  into  oblivion, 
and  as  ten  to  fifteen  millions  must  be  an- 
nually spent  upon  the  navy,  we  don't 
dwell  much  on  the  burden  of  these 
"  fighting  machines."  But  were  the  real 
blast  of  war  to  blow  in  our  ears,  and 
with  worthy  opponents  such  as  may  be 
■discerned  in  the  not  distant  future,  the 
loss  of  ten  or  twenty  of  these  costly 
monsters  would  simultaneously,  or  with- 
in a  few  months,  command  the  attention 
of  the  nation  in  a  very  different  way. 
No  nation,  not  even  one  with  the  creative 
power  and  wealth  of  England,  is  rich 
enough  to  carry  on  a  great  war  for  any 
length  of  time  upon  a  system  which  plays 
with  half -million  stakes  upon  the  chances 
of  a  single  cannon  shot,  anc]  where  the 
superiority  won  by  courage,  daring,  and 
seamanship  of  former  days  is  so  much 
neutralized  by  mere  mechanism,  as  is 
now  the  case,  and  must  continue  to  be, 
-while  we  continue  the  race  of  gun  against 
plate.  In  the  mean  time  it  is  one  of  the 
curious  features  of  the  case  that  science 
and  invention  have  been  hard  at  work 
upon  methods  of  attack  which,  if  suc- 
cessful, as  some  of  them  at  least  seem 
likely  to  be,  must  render  absolutely 
nugatory  all  this  ponderous  armor  as  a 
means  of  defence  and  tremendous  artil- 
lery for  that  of  naval  attack.  With  all 
the  invulnerability  of  her  sides,  the  bot- 
tom of  the  iron-clad  is  as  defenceless 
against  underwater  explosion  as  is  the 
belly  of  the  poor  crab  against  the  tear- 
ing bill  of  the  octopus.  As  a  means  of 
maritime  defence  the  torpedo  system  has 
already  proved  itself  powerful.  The 
skilful  barriers  of  moored  torpedoes,  by 
which  Austria  barred  the  entrance  to 
Venice,  were  such  as  even  British  ships 
and  crews  would  scarcely  have  dared  to 
face,  so  certain  and  inevitable  under  al- 
most all  circumstances  were  these  unseen 
means  of  destruction.  At  Pola,  also, 
and  in  the  American  civil  war,  this 
means  of  defence  proved  corresponding- 
ly effective,  but  as  a  means  of  maritime 
■attack  the  torpedo  stands  in  a  very  dif- 
ferent category.  If  we  can  only  bring 
the  explosive  instrument  into  contact 
with  the  enemy's  ship  the  result  is  pretty 


certain,  but  therein  lies  the  difficulty  ; 
against  the  defensive  torpedo,  an  enemy's 
ship  or  fleet  must  either  keep  aloof  or 
run  all  the  risks  of  a  perhaps  triple  line 
of  formidable  and  undiscoverable  dan- 
gers ;  whilst  as  a  means  of  attack  there 
is  added  to  the  difficulties  of  directing  a 
torpedo  at  all  in  any  designed  under- 
water transit,  even  against  a  fixed  object, 
all  those  dodges  and  devices  that  vigil- 
ance and  seamanship  can  suggest  to  en- 
able the  intended  victim  to  evade  the 
dreaded  contact.  We  may  here  in  pass- 
ing direct  the  reader's  attention  to  the 
critical  and  descriptive  accounts  to  be 
found  in  our  columns  for  the  years  186*7— 
68  of  what  had  been  achieved  up  to  that 
period  in  the  employment  of  torpedoes, 
both  for  defence  and  attack.  The  idea  of 
an  attacking  torpedo  is  far  from  being  a 
modern  one.  The  "fire-ship"  of  Guian- 
elli,  the  Italian  engineer  in  the  sixteenth 
century,  of  the  city  of  Antwerp,  was  in 
reality  a  torpedo,  which  floated  down 
with  the  tide  and  laid  broadside  on 
against  the  immense  wooden  bridge 
across  the  Scheldt,  by  which  the  Span- 
iards, under  Parma,  were  steadily  ap- 
proaching the  besieged  city,  was  com- 
pletely successful.  Bushnell,  an  Ameri- 
can engineer,  very  nearly  succeeded  in 
destroying  a  British  frigate  moored  in 
American  waters,  by  a  torpedo  brought 
to  the  ship  and  attached  by  the  operator 
from  his  submarine  boat,  the  torpedo 
being  provided  with  a  time  lock. 

About  1840,  the  well-known  Captain 
Warner  destroyed  off  Brighton  a  mer- 
chant ship  placed  at  his  disposal  by 
what  he  called  his  invisible  shell,  which 
was  in  reality  a  torpedo  drawn  by  a  cord 
under  the  hull  of  the  ship,  and  fired  by 
the  contact  ;  but  up  to  the  advent  of 
iron  war  shipping  after  the  Crimean  War 
little  farther  attention  was  given  to  this 
method  of  naval  attack,  the  old  system 
of  cannonade,  with  the  modern  addition 
of  firing  live  shells,  which  proved  so  tre- 
mendously destructive  to  the  Turkish 
fleet  at  Sinope,  proving  more  than  suffi- 
cient for  the  destruction  of  any  timber 
ship.  Not  long  after  the  Crimean  war 
a  project  was  laid  before  our  Admiralty 
for  an  attacking  torpedo,  consisting  of  a 
large  shell  suspended  from  the  long  bow- 
sprit of  the  attacking  ship,  and  so 
arranged  that  it  could  instantaneously 
be  let  go,  and  swing  like  a  pendulum 


MARITIME  ATTACK   BY   TORPEDOES. 


255 


against  the  quarter  or  side  of  an  enemy's 
ship,  on  contact  with  which  it  exploded. 
A  complete  description  of  this  early  pro- 
ject exists  in  the  archives  of  the  Admi- 
ralty, and  we  shall  probably  be  in  a 
position  at  a  future  time  to  give  its  de- 
tails and  the  name  of  the  proposer. 
Several  years  afterwards  very  nearly  the 
same  idea  was  proposed  to  his  own 
Government  by  the  Russian  Admiral 
Popoff,  and  is  understood  to  have  been 
adopted  into  that  service.  In  this  case, 
the  pendulum  shell  was  suspended  from 
a  derrick  projecting  to  a  considerable 
distance  from  the  broad  side  of  the  ship, 
an  arrangement  in  every  respect  inferior 
to  the  previous  one,  because  it  exposes 
the  broadside  of  the  attacking  ship  to 
the  stroke  of  its  own  torpedo,  with  dis- 
tance only  to  diminish  the  shock,  in  place 
of  opposing  to  it  her  sharp  bows,  and 
also  because  a  ship,  discovered  by  the 
■enemy's  telescopes  with  the  extraordinary 
appendage  of  a  derrick  projecting  from 
her  side,  must  create  suspicion  and  be 
given  a  wide  birth. 

All  such  projects  were  at  that  period 
coldly  received,  and  generally  met  with 
the  request  that  they  should  remain  in 
the  Admiralty  archives,  and  not  be  pub- 
licly mooted  until  a  more  convenient 
season.  Since  that  time,  and  especially 
during  the  last  ten  years,  a  great  deal  of 
attention  has  been  directed,  though  in  a 
way  so  unobtrusive  as  to  escape  much 
public  notice,  by  our  naval  and  military 
authorities  to  experiments,  upon  the  vari- 
ous contrivances  brought  to  its  notice  by 
officers  of  either  service,  as  well  as  by 
outside  inventors.  Amongst  these,  both 
in  America  and  in  England,  were  various 
projects  for  firing  torpedoes,  either  from 
a  large  vessel  like  the  Spuyten  Duyvel, 
provided  with  an  underwater  tunnel, 
from  out  of  which  the  torpedo  was  thrust, 
or  by  a  torpedo  fixed  at  the  end  of  a 
boom  or  underwater  bowsprit,  carried  by 
some  description  of  small  craft,  and  fired 
by  contact,  but  neither  of  these  projects 
could  be  feasibly  applicable,  except  un- 
der very  exceptional  conditions,  and  thus 
the  great  problem  remained  open  of  some 
effective  method  of  directing  from  a  dis- 
tance a  torpedo  which  should  come  into 
contact  with  the  hull  of  an  enemy's  ship 
and  there  explode.  Among  the  more 
noticeable  of  these  have  been  Harvey's 
torpedo,  which  floated   forth   from  the 


attacking  vessel  at  a  known  depth  from  • 
the  surface,  is  sent  down  upon  the  ves- 
sel to  be  attacked,  whether  by  current 
or  by  its  contained  power,  direction 
being  given  to  it  by  its  peculiar  trap- 
ezoidal horizontal  section,  and  by  means 
of  directing  guy  cords  or  wires.  What- 
ever favorable  results  may  have  been 
stated  to  have  been  obtained  with  this 
machine,  it  is  obvious  that  the  mean-  of 
direction  must  prove  wholly  ineffective 
if  the  distance  between  the  /mips  be 
great,  and  any  transverse  current  or 
wave  action  has  to  be  encountered. 
The  means  of  propulsion  contained  with- 
in the  body  of  a  torpedo  is,  like  those 
for  its  direction,  a  matter  of  much  diffi- 
culty. The  relative  density  of  the  tor- 
pedo must  be  unaltered  during  its  transit, 
for  it  must  not  alter  its  level  beneath 
the  surface  of  the  water.  Two  concen- 
tric screw  propellers,  revolving  in  reverse 
directions,  and  actuated  from  within  by 
compressed  carbonic  acid,  or  some  other 
elastic  vapor  or  gas,  or  by  coiled-up  me- 
tallic springs,  or  by  electro-motive 
power,  generated  within  the  torpedo  or 
in  the  attacking  ship,  and  transmitted 
through  an  insulated  wire,  as  in  Way's, 
and  one  or  more  American  inventions, 
have  been  among  the  mose  promising 
methods  of  propulsion  employed,  but  in 
all  these  the  rate  of  transit  through  the 
water  is  not  great,  and  the  less  that  is, 
the  less  certain  becomes  the  aim  that  can 
be  taken  at  the  ship  to  be  struck. 

Within  the  last  year  or  two,  experi- 
ments have  been  conducted  at  Woolwich 
upon  a  form  of  torpedo,  the  invention  of 
Mr.  Whitehead,  an  English  engineer,  for 
some  time  employed  by  the  Austrians  in 
experimenting  upon  torpedoes  at  the 
naval  port  of  Pola,  on  the  Adriatic.  Mr. 
Whitehead's  torpedo,  with  self-contained 
propulsive  power,  is  stated  to  have  been, 
in  the  judgment  of  the  Austrian  authori- 
ties, so  successful  as  to  have  received  a 
reward  of  £15,000.  His  invention  was 
subsequently  communicated  by  himself 
to  our  Government,  and  its  merits  suffi- 
ciently recognized — if  we  be  rightly  in- 
formed— by  a  large  payment  made  to  the 
inventor.  It  is  also  said  to  have  been 
purchased  by  the  American  as  well  as  by 
the  French  Government  for  large  sums  ; 
so  that  Mr.  Whitehead  has  already  re- 
ceived a  very  ample  reward  for  his  in- 
vention.     His    torpedo    consists   of   an 


256 


VAN  NOSTRAND'S   ENGINEERING   MAGAZINE. 


elongated  metallic  vessel,  provided  with 
projecting  flanges  or  fins  intended  for 
securing  its  direction  of  motion  only,  the 
explosive  agent  being  contained  at  the 
forward  end,  while  the  after  end  incloses 
a  cavity  into  which  air  is  compressed 
to  a  very  high  pressure  (100  or  more 
atmospheres),  which  thus  requires  a  ves- 
sel of  great  thickness  and  strength. 
Much  secrecy  has  been  observed  with 
respect  to  what  is  contained  besides 
within  the  torpedo.  The  compressed 
air,  however,  is  caused  to  act  upon  a 
double  or  concentric  pair  of  right  and 
left  screw  propellers  by  means  of  a  little 
pair  of  air-engines  ;  the  torpedo  is  also 
provided  with  a  rudder,  which  may  be 
set  to  various  angles  so  as  to  counteract 
lateral  drift  way,  and  it  is  stated  or  sur- 
mised that  the  obliquity  of  this  rudder 
may  be  automatically  altered  in  the  event 
of  the  transverse  current  or  other  divel- 
lent  force  altering  during  the  transit. 
This  torpedo  has  been  reported  on  by  an 
American  experimental  commission,  ex- 
cerpts from  which  report  will  be  found 
in  The  Engineer,  vol.  xxxvii:,  page  141. 
The  enormous  air  pressures  necessarily 
employed  in  this  torpedo  for  even  very 
moderate  distances  of  transit  form  a 
great  objection  to  its  use,  and  already 
the  experimental  trials  of  it  in  this  coun- 
try have  been  attended  with  fatal  results. 
Notwithstanding  which,  the  rate  of  pro- 
pulsion attained  up  to  a  very  recent 
period  does  not  appear  to  have  reached 
more  than  about  ten  miles  an  hour, 
although,  if  the  reports  which  have 
reached  us  be  quite  reliable,  a  speed 
largely  exceeding  this  has  been  obtained 
at  Woolwich  in  trials  made  in  the 
Arsenal  canal,  in  which  a  straight  reach 
of  considerable  length  exists.  The  great- 
est experimental  distance  of  transit  which 
limits  the  distance  between  the  attacking 
and  attacked  ships  does  not  as  yet  appear 
to  have  exceeded  about  600ft.,  although 
the  torpedo  let  loose  in  the  water  is 
capable  of  making  a  transit  of  about 
four-fifths  of  a  mile,  but  no  doubt  with 
great  uncertainty  as  to  direction  and  re- 
duction in  speed. 

If  a  velocity,  as  said  to  have  been  at- 
tained at  Woolwich,  approaching  30ft. 
per  second,  or  even  one  a  good  deal  less 
than  that,  has  actually  been  attained, 
the  submarine  torpedo  promises  to  be- 
come a  really  effective  weapon  of  attack. 


Most  of  the  experiments  hitherto  made 
with  this  class  of  torpedoes  have  been 
conducted  at  distances  not  exceeding  300 
yards  between  the  attacking  and  attacked 
ships,  it  being  assumed  that  at  that  dis- 
tance the  attacking  ship  would  be  com- 
paratively safe  from  the  artillery  of  her 
opponent,  the  accuracy  of  aim  decreasing 
rapidly  with  the  distance  through  the 
movements  of  both  ships,  the  smallness 
of  the  mark  presented,  and  deviations  in 
flight.  Now,  at  the  above  rate,  300 
yards  of  water  would  be  run  through  in 
less  than  two  minutes,  and  bearing  in 
mind  that  every  deviating  force  upon  the 
torpedo  due  to  wave  or  current  action, 
and  every  disturbing  influence  arising 
from  the  movements  of  both  ships,  must 
be  produced  in  proportion  as  the  velocity 
of  torpedo  transit  is  greater,  it  would 
seem  probable  that  here  at  length  a 
reasonable  chance  is  presented  for  strik- 
ing the  enemy's  hull,  and  thus  one  prime 
difficulty  of  torpedo  attack  be  overcome, 
though  many  others  still  remain  to  be 
surmounted.  We  are  enabled  to  state, 
however,  that  in  1861-2,  Mr.  Charles 
Lancaster  presented  to  our  War  Depart- 
ment designs  and  description  for  a  tor- 
pedo which,  like  Whitehead's,  contained 
its  own  means  of  propulsion.  These 
designs  were  received  and  acknowledged 
with  the  request  that  they  should  be 
allowed  by  the  inventor  to  repose  in  the 
archives  of  the  War  Department  until 
some  future  necessity  might  arise  for  the 
employment  of  such  a  destructive  mode 
of  warfare,  and  so  the  matter  did  rest 
until  a  comparatively  recent  period, 
when,  having  heard  of  Mr.  Whitehead's 
success,  Mr.  Lancaster  called  the  atten- 
tion of  the  authorities  to  his  anticipation 
of  the  invention  in  1861-62,  or  twelve  or 
thirteen  years  since.  From  the  nature 
of  Mr.  Lancaster's  propulsive  agent,  a 
transit  velocity  equal  at  least  to  any- 
thing said  so  far  to  have  been  attained 
by  Whitehead's  and  one  that  might  be 
made  greatly  to  exceed  that  of  the 
latter,  is  physically  possible,  and  would 
be  attended  with  no  danger  to  the  opera- 
tors. The  torpedo  itself  might  be  much 
lighter,  simpler,  and  less  expensive  both 
in  construction  and  use,  and  if  the  splen- 
did reward  of  £10,000  has  been  paid  to 
Whitehead,  it  seems  but  hard  lines  that 
Lancaster  should  not  be  rewarded  for 
his   invention,    which  has    been   in   the 


THE   MARINE   ENGINE   OF   TO-DAY. 


257 


hands  of  Government  for  twelve  or  thir- 
teen years,  and  which  offers  some  posi- 
tive advantages  over  Whitehead's  inven- 
tion. There  are  two  vulnerable  places  in 
every  ironclad  as  yet  constructed — the 
bottom  and  the  deck — and  whether  the 
problem  of  attack  by  torpedo,  and 
whether  by  Lancastre  or  by  Whiting,  be 
already  solved,  or  on  the  way  to  solution, 
the  attack  by  the  vulnerable  deck,  re- 
mains an  almost  untouched  subject  for 
the  inventive  skill  of  the  naval  artillerist. 
A  single  very  large  shell  lobbed  in  upon 
the  upper  deck  and  there  exploded, 
would  almost  certainly  put  any  ironclad 
hors  de  combat. 

It  was  proved  at  Woolwich  Marshes 
that  a  charge  of  only  10  lb.  of  powder 
sent  a  36in.  shell,  weighing  above  a  ton, 
a  horizontal  range  of  360  yards,  while 
with  20  lb.  charge  the  range  was  in- 
creased to  more  than  900  yards,  and  with 
such  small  charges  such  shells  might  be 
fired  from  a  mortar  or  howitzer  weighing 
far  less  than  an  18-ton  gun.  Probably 
spherical  shells  would  not  be  the  best  for 
remaining  where  lodged  upon  a  deck  un- 


til the  explosion  took  place,  but  the 
whole  subject  presents  an  excellent  field 
for  investigation,  for  the  possibility  of 
lodging  a  large  shell,  whether  spherical 
or  of  some  other  form,  upon  an  enemy's 
deck  at  such  very  short  ranges  can 
scarcely  admit  of  debate,  and  if  a  ship 
of  war  may  venture  to  approach  another 
within  300  yards  for  the  purpose  of  dis- 
charging a  somewhat  uncertain  under- 
water torpedo,  she  may  unquestionably 
do  the  same  for  the  purpose  of  landing 
upon  her  opponent's  deck  a  destructive 
shell,  even  though  the  latter  be  still  sub- 
ject to  the  possibility  of  missing  its 
mark.  Under  circumstances  otherwise 
alike,  the  attacking  ship  thus  employed 
would  have  one  element  of  safety  which 
is  scarcely  possible  if  the  attack  be  made 
by  torpedo.  The  torpedo  ship  must  ar- 
rest her  course  and  become  stationary 
before  she  can  with  any  certainty  launch 
her  weapon  ;  the  mortar  ship,  on  the 
contrary,  may  keep  on  her  way  without 
her  motion  deranging  sensibly  that  of 
the  shell  fired  in  the  direction  of  her 
bows  during  its  very  short  flight. 


THE  MARINE  ENGINE  OF  TO-DAY. 


From  "  Naval  Science." 


The  more  rapid  decay  of  the  boiler 
which  has  attended  the  comparatively 
slight  increase  of  the  pressure  of  the 
steam  in  the  marine  engine  during  the 
past  few  years  presents  a  problem  to  the 
solution  of  which  much  attention  is  be- 
ing paid,  and  probably,  ere  long,  means 
will  be  found  to  remedy  an  evil  which 
goes  far  to  neutralize  the  gain  in  econo- 
my of  fuel  due  tothe  use  of  high-press- 
ure steam.  The  mechanical  difficulties 
to  be  met  in  the  construction  of  a  sec- 
tional marine  boiler  for  extreme  pres- 
sures appear  already  to  have  been,  in  a 
great  measure,  overcome,  and  no  doubt 
perfectly  trustworthy  boilers  of  this 
kind  can  be  made  which  will  generate 
steam  as  efficiently  as  the  boilers  now  in 
use,  but  advances  in  the  direction  of 
higher  pressures  must  necessarily  be 
slow  in  the  case  of  the  more  important 
sea-going  ships.  Sufficient  experience 
has,  however,  been  gained  with  steam  of 
from  60  to  80  lbs.  pressure  to  enable 
Vol.  XIII.— No.  3—17 


the  boilers  now  ordinarily  in  use  at  sea 
to  be  kept  in  fair  order  under  the  condi- 
tions to  which  they  are  subject  in  the 
majority  of  sea-going  commercial  ships, 
and  for  some  time  to  come  this  must  be 
regarded  as  the  working  pressure  of 
ocean  steamers. 

The  compound  type  of  engine  in  gener- 
al use  at  this  pressure  at  the  present  time 
in  the  merchant  service  of  this  country, 
and  adopted  for  the  Royal  Navy  within 
the  past  few  years,  is  one  which,  Avhile 
possessing  some  evident  advantages, 
also  possesses  serious  defects ;  and  not- 
withstanding the  risks  which  attend  the 
trial  of  novel  machinery  on  shipboard, 
attempts  have  been  made  on  a  consider- 
able scale  in  the  commercial  marine  to 
introduce  simple  expansive  engines. 
With  the  exception  of  the  North  Ger- 
man Lloyd's  Co.,  the  steamship  compa- 
nies on  this  side  of  the  Atlantic  who 
have  tried  machinery  of  this  kind  do  not 
appear  to  have  met  with  any  measure  of 


258 


VAN  nostrand's  engineering  magazine. 


success,  but  in  numbers  of  American 
steamers  the  single  expansive  engine  is 
used  with  most  satisfactory  results,  and 
in  a  form  which,  to  many  English  marine 
engineers,  appears  to  be  the  most  objec- 
tionable, a  single  cylinder  and  crank  only 
being  used.  The  relative  merits  of  the 
two  types  of  engine  have  formed  the 
subject  of  much  discussion  in  the  techni- 
cal press,  and  among  the  various  engin- 
eering societies.  We  have  ourselves  de- 
voted some  space  to  the  consideration  of 
the  subject,  especially  with  reference  to 
the  use  of  the  rival  engines  in  ships-of- 
war,  and  the  conclusions  we  arrived  at 
were  not  favorable  to  the  compound  en- 
gine. The  greater  difficulty  of  rapidly 
handling,  and  the  much  greater  liability 
to  disablement,  of  this  form  of  engine, 
its  greater  complication,  and  the  larger 
space  occupied  by  it  in  the  ship  as  com- 
pared to  the  simple  engine,  renders  its 
use  in  fighting  ships  specially  objection- 
able. The  objections  to  it  in  these  re- 
spects apply  in  a  minor  degree  to  its  ap- 
plication to  commercial  steamers,but  they 
are  sufficiently  grave  to  warrant  the  use  of 
the  rival  engine  in  many  cases,  even  at  a 
possible  sacrifice  in  point  of  economy  of 
fuel.  What  sacrifice  would  result,  or 
whether  any  loss  at  all  would  occur,  in 
the  large  engines  of  ocean  steamers,  is  a 
matter  upon  which  no  absolutely  decis- 
ive evidence  at  present  exists,  but,  mak- 
ing use  of  such  data  as  recent  experience 
furnishes,  we  will  endeavor  in  the  pres- 
ent article  to  place  the  matter  in  such  a 
form  as  to  enable  our  engineering  read- 
ers to  arrive  at  a  conclusion  as  to  what 
are  the  probabilities  in  this  respect. 

The  advisability  has  been  suggested  of 
introducing  some  more  trustworthy  sys- 
tem of  trial,  and  proposed,  for  these 
runs,  the  registration  of  the  weight  of 
condensed  steam  discharged  from  the 
surface-condensers  and  jackets  with  the 
object  of  determining  the  efficiency  of 
the  steam  in  the  engine.  A  trial  of  an 
engine  of  the  compound  marine  type 
was  made  at  Chatham  Dockyard,  last 
July,  in  this  way.  The  particulars  of 
this  trial,  which  are  of  considerable  in- 
terest, have  just  been  published  in  the 
Prize  Essay  of  the  Junior  Naval  Pro- 
fessional Association,*  together  with  the 


*  "  The  Relative  Merits  of  Simple  and  Compound  En- 
gines ae  Applied  to  Ships  of  War."  Prize  Essay.   By  Niel 


results  of  an  important  series  of  experi- 
ments recently  made  in  the  same  way  in 
America.  For  full  particulars  of  these 
experiments  and  analyses  of  the  results 
we  must  refer  our  readers  to  the  Essay, 
confining  ourselves  to  using  the  figures 
given  so  far  only  as  they  bear  upon  the 
points  to  which  we  wish  to  direct  special 
attention. 

When  examined  before  the  Committee 
on  Admiralty  Designs,  in  the  early  part 
of  1871,  Mr.  Reed  strongly  expressed  an 
opinion  that  the  economy  stated  to  be 
due  to  the  compound  form  of  engine  had 
been  greatly  exaggerated,  and  the  evi- 
dence now  accumulating  confirms  the 
opinion  formed  upon  the  imperfect  data 
available  at  that  time.  Figures  like  1.3 
or  1.5  lbs.  of  fuel  per  indicated  horse- 
power per  hour  have  been  constantly 
quoted  for  compound  engines  working 
at  sea  at  pressures  varying  from  60  lbs. 
to  90  lbs.  absolute  at  the  outside,  and,  as 
engineers  who  have  really  studied  the 
question  are  aware,  a  combination  of  the 
most  impossibly  favorable  circumstances 
is  required  in  order  to  attain  such  a  re- 
sult. 

In  the  first  place,  the  quantity  of 
heat  available  for  the  performance  of 
useful  work  in  a  steam  engine  is  such 
that,  in  a  condensing  engine  supplied 
with  steam  from  an  ordinary  marine 
boiler  evaporating  8  lbs.  of  water  per  lb. 
of  fuel,  the  coal  used  could  not  be  less 
than  1.15  lbs.  per  indicated  horse-power 
per  hour  at  60  lbs.  pressure  absolute,, 
presuming  that  all  the  ordinary  causes  of 
loss  were  eliminated.  In  order  to  obtain 
this  result,  losses  from  radiation,  leak- 
age, clearances,  induced  liquefaction^ 
due  to  causes  other  than  the  performance 
of  work  during  expansion,  would  require 
to  be  got  rid  of,  and  the  expansion 
would  have  to  be  carried  out  to  the  low- 
er limit  of  temperature,  that  of  the 
condenser,  taken  in  this  case  at  100° 
Fahrenheit.  Under  these  circumstances 
the  weight  of  steam  theoretically  re- 
quired for  pressures  up  to  120  lbs.  abso- 
lute, as  given  by  Professor  Cotterill  in 
his  "  Notes  on  the  Theory  of  the  Steam 
Engine,"  is  as  follows  : 


McDougall,  Assoc.  I.  C.  E.,  M.  I.  N.  A.,  of  the  Department 
of  the  Controller  of  the  Navy.  (Griffin  &  Co.,  15  Cockspur 
Street,  Pall  Mall,  LondoD,  and  2  The  Hard,  Portsea^ 
Portsmouth,) 


THE   MARINE   ENGINE   OF   TO-DAY. 


259 


Pressure 

in 

atmospheres. 


No.  of  lbs.  of  steam  re- 
quired per  horse-power 
per  hour. 


2 

11.2 

4 

9.2 

6 

8.3 

8 

7.7 

The  accuracy  of  these  figures  can  readily 
be  demonstrated  from  the  known  proper- 
ties of  saturated  steam,  but  the  weight 
of  steam  actually  required  per  H.  P.  for 
any  given  engine  is  a  matter  upon  which 
but  little  trustworthy  information  is 
available.  It  is  necessarily  much  in  ex- 
cess of  the  theoretical  weight,  bearing 
no  definite  relation  to  it.  As  a  check 
upon  the  unhealthy  spirit  of  emulation 
in  the  production  of  remarkable  figures 
which  the  demand  for  economy  of  fuel 
has  engendered,  it  is  well,  however,  to 
keep  the  theoretical  figures  in  view  in 
considering  the  probable  accuracy  of  re- 
sults stated  to  have  been  obtained  in  ac- 
tual practice. 

It  is  to  the  loss  from  condensation  in 
the  cylinder  that  the  difference  between 
the  theoretical  and  the  actual  weight  of 
steam  used  expansively  is  in  most  engines 
chiefly  due,  and  it  is  to  the  prevention  of 
the  losses  from  this  source  that  improve- 
ment in  the  steam  engine  has  been  for 
some  time  in  a  great  measure  directed, 
although  no  definite  knowledge  of  the 
extent  of  the  loss  traceable  to  condensa- 
tion in  the  modern  engine  has  existed. 
That  it  is  actually  greater,  and  that  its 
effectual  prevention  in  practice  is  more 
difficult  than  has  been  supposed  by  emi- 
nent authorities,  appears  to  be  evident 
from  the  most  recent  experiments.  Pro- 
fessor Rankine  appears  to  have  regarded 
its  prevention  as  a  matter  of  no  great 
difficulty,  and  to  have  considered  that 
the  extent  to  which  expansion  could  be 
carried  with  useful  effect  should  be  de- 
termined from  the  back  pressure  in  the 
cylinder  and  the  resistance  due  to  the 
friction  of  the  engine,  the  terminal  for- 
ward pressure  of  the  steam  for  maximum 
efficiency  being  just  sufficient  to  balance 
these  two.  In  a  paper  on  the  "  Economy 
of  Power  in  Compound  Marine  Engines," 
submitted  to  the  Committee  on  Admi- 
ralty Designs,  he  states  : 

"It  is  obvious  that  work  continues  to 
be  done  by  the  steam  in  driving  the  pis- 


ton so  long  as  the  pressure  behind  the 
piston,  or  forward  pressure,  continue-  to 
be  greater  than  the  pressure  in  front,  or 
back  pressure,  exerted  by  the  steam 
which  has  already  done  its  work,  and 
which  the  piston  is  expelling  from  the 
cylinder ;  and  hence  it  follows  that  in 
order  to  realize  the  greatest  quantity  of 
work  which  the  steam  is  capable  of  j>er- 
forming  the  expansion  ought  to  be  car- 
ried on  until  the  forward  pressure  of  the 
steam  behind  the  piston  has  fallen  so 
low  as  to  be  just  sufficient  to  overcome 
the  back  pressure  ;  and  that  to  end  the 
expansive  working  of  the  steam  at  an 
earlier  period  of  the  stroke  is  to  throw 
away  part  of  the  power  of  the  steam. 

"  This  statement  must,  however,  be 
taken  with  the  qualification  that  when 
the  excess  of  the  forward  pressure  above 
the  back  pressure  falls  below  the  press- 
ure which  is  just  sufficient  to  overcome 
the  friction,  the  work  done  is  no  longer 
partly  useful  and  partly  wasteful,  but  is 
wholly  wasteful ;  whence  it  follows  that 
although,  in  order  to  obtain  the  greatest 
indicated  work  from  a  given  weight  of 
steam,  the  expansion  should  be  continued 
until  the  forward  pressure  becomes  just 
equal  to  the  back  pressure,  the  greatest 
useful  work  is  obtained  by  making  the 
expansion  cease  when  the  forward  press- 
ure is  just  equal  to  the  back  pressure 
added  to  a  pressure  equivalent  to  the 
friction  of  the  engine." 

And  further  : 

"In  order  to  realize  the  theoretical 
greatest  efficiency  in  the  exjjansive  work- 
ing of  steam,  the  expansion  ought  to 
take  place  in  a  non-conducting  cylinder, 
with  a  non-conducting  piston.  This  con- 
dition cannot  be  absolutely  realized  in 
practice ;  but  means  may  be  taken  to 
diminish  the  loss  of  efficiency  arising 
from  the  conducting  power  of  the  cylin- 
der and  piston  until  they  become  unim- 
portant." 

For  the  proportions  of  cylinder  usual 
in  compound  marine  engines  the  pressure 
per  square  inch  required  to  overcome  the 
friction  in  engines  of  good  construction 
is  such  that  the  friction  diagrams  at  the 
speeds  at  which  they  are  usually  taken 
become  a  mere  line,  and  for  all  practical 
purposes  the  size  of  the  low  pressure 
cylinder  might  be  determined  on  the 
supposition  that  the  forward  terminal 
pressure  would  correspond  with  the  or- 


260 


VAN  nostrand's  engineering  magazine. 


dinary  back  pressure  if  the  maximum 
efficiency  of  the  steam  were  to  be  at- 
tained in  the  manner  indicated  by  Pro- 
fessor Rankine.  It  appears  to  be  evident, 
however,  that  the  losses  from  the  clear- 
ances and  condensation  at  the  higher 
grades  of  expansion  affect  the  perform- 
ance of  the  engine  so  seriously  that  the 
maximum  efficiency  of  the  steam  is 
reached  at  a  rate  of  expansion  which 
places  the  terminal  forward  pressure 
much  above  that  of  the  combined  re- 
sistance of  friction  and  back  pressure, 
as  will  be  plainly  seen  from  the  Ameri- 
can experiments  quoted  further  on.  This 
remark  applies  to  engines  of  both  the 
compound  and  simple  types,  and  before 
discussing  the  relative  economy  of  the 
two  kinds  of  engine  it  will  help  to  form 
a  just  estimate  if,  in  the  first  place,  some 
idea  can  be  given  of  the  value  to  be  at- 
tached to  the  remarkably  good  results  in 


point  of  economy  so  frequently  claimed 
for  the  compound  engines  now  in  ordin- 
ary use  at  sea. 

The  results  of  the  trial  at  Chatham 
Dockyard,  published  in  the  Prize  Essay 
of  the  Junior  Naval  Professional  Asso- 
ciation, are  of  considerable  interest,  as 
the  engines  are  of  the  same  type,  but 
placed  vertically,  as  those  of  the  now 
well-known  '  Briton '  class.  The  engines 
are  by  the  same  makers  as  those  of  this 
ship,  and  are  jacketed  in  the  same  way, 
the  low  pressure  cylinder  only  being- 
jacketed.  The  trial  is  the  only  one  of  a 
large  compound  engine  of  the  marine 
type  conducted  in  this  country  with 
which  we  are  acquainted  in  which  pro- 
vision has  been  made  to  determine  the 
efficiency  of  the  engine  apart  from  that 
of  the  boiler,  and  we  here  reprint  the 
principal  particulars,  as  they  are  also  of 
special  interest  on  this  account  : 


Tkial  of  Dock  Pumping-Engines  H.  M.  Dockyard,  Chatham,  July  13th,  1874. 

Diameter  of  Cylinders H.  P.  48  ins.,  L.  P.  75  ins. 

Length  of  stroke ; 2  ft.  9  ins. 

Mean  pressure  of  steam  in  the  boilers 53.5  lbs.  per  square  inch. 

Mean  number  of  revolutions  per  minute- 87.6. 

Mean  pressure  in  cylinders High  23.784,  Low  5.993. 

Indicated,  horse-power High  505,  Low  387— Total  892. 

Duration  of  trial 3  hours  32-^  minutes. 

Description  of  coal  used Fothergill's  Aberdare. 

Quantity  of  coal  used 12,320  lbs. 

Quantity  of  coal  used  per  I.  H.  P.  per  hour 3.74  lbs. 

Water  collected  from  hot-well 60,228  lbs. 

Water  collected  from  hot-well  per  I.  H.  P.  per  hour 18.42  lbs. 

Water  collected  from  steam-jacket 1,312  lbs. 

Water  collected  from  steam-jacket  per  I.  H.  P.  per  hour 0.401  lbs. 

Water  collected  from  steam-pipes 315  lbs. 

Total  quantity  of  water  per  I.  H.  P.  per  hour .18.922  lbs. 

Quantity  of  coal  burnt  per  square  foot  of  fire-grate 17.8  lbs.  per  horn'. 

Velocity  of  piston,  feet  per  minute 481.8. 

Volume  swept  by  piston  per  I.H.P.  per  minute,  L.P.  cylinder.  16. 57  cubic  feet. 
Volume  swept  by  pistons  per  I.  H.  P.  per  minute Total. . .  22.03  cubic  feet. 


It  is  remarked  in  the  Essay  with  re- 
gard to  the  results  : 

"It  will  be  seen  that  the  consump- 
tion of  fuel  determined  in  the  same  way 
as  on  the  six  hours'  runs  was  found  to 
be  3.74  lbs.  per  I.  H.  P.  per  hour.  On  a 
previous  trial  of  If  hours'  duration,  as  a 
check  upon  which  the  present  trial  was 
ordered,  the  consumption  of  fuel  had 
been  calculated  at  3.42  lbs.  The  steam 
is  supplied  from  ordinary  double-flued 
mill  boilers,  and  upon  subsequent  evapo- 
ration trials  of  one  of  the  boilers  at  at- 


*  The  engines  drive  large  -centrifugal  pumps,  and  the 
revolutions  varied  with  the  height  of  lift. ^ 


mospheric  pressure  it  was  found  that 
the  weight  of  water  evaporated  per  lb. 
of  fuel  from  100°  was  9.103  lbs.  when 
burning  17.53  lbs.  of  fuel  per  square  foot 
of  grate  per  hour,  the  estimated  rate  of 
combustion,  as  will  be  seen  above,  on 
the  trial,  having  been  17.8  lbs. 

"  As  will  also  be  seen,  the  total  weight 
of  steam  or  water,  as  measured,  was 
18.92  lbs.  per  I.H.P.  per  hour.  This 
would  give  only  5.59  lbs.  of  water  evap- 
orated per  lb.  of  fuel  by  the  boiler,  the 
lowest  evaporative  trial  of  which  at  at- 
mospheric pressure  gave  7.843  lbs.  The 
coal  used  on  all  the  trials  was  of  first- 


THE  MARINE   ENGINE   OF   TO-DAY. 


261 


rate  quality,  and  its  evaporative  power 
when  tried  in  the  marine  test-boiler  was 
found  to  be  9.635  lbs.  of  water  from  100° 
per  lb.  of  fuel. 

"  There  are  two  things  which  are 
probable  here — first,  that  the  coal  per 
H.  P.  as  calculated  is  too  high  ;  and  sec- 
ond, that  the  weight  of  steam  per  H.  P., 
as  measured,  is  too  low.  It  would  be 
impossible  to  fix  accurately  the  weight 
of  steam  and  fuel  actually  used,  but 
making  the  liberal  allowance  of  one- 
fourth,  or  25  per  cent.,  for  error,  we 
have  2.82  lbs.  of  coal  per  I.  H.  P.  per 
hour  as  the  probable  consumption  for  an 
engine  of  the  '  Briton '  type,  driven  by 
ordinary  Lancashire  boilers,  using  the 
best  Welsh  coal,  the  probable  rate  of 
combustion  being  then  only  13.35  lbs. 
per  square  foot  of  grate  per  hour,  and  if 
we  assume  that  8  lbs.  of  water  were 
evaporated  by  the  boiler  per  lb.  of  fuel, 
we  have  22.56  lbs.  of  steam  per  I.  H.  P. 
per  hour  used  by  the  engine." 

These  figures  certainly  form  a  remark- 
able contrast  to  the  results  of  the  lower 
power  trials  of  the  early  high  presssure 
compound  engines  tried  in  the  Navy,  and 
to  the  figures  constantly  given  for  the 
compound  engines  of  the  merchant  ser- 
vice. An  ordinary  Cornish  or  Lanca- 
shire boiler  at  so  low  a  rate  of  combus- 
tion as  13.35  lbs.  of  coal  per  square  foot 
of  grate  might  be  expected  to  be  nearly, 
if  not  quite,  as  economical  as  a  cylin- 
drical marine  tubular  boiler  burning  20 
lbs.  per  square  foot  of  grate  at  sea. 
Looking,  therefore,  at  the  probable  re- 
sult of  2.82  lbs.  of  the  Chatham  trial, 
and  keeping  the  theoretical  consumption 
of  1.15  lbs.  of  fuel  per  H.  P.  in  view, 
the  value  to  be  attached  to  such  figures 
as  1.3  lbs.  or  1.5  lbs.,  given  for  engines 
working  as  a  rule  with  steam  of  about 
45  lbs.  or  50  lbs.  supplied  from  boilers 
burning  coal  certainly  not  superior  to 
FothergilPs  Aberdare,  may  be  judged  of. 
Although,  apparently,  figures  like  these 
have  been  widely  accepted  as  trust- 
worthy, we  have  by  no  means  been  alone 
in  expressing  our  doubts  as  to  their  ac- 
curacy. In  a  most  interesting  report  by 
a  board  of  American  engineers  to  the 
Secretary  of  the  United  States  Navy, 
published  in  1874,  the  gain  in  economy 
by  the  use  of  the  compound  engine  with 
60  lbs.  pressure,  as  compared  to  the 
simple  engine  of  that  Navy  worked  at 


30  lbs.  pressure,  is.  calculated  at  29.26 
per  cent.,  the  weight  of  steam  per  horse 
power  for  the  compound  engine  being 
determined  as  22.46  lbs.  The  report 
states  : 

"The  gain  of  29.26  per  centum  in  the 
cost  of  the  indicated  power  is  much  less 
than  that  usually  claimed  for  the  com- 
pound engines  by  persons  interested  in 
their  manufacture.  If,  as  is  often  as- 
serted, the  indicated  horse  power  is  ob- 
tained at  a  cost  of  only  two  jDounds  of 
coal  per  hour,  the  boilers  employed  must 
evaporate  11.23  pounds  of  water  per 
pound  of  coal.  This  quantity  is  much 
greater  than  has  ever  been  evaporated 
by  boilers  of  the  types  employed  with 
the  compound  engines  under  considera- 
tion. The  quantity  of  water  evaporated 
in  such  boilers  per  pound  of  coal,  at  the 
high  rates  of  combustion  generally  em- 
ployed in  English  practice,  will  be  found 
not  to  exceed  eight  pounds  of  water  from 
a  temperature  of  100°  Fahrenheit. 
When  the  apparent  evaporation  is  great- 
er the  increase  may  be  due  to  superheat- 
ing the  steam,  the  results  of  which 
practice  may  be  equally  advantageous 
in  the  case. of  engines  of  either  type. 
The  cost  of  the  indicated  horse  power, 
then,  in  lbs.  of  coal  per  hour  would  be 

2-M_6  =  2.81." 


The  coal  trials  conducted  in  the  Eoyal 
Dockyards  furnish  ample  evidence  that 
the  evaporation  of  8  lbs.  of  water  per 
pound  of  coal  is  a  very  good  per- 
formance for  a  marine  boiler  under 
ordinary  working  conditions  at  sea, 
while  from  the  recent  American  trials  it 
appears  to  be  probable  that  expansion 
is  carried  to  too  great  an  extent  for 
economy  in  the  generality  of  compound 
engines  of  English  design.  The  best 
result  given  by  the  compound  engine  in 
these  trials  was  attained  by  the  '  Rush ' 
with  a  ratio  of  expansion  of  6.2,  the 
volume  swept  by  the  piston  of  the  low 
pressure  cylinder  being  only  9.42  cubic 
feet  per  horse  power  per  minute.  The 
cylinders  in  this  case  were  completely 
jacketed,  and  with  a  boiler  evaporating 
8  lbs.  of  water  per  pound  of  coal  the 
consumption  of  fuel  per  H.  P.  per  hour 
would  be  2.3  lbs.  The  engine,  as  will 
be  seen  further  on,  was  of  small  size, 
but  a  comparison  of  the  result  with  that 


262 


TAN   NOSTRAND's   ENGINEERING   MAGAZINE. 


of  the  Chatham  engines  is  instructive, 
and,  taken  in  conjunction  with  the  result 
of  the  '  Bache '  trials,  it  tends  to  show 
that  the  capacity  of  cylinder  in  engines 
of  English  design  is  unnecessarily 
large. 

For  engines  of  large  size  the  figures 
given  for  the  Admiralty  six  hours'  runs 
are  probably  the  most  trustworthy  yet 
available,  as  the  coal  used  on  all  occa- 
sions is  of  practically  the  same  quality 
from  the  best  Welsh  beds.  Referring 
to  the  table  below,  it  will  be  seen  that 
the  four  last  trials  of  the  compound  en- 
gines do  not  differ  materially,  and  a 
mean  of  the  five  trials  gives  2.4  lbs.  of 
the   best   Welsh   coal    used    per   horse 


power  per  hour.  This  is  below  the  prob- 
able result  of  the  Chatham  trial,  but 
comparing  it  with  the  results  given  by 
five  simple  low  pressure  engines  a  gain 
of  18  per  cent,  by  the  use  of  the  com- 
pound high  pressure  engine  is  shown. 
To  obtain  this  result  the  capacity  of  the 
cylinder  has  been  increased  50  per  cent., 
and  the  pressure  above  the  atmosphere 
has  been  doubled.  The  trials  are  all  at 
full  power,  but  it  is  pretty  evident  from 
the  American  experiments  that  the  max- 
imum expansion  for  economy  had  been 
reached  in  the  compound  engines,  and 
that  at  lower  power  any  further  econ- 
omy would  simply  be  due  to  increased 
efficiency  of  the  boiler. 


Name  of  Vessel. 


Monarch. . . . , 
*Devastation 
Hercules. .    . , 

Sultan 

Druid 

Briton 

Thetis 

Thetis 

Amethyst  . ; . 
Encounter. . . 


When 
tried. 


1869 
1873 
1869 
1871 
1871 


1870 
1872 
1873 
1873 
1873 


Steam  pressure  ; 

lbs.  per  sq.  in. 

above 

atmosphere . 


lO  *3 


I.  H,  P. 


7470 
5652 
7187 
8778 
2038 


2019 
2036 
2000 
1990 
2030 


Volume  swept  per 
I.  H.  P.  per  min. 

by  piston. 


Cubic  feet 
11.8 
11.64 
12.5 
11.19 
12.6 
L.  P. 
cylinder. 
13.4 
13.6 


14.7 
14.5 


Total. 

17.8 
18.0 


19.6 
19.4 


Coal  used 

per 
I.  H.  P. 
per  hour. 


lbs. 
2.79 
2.928 
2.811 
3.109 
3.001 


1.981 
2.545 
2.600 
2.463 
2.425 


There  can  be  no  doubt  that  in  some 
minds  the  belief  in  the  efficacy  of  pass- 
ing steam  through  a  succession  of  cylin- 
ders amounts  to  little  short  of  a  supersti- 
tion, and  in  such  cases  the  important  in- 
ferences to  be  drawn  from  figures  like 
those  given  above  are  lost  sight  of.  The 
fact  is  overlooked  or  forgotten  that  it 
was  not  until  the  compound  engine  was 
worked  at  higher  pressure  than  the  en- 
gines it  has  superseded  that  its  superior 
economy  could  be  distinguished  at  sea  ; 
that  on  land  low  pressure  compound  en- 
gines have  been  superseded  wholesale  by 
high  pressure  simple  expansive  engines  ; 
that   there   is   abundant   evidence    that 

*  Twin  Screws. 


an  increase  in  the  pressure  of  the  steam 
is  followed  by  increased  economy  in  the 
simple  as  in  the  compound  engine,  and 
that,  therefore,  on  the  broadest  possible 
grounds,  it  might  be  expected  that  with 
equal  steam  pressure  the  difference  be- 
tween the  performance  of  the  two  en- 
gines, as  shown  above,  would  be  largely 
reduced,  if  it  did  not  entirely  disappear. 
The  experiments  with  the  engines  of 
the  'Dexter'  furnish  direct  evidence  of 
the  economy  which  results  from  the  use 
of  higher  steam  pressure  in  the  simple 
engine.  Taking  trials  Nos.  3  and  1  for 
comparison,  it  will  be  seen  below  that  in 
the  same  engine  the  horse  power  cost 
20|  per  cent,  more  at  40  lbs.  pressure 
than  at  70  : 


THE   MARINE   ENGINE   OF   TO-DAY. 


263 


No.  of  trial < 

Mean  boiler  pressure  above  atmosphere  lbs 

Indicated  H.  P 

Weight  of  water  used  per  I.  H.  P.  lbs 23.8572 

Ratio  of  expansion |        4 .  557 


7 

40.025 

124.267 

28.802 


This  was  in  a  completely  clothed  but 
nn jacketed  cylinder. 

The  very  different  results  which  may 
he  obtained  from  steam  of  the  same 
pressure  in  different  engines  of  the  same 


type  is  very  cleai'ly  shown  by  comparing 
the  results  of  the  trial  of  the  American 
steamer  '  Mackinaw '  (tried  by  Mr.  Isher- 
wood  in  1864)  with  those  given  by  the 
engines  of  the  '  Dallas,'  recently  tried. 


'Mackinaw.'    Saturated  Steam. 

Diameter  of  cylinder. . .   58  ins. 

Length  of  stroke 8  ft.  9  in. 

Clearances q  g. 

Effective  capacity  of  cylinder' ' 


Ratio  of  expansion. ...   

Cut-off 

Boiler  pressure  above  atmosphere       lbs 

Absolute  initial  pressure  in  cylinder  lbs 

Feed  water  used  per  I.H.P.  per  hour  lbs 

Proportion  of  feed  water  accounted  for  by  the  indi- 
cator  

Revolutions  per  minute 


3.68 

.21 

38 

53.0 

36.04 

.6218 
56.09 


Dallas.'     Saturated  Steam. 


Diameter  of  cylinder 

Length  of  stroke 

Clearances 
Effective  capacity  of  cylinder" 


.36  inches. 
.30  inches. 

.0.0802. 


Ratio  of  expansion 

Cut-off 

Boiler  pressure  above  atmosphere         lbs 

Absolute  initial  pressure  in  cylinder    lbs 

Feed  water  used  per  I.  H.  P.  per  hour  lbs 

Proportion  of  feed  water  accounted  for   by  the   indi- 
cator.  

No.  of  revolutions  per  minute 


5.067 
.132 
35.40 
46.90 
26.68 

.7195 
48.68 


The  ratio  of  clearances  to  effective 
capacity  of  cylinder  was  practically  the 
same  in  the  two  cases,  and  under  like 
conditions  in  other  respects  the  larger 
engine  might  be  expected  to  be  the  more 
economical.  That  the  loss  in  the  '  Mack- 
inaw' was  directly  due  to  liquefaction  is 
evident  from  the  fact  that  the  proportion 
of  steam  accounted  for  by  the  indicator 
gradually  decreased  at  the  higher  grades 
of  expansion,  the  proportion  liquefied  in 
the  'Dallas'  remaining  practically  con- 


stant at  all  grades.  It  was  also  found  in 
the  'Mackinaw'  that  on  superheating 
the  steam  to  such  an  extent  that  the  in- 
dicator showed  approximately  the  same 
weight  of  steam  as  actually  used  (the 
weight  being  calculated  from  the  dia- 
grams on  the  assumption  that  the  volume 
indicated  was  that  of  saturated  steam), 
the  steam  used  per  indicated  H.  P.  fell 
considerably  below  that  required  for  the 
'Dallas,' using  saturated  steam,  the  fig- 
ures beino-  as  under  : 


264 


van  nostrand's  engineering  magazine. 


Mackinaw.'    Superheated  Steam. 


Cast-off 

Boiler  pressure  above  atmosphere .lbs. 

Absolute  initial  pressure  in  cylinder lbs. 

Feed  water  used  per  I.  H.  P.  per  hour lbs. 


The  cylinder  of  the  '  Mackinaw,'  like 
those  of  the  other  engines  tried  by  Mr. 
Isherwood,  was  unjacketed  and  only 
partially  covered  with  felt,  the  ends  and 
slide-casing  being  unprotected.  The  cy- 
linder of  the  '  Dallas,'  on  the  other  hand, 
was  thoroughly  protected,  but  the  supe- 
rior economy  of  this  engine  with  satu- 
rated steam  must  have  been  mainly  due 
to  its  greater  speed.  Although  on  ac- 
count of  its  smaller  size  two  square  feet 
of  condensing  surface  were  presented  in 
the  cylinder  of  the  'Dallas'  for  every 
cubic  foot  of  steam  room,  against  one 
square  foot  in  the  '  Mackinaw,"  yet  the 
time  occupied  in  making  a  stroke  was 
only  one-ninth  of  that  taken  by  the  pis- 
ton of  the  larger  engine.  In  the  absence 
of  information  as  to  the  relative  dryness 
of  the  steam  used  in  the  two  engines,  it 
is  of  course  impossible  to  attach  an  ex- 
act value  to  the  influence  of  the  greater 
speed  in  presenting  liquefaction,  but  the 
trials  of  these  two  ships  may  fairly  be 
taken  as  showing  the  importance  of  high 


speed  as  an  element  of  economy  at  the 
higher  grades  of  expansion  in  unjacket- 
ed cylinders. 

Whether  the  speed  of  the  piston  can 
be  increased  to  such  an  extent  in  practice 
as  to  render  the  jacket  superfluous  is  a 
question  upon  which  it  is  impossible  to 
speak  with  any  degree  of  certainty. 
Judging  from  experience  with  the  loco- 
motive, using  steam  almost  invariably 
super-saturated,  it  appears  to  be  possible 
that  this  is  the  case.  "With  saturated 
steam  used  expansively  at  ordinary 
speeds  of  piston,  however,  the  jacket  is 
essential  to  economy,  and  the  recent 
American  experiments  show  this  plainly, 
although  they  also  appear  to  show  that 
its  influence  is  not  sufficient  to  admit  of 
expansion  being  carried  out  to  any  great 
extent  with  adequate  gain  in  economy. 

Tabulated  in  Table  1  are  leading  par- 
ticulars of  some  of  the  recent  trials,  and 
in  Figs.  1  and  2  are  shown  diagrams 
from  the  engines  of  the  'Rush.'  The 
great    difference    between    the    results 


Fig.  1. — U.  S.  Revenue  Steamer  'Rush.'    High-Pressure  Cylinder. 
Scale  of  indicator,  40  lbs.  per  inch. 
90  -t 
80- 
70- 
60 
50 
40 
30 
20 
10- 


£iiie  of  no  J^ressuTr 


Fig.  2.— Low-Pressure  Cylinder. 
Scale  of  indicator,  16  lbs.  per  inch. 


THE  MARINE   ENGINE   OF   TO-DAY. 


265 


Table  No.  1. 


Jacketed  Cylinders. 


Kush  compound 
engine. 


High 

Pressure. 


Number  of  trials  for  reference 

Diameter  of  cylinder  j  Lo??— ins! ! ! 
Stroke  of  pistons ins. . . 

Date  of  trial 

Duration  of  trial hours 

Mean  steam  pressure  in  boiler.  ..lbs. 

Ratio  of  expansion 

Mean  vacuum  in  condenser ins. 

Mean  number  of  revolutions  per  min. 

Initial  pressure  in  cylinder  above  j 
atmosphere ( 

Absolute  initial  pressure  in  cylin- 
der  

Mean  effective  pressure lbs.  -j 

Estimated  friction  pressure  . .  .lbs. 

Indicated  horse-power 

Effective  horse-power. 

Steam  per  I.  H.  P.  per  hour lbs. 

Steam  per  effective  H.P.  per  hr.  .lbs. 
Coal  per  I.  H. P.  f  Calculated  for  ] 

per  hour. . . .  |      evaporation  [  lbs 
Coal  per  effec--{      of  nine  lbs.  }■ 

tive  H.  P.  per  j      water     per  | 

hour  .......[     lb.  of  fuel  .  J  lbs 

Ratio  of  L.  P.  to  H.  P.   cylinder  ( 

capacity } 

Effective  capacity  of  cylinder,  cub-  \ 

ic  ft.  per  I.  H.  P.  per  minute . . .  { 
Velocity  of  piston  per  minute. . .  .ft. 


1 

24 

38 

27 

Aug. 

1874 

55 

69.06 

6.21 

26.49 

70.84 

H.  P.  67.46 

L.  P.    8.65 

H.  P.  82.27 

L.  P.  23.46 

H.P.  29.68 

L.  P.  12.72 

H.P.    2.5 

L.  P.    1.5 

266.54 

239.43 

18.383 

(  20.46 

2.042 


2.273 

2.25 

H.  P.  3.76 
L.  P.  9.42 

318.8 


Low 
Pressure. 


Unjacketed  Cylinders. 


High  pressure.        I  Low  pres. 


Bach 

compound 

engine. 


24 

38 

27 
Aug. 
1874 

6 
36.73 

4.03 
26.21 
55.47 
35.44 

7.18 
50.24 
21.98 
18.88 
12.29 

2.5 

1.5 

168.65 

145.17 

22.094 

25.66 

2.455 


2.851 
2.25 

4.65 

11.65 
249.6 


2 

15.98 

25 

24 
May 
1874 

2.06 
80.28 

6.65 
24.32 
47.69 
76.33 

2.45 
91.05 
17.15 
43.51 

9.75 

0.75 

2.25 
77.06 
69.81 
23.036 
25.427 

2.559 


2.825 
2.5 

3.46 

8.44 
190.8 


Dexter 

simple 
engine. 


5 
26 

36 
Aug. 
1874 
34.5 
67.12 

3.48 
25.45 
61.06 

64.40 
79.20 
37.53 

3.0 

218.97 
201.47 
23.905 
25.98 

2.656 


6.17 
366.4 


Dallas 
simple 
engine. 


12 
30 

30 
Aug. 
1874 

31 
31.96 

3.13 
25.20 
61.51 

31.85 
46.58 
23.52 

2.5 

221.44 

197.91 

26.94 

30.14 

2.993 


3.349 


9.81 
307.5 


given  by  the  jacketed  and  unjacketed 
compound  engine  will  at  once  be  seen, 
the  unjacketed  engine  of  the  '  Bache ' 
using  as  much  steam  per  H.  P.  at  80  lbs. 
pressure  as  that  of  the  completely  jack- 
eted engine  of  the  'Rush'  at  37  lbs. 
How  much  of  this  difference  was  direct- 
ly due  to  the  jacket  in  this  case  is  not 
evident,  however.  In  Table  2  it  will  be 
seen  that  the  compound  engine  of  the 
'  Bache '  was  not  so  economical  as  that 
of  the  '  Rush,'  even  when  using  the  jack- 
et, and  Mr.  Emery  suggests  as  an  ex- 
planation, in  his  analysis  of  the  experi- 
ments, that  from  the  form  of  boiler  the 
steam  used  in  the  cylinders  of  the  '  Rush' 
might  have  been  slightly  superheated. 


The  smaller  size  of  cylinders,  lower 
speed,  and  the  fact  that  the  large  cylin- 
der only  was  jacketed  in  the  'Bache,' 
all,  probably,  tended  to  a  less  economical 
result.  Judging  from  the  evidence  of 
the  indicator  diagram,  so  far  as  it  can 
be  trusted,  this  type  of  compound  en- 
gine, having  one  cylinder  above  the 
other,  could  hardly  be  expected  in  any 
case  to  be  quite  as  economical  as  that  of 
the  '  Rush,'  having  two  cylinders  side  by 
side  with  cranks  at  right  angles.  The 
most  direct  evidence  of  the  utility  of  the 
jacket  is,  however,  given  by  the  trials  of 
the  '  Bache,'  and  here  it  will  be  found 
from  trials  Xo.  13  and  16  (Table  2)  that 
the  gain  in  the  simple  engine  by  the  use 


266 


VAN   NOSTRAND'S   ENGINEERING   MAGAZINE. 


Table  No.   2. 
Bache. 


Number  of  trial  for  reference. 
Diameter  of  cylinder  |  Swains' '.' 
Stroke  of  pistons ins. 

Date  of  trial 

Duration  of  trials hours 

Mean  steam-pressure  in  boilers. lbs 

Ratio  of  expansion 

Mean  vacuum  in  condenser. . .  .ins 
Mean  No.  of  revolutions  per  min. 
Initial  pressure  in  cylinder  above  j 

atmosphere } 

Absolute  initial  pressure  in  cylin-  \ 

der j 

Mean  effective  pressure lbs.  ■] 

Estimated  friction  pressure,  .lbs.  j 

Indicated  horse-power 

Effective  horse-power , 

Steam  per  I.  H.  P.  per  hour lbs 

Steam  per  effective  H.P.  per  hr. lbs 
Coal  per  I.  H.  P.  f  Calculated  "] 

per  hour  ...  I  for  evapora-  j 
Coal  per  effec— |  tionof  9  lbs.  J- lbs, 

tive  H.P.  per  |  water  per  lb.  | 

hour [  of  fuel J  lbs 

Effective    capacity  of    cylinder,  j 

cubic  ft.  per  I.  H.  P.  per  min. .  ( 
Velocity  of  piston  per  minute 


Compound  Jacketed. 


15.98 

25 

24 
May  12, 

1874 

1.983 
80.12 

5.732 
26.56 
56.34 
75.41 

8.66 
90.30 
23.55 
42.93 
15.88 

0.75 

2.25 
110.51 
102.06 
20.3648 
21.9989 


2.263 

2.444 
2.8 
6.9 
225 


15.98 
25 
24 
May  14, 
1874 
7.066 
79.96 
5.707 
26.11 
55.29 
H.  P.  75.32 
L.  P.    8.96 
H.  P.  90.04 
L.  P.  23.68 
H.  P.  45.37 
L.  P.  13.96 
H.  P.    0.75 
L.  P.    2.25 
106.028 
97.7 
21.9661 
23.8385 


2.441 

2.649. 
H.  P.  2.9 
L.  P.  7.1 

9,9,9, 


9 

15.98 
25 

24 
May  15, 

1874 

15.233 

79.77 

5.097 
24.39 
53.62 
74.47 

7.52 
88.78 
22.83 
43.06 
14.908 

0.75 

2.25 

102.263 

94.2 

22.3798 

24.287 


2.487 

2.699 
2.9 

7.1 
214 


Simple 
not 
Jack- 
eted. 


13 

25 

24 

May  18. 
1874 

2.05 
78.11 

5.32 
24.22 
47!  07 

72.75 
87.39 
32.328 

2.25 

89.1 
82.9 
26.247 
28.21 


2.917 

3.134 

7  9, 


Simple 
Jack- 
eted. 


16 


24 

May  18. 
1874 

2.116 
79.5 

5.11 
25.52 
53.84 

76.1 

90.74 

36.94 

2.25 

116 
109.37 
23.154 
24.56 


2.573 

2.729 

6.3 

215 


Com- 
pound 
not 
Jacketed 


3 

15.98 

25 

24 

May  14, 

1874 

2.133 
80.31 

5.634 
24.656 
49.265 
73.00 

3.9 
87.72 
18.62 
45.137 
11.2756 

0.75 

2.25 
85.81 
78.447 
23.21 
25.3887 


2.579 

2.821 
3.0199 
7.811 
197 


of  the  jacket  amounted  to  llf  per  cent., 
the  gain  in  the  compound  engine  not 
being  so  much  as  this  in  the  trials,  the 
results  of  which  are  given  in  Table  2. 
But  a  comparison  of  other  trials  of  the 
same  compound  engine  (trials  Nos.  2  and 
6)  shows  the  same  gain  as  in  the  simple 
engine. 

That  increased  economy  is  obtained  by 
the  use  of  steam  of  higher  pressure  in 
the  simple  engine  is  obvious,  and  the 
utility  of  the  jacket,  superheating,  and 
high  speed,  as  means  of  preventing  loss 
from  condensation,  is  also  evident.  The 
question,  then,  is,  first,  to  which  of  the 
rival  types  of  engine  are  these  means  of 
preventing  waste  most  applicable  in 
practice,  and  second,  whether  the  com- 
pound engine  when  used  under  the  con- 
ditions which  experience  has  shown  to 
be  necessary  for  its  satisfactory  working 


is  likely  to-  be  superior  in  economy  at 
present  pressures  to  the  simple  engine 
designed  in  accordance  with  the  lessons 
which  the  limited  experience  with  it  have 
taught. 

At  pressure  of  60  lbs.  to  80  lbs.  per 
square  inch  experience  has  shown  that 
the  siTperheater  cannot  be  used  with  any 
degree  of  safety  for  the  compound  en- 
gine on  account  of  the  scoring  of  the 
cylinders  and  valve  faces  due  to  the  high 
temperature  and  dryness  of  the  steam. 
In  the  simple  engine  the  lower  mean 
temperature  of  the  cylinder,  as  compared 
with  the  high  pressure  cylinder  of  the 
compound  engine,  would,  enable  the 
superheater  to  be  used  with  somewhat 
greater  safety,  but  the  valve  faces  would 
suffer  in  the  same  way  in  both  cases,  and, 
so  far  as  we  are  aware,  the  superheater 
has  not  been  used  in  any  case  with  the 


THE   MARINE   ENGINE   OF   TO-DAY. 


267 


high  pressure  simple  expansive  engine  at' 
sea.  With  boilers  having  sufficient 
steam  room  to  insure  approximately  dry 
saturated  steam  being  supplied  to  the 
engine,  it  appears  to  be  decidedly  better 
to  use  the  jacket  in  preference  to  the 
superheater  in  either  type  of  engine. 
Here  we  find  that  in  the  compound  en- 
gine with  the  high  temperature  main- 
tained in  the  high  pressure  cylinder  the 
use  of  the  jacket  on  this  cylinder  has  so 
frequently  led  to  rapid  wear,  that  in  the 
practice  of  many  engineers  it  has  been 
abandoned  on  this  account,  and  its  use, 
where  fitted,  has  been  largely  abandoned 
at  sea.  In  some  of  the  most  successful 
compound  engines  the  jacket  on  the  low 
pressure  cylinder  has  also  been  dispensed 
with,  not,  however,  in  this  case  on  ac- 
count of  wear,  but  for  the  sake  of  sim- 
plicity, it  being  considered  that  any  gain 
in  economy  which  might  be  due  to  the 
jacket  is  not  sufficient  to  counterbalance 
the  additional  cost  and  complication  in- 
volved in  the  construction  of  an  already 
sufficiently  complex  engine.  It  may  be 
noted  also  that  some  of  the  experiments 
with  the  '  Bache  '  appear  to  bear  out  the 
supposition  that  with  the  steam  but 
slightly  expanded  in  each  cylinder  the 
use  of  the  low  pressure  cylinder  jacket 
is  not  attended  by  any  marked  advant- 
age in  engines  of  this  type. 

With  the  greater  range  of  tempera- 
ture of  the  cylinder  of  the  simple  engine, 
the  effect  of  the  jacket  in  inducing  rapid 
wear  could  not  be  expected  to  be  so  great 
as  in  the  high  pressure  cylinder  of  the 
compound  engine,  and  there  is  nothing 
to  show  that  any  ill  effects  traceable  to 
its  use  have  been  found  at  sea. 

_  So  little  is  known  as  to  the  value  of 
high  speed  in  preventing  liquefaction  in 
jacketed  cylinders,  that  it  is  impossible 
to  speak  with  any  degree  of  accuracy 
with  regard  to  it.  The  loss  of  pressure 
which  takes  place  in  the  steam  pipes  and 
passages  of  high  speed  engines,  and  the 
importance  of  providing  large  passages, 
are,  however,  familiar  to  all  engineers  of 
experience,  and  there  cannot  be  any  doubt 
that  the  loss  invariably  shown  in  the 
combined  diagrams  of  compound  en- 
gines is  due  in  a  great  measure  to  the  re- 
sistance of  the  intermediate  passages 
between  the  cylinders.  It  may  safely 
be  concluded,  therefore,  that  any  increas- 
ed economy  due  to  high  speed  is  coun- 


terbalanced in  a  measure  in  the  com- 
pound engine  by  increased  loss  between 
the  cylinders. 

So  far  as  economy  in  actual  working 
is  Concerned,  it  appears,  therefore,  that 
superheating  or  drying,  wherever  it  can 
safely  be  resorted  to,  is  quite  as  capable 
of  application  to  the  simple  engine  as 
to  the  compound  ;  that  the  jacket  can 
be  used  on  the  simple  engine  and  on  the 
low  pressure  cylinder  of  the  compound 
engine,  but  that  its  use  on  the  high  pres- 
sure cylinder  is  objectionable,  and  that 
while  increased  economy  may  be  ex- 
pected from  increased  speed  in  both  en- 
gines (and  certainly  so  in  the  case  of  un- 
jacketed  cylinders),  high  speed  is  accom- 
panied by  an  increase  of  the  loss  between 
the  cylinders  of  the  compound  engine, 
the  loss  varying  with  the  nature  of  the 
passages  according  to  the  form  of  en- 
gine. 

The  most  important  lesson  definitely 
taught  by  the  American  experiments  is 
that  which  we  have  already  indicated — 
namely,  that  expansion  cannot  be  car- 
ried in  jacketed  cylinders  with  increased 
economy  to  so  great  an  extent  as  has 
been  supposed.  In  the  simple  engines 
tried,  no  provision  against  loss  from  the 
clearance  spaces  by  cushioning  in  the 
exhaust  was  made,  and  the  maximum  effi- 
ciency of  the  steam  was  therefore  reach- 
ed at  a  lower  grade  of  expansion  than 
would  have  been  the  case  had  cushioning 
been  provided  for.  The  lowest  consump- 
tion registered  for  the  jacketed  com- 
pound engine  of  the  'Bache'  was  obtain- 
ed on  the  trial  No.  1  (see  Table  2),  at 
the  ratio  of  expansion  5. 74,  while  in  the 
simple  jacketed  engine  the  maximum 
efficiency  appears  to  have  been  reached 
at  the  ratio  5.11  (trial  No.  16,  Table  2). 
As  will  be  seen  next  page,  the  weight  of 
steam  used  rapidly  increased  at  the 
higher  expansion  in  both  types  of  en- 
gine, the  loss  being  greatest  in  the 
simple  engine  and  the  unjacketed  com- 
pound engine. 

Referring  to  the  diagrams  from  the 
'  Bache,'  Fig.  3,  it  will  be  seen  that  the 
simple  engine  was  worked  at  a  disad- 
vantage in  the  absence  of  cushioning, 
and  this  must  necessarily  have  affected 
its  performance  to  a  considerable  extent 
at  the  higher  expansion.  Taking  the 
performances  of  the  engines  of  both 
types  as  a  whole,  however,  the  soundness 


26S 


VAX  nostrand's  engineering  magazine. 


BACHE. 


Compound. 

Not  Jacketed. 

Jacketed. 

Ratio  of  expansion 

Weight  of  steam  per  ( 
effective    horse  -  < 
power lbs.  / 

8.57 
26.23 

12.62 
29.99 

6.658 
25.42? 

9.146 
26.285 

9.19 

22.81 

16.85 
28.698 

Fig.  3.—'  BACHE.'     Simple  Engine  using  Steam  Jacket. 
Scale  of  indicator,  60  lbs.  per  inch. 


of  the  conclusion  arrived  at  by  Mr. 
Emery,  the  designer  of  the  engines  of 
the  'Rush,'  that  a  greater  ratio  of  ex- 
pansion than  from  4  to  5.3  at  pressures 
of  from  60  lbs.  to  80  lbs.  is  unnecessary, 
appears  to  be  evident.  In  long-stroke, 
■well-jacketed  engines  in  which  the  losses 
from  the  clearances  are  reduced,  either 
by  cushioning  or  by  reducing  the  clear- 
ances to  a  minimum,  as  in  the  Corliss  sys- 
tem, expansion  with  saturated  steam  can 
undoubtedly  be  carried  to  a  greater  ex- 
tent than  this  with  a  positive  gain  in 
economy,  and  in  drawing  conclusions 
from  these  trials  the  small  size  of  the 
engines  must  also  be  borne  in  mind. 
Comparing,  however,  their  performance 
with  that  of  the  much  larger  Chatham 
engines,  and  with  the  results  given  for, 
the  six  hours'  runs,  it  is  evident  that  the 
American  engines  were  very  economical, 
the  result  given  by  the  engines  of  the 
'Rush,'  with  a  ratio  of  expansion  of  6.21 
only,  being  remarkably  good.  There 
cannot  be  any  doubt  that  the  economy 
shown  here  was  due  in  a  great  measure 
to  the  fact  that  expansion  had  not  been 
carried  too  'far. 

In  the  commercial  marine  it  is  to  the 
ships  of  the  mail  service  that  the  simple 
engine  is  most  applicable.  It  is  here 
that  competition  in  speed  of  ship  is 
keenest,  that  the  danger  of  disablement 


of  the  machinery  is  most  to  be  dreaded, 
and  it  is  also  here  that  saving  of  space 
is  most  important,  and  that  intelligent 
handling  of  the  machinery  can  be  de- 
pended upon.  Of  the  most  successful 
of  the  great  lines  engaged  in  the  most 
important  and  most  rapid  steam-ship 
traffic  in  the  world,  that  across  the  At- 
lantic, the  ships  of  the  White  Star  Line 
may  fairly  be  taken  as  foremost  in  point 
of  speed.  The  builders  of  these  ships, 
Messrs.  Harlan d  &  Wolff,  of  Belfast, 
have  taken  the  lead  in  the  construction 
of  the  long  ships  specially  fitted  for 
this  traffic,  and  in  the  choice  of  a  com- 
pound engine  they  appear,  as  in  other 
matters  connected  with  their  vessels,  to 
have  exercised  a  sound  judgment.  The 
compound  engines  of  the  ships  of  the 
White  Star  Line,  as  most  of  our  engin- 
eering readers  will  be  aware,  are  of  the 
vertical  inverted  cylinder  type,  having 
two  cranks  at  right  angles  and  four 
cylinders,  the  high  pressure  cylinders 
being  placed  above  the  low  pressure 
ones  with  the  pistons  connected  to  one 
rod.  Although  probably  not  quite  so 
economical  as  the  type  of  compound  en- 
gine with  cylinders  side  by  side,  this 
form  of  the  compound  engine  possesses 
for  the  service  to  which  it  is  applied  in 
the  White  Star  vessels  many  prominent 
advantages.     The  continually  increasing 


THE   MAEINE   ENGINE   OF   TO-DAY. 


269 


power  applied  to  the  Transatlantic  steam- 
ers has  led  to  a  corresponding  increase 
in  the  dimensions  of  the  cylinders,  cul- 
minating apparently  in  the  engines  of 
the  '  City  of  Chester,'  fitted  by  Messrs. 
Caird  with  two  cylinders  of  72  and  120 
in.  diameter.  The  stroke  of  these  en- 
gines is  5  ft.  6  in.,  the  cylinders  being 
placed  side  by  side  with  the  cranks  at 
right  angles.  The  difficulties  to  which 
the  great  size  of  the  cylinders  of  this 
type  of  engine  have  led  are  many.  The 
difficulty  of  obtaining  sound  castings; 
the  impossibility  of  efficiently  balancing 
the  enormous  weight  of  the  low  press- 
ure piston  and  gear,  and  of  distributing 
equally,  under  all  conditions,  the  power 
transmitted  to  the  two  cranks,  has  given 
rise  to  endless  trouble  in  the  breaking  of 
pistons,  the  failure  of  crank-shafts,  and 
other  mishaps. 

In  large  steamers  of  recent  build,  in 
which  the  form  of  compound  engine 
with  high  and  low  pressure  cylinders 
side  by  side  is  adhered  to,  the  capa- 
city of   the   low  pressure   cylinder  has 


been  divided  between  two  cylinders, 
there  being  thus  three  cylinders  ranged 
fore  and  aft  in  the  ship.  With  a  com- 
pound engine  the  space  taken  up  in  this 
way  is  objectionably  large  as  compared 
with  that  required  for  engines  of  the 
type  in  use  in  the  White  Star  Line.  In 
these  engines  also  the  effort  transmit  ted 
to  each  crank  is  approximately  equal 
under  all  circumstances  as  to  variation 
of  power,  while  as  compared  to  the  large 
engines  of  the  '  City  of  Chester '  type, 
for  which  the  three-cylinder  compound 
engine  is  being  substituted,  they  un- 
doubtedly possess  great  advantages  in 
point  of  facility  of  handling  and  in  man- 
ageable dimensions  of  cylinders.  Tak- 
ing success  in  the  hardest  service  to 
which  a  steam  engine  can  well  be  put — 
that  of  driving  a  steamer  at  full  speed, 
in  all  weathers,  across  the  Atlantic — as 
a  test  of  efficiency,  we  do  not  think  that 
a  better  selection  could  be  made  for 
comparison  with  a  simple  engine  than 
one  of  the  compound  engines  of  the 
White  Star  Line. 


Designation  of  Engine. 


B. 


C.  (Britannic) 


Length  of  stroke feet. 

No.  of  revolutions  per  minute feet. 

Initial  pressure  taken  at lbs . 

No.  of  cylinders lbs. 

Diameter  of  each  cylinder.... ins. 

Velocity  of  piston  per  minute feet. 

Distance  of  cranks  apart deg. 

Maximum  turning  force  on  crank-pin  (one  engine). . .  .tons. 

Mean  •  do.  ...  .tons, 
•■(a)  Maximum  twisting  moment  on  crank-shaft  (engines  com- 
bined)  foot-tons. 

(b)  Mean  do.  •  foot-tons . 

Minimum  do.  foot-tons . 


Volume  swept  by  piston  per  I.  H.  P.  per  minute c.  ft. 

Total  capacity   of   cylinders,  showing  the  relative  space 
which  they  actually  occupy  in  the  ship c.  ft. 


7 

60 
60 


62f 

840 
90 

71.8 
28.29 

311.8 

198 

105 

1.57 

7.22 

301 


5 

GO 
60 


60f 

600 
120 

67.2 
26.41 

248 

198 

170.5 

1.25 

7.22 

301 


o 

58 
60 

1  2  L.  P. 

\  H.  P.  43 
1  L.  P.  83 
580 
90 
75.7 
39.62 

269 

205 
172.5 

1.31 

(  H.  P.  2.9 
]L.  P.  S.7 
501 


The  engines  are  by  various  makers, 
but,  taking  the  dimensions  given  for  the 
engines  of  the  'Britannic,'  recently  en- 
gined  by  Messrs.  Maudslay,  we  will  en- 
deavor to  give  an  idea  of  the  probable 
gain  which  might  be  expected  to  result 
from  the  adoption  of  simple  engines  in 
the  Transatlantic  steamers.     In  column 


C,  in  the  table  above,  are  given  results 
calculated  for  the  engines  of  the  *  Brit- 
annic,' well  known  as  being  fitted  with 
Mr.  Hal-land's  lifting  screw.  At  about 
58  revolutions  per  minute  the  engines 
develop  their  highest  power  of  5.000 
horses,  the  volume  swept  by  the  pistons 
per  H.  P.  per  minute  being  then  about 


270 


VAN  NOSTRAND'S   ENGINEERING   MAGAZINE. 


30  per  cent,  less  than  in  the  compound 
engines  of  the  Royal  Navy,  particulars 
of  which,  when  working  at  full  power, 
have  already  been  given.  It  will  thus 
be  understood  that  in  selecting  the  en- 
gines of  the  'Britannic,'  we  have  taken 
a  case  in  which  one  objectionable  feature 
of  the  compound  engine,  that  of  a  large 
cylinder  capacity  in  proportion  to  the 
power  developed,  has  been  reduced  to  a 
minimum.  We  are  not  aware  of  any 
compound  engine  of  large  size  in  which 
the  horse  power  has  been  produced  with 
a  less  capacity  of  cylinder  than  in  this 
ship. 

In  determining  the  capacity  of  cylin- 
der for  marine  engines,  the  reduction  of 


the  pressure  as  the  boilers  become  worn 
has  to  be  kept  in  view,  but  for  all  prac- 
tical purposes  in  the  case  we  propose  to 
consider  this  may  be  supposed  to  be  pro- 
vided for  by  basing  the  capacity  of 
cylinder  on  the  maximum  horse  power 
required,  and  on  the  maximum  ratio  of 
expansion  which  the  recent  experiments 
indicate  as  desirable. 

Taking  the  ratio  of  expansion  at  5,  the 
clearances  at  one-fifteenth  of  the  effect- 
ive capacity,  and  making  an  allowance 
for  cushioning,  the  volume  swept  by  the 
piston  per  horse  power  per  minute  in  the 
proposed  simple  engine  would  be  7.22 
cubic  feet,  the  indicator  diagram  being 
of  the  form  shown  in  Fia\  4.     Particu- 


Fio.  4. 


Saturated  steam  in  jacketed  cylinder  pr.  r»  =  const. 


lars  of  the  engine  are  given  in  column  A 
of  the  table.  At  60  revolutions  per 
minute  the  total  effective  cylinder  capa- 
city would  then  be  300  cubic  feet  in  the 
simple  engine  for  5,000  H.  P.,  against 
500  cubic  ft.  in  the  compound,  developing 
the  same  power  at  58  revolutions.  It 
will  be  seen  that  there  is  a  gain  here  of 
40  per  cent,  in  capacity  of  cylinder  as 
compared  with  the  compound  engine  of 
minimum  capacity. 

In  engine  A  this  cylinder  capacity  has 
been  divided  between  two  cylinders  of 
1  feet  stroke,  an  arrangement  which 
would  give  the  greatest  advantages  in 
point  of  simplicity.  A  gain  in  length  of 
engine  room  (about  4  feet)  would  be  ob- 
tained here,  and  presuming  no  back 
guides  to  be  fitted,  there  would  also  be 
a   considerable    gain    in    height.      The 


stroke  would  be  eighteen  inches  longer 
than  that  of  the  engines  of  the  '  City  of 
Chester,'  the  diameter  of  cylinder,  how- 
ever, being  little  more  than  half  that  of 
the  low  pressure  cylinder  of  this  ship. 
Keeping  this  in  view,  and  also  the  fact 
that  the  speed  is  obtained  with  only  2 
revolutions  per  minute  more  than  that 
of  the  engines  of  the  '  Britannic,'  which 
have  two  pistons,  one  of  83  and  one  of 
48  inches,  acting  on  one  crank,  it  will  be 
seen  that,  as  compared  with  English 
practice,  the  speed  of  840  feet  per  minute 
is  not  alarming,  while  as  compared  with 
the  piston  speed  of  the  long  stroke  Am- 
erican engines  the  rates  is  moderate.  It 
must  also  be  borne  in  mind  that  we  are 
dealing  in  all  cases  with  the  maximum 
figures. 

Considerable  importance  is  frequently 


THE   MARINE   ENGINE   OF   TO-DAY. 


271 


attached  to  the  fact  that  the  variation  in 
the  turning  force  due  to  the  variation  of 
the  steam  pressure  during  expansion  is 
not  so  great  in  the  compound  as  in  the 
simple  engine,  although  in  view  of  the 
results  given  by  the  single  crank  engines 
of  Messrs.  Holt's  steamers  and  the  Amer- 
ican single  cylinder  engines,  it  is   not 


clear  upon  what  grounds  objection-  on 
this  score  can  be  seriously  urged.  The 
difference  between  the  two  engines  we 
are  comparing  in  this  respect  will  be 
best  understood  from  a  graphic  illustra- 
tion. 

In  Figs.  5  and  6  is  shown  the  turning 
effort  due  to  the  pressure  of  the  steam 


Simple  Engine  A.     2  Cylinders.     With  Cranks  at  Right  Angles. 

Fig.  5. 

Turning  forces  combined  for  a  complete  revolution. 


Turning  forces  on  each  crank-pin  shown  independently. 


a  and  b  forward  strokes.        a'  and  b'  return  strokes. 


upon  the  crank  pins  of  engine  A  for  a 
complete  revolution.  In  the  lower  dia- 
gram, Fig.  6,  the  turning  effort  on  each 
crank  is  shown  independently,  and  the 
pressure  in  tons  upon  the  piston  during 


a  stroke  is  also  shown.  This  diagram  is 
arranged  for  the  sake  of  clearances  for 
an  engine  having  the  two  cylinders 
placed  at  right  angles,  the  effect  being- 
the  same  as  if  the  cranks  were  placed  at 


272 


VAN   NOSTRAND'S   ENGINEERING   MAGAZINE. 


right  angles.  For  comparison  diagrams 
arranged  in  the  same  way  for  engine  C 
are  shown  in  Fiffs.  1  and  8.     The  mean 


twisting  moment  on  the  crank  shaft  in 
the  two  engines  is  nearly  the  same, 
there  being  only  the  slight  difference  due 


Compound  Engine  C.     4  Cylinders.     With  2  Cranks  at  Right  Angles. 

Fig.  7. 
Turning  forces  combined  for  a  complete  revolution. 


100 
90 

'80 
70 

CO 
50 
4-OH 
30 
20 
10 


Elfij, 


S 


Turning  forces  on  each  Crank-pin  shown  independently. 


a  and  b  forward  strokes. 


a'  and  V  forward  strokes. 


to  the  difference  of  2  per  minute  in  the 
revolutions.  On  referring  to  the  dia- 
grams and  table,  however,  it  will  be  seen 
that  the  mean  turning  effort  on  the  crank 
pin  is  only  28  tons  in  engine  A  against 
40  tons  in  engine  C.  The  bete  noire  of 
the  engineer  at  sea,  a  hot  bearing,  is  due, 
as  a  rule,  when  not  occasioned  by  the 
use  of  improper  materials  or  bad  con- 
struction, simply  to  excess  of  pressure 
at  the  surfaces  in  contact.  There  is 
ample  evidence  in  practice  that  bearings 


can  be  run  at  almost  any  speed  without 
danger  of  heating  if  the  pressure  upon 
them  be  not  too  great.  The  friction  of 
sliding  surfaces,  as  a  matter  of  fact,  ap- 
pears to  decrease  as  the  velocity  increas- 
es.* "  Friction  diagrams "  taken  from 
marine  engines  at  different  speeds  show 
an   increase  in  the   j>ower   required   to 

*  This  was  shown  to  be  the  case  in  a  number  of  ex- 
periments described  in  a  paper  by  M.  H.  Bochet,  an  ab- 
stract of  which  appeared  in  the  Comptes  Eendus  of  the 
French  Academy  of  Sciences  for  185S.  See  Professor 
Rankine's  Machinery  and  Millwork,  p.  349.. 


THE   MAKINE   ENGINE   OF  TO-DAY. 


273 


•drive  the  engine  at  the  higher  speeds, 
but  the  increased  resistance  shown  is,  no 
doubt,  chiefly  due  to  the  increased  power 
required  to  drive  the  pumps  at  the  high- 
er velocity. 

An  increase  of  the  length  of  stroke 
not  only  reduces  the  turning  effort  on 
the  crank  pin,  but  it  also  reduces  the  di- 
rect thrust  on  the  shaft  bearings,  and 
for  engines  of  the  same  type  the  diminu- 
tion of  the  loss  from  friction  and  tend- 
ency to  heat  the  bearings  may  be  taken 
as  directly  proportional  to  the  increase 
in  the  length  of  stroke.  It  will  be  seen, 
however,  from  the  diagrams,  that,  al- 
though the  mean  turning  force  is  much 
less  in  engine  A  than  in  engine  C,  there 
is  a  greater  irregularity  in  the  force 
transmitted  to  the  crank,  and  it  might, 
therefore,  be  supposed  that  some  loss 
from  this  cause  might  be  found  in  prac- 
tice. There  is  direct  evidence,  however, 
in  the  trials  of  the  gunboats  '  Swinger ' 
and  '  Goshawk,'  which  we  have  frequent- 
ly quoted,  that  there'  is  no  loss  of  effi- 
ciency from  this  source.  Diagrams  from 
the  '  Swinger,'  fitted  with  simple  engines, 
have  been  published  in  the  Prize  Essay 
of  the  Junior  Naval  Professional  Asso- 
ciation, and  from  them  it  is  evident  that 
the  inequality  in  the  turning  force  must 
have  been  considerably  greater  in  this 
case  than  in  engine  A.  Both  on  the 
measured  mile  trials,  when  tried  at  the 
same  draught  of  water,  and  when  the 
boats  were  run  side  by  side,  the  results 
were  slightly  in  favor  of  the  engines  of 
the  'Swinger."  The  six  hours'  run  side 
by  side  may  be  taken  as  practically  con- 
clusive on  this  point,  the  displacement 
coefficients  being  152  for  the  '  Swinger,' 
against  148  for  the  '  Goshawk.' 

The  comparison  we  have  here  made 
between  a  simple  engine  and  a  compound 
engine  of  type  C  is  the  more  interesting 
as  we  have  direct  evidence  in  the  Amer- 
ican trials  as  to  the  relative  economy  of 
the  two  forms  of  engine.  The  engine 
of  the  'Bache,'  as  already  stated,  has 
the  high  pressure  cylinder  on  the  top  of 
the  low  as  in  type  C,  and  the  trials,  par- 
ticulars of  which  are  given  in  Table  No. 
2,  show  that  there  was  a  positive  gain  in 
economy  by  using  the  low  pressure  cylin- 
der as  a  simple  engine  when  the  jacket 
was  used  as  compared  with  the  com- 
pound engine  not  using  the  jacket.  In 
comparing  the  two  types  of  engine  for 
Vol.  XIII.— No.  3—18 


absolute  economy,  it  is  evident  that 
when  the  high  pressure  cylinder  is  dis- 
pensed with  there  is  a  reduction  of  the 
friction  of  the  moving  parts  to  the  ex- 
tent due  to  this  cylinder,  and  that  there 
is  therefore  a  corresponding  increase  in 
the  power  available  for  useful  work. 
The  friction  pressure  for  each  cylinder 
was  determined  in  the  American  trials, 
and  the  two  forms  of  engine  can  there- 
fore be  compared  in  a  rational  manner 
by  taking  the  weight  of  steam  used  per 
effective,  or,  as  termed  by  the  American 
engineers,  "  net "  horse  power,  as  a 
measure  of  their  absolute  economy.  On 
referring  to  Table  2  it  will  be  seen  that 
the  short  trial  No.  1  of  the  compound 
engine  with  the  jacket  shows  a  consid- 
erable gain  by  the  use  of  the  compound 
engine,  but  the  accuracy  of  the  results 
of  this  trial  is  not  borne  out  by  the 
figures  given  for  the  seven  hours'  trial, 
No.  8,  at  the  same  ratio  of  expansion, 
which  shows  a  gain  of  only  3  per  cent, 
by  compound  expansion.  Some  gain 
would  certainly  have  resulted  from 
cushioning  in  the  simple  engine,  so  that 
practically  the  same  economy  might  have 
been  expected  from  the  two  engines  with 
the  jacket  in  use  in  both  cases,  while 
there  appears  to  be  no  room  for  doubt  as 
to  the  actual  superiority  of  the  simple 
jacketed  engine  as  compared  to  the  un- 
jacketed  compound  engine  in  the  case  of 
the  '  Bache.' 

From  the  various  particulars  we  have 
given  it  will  be  seen  that  the  perform- 
ance of  engines  is  affected  so  seriously 
by  the  initial  condition  of  the  steam 
used,  by  the  speed  of  piston  and  by  the 
proportion  and  size  of  the  cylinders,  that 
it  is  very  difficult  to  arrive  at  a  correct 
conclusion  as  to  the  real  cause  of  differ- 
ent results  being  given  by  engines  work-* 
ing  under  the  same  conditions  as  to 
boiler  pressure  and  rate  of  expansion. 
A  comparison  of  different  engines  must, 
therefore,  always  be  a  dubious  one.  In 
the  case  of  the  'Bache,'  however,  we 
have  the  same  cylinder  supplied  by  steam 
from  the  same  boiler  and  with  the  engine 
running  at  the  same  speed,  the  result 
being  that  given  above.  It  is  evident  that 
the  best  that  could  be  said  in  favor  of 
the  addition  of  the  high  pressure  cylin- 
der to  this  engine  would  be  that  it  ena- 
bled the  jacket  to  be  in  a  measure  dis- 
pensed with,  and  it  need  hardly  be  point- 


274 


VAN   NOSTRAND'S   ENGINEERING   MAGAZINE. 


ed  out  that  a  complete  cylinder,  with  all 
its  fittings,  is  rather  an  expensive  substi- 
tute for  an  independent  liner  fitted  in  a 
simple  cylinder. 

Taking  the  particulars  we  have  given 
as  a  whole,  the  result  of  the  comparison 
we  have  made  can  hardly  be  considered 
otherwise  than  as  favorable  to  engine  A, 
the  only  dubious  points  as  compared 
with  English  practice  being  the  increas- 
ed length  of  stroke  and  the  higher  speed 


of  piston.  With  the  same  capacity  of 
cylinder  as  in  engine  A,  however,  a  three 
cylinder  simple  engine  could  be  made 
which,  with  the  same  length  of  stroke 
and  speed  of  piston  as  in  engine  Ct 
would  be  decidedly  superior  to  this  en- 
gine in  regularity  and  balance  of  turn- 
ing forces.  Particulars  of  an  engine  of 
this  kind  are  given  in  column  B  of  the 
table,  and  crank  effort  diagrams  are 
given  under  (Figs.  9  and  10). 


Simple  Engine  B.     3  Cylinders.     With  Cranks  at  1 

Fig.  9. 
Turning  forces  combined  for  a  complete  revolution. 


20°. 


ale  forward  strokes. 

This  is  the  form  of  high  pressure  sim- 
ple expansive  engine,  the  use  of  which  is 
advocated  for  ships  of  war  in  the  Prize 
Essay  we  have  quoted  from,  special  pro- 
vision being  proposed  to  be  made  for 
eadily   disconnecting   the   cylinders  at 


a'  b'  c'  return  strokes. 

low  speeds,  or  when  disabled.  In  the 
more  important  ships  of  war  the  diffi- 
culty to  be  met  with  is,  that  on  extra- 
ordinary occasions,  as  when  chasing  or 
being  chased,  a  power  of  about  six  or 
seven    times    that    ordinarily    required 


SCIENTIFIC    DATA   OF   THE   MISSISSIPPI   HIVEB. 


275 


must  be  available,  and  it  is  essential  that 
sufficient  capacity  of  cylinder  be  given 
to  insure  economy  in  the  engine  itself  at 
the  highest  power.  It  is  then  that  waste 
from  forced  firing,  and  from  generally 
decreased  efficiency  of  the  boiler,  takes 
place,  the  enormous  quantity  of  coal 
expended,  and  the  comparatively  small 
quantity  which  can  be  stowed  in  the 
ship,  necessitating  the  utmost  economy 
under  these  conditions.  In  working  at 
the  lowest  powers  with  the  large  cylin- 
der capacity  thus  necessarily  provided, 
enormous  loss  from  condensation  takes 
place,  and  the  only  effective  way  out  of 
the  difficulty  is  to  disconnect  a  part  of 
the  cylinder  capacity  entirely.  The 
three  cylinder  form  of  engine,  therefore, 
presents  for  this  service  many  advant- 
ages, the  American  experiments  render- 
ing it  evident  that,  with  cylinders  fitted 
to  disconnect,  such  an  engine  would  be 
more  economical  than  a  compound  en- 
gine using  the  whole  of  the  cylinder 
capacity  (and  with  inter-dependent  cylin- 
ders this  is  necessarily  the  case)  at  low 
speeds. 

In  the  service  to  which  our  remarks 
have  been  directed,  however,  the  range 
of  power  required  under  ordinary  work- 
ing conditions  is  slight,  the  ship  being 
usually  driven  at  nearly  the  full  power 
the  engine  is  capable  of  developing,  and 
except  in  the  case  of  larger  powers 
than  that  of  the  present  steamers,  there 
appears  to  be  no  necessity  for  introduc- 
ing a  third  cylinder.  Keeping  in  view 
the  results  given  by  the  American  single 
cylinder  engines  and  the  engines  of 
Messrs.  Holt's  steamers,  it  could  hardly 
be  expected  that  any  gain  of  commercial 
value  would  be  obtained  by  substituting, 
in  the  case  we  have  considered,  a  three 
cylinder  engine  for  engine  A,  with  the 
the  object  of  gaining  greater  efficiency 
of  the  mechanism. 

We  trust  we  have  succeeded  in  placing 
prominently  before  our  readers  the  fact 
that  all  the  available  evidence  shows 
that  practically  equal  results  in  point  of 
economy  of  fuel  may  be  obtained  with 
either  type  of  engine,  when  the  same 
pressure  of  steam  is  used  under  the  con- 
ditions we  have  chosen  for  illustration. 
Let  this  be  understood,  and  the  gain  in 
space,  weight,  simplicity,  facility  of 
handling,  the  less  liability  to  total  break 
downs,  and  less  first  cost  of  the  simple 


engine  when  intelligently  designed  be 
fairly  realized,  and  shipowners  on  this 
side  of  the  Atlantic  will,  no  doubt,  give 
it  further  trial.  American  experience 
shows  that  so  far  as  wear  of  pistons  and 
cylinders  is  concerned,  jacketed  engines 
of  this  type  can  be  kept  in  perfect  order, 
while  the  experience  gained  with  the 
high  pressure  valve  gear  of  the  compound 
engine  has  enabled  engineers  to  meet 
with  confidence  the  difficulties  arising 
from  the  increased  pressure  of  the  steam 
so  far  as  it  affects  the  wear  of  the  valves. 
Difficulties  of  this  kind,  to  which,  to- 
gether with  unnecessary  large  cylinders, 
the  unsatisfactory  working  of  simple  en- 
gines on  this  side  of  the  Atlantic  may  lie 
traced,  are  now  being  met  on  the  largest 
scale  by  the  eminent  firm  of  Messrs.  John 
Penn  &  Son,  who  have  in  hand  for  ships 
of  war  two  sets  of  engines,  amounting  to 
an  aggregate  power  of  10,000  horses. 
These  are  intended  to  work  at  their  full 
power  as  simple  expansive  engines,  and 
we  have  no  doubt  that  other  firms  of 
equal  enterprise  are  prepared  to  construct 
simple  engines,  specially  fitted  for  the 
Transatlantic  traffic,  which,  there  is  every 
probability,  would  be  found  to  work 
with  greater  satisfaction  to  the  engineers 
and  shipowners  than  the  cumbrous  ma- 
chinery now  in  general  use. 


Captain  Eads  has  had  compiled  the 
following  interesting  and  scientific  data 
cencerning  the  Mississippi  River,  the 
work  at  whose  mouth  he  has  already  be- 
gun :  1.  Quantity  of  water  discharged 
by  the  river  annually,  14,8S3,360,636,8SO 
cubic  ft.  2.  Quantity  of  sediment  dis- 
charged annually,  28,188,083,892  cubicft. 
3.  Area  of  the  delta  of  the  river,  13,000 
square  miles.  4.  Depth  of  the  delta, 
1,056  ft.  5.  The  delta,  therefore,  con- 
tains 400,378,429,440,000  cubic  feet,  or 
2,720  cubic  miles.  6.  It  would  require 
for  the  formation  of  one  cubic  mile  of 
delta,  five  years  and  eighty-one  days.  7. 
For  the  formation  of  one  square  mile,  of 
the  depth  of  1,056  feet,  one  year  and 
sixteen  and  1-5  days.  8.  For  the  forma- 
tion of  the  delta,  14,268  4-5  years.  9. 
The  Valley  of  the  Mississippi  from  Cape 
Girardeau  to  the  delta,  is  estimated  to 
contain  16,000  square  miles  of  150  feet 
depth.  It,  therefore,  contains  66,9S0,160,- 
000,000  cubic  feet  or  454^  cubic  miles. 


ENGINEERING   MAGAZINE. 


ENGINEERING   ON  THE  DANUBE. 


From  "  The  Building  News. 


Eon  many  years  it  has  been  debated 
among  engineers  whether  the  natural 
obstructions  to  the  navigation  of  the 
Danube  might  not  be,  by  the  aid  of 
science,  removed.  The  obstacles  were 
two — the  one,  however,  closely  associated 
with  the  other — a  set  of  dangerous  rocks, 
and  a  series  of  equally  dangerious  rap- 
Ids.  A  project  had  long  been  matured, 
by  a  company  of  American  speculators, 
to  clear  this  important  channel  ;  but 
political  considerations  intervened,  and 
a  great  European  water-way  was  left  in 
something  like  the  condition  of  a  half- 
ohoked  canal.  The  reason  was  that,  as 
visual,  rival  schemes  were  contemplated, 
as  in  the  case  of  the  Tiber,  to  which  we 
lately  referred.  There  was,  for  instance, 
the  idea  of  a  canal,  to  run  parallel  with 
the  stream  ;  there  was  the  proposal  to 
lolast  away  a  shelf  of  rocks  forming  the 
Orsova  rapids  ;  and  there  was  also  the 
.-suggestion  of  blowing  up  the  Iron  Gates, 
or  granite  bar,  crossing 'the  entire  breadth 
of  the  river,  and  checking  even  the  light 
Austrian  Steamboats  on  their  course. 
Here  the  water,  as  a  rule,  though  its 
flow  is  wide,  has  a  depth  of  no  more  than 
twenty  inches,  and  the  inconvenience  to 
traffic  of  all  kinds  is  enormous.  The 
work,  however,  although  decided  upon  so 
long  ago  as  1871,  remains  to  be  carried 
out  in  its  entirety,  when  the  celebrated 
Jron  Gates  will  be  no  more,  and  Trajan's 
■towing-path  a  mere  memorial  of  anti- 
quity. Now,  the  Danube,  through  its 
position  in  Europe,  the  extent  of  its 
available  course,  the  importance  and 
"wealth  of  the  territories  traversed  by  it, 
should  rank  as  the  first  river  of  Europe, 
a  great  facility  for  inland  communication, 
and  a  grand  link  between  the  land  and 
sea. 

With  the  public  influences  which 
have  hitherto  established  a  sort  of  block- 
ade upon  its  waters  this  present  writing 
lias  nothing  to  do,  the  question  for  us 
being  whether  a  generation  that  has 
canalized  the  Isthmus  of  Suez,  and  tun- 
nelled the  Alps,  should  allow  the  splen- 
did border  stream,  as  it  may  almost  be 
termed,  of  the  Continent,  to  be  trammeled 


by  a  complication  of  geological  embar- 
rassments.    It  was   thus,  in  an   almost 
similar  degree,  at  one  period,  with  the 
Rhine.     The   Rhine   had,  naturally,   no 
navigable   outlets  ;  it  had    no  mouths  ; 
its   only   practicable  way  to  the   ocean 
was  stopped  by  a  bar,    and  it   took   a 
quintuple  treaty  to  get  rid  of  this  ob- 
struction. '  A   convention   of   the   same 
character   set   the  Dunube   free   to   the 
flags  of  all  nations  ;  but  it  did  not  blow 
up    the   rocks,    or    abolish    the    rapids. 
The  Danube  is,  perhaps,  regarded  from 
a  practical  point  of  view,  the  most  re- 
markable river  in  Europe.    After  cutting 
through    the    chalk     mountains    which 
stretch  from  north  to  south  between  the 
Balkan  and  Carpathian  ranges,  in  a  nar- 
row channel  where  the  waters  boil,  as  if 
with   impatience    to    escape,    it   widens 
like  the  Nile,  intersects  a  valley  nearly  a 
hundred  miles  in  breadth,  passes  under 
precipices  on  one  side,  and  along  marsh 
lands  on  the  other,  branches  in  every  di- 
rection, forms  clusters  of  islets,  and  then 
rebels   against   the    Iron   Gates.      Two 
commissions   of    French  and   American 
engineers  have  reported  that  these  are 
the  main  impediments  to  the  utilizing  of 
the  river,  which  at  its  embouchure,  gives 
soundings  of  fifty  fathoms,  on  a  bottom 
of  shell  and  sand — a  fact  clearly  prov- 
ing that  the  Gates  lock  up,  or  largely 
obstruct,  the  possible  trade  of  the  inte- 
rior.   In  spite  of  all  this,  not  many  years 
ago  the   accumulations  at  the  entrances 
of  the  Danube    absolutely  closed  them 
against  vessels  of  even  moderate  tonnage ; 
the  mud   and  silt  rose  yard   by  yard  in 
height ;  a  few  cyclopean  rakes  were  idly 
employed  in  the  attempt  to  remove  them, 
and  the  Russian  Government  ordered  a 
dredging  machine,  which,  after  .  having 
been  worked  for  a  very  short  time,  was 
declared  to  be  out  of  order,  and  has  been 
laid  up  in  ordinary  ever  since.     But  the 
scour  of  the  stream,  supposing  the  bar- 
riers   farther    up    the  valley   removed, 
would  have  effected  more  than  all  the 
dredging    engines    ever    manufactured. 
And  what  is  the  interest  of  the  world  in 
this  grand  artery  of  intercommunication, 


ENGINEERING   ON   THE   DANUBE. 


277 


concerning  which  the  engineers   are  so 
busy  just  now  ?     The  Danube,  which  it 
is  proposed,  to  unite  by  a  canal  with  the 
Adriatic — although  the  proposed  cost  of 
the  schemes  has  frightened  even  its  pro- 
jectors— begins  its  navigation   at  Ulm, 
an     emporium     of     merchandise     from 
France,  Germany,  and  the  banks  of  the 
Rhine.     In  its  course  it  passes  through 
the  territories  of  four  States,  and  receives 
the   tribute  of    a  hundred    and   twenty 
rivers.     But  the  Iron  Gates — the  Porta 
Ferrea  of  the  Romans — close  the  upper 
valley  against  all  craft  except  the  class 
of  barges  ;  and  even  these,  when  heavily 
laden,  often  find  themselves  stuck,  most 
unwillingly,  in  rocky  labyrinths,    or  on 
heaps  of  sand,  even  supposing  them  to 
have  passed  the  thirty  miles  of  broken 
rapid,  which,  it  is  now  believed,  may  be 
blasted  into  a  smoother  bed.     That  such 
labor  was,  at  one  time,  regarded  as  being 
among  the    Quixotisms   of    speculative 
science  is  shown  by  the  gigantic  expen- 
diture and  toil  bestowed  upon  tunneling 
a  carriage-way  through  the  body  of  per- 
pendicular rocks  here   overhanging  the 
river — a  work   effected   by   gunpowder 
throughout,  and  quite  equal  in  grandeur 
to  the   artificial   road   of   the    Simplon. 
But  all  modern  enterprise,  as  yet,  has 
failed  to  emulate  the  mighty  monument 
of  the  Romans  in  that   historic  valley. 
Those  Builders  did  not  excavate  ;  their 
tools  and  other  appliances  did  not  serve 
them  adequately.     They,  therefore,  con- 
structed a  covered  gallery  of  wood  along 
the  face  of  the  precipices,  supported  by 
strong    buttresses,   projecting   over   the 
stream,  at  the  height  of  about  six  feet 
above  its  greatest  altitude,  and  extending 
for  a  distance  of  nearly  fifty  miles.     The 
holes  for  the  reception  of  the  horizontal 
buttresses  on  which  the  platform  rested 
are    as  perfect  now — as  we   have   seen 
them — as  they  may  be  imagined  to  have 
been  sixteen  centuries  ago  ;  and,  although 
the  continuous  line  is  occasionally  inter- 
rupted by  the  dense  masses  of  brushwood 
which  have  sprung  up  with  the  lapse  of 
time,    their   course   may    be     distinctly 
traced  along  the  base  of  the  mountains. 
In  many  places,  indeed,  a  double  set  of 
holes  may  be  observed,  as  if  the  lower 
ones   had   been    constructed  to   receive 
brackets  to  aid  in  supporting  the   but- 
tresses   above.      All   antiquity  notwith- 
standing, however,  the  principle  impor- 


tance in  connection  with  every  subject 
of  the  kind  belongs  to  the  present  day  ; 
but  it  is  especially  interesting  to  note 
how,  while  awaiting  the  final  triumph  oi 
engineering  enterpi-ise  over  the  difficul- 
ties of  the  Danube,  they  have  been  less- 
ened and  mitigated  for  the  sake  of  tran- 
sit and  commerce.     The   Austrian  Dan- 
ubian      Steam     Navigation    Company, 
founded   about    forty    years    ago,    and 
building  and  buying  in  the  valley  itself„ 
though  getting  much  of  its  machinery 
from  Switzerland,  works  over  three  thou- 
sand miles  of  water,  and  keep  five  power- 
ful dredging-machines,  strangely  enough,, 
in  constant  employment.    The  operations 
forthwith  to  be  undertaken  will  relieve   ■ 
them  from  this   neccesity.     They   com- 
prise  a   blasting  and   an   embankment, 
and  will  be  watched  with  curiosity  from 
every  quarter  of  Europe.     It  is  believed 
that  the  cost  of  the  works  will  be  con- 
siderable less  than  that  at  which  it  was 
estimated  by  the  American  projectors;, 
but  they,  it   should  be  remembered,   in- 
cluded in  their  design   a  lateral  canal, 
with  three  approaches  to  the  sea.     The 
Commission    of    Austrian    and    Turkish 
engineers  who,  during  the  last  two  years, 
have  been  studying  the  problem  on  the 
spot,  has   not,   indeed,  reported   in  the 
most  favorable  terms  ;  but  their  opinion, 
nevertheless,  sanctions  the  idea,  and  sug- 
gests a  plan  for  defraying  the   expense 
of  developing  it.     That  the  Iron  Gates 
are  still  practically  shut  is  a  reproach  to 
the  civilization   of    Europe  ;  that    they~ 
should  remain  so  indefinitely  seems  im- 
possible.    England,  at  a  far  greater  cost 
than  is  now  threatened,  cleared  the  im- 
portant Paumban  Pass,  now  the   great 
water   highway  between  Ceylon  and  the 
mainland    of   India,    and    sounded    and 
measured  every  depth  and  shallow  of  the 
Red  Sea.     It  would  appear,  then,  to  be 
a  paradox  now   that   a   splendid   river, 
such  as  the  Danube  is,  should  be  closed 
against  the  higher  necessities  of  trade 
and  passage  by  a  few  bars  of  rock,  and 
a  few  miles  of   rapids,  which  engineers 
declare  may  be  blown  out  of  the  way 
withoitt  difficulty  or  danger.     The  Dan- 
ube is  to  Europe  what  the  ^Mississippi  is- 
to  America — "  the  father  of  waters."  and 
only  requires  a  clear  channel  to  become 
next  in  importance  to  a  sea.    Mechanical 
objections  there  are  none  to  its  perfect 
physical  liberation. 


278 


VAN   NOSTRAND'S   ENGINEERING   MAGAZINE. 


ROTARY   PUDDLING. 

From  "Engineering." 


If  we  may  judge  from  the  interest 
manifested  in  the  remarks  made  by  Mr. 
Menelaus  in  his  inaugural  address  to  the 
members  of  the  Iron  and  Steel  Institute, 
and  from  the  reports  which  reach  us 
from  the  various  ironmaking  districts, 
the  problem  of  mechanical  puddling  is 
now  being  regarded  as  of  ever-increasing 
importance.  Our  own  views  on  this 
subject  are  well  known  to  our  readers. 
We  regard  the  present  system  of  hand- 
puddling  as  a  blot  upon  the  progress 
which  has  been  made  in  our  iron  manu-  \ 
f  acture,  and  as  entirely  inconsistent  with 
the  growth  of  our  metallurgical  pro- 
cesses. As  we  have  pointed  out  on 
more  than  one  occasion,  the  whole  ten- 
dency of  the  modern  development  of  our 
iron  manufacture  is  towards  the  treat- 
ment of  the  material  in  large  quantities, 
and  with  the  aid  of  the  least  possible 
amount  of  hand  labor  ;  but  the  ordinary 
puddling  process  is  totally  opposed  to 
this  kind  of  development,  the  material 
being  treated  in  small  charges,  and  by 
the  exertion  of  manual  labor  of  the  most 
severe  kind.  Considering  these  facts  we 
think  that  everything  tends  to  show  that 
the  puddling  process  of  the  future  will 
be  carried  out  in  rotary  furnaces  capable 
of  dealing  with  large  charges,  and  worked 
in  .connection  with  plant  capable  of  deal- 
ing easily  with  the  enormous  puddle 
balls  thus  produced,  these  balls  being 
subsequently  cut  into  pieces  of  convenient 
size  and  dealt  with  by  existing  ma- 
chinery ;  and  we  believe  that  the  time 
has  arrived  when  our  ironmasters  should, 
as  a  body,  consider  this  subject  more 
earnestly  than  they  hitherto  have  done. 
In  making  this  last  remark  we  have  no 
desire  to  underrate  the  progress  which 
has  been  already  made  ;  but  this  pro- 
gress has  been  due  rather  to  the  energy 
of  a  few  particular  firms  and  individuals 
than  any  action  taken  by  the  iron  trade 
as  a  whole,  and  it  has  thus  been  smaller 
than  it  need  have  been. 

The  only  united  action  which  has 
taken  place  has  been  that  organized  un- 
der the  auspices  of  the  Iron  and  Steel 
Institute — a  body  which,  although  the 
youngest  of  our  important  scientific  so- 


cieties, has  set  an  excellent  example  to 
its  seniors  by  its  energy  in  promoting 
the  industries  it  represents.  As  we 
pointed  out  on  a  recent  occasion,  the 
commission  sent  to  the  United  States  by 
the  Iron  and  Steel  Institute  to  examine 
into  the  working  of  the  Danks  furnace, 
has  been  attended  with  valuable  results. 
It  is  true  that,  as  regards  the  Danks  fur- 
nace itself,  the  early  anticipations  set 
forth  by  the  report  of  the  commission 
have  not  been  completely  fulfilled  ;  but 
this  we  regard  as  a  small  matter  com- 
pared with  the  fact  that  English  iron- 
masters have  been  familiarized  with  the 
results  which  can  be  obtained  by  rotary 
puddling,  and  that  competent  men,  such 
as  Siemens,  Spencer,  Crampton,  and 
others,  have  been  led  to  experiment  fur- 
ther with  that  system  of  puddling,  and 
to  contribute  towards  making  it  a 
thorough  success. 

The  process  of  mechanical  puddling  is 
essentially  one  requiring  to  be  developed 
by  experimental  inquiry.  To  be  com- 
mercially successful,  machinery  for  pud- 
dling mechanically  must  not  only  be 
capable  of  turning  out  a  product  at  least 
equal  to  that  obtained  by  ordinary  hand 
work,  but  it  must  also  be  enduring  and 
be  capable  of  being  worked  without 
"  nursing"  and  without  giving  trouble 
from  frequent  breakdowns.  It  is  this 
quality  of  endurance  under  the  rough 
usage  experienced  in  iron  works  which 
has  proved  so  difficult  to  obtain  in  pud- 
dling machinery,  and  it  is  a  quality  the 
possession  or  non-possession  of  which  in 
many  instances,  can  only  be  determined 
by  actual  practice.  We  say  in  many  in- 
stances— not  in  all — for  there  have  been 
undoubtedly  cases  of  the  introduction 
into  iron  works  of  puddling  machinery 
which  would  have  been  at  once  con- 
demned at  sight,  had  it  come  under 
the  inspection,  of  a  competent  mechanic. 
Setting  aside  these  exceptional  cases, 
however,  we  may  assume  it  to  be  an  un- 
doubted fact  that  the  capabilities  of  pud- 
dling machinery  can  only  be  fairly  tested 
by  actual  practical  experience,  and  this 
being  so  the  various  failures  of  such 
machinery  which  have  occurred,  can  only 


EOTARY   PUDDLING. 


279 


be  regarded  as  so  many  stepping-stones 
deposited  on  the  road  to  success. 

Thanks  to  these  failures,  indeed,  and 
to  the  labors  of  those  who  have  en- 
deavoured to  overcome  them,  we  may 
say  that  at  the  present  time  mechanical 
puddling  has  been  made  a  practical 
process,  and  has  been  brought  to  such  a 
stage  that  its  future  development  de- 
pends less  upon  individual  exertion  than 
upon  its  introduction  into  various  iron- 
making  districts  and  the  consequent  im- 
provement of  details  of  manipulation 
certain  to  result  from  more  extended  ex- 
perience. 

When  the  Danks  furnace  was  first  in- 
troduced into  this  country,  it  was  in 
many  quarters  assumed — somewhat  too 
hastily — that  it  was  practically  perfect, 
and  the  earlier  experiences  of  Mr.  Mene- 
laus,  Tooth,  and  others  in  the  same  field 
were  temporarily  forgotten.  Practical 
trials,  however,  on  a  commercial  scale 
■developed  more  or  less  serious  difficulties 
in  the  working  and  maintenance  of  the 
furnace,  and  from  that  time  to  the 
present  constant  efforts  have  been  made 
to  effect  improvements.  The  present 
state  of  the  matter  as  far  as  the  Danks 
furnace  is  concerned  is  fairly  set  forth 
in  the  letter  from  Mr.  Jones,  of  the 
Erimus  Works,  incorporated  in  the  in- 
augural address  of  Mr.  Menelaus,  already 
referred  to,  and  published  by  us  the 
week  before  last.  According  to  Mr. 
Jones  the  difficulty  of  the  lining  has 
been  entirely  overcome  and  "  fettling  can 
be  procured,  suitable  to  any  district," 
while  he  also  speaks  in  hopeful  terms  of 
the  means  adopted  to  reduce  the  tend- 
ency to  mechanical  failures.  As  we 
pointed  out  a  fortnight  ago  in  our  com- 
ments on  Mr.  Menelaus's  address,  the 
leading  improvement  introduced  in  the 
modified  Danks  furnaces  at  the  Erimus 
Works — namely,  the  water-jacket  ar- 
rangement— is  one  of  the  chief  features 
in  the  Crampton  furnace.  We  have  no 
intention  here  of  entering  into  any  dis- 
cussion relating  to  priority  of  design  ; 
but  the  fact  of  the  Danks  furnace  being 
thus  made  to  approximate  in  construction 
to  the  Crampton  furnace  as  regards  the 
mode  of  cooling  by  water  irresistible 
suggests  certain  comparisons  between 
the  two  systems  of  working,  which  in 
the  present  state  of  the  puddling  ques- 
tion are  worthy  of  consideration. 


As  regards  speed  of  working,  there  is 
probably  nothing  to  choose  between  the 
two  systems  so  long  as  both  furnaces  are 
in  equally  good  condition  ;  but  in  regu- 
lar work  the  amount  of  the  output  from 
any  given  furnace  is  of  course  largely 
dependent  upon  the  ease  of  maintenance 
of  that  furnace.  As  to  what  would  be 
the  relative  endurance  of  two  furnaces, 
each  constructed  on  Mr.  Crampton's  plan 
with  water-jacket  arrangements,  but  one 
worked  on  the  Danks  system  and  the 
other  with  dust  fuel,  there  are  no  data 
for  actually  determining  ;  but  there  are 
certainly  no  reasons  for  believing  that 
the  results  would  be  in  favor  of  the  for- 
mer. With  reference  to  this  point  we 
may  remark  that  in  the  Crampton  fur- 
nace the  5-in.  cock  revolving  with  the 
casing  and  through  which  the  water 
supply  enters  the  latter,  is  not  liable  to 
derangement,  and  has  stood  the  test  of 
long  practical  working,  while  this  can 
scarcely  be  expected  to  be  the  case  with 
the  Danks  furnace,  as  to  effectively  sup- 
ply water  to  the  latter  involves  the  use 
of  what  may  be  regarded  as  a  revolving 
cock  7  ft.  in  diameter,  the  wearing  sur- 
faces of  which  have  thus  a  comparativrely 
high  speed.  As  regards  quality  of  pro- 
duct, the  difference,  if  any,  may  fairly 
be  expected  to  be  in  favor  of  the  Cramp- 
ton furnace,  on  account  of  the  high  and 
uniform  temperature  which  can  be  main- 
tained and  the  regularity  of  the  working 
— both  matters  which  practice  has  shown 
to  be  of  a  vast  importance.  Taking, 
therefore,  even  the  view  of  the  question 
most  favourable  for  the  Danks  system, 
we  see  no  reasons  why  that  system  of 
working  should,  as  regards  quality  or 
quantity  of  products,  show  any  advan- 
tage over  that  of  Mr.  Crampton. 

If  now  we  consider  the  matter  further, 
and  examine  the  other  qualifications  which 
go  to  make  up  a  successful  rotary  pud- 
dling furnace,  we  find  that  Mr.  Cramp- 
tons's  system  possesses  most  important 
advantages.  Thus,  in  the  first  place, 
the  use  of  the  dust  fuel  as  carried  out 
by  Mr.  Crampton  gives  a  power  of  con- 
trolling the  action  of  the  furnace  which 
is  utterly  unattainable  so  long  as  ordin- 
ary fires  are  used.  We  have  frequently 
spoken  upon  this  point,  and  the  con- 
tinued experience  at  Woolwich  only 
serves  to  confirm  all  we  have  said.  By 
shifting  the  handles  regulating  the  sup- 


280 


VAN  nostrand's  engineering-  magazine. 


plies  of  air  and  fuel,  the  temperature 
can  be  altered  or  flame  made  oxydizing 
or  non-oxydizing  at  will,  without  a  par- 
tical  of  coal  getting  into  the  iron,  while 
by  simply  leaving  the  handles  alone  any 
given  condition  can  be  maintained  for 
hours,  if  desired,  absolutely  without 
trouble.  The  ease  and  completeness 
with  which  the  combustion  of  dust  fuel 
can  be  controlled  is,  in  fact,  so  striking 
that  we  are  inclined  to  think  that  it  can 
only  be  thoroughly  appreciated  by  those 
who  have  examined  it  in  operation,  and 
who  are,  at  the  same  time,  conversant 
with  the  difficulties  of  managing  ordin- 
ary fires.  One  result  of  the  perfection 
of  the  combustion  obtained  with  the 
dust  fuel  is  the  rapidity  with  which  the 
furnace  can  be  heated,  the  Woolwich 
furnace,  when  cold,  having  been  re- 
peatedly raised  to  a  working  heat  in 
three-quarters  of  an  hour  with  an  ex- 
penditure of  three  and  a  half  cwt.  to  four 
cwt.  of  fuel. 

Another  advantage  of  the  Crampton 
system  of  working  is  that  it  does  away 
with  the  construction  and  maintenance 
of  all  brick-built  furnaces,  and  leaves 
the  revolving  furnace  itself  quite  free  at 
one  end,  the  products  of  combustion  re- 
turning through  the  same  opening 
through  which  the  jets  of  dust  fuel  are 
injected,  and  the  furnace  forming  within 
itself  a  gas  producing,  gas  consuming, 
and  puddling  chamber.  We  may  re- 
mark, by-the-by,  that  during  his  earlier 
trials  Mr.  Crampton  employed  two 
chambers,  but  the  alteration  of  the  fur- 
nace so  as  to  have  one  chamber  only  was 
found  to  save  at  least  one-third  of  the 
fuel.  Moreover,  the  Crampton  furnace, 
instead  of  having  two  revolving  joints 
to  keep  tight  (to  prevent  the  liquid  iron 
from  escaping),  as  in  the  case  with 
Danks',  has  one  only,  while  every  facil- 
ity is  given  for  the  expansion  and  con- 
traction of  the  revolving  furnace  itself. 
All  firebars,  too,  are  done  away  with. 
These,  we  think,  are  mechanical  advan- 
tages having  no  unimportant  influence 
on  the  cost  of  maintenance,  while  as 
collateral  advantages  we  have  the  effect- 
ive utilization  of  slack  coal  and  its  com- 
bustion without  the  production  of 
smoke.  The  fact  of  the  fuel  being  con- 
veyed to  the  Crampton  furnaces  by 
mechanical  means,  and  all  wheeling  of 
coal  to  the  furnaces  being  thus  avoided, 


is  also  a  feature  of  the  system  which 
should  be  borne  in  mind. 

The  Crampton  furnace  at  Woolwich, 
after  being  in  operation  two  years,  was 
when  we  last  saw  it  a  few  weeks  since, 
in  as  perfect  condition  as  when  it  left 
the  boiler-maker's  hands,  it  not  even 
showing  signs  of  distortion.  During  its 
working  the  liquid  iron  never  issues  from 
the  revolving  joints,  while  the  friction 
is  so  small  that  the  engines  driving  it 
require  less  than  one-fourth  the  capacity 
of  those  found  necessary  on  the  Danks 
system.  During  the  working  of  the 
furnace  at  Woolwich,  there  have  been 
puddled,  alone  and  mixed,  large  charges 
of  Swedish  charcoal  iron,  hematite, 
Northamptonshire,  Derbyshire,  South 
Yorkshire,  and  Cleveland  irons,  and 
judging  from  the  exhaustive  tests  ap- 
plied, the  Cleveland  pig  has  produced 
tin-plates,  sheets,  wire,  rails,  bars,  and 
plates  equal  in  quality  to  the  products 
obtained  from  the  best  'brand*.  More- 
over, the  steel  made  in  pots  and  in  the 
Siemens-Martin  furnace  from  Cleveland 
puddled  bars  has  proved  equal  to  the 
best  pot  steel  produced  from  Swedish 
charcoal  iron.  Most  of  these  results 
were  obtained  during  the  time  that  the 
furnace  was  under  the  charge  of  inde- 
pendent manufactures  who,  after  treat- 
ing the  puddled  blooms  in  their  own 
works,  forwarded  samples  of  their  pro- 
ducts to  Mr.  Crampton,  who  has  thus 
been  enabled  to  arrange  at  his  offices  at 
4  Victoria  Street,  Westminster,  a  most 
remarkable  and  instructive  collection  of 
materials  produced  by  mechanical  pud- 
dling— a  collection  which  is  well  worthy 
of  examination  by  those  interested  in  the 
subject. 

Altogether  when  we  consider  the  nu- 
merious  advantages  attendant  upon  the 
employment  of  fuel  in  the  form  of  dust, 
and  the  general  excellence  of  the  me- 
chanical arrangements  which  Mr.  Cramp- 
ton has  designed  and  practically  carried 
into  effect  for  the  utilization  of  such 
fuel,  we  cannot  but  regard  the  Crampton 
furnace  as  the  most  advanced  solution 
of  the  problem  of  mechanical  puddling.. 
and  we  look  forward  with  very  consid- 
erable interest  to  the  results  which  may 
be  expected  as  soon  as  the  Crampton 
furnaces  now  nearly  completed  in  the 
Middlesbrough  district  are  fairly  at 
work  ;  our  interest  being,  we  are  sure., 


IKON   AND    STEEL   NOTES. 


281 


shared  by  all  concerned  in  our  iron 
manufacture.  It  is  anticipated  that 
these  results  will  be  even  superior  to 
those  already  obtained  at  Woolwich, 
and  from  the  completeness  of  the  arrange- 
ments we  have  every  hope  that  this 
anticipation  may  be  realized. 

REPORTS  OF  ENGINEERING  SOCIETIES. 

Master  Mechanics'  Association. — The  fol- 
lowing are  the  subjects  for  investigation 
and  discussion  the  coming  year,  as  reported  by 
the  Committee  on  Subjects,  consisting  of  Reu- 
ben Wells,  James  M.  Boon  and  John  H.  Flynn  : 

1.  Locomotive  Tests. 

2.  Beet  Material,  Form  and  Proportion  of  Lo- 
comotive Boilers  and  Fire  Boxes. 

3.  Locomotive  Construction. 

4.  Locomotive  Tire,  Truck  and  Tender 
"Wheels. 

5.  Best  and  Most  Economical  Metal  for  Lo- 
comotive and  Tender  J  ournal  Bearings. 

6.  Is  it  Economical  to  use  Injectors  on  Loco- 
motives, and  to  what  Extent  ? 

7.  Boiler  Explosions. 

There  were  reports  on  the  first  four  of  these 
last  year,  but  the  subjects  and  committees  were 
continued. 

The  following  is  the  report  of  the  Commit- 
tee on  Narrow  and  Broad  Gauge  Rolling  Stock  : 
To  the  American  Railway  Master  Mechanics'  Asso- 
ciation : 

Gentlemen — Replies  were  received  from 
twelve  roads,  and  the  information  obtained  is 
embodied  in  accompanying  table.  Very  full 
reports  were  made  by  Mr.  Peddle,  of  the  St. 
Louis,  Vandalia,  Terre  Haute  &  Indianapolis 
R.,  and  Mr.  Wells,  of  the  Jeffersonville,  Mad- 
ison &  Indianapolis  R. 

To  the  question,  "From  your  experience, 
which  is  the  best  gauge,  narrow  or  ordinary 
(4  ft.  8£  in.)? "  Mr.  Peddle  replies  as  follows: 

"  From  my  experience  I  would  prefer  5-feet 
gauge  to  either  of  the  other  gauges,  for  two 
reasons:  The  first  is,  that  a  wider  wheel-base 
would  enable  the  modern  raised-deck  coaches 
and  sleeping  cars,  in  which  the  centre  of  grav- 
ity is  much  higher  than  in  the  old-style 
coaches,  to  be  run  with  greater  steadiness  and 
freedom  from  oscillation  at  high  speeds. 
Another  reason  is,  that  it  would  give  locomo- 
tive builders  more  room  between  the  frames 
and  enable  them  to  lower  the  barrel  of  the 
boiler,  and  also  widen  the  fire-box  and  do 
away  with  the  off-set  in  the  sides,  in  the  vicin- 
ity of  the  tubes,  a  very  objectionable  feature, 
and  make  them  straight  or  narrower  at  the 
top." 

The  information  in  relation  to  narrow 
gauges  (viz.,  less  than  4  ft.  84  in.)  is  too 
meagre  to  make  a  fair  comparison  between 
them  and  the  ordinary  gauge. 

From  the  table  it  will  be  seen  that  five  pre- 
fer 4  ft.  8+  in.  or  5  ft.  to  the  narrow  gauge  or 
gauges.     Two  prefer  gauges  of  3  ft. 
Wit.  S.  Hudson,  ) 
H .  G.  Brooks,      [•  Committee. 
H.  N.  Spragtje,  ) 
—  Chicago  Railway  Review. 


IRON  AND  STEEL  NOTES. 

C arbitration  of  Iron. — M.  Boussingault 
has  communicated  the  results  of  hi-  ex- 
periments on  the  combinations  of  carbon,  to 
the  academy  of  sciences  of  Paris.  M.  Bouss- 
ingault has  found  by  most  careful  experiments 
that  carbon  exists  in  carburated  iron  in  vari- 
ous proportions.  Steel  contains  from  7  to  10 
1000th  parts  when  hard,  and  soft  10  to  15. 
Pig-iron  contains  2  to  4  lOOths,  and  sometimes 
5  iOOths.  The  quantity  is  difficult  to  settle, 
as  it  can  only  be  ascertained  in  analysis  by  the 
difference  with  manganese,  silicium,  phos- 
phorus, sulphur,  and  chromium.  The  aver- 
age of  the  results  is  4  4c.  When  gray  the  iron 
has  given  up  its  carbon  in  the  form  of  graphite;, 
but  M.  Boussingault  found  no  sensible  differ- 
ence in  the  quantity  of  carbon  in  gray  and 
white  pig.  In  all  cases,  if  the  real  combination 
of  iron  with  carbon  be  admitted,  it  takes  place 
thus — 5  equivalents  of  iron  for  one  of  carbon. 
Whatever  be  the  temperature  it  is  impossible, 
says  M.  Boussingualt,  to  make  more  than  5  per 
cent,  of  carbon  enter  the  iron  ;  this  is  the 
limit. — Iron. 

Utilizing  Furnace  Slag.— Mr.  W.  Harold 
Smith,  of  this  city,  has  been  experiment- 
ing for  some  time  with  furnace  slag,  endeavor- 
ing to  make  from  it  a  cheap  and  serviceable 
substitute  for  bricks  and  stone  in  paving  and 
building.  He  has  taken  slag,  from  Robbins  tfc 
Sons'  Philadelphia  Furnace,  granulated  as  it 
came  from  the  stack,  then  mixed  it  with  two- 
thirds  its  weight  of  cement,  subjected  it  to 
heavy  pressure,  and  has  succeeded  in  making 
firm,  smooth,  solid  blocks,  which  have  en- 
dured the  following  tests:  They  have  been 
very  highly  compressed  without  crushing, 
were  laid  for  pavement  last  fall  and  endured 
the  winter's  frost  without  damage,  have  been 
heated  to  a  white  heat  and  then  thrown  into 
water  without  disintegration,  a  35-foot  column 
of  water  was  forced  against  one  of  the  blocks 
without  penetrating  it,  and  they  were  found 
to  endure  heat  "which  would  melt  an  ordinary 
red  brick. 

Mr.  Smith  proposes  to"  unite  with  any  fur- 
nace owner  in  the  manufacture  of  stones  for 
flagging  sidewalks,  from  15  to  24  inches 
square  and  3  inches  thick,  afterwards,  as  the 
demand  improves,  entering  into  the  manu- 
facture of  other  forms;  or  lie  will  sell  a  fur- 
nace right  at  a  reasonable,  figure.  Mr.  Smith 
claims  that  his  stone,  which  he  has  named 
"  Phoenix  stone,"  can  be  made  so  cheaply  and 
sold  so  readily  that  a  furnace  owner  can  make 
as  much  out  of  his  slag  as  he  can  out  of  his 
iron.  His  address  is  227  North  Thirteenth 
Street,  and  his  office  is  at  224  South  Third 
Street,  Philadelphia.  He  solicits  correspond- 
ence, and  invites  attention  to  samples  of 
"  Pho?nix  stone"  on  exhibition  at  the  office. 
We  have  seen  these  samples  and  believe  they 
will  make  a  good  substitute  for  stone  or  brick. 
— Bulletin. 

Belgian  Competition  in  the  Iron  Trade. 
— Now  there  is  so  much  talk  of  Belgian 
competition  with  our  iron  manufacturers," the 
following  passages  from  the  report   of  Sir  H. 


282 


van  nostrand's  engineering  magazine. 


Barron,  on  the  commerce,  &c,  of  Belgium, 
just  published  among  the  reports  of 
her  Majesty's  Secretaries  of  Legation, 
may  be  read  with  some  interest.  The 
competion,  it  would  appear,  must  have 
arisen  from  the  general  depression  in  the  iron 
trade  first  reaching  Belgium,  so  that  Belgian 
manufacturers  were  forced  to  great  sacrifices  to 
find  a  market  of  any  kind.  At  any  rate,  Bel- 
gian trade  has  not  been  prosperous  : — "  On 
the  whole,"  Sir  H.  Barron  says,  "  the  activity 
of  all  branches  of  trade  in  1872  was  rare  and 
unparalleled.  Above  all,  the  trade  connected 
with  the  manufacture  and  working  of  iron  en- 
joyed an  exceptional  prosperity.  All  the 
smelting  furnaces,  iron  works,  rolling  mills, 
machine  works,  foundries,  and  nail  makers 
worked  without  intermission  during  the  whole 
year.  Many  new  factories  were  erected,  many 
of  the  old  ones  were  enlarged.  At  the  same 
time  the  price  of  iron  and  its  products  rose, 
without  a  check  from  the  beginning  to  the  end 
of  the  year,  to  figures  previously  unknown. 
Pig-iron  doubled  in  value  during  the  twelve 
months.  These  prices  left  the  producers 
good  profits  during  the  first  six  months. 
But  the  prices  of  labor  and  of  coal 
rose  to  such  exorbitant  rates  as  to  absorb 
finally  the  whole  profits  of  the  iron  trade. 
Thus,  the  year  which  began  so  rich  in  promise 
ended  in  disappointment.  The  masters  now 
find  that  they  cannot  tempt  buyers  at  the 
present  prices  of  iron,  and  cannot  reduce  those 
prices  on  account  of  the  excessive  cost  of  pro- 
duction. Many  works  have  been  closed  and 
furnaces  blown  out  in  1873,  so  that  the  trade 
is  falling  into  a  state  of  general  stagnation. 
The  present  year  will  leave  no  profits  to  the 
iron-masters  in  general,  save  to  such  as  pos- 
sess colleries  of  their  own,  as,  for  instance,  the 
monster  establishments  of  Seraing,  Couillet, 
Solessin,  &c."  Our  trade,  therefore,  has  not 
been  suffering  from  the  competition  of  pros- 
perous Belgian  ironmasters  who  were  making 
a  profit  when  our  makers  had  none,  but  from 
manufacturers  who  were  unable  to  get  profit- 
able orders. — Iron. 

T'he  U.  S.  Commission  on  Testing  Metals. 
— The  following  circular  has  been  recently 
issued: 

The  U.  S.  Commission  on  the  Tests  of  Iron, 
Steel,  and  other  Metals,  proposes  making  a 
series  of  determinations  of  the  effects  of  car- 
bon, phosphorus,  silicon,  manganese,  and 
other  elements,  upon  the  strength,  toughness, 
elasticity,  and  other  qualities  of  Iron  and 
Steel.  The  specimens  will  be  analyzed  by  the 
chemists  attached  to  the  Commission  and  sub- 
jected to  tension,  torsion,  compression,  and 
other  mechanical  tests.  All  experiments  will 
be  repeated  often  enough  to  reduce  errors  to 
their  minima. 

You  would  greatly  aid  the  Commission,  as 
well  as  the  Iron  Trade,  by  furnishing  Iron  and 
Steel  bars,  as  follows: 

Bars  to  be  7  ft.  long  and  l£  in.  round. 

Bars  to  be  rolled,  in  case  you  have  suitable 
rolls;  if  not,  hammered  billets,  3  in.  square  by 
18  in.  long,  to  be  furnished  in  place  of  bars. 

Bars  to  be  stamped  on  one  end  with  the  initials 


of  the  maker,  and  the  number  of  the  heat  or 
charge  at  which  they  were  made;  or,  in  case 
there  is  no  such  record,  to  be  stamped  with  the 
initials  of  the  maker  and  numbered  on  one 
end. 

A  full  description  of  the  kind  and  make  of 
raw  materials,  and  of  processes  employed  in 
the  manufacture  of  the  bars,  and  also  of  the 
size  of  the  ingot  or  pile,  the  number  of  re- 
heats, and  the  extent  to  which  hammering  or 
rolling  were  employed  in  the  reduction,  to  be 
kept  in  a  reference  book — each  description 
having  a  number  corresponding  with  that  of 
the  bar — would  be  of  great  value.  Such  a 
record  is,  therefore,  particularly  requested. 

Tour  ovm  analyses,  including  color  carbon 
tests — in  case  you  have  made  them — to  be 
given  in  the  above  description. 

Your  mechanical  tests  of  the  material  fur- 
nished, with  statement  of  shape  and  dimen- 
sions of  specimens  tested,  to  be  also  recorded 
and  furnished. 

Please  store  the  bars  until  the  Commission  in- 
forms you  where  to  send  them. 

KIND  OF  IKON  AND  STEEL  WANTED. 

Any  or  all  the  following : 
1  bar  of  Steel,  containing 0.10  %  carbon. 


0.20 
0.30 
0.40 
0.50 
0.60 
0.70 
0.80 
0.90 
1.00 


After  selecting  these  bars  by  means  of  your 
carbon  tests,  please  repeat  the  tests,  so  that 
there  may  be  no  error. 

It  is  very  important  that  the  other  elements 
should  be  uniform;  therefore,  these  bars  should 
be  selected  from  charges  made  as  far  as  possi- 
ble from  the  same  raw  materials,  and  under 
similar  conditions. 

Also,  please  furnish — 1  bar  of  each  of  such 
Irons  or  Steels  as  may  show  any  particularly 
good  or  particularly  bad  qualities,  or  such  as 
may  exhibit  any  very  marked  or  unusual  cha- 
racteristics. 

1  bar  of  your  best  wrought  Iron,  with  its 
trade  mark  stamped  on. 

1  bar  of  veiy  hard,  but  not  cold  short 
wrought  Iron. 

1  bar  of  extremely  soft  wrought  Iron. 

1  bar  of  average  '.'  puddled  Steel." 

Any  bars  which  you  think  may  be  usefully 
subjected  to  these  tests — specially  describing 
the  materials  and  processes  employed  in  mak- 
ing them,  and  their  characteristics. 

When  the  bars  are  tested,  it  is  proposed  to 
test  a  series  in  which  the  manganese  varies  by 
tenths  of  a  per  cent.,  other  elements  remaining 
the  same,  and  another  series  for  phosphorus, 
and  so  on. 

Tool  Steels  will  be  tested  in  another  series 
of  experiments. 

These  determinations  must,  of  course,  re- 
quire thousands  of  specimens,  and  be  con- 
tinued through  a  series  of  years.  The  final 
result  must  inevitably  lead  to  a  scientific  syn- 


EAILWAY   NOTES. 


283 


thesis  in  the  Iron  and  Steel  manufacture,  by 
which  all  required  mechanical  qualities  can 
be  accurately  produced  at  pleasure. 

A.  L.  Holley, 
Chairman  Committee  on  Chemical  Research, 
and  on  Steels  produced  by  modern  pro- 
cesses. 

•«£>« 

RAILWAY  NOTES. 

Traction  Engines  on  Roads. — The  Larne 
traction  engine  nuisance  case  has  occupied 
a  great  deal  of  time  in  its  hearing,  and  a  very 
considerable  amount  of  our  space.  We  do 
not  say  that  either  the  time  or  the  space  was 
wasted;  but  we  feel  sure  that  even  our  good 
friends  in  the  neighborhood  of  Larne  must  be 
gratified  that  the  case  has  at  last  been  conclud- 
ed. The  magistrates  gave  their  decision  yes- 
terday. It  was  adverse  to  the  plaintiffs,  as  the 
court  held  that  a  traction  engine  traversing  the 
public  road  did  not  constitute  a  nuisance. 
Railways  frequently  ran  close  to  public 
roads;  and  their  engines  might  practically  be 
regarded  as  forming  a  nuisance  equally  with 
traction  engines,  supposing  these  were  nuis- 
ances; but  railways  run  under  Acts  of  Parlia- 
ment and  could  not  be  prosecuted  as  nuisances. 
The  magistrates  held  that  traction  engines  also 
had  the  sanction  of  Parliament,  and  did  not 
think  that  in  this  particular  instance  a  nuisance 
had  been  proved.  In  particular,  it  was  re- 
marked that  though  the  engine  was  regularly 
driven  through  the  town  of  Larne,  none  of  its 
inhabitants  had  come  forward  to  complain  of 
it.  The  charge  was,  therefore,  dismissed;  and 
we  think  there  is  substantial  justice  in  the  de- 
cision. It  is  no  doubt  very  annoying  to  own- 
ers of  horses  to  have  them  frightened  on  the 
public  road;  but  the  evidence  on  this  point 
was  not  particularly  strong,  and  without  a  very 
strong  case  indeed,  the  court  would  not  have 
been  justified  in  giving  a  judgment  which 
would  have  had  the  effect  of  prohibiting  the* 
use  of  traction  engines  altogether. — Northern 
Whig,  Belfast. 

Boilers  Lined  with  Copper. — An  Austrian 
railway  engineer  has  had  the  idea  of  pro- 
tecting the  boilers  of  locomotives  against  in- 
crustation by  means  of  copper  plates.  The 
front  and  back  plates  of  the  bottom  of  the 
boiler  of  an  engine  were  covered  with  a  sheet 
of  copper  1  millimetre  in  thickness,  the  mid- 
dle plate  of  the  boiler  being  left  unprotected. 
The  engine  was  worked  for  two  years  on  a 
portion  of  the  line  of  the  State  railways  where 
the  water  was  of  very  bad  quality.  When  the 
tubes  were  taken  out  the  incrustation  was 
found  to  be  10  millimetres  in  thickness  on  the 
surface  of  the  iron,  and  only  2  to  3  millimetres 
thick  on  the  copper  plates .  The  iron  was  in 
many  places  corroded  to  the  depth  of  14- 
millimetres,  while  the  copper  was  entirely  un- 
affected, and  the  iron  plate  beneath  it,  when 
uncovered,  looked  perfectly  new.  The  par- 
ticles of  incrustation  were  larger  on  the  iron 
than  on  the  copper.  The  cost  of  the  copper 
covering  is  stated  to  be  from  250  to  750  fr.  per 
boiler.  Another  engineer,  who  examined  and 
reported  on  the  arrangement,  says  that  the 
duration  of  the  boilers  is  doubled  or  tripled  by 


the  application  of  the  copper  plates,  which 
afford  extraordinary  security  against  explosion. 
The  incrustation  is  much  less  on  copper  than 
on  iron  and  steel,  which  is  porous  and  slightly 
oxidized,  and  consequently  the  vaporization  is 
more  complete,  and  there  is  a  corresponding 
saving  of  fuel.  In  the  construction  of  a  boik-r 
to  be  lined  with  copper  the  iron  plates  may 
be  of  less  thickness  without  risk;  the  weight 
of  the  boiler  is  thus  considerably  reduced,  and, 
lastly,  the  expense  for  repairs  is  considerably 
diminished. 

[This  combination  of  copper  and  iron  in  iron 
ships  has  been  found  very  injurious  on  account 
of  the  galvanic  action  between  the  two  metals, 
and  we  would  need  more  satisfactory  experi- 
ments with  water  of  different  qualities,  and 
particularly  with  the  acid  water  common  in 
coal  mines  before  placing  much  value  on  this 
"  improvement."] — Engineering  and  Mining 
Journal. 

Steel  Rails  was  the  subject  of  a  paper  re- 
cently read  before  the  Institution  of  Civil 
Engineers,  London. 

The  object  of  this  paper  was  to  endeavor, 
briefly,  to  show  that  with  care  in  manipulation 
and  in  selection  of  materials,  Bessemer  steel 
might  be  produced  constant  in  quality,  and 
that  certain  inexpensive  tests  might  be  applied 
which  would  absolutely  determine  the  quality 
of  the  material,  in  most  if  not  all  of  its  cha- 
racters, so  far  as  was  required  for  railway 
and  structural  purposes. 

After  an  entensive  experience  in  the  manu- 
facture of  Bessemer  steel  rails,  the  author 
could  only  come  to  the  conclusion,  that  the 
present  system  of  inspection  was  highly  un- 
satisfactory, and  that,  whilst  it  sacrificed  a 
great  number  of  rails,  it  gave  anything  but  re- 
liable results.  The  object  appeared  to  be  to 
test  each  individual  rail  in  such  a  manner  that 
its  value  should  not  be  deteriorated.  With 
this  view  many  experiments  had  been  made; 
and  it  was  hoped  that  a  system  had  been 
developed  which,  although  primarily  adopted 
for  rails,  might  be  made  available  for  any 
other  form  of  steel.  The  experiments  appeared 
to  prove  that  if  it  was  possible  to  determine  the 
hardness  of  the  material,  all  the  other  proper- 
ties might  be  calculated  therefrom .  If,  there- 
fore, the  fish-plate  holes  in  the  rails  were 
punched  by  a  registering  punching  press,  an 
index  was  obtained  for  the  real  quality  of  the 
steel.  Experiments  had  shown  that  this  force 
increased  according  to  the  thickness  of  the 
metal,  in  strictly  arithmetical  progression:  for 
a  hole  |  in.  in  diameter  the  force  required  was 
about  8  tons  per  ^  in. 

Experiments  had  demonstrated  that  the  zone 
of  metal  injured,  by  punching  steel  having  a 
tensile  strength  up  to  32  tons,  did  not  exceed 
3%  in.  in  breadth,  and  that  if  the  fish-plate  holes 
were  first  made  with  a  small  punch  and  then 
enlarged,  by, drilling  to  the  required  size,  the 
steel  was  not  more  injured  than  if  the  hold 
had  been  drilled  only.  The  Barrow  Steel 
Company  had  shipped  to  Canada  more 
than  100,000  tons  of  rails  treated  in  this  man- 
ner ;  and  as  there  had  been  no  case,  to  their 
knowledge,  where  rails  had  broken  through 


284 


VAN  nostrand's  engineering  magazine. 


the  fi«h-plate  holes,  they  considered  it  a  satis-  :  poses.  A  member  of  the  council  said  that  re- 
factory  proof  that  no  danger  need  be  feared.  !  cent  discoveries  had  been  made,  which  prom- 
On  the  contrary,  this  mode  of  punching  vras  ised  that  the  sewage  might  be  purified  suffi- 
one  of  the  best  practical  tests  of  the  quality  of  ,  ciently  to  be  turned  into  the  Seine  without 
the  steel;  as  however  hard  (unless  in  an  ex-  any  inconveniences;  but  the  council,  knowing 
ceptional  degree)  it  might  be,  the  particular  bow  little  had  in  reality  been  effected  in  the 
rails,  if  drilled,  might  be  overlooked  by  the  wav  of  artificial  purification,  and  how  costly 
management;  whilst  if  the  steel  had  a  greater  ;  all  the  processes  are,  passed  over  that  part  of 
tensilS  strength  than  34  tons  to  35  tons,  the   the  subject,  discussed  the  general  subject,  and 


finally  adopted  the  report.  This  will  form  an 
important  link  in  the  long  chain  of  the  appli- 
cation of  the  sewage  of  Paris,  as  the  depot  of 
La  Villette  is  the  receptacle  of  an  immense 
quantity  of  night  soil. — Engineer. 

The  Kansas  City  Bridge. — An  absurd  and 
injurious  rumor  appeared  last  week  in  an 
Atchison  paper  to  the  effect  that  the  piers  of 
the' railway  bridge  at  Kansas  City  are  being 
undermined  by  the  current,  and  that  negotia- 
tions are  making  for  a  ferry  boat  for  imme- 
diate use  with  which  to  transport  the  cars 
across  the  river.  This  would,  indeed,  be  a 
To"sam  uplhe"  experiments  on  Bessemer  I  misfortune  if  true,  forsome  forty  trains  cross 
steel  rails,  it  might  be  stated  generally,  that  the  bridge  daily,  and  it  would  be  impossible 
the  most  lengthened  wear,  under  the  heaviest  to  provide  for  their  passage  in  any  other  way 
traffic,  did  not  appear  in  the  slightest  degree  to  than  by  the  construction  of  a  new  bridge.— 
deteriorate  any  portion  of  the  rail,  except  the  :  rhere  is,  however,  a  certain  basis,  or  occasion 
wearing  surface  to  an  inconsiderable  depth.  for  a  rumor,  exaggerated  and  false  as  it  is.  _  It 
But  this  part  of  the  rail,  however  hard  and  has  been  "  an  open  secret  that  the  pivot  pier- 
capable  of  resisting  impact,  lost  almost  the  1S  partially  undermined  (on  the  north  side  we 
whole  of  its  ductility,  which  was  apparently  believe)  a  fact  known  almost  from  the  erection 
due  to  the  extreme  molecular  tension  of  the  of  the  bridge,  but  not  to  an  extent  immediately 
particles  of  the  metal.  If  a  worn  double-  impairing  its  stability.  However  it  was  deem- 
headed  rail  was  turned,  though  the  new  wear-  ed  best  to  apply  the  ounce  of  preventive  which 
ing  table  would  be  as  strong  as  when  first   is  better  than  the  pound  of  cure;  and  so,   in 

December  last,    a  thorough    examination  of 


punch  would  break,  when  the  rail  would  nee 
essarily  be  rejected. 

The  results  of  experiments  on  rails,  for  the 
Furness  Railway,  also  proved,  that  the  punch- 
ing strain  was  a  true  index  of  the  steel  as  to 
its  carbon  percentage,  tensile  resistance,  duc- 
tility, and  the  force  required  to  give  a  perma- 
nent set.  A  fresh  series  of  experiments  on 
rails,  which  had  been  in  use  for  several  years 
on  the  same  line  of  railway,  proved  that,  con- 
trary to  what  might  have  been  anticipated, 
greater  hardness  had  not  conduced  to  the 
longevity  of  the  rails,  and  that  the  softer  ones 
showed  the  minimum  of  wear 


made,  yet  the  total  strength  of  the  rail  was 
materially  lessened  by  the  weak  under-table, 
by  which  much  of  the  elasticity  of  the  rail 
was  destroyed;  though,  by  planing  off  a  thin 
section,  this,  as  had  been  demonstrated  by 
experiment,  could  be  entirely  restored,  allow- 
ing for  a  proportionate  decrease  in  the  weight 
of  metal. 


ENGINEERING  STRUCTURES. 


the  defective  foundation  was  made  by  a  sub- 
marine diver.  It  was  found  that  a  small  por- 
tion, not  exceeding  one-twentieth  of  the 
whole,  is  defective,  though  there  is  no  evi- 
dence that  the  break  in  the  masonry  has 
increased  for  some  time.  The  examination 
was  made  by  Mr.  0.  B.  G-unn,  who  suggested 
a  plan  for  repair,  under  which  a  contract  was 
made  in  February  last  with  the  American 
Bridge  Company  of  this  city,  which  is  now 
prosecuting  it  under  the  supervision  of  Major 
Gunn.  The  plan  is  that  of  a  caisson  to  be 
built  at  the  site  of  the  pier  and  sunk  around 
it;  the  intervening  space  being  then  relieved 


The  Sewage  of  Paris. — The  question  of  dis- 
posing of  the  sewage  of  Paris  is  constantly 
being  discussed  from  one  point  of  view  or  ;  of  water,  the  masonry  will  be  restored  beneath 
another.  The  municipal  council  received  a  the  pier,  which  will  then  be  surrounded  by  a 
report  the  other  day  from  M.  Desouches  on  solid  wall  of  masonry  and  caisson  work,  11 
the  construction  of  a  proposed  sewer  to  con-  i  feet  thick,  making  it  as  secure  and  permanent 
nect  the  departmental  collector  of  the  Rue  as  any  pier  on  the  Missouri  River.  When  the 
d'Allemagne  with  the  great  receptacle  of  night  contract  was  made,  in  February,  as  Major 
soil  at  La  Villette,  and  thus  allow  of  the  sew-  Gunn  explains,  it  was  too  late  to  take  advan- 
age  of  the  Pantin  sewer,  which  now  falls  into  tage  of  the  ice,  and  the  unprecedented  flood 
the  Seine  at  Saint  Dennis,  being  carried  on  to  of  April  which  has  so  delayed  work  upon  the 
the  plain  of  Gennevilliers,  where  it  may  be  ,  Atchison  bridge,  has  prevented  the  repairs 
employed  in  irrigation.  M.  Desouches  recom-  being  made  before  this  time.  All  the 
mended  that  the  sewer  should  be  constructed,  machinery,  tools,  timber,  stone,  etc.,'  required 
but  that  the  contents  should  be  conducted  to  '  are,  however,  delivered,  and  the  caissons  are 
the  plain  in  question  only  as  an  experiment,  framed,  ready  to  be  built  and  sunk  around  the 
and  after  being  diluted  with  at  least  five  or  six  pier  as  soon  as  the  water  is  at  a  favorable  stage, 
times  its  volume  of  the  water  of  the  Ourcq.  by  the  same  men  who  have  sunk  the  piet's  of 
It  should  be  mentioned  that  the  water  of  the  the  Atchison  bridge,  quicker  and  more 
Ourcq,  brought  to  Paris  by  the  canal  which  successfully  than  any  work  of  the  same  mag- 
runs  under  "the  Place  de  la  Bastille,  is  very  |  nitude  ever  heretofore  done  in  this  country. — 
impure  water,  only  used  for  cleansing  pur-   Raihoay  Review. 


BOOK   NOTICES. 


285 


ORDNANCE  AND  NAVAL. 

The  twentieth  iron  steamship  launched  from 
the  yard  of  John  Roach  &  Son  since 
October,  1871,  went  into  the  water  at  Chester, 
Penn.,  on  Saturday,  5th  June.  Her  name  is 
the  "City  of  New  York,"  and  she  was  built  for 
the  Pacific  Mail  Steamship  Company,  being  the 
second  of  their  last  order  of  three  vessels  now 
in  different  stages  of  completion.  Each  of  these 
three  ships  is  353  feet  long,  by  40£  feet  wide, 
with  a  depth  of  39£  feet  from  the  hurricane 
deck  and  31  feet  from  the  spar  deck.  They 
will  each  be  of  a  capacity  of  3,500  tons,  cus- 
tom-house measurement,  with  accommodations 
for  153  first  cabin  and  1,200  steerage  passen- 
gers.— Bulletin. 

The  trial  trip  of  the  Solimoes,  a  monitor  re- 
cently launched  by  the  Compagnie  des 
Forges  et  Chantiers  de  la  Mediterranee,  was 
made  a  few  weeks  since.  This  vessel,  which 
is  built  for  the  Brazilian  Government,  is  a 
specimen  of  the  latest  improvements  in  naval 
architecture,  gunnery,  and  engineering.  The 
deck  is  only  90  cent,  above  water  line,  and 
hence  has  the  appearance  of  a  large  raft  78 
metres  in  length  by  18  beam,  with  a  draught 
of  about  lift.  The  cabins  and  engine-room  are 
naturally  below  water  line.  She  is  propelled 
by  a  beautifully  finished  pair  of  engines  of 
550  nominal  horse-power,  but  indicating  2000 
horse-power.  This  vessel  carries  four  Whit- 
worth's  guns  weighing  25  tons  each,  mounted 
two  to  each  turret.  The  weight  of  the  pro- 
jectiles is  275  kils.,  requiring  a  charge  of  35 
kils.  of  powder.  These  guns  have  given  ex- 
cellent results,  and  at  a  trial  of  their  range 
carried  a  shot  of  275  to  a  distance  of  11  kils. 
{nearly  7  miles). 

The  Alexandra  will  be  propelled  by  vertical 
compound  twin-screw  engines,  which  are 
to  indicate  not  less  than  8,000  horse-power. 
There  are  three  cylinders  to  each  set  of  en- 
gines, two  low  pressure  cylinders  of  90  in. 
diameter  being  placed  on  either  side  of  the 
high-pressure  cylinder,  which  is  70  in.  in 
diameter,  with  a  stroke  of  4  ft.  The  surface 
condensers  will  have  more  than  14,000  solid 
drawn  brass  tubes,  7  ft  4  in.  in  length,  and  f 
of  an  inch  outside  diameter;  the  water  for  the 
condenser  will  be  driven  by  means  of  centri- 
fugal pumps  worked  by  separate  engines.  To 
ensure  perfect  command  when  handling,  sepa- 
rate starting  engines  are  provided.  To  give 
proper  ventilation  for  the  stokeholes,  venti- 
lating engines  and  fans  are  fitted.  Steam  will 
be  supplied  by  twelve  boilers,  placed  in  two 
stokeholes  forward  of  the  engines.  The  boil- 
ers are  proved  to  120  lb.  to  the  square  inch, 
but  will  be  worked  only  to  about  60  lb.  The 
brass  stern  tubes,  in  connection  with  the  screw 
propellers,  are  the  largest  and  longest  in  the 
English  navy.  Each  is  cast  in  one  piece,  is 
34  ft.  in  length,  and  weighs  several  tons. 

Merchant  Navies. — The  Magdeburg  Gazette 
publishes  statistics  showing  that,  al- 
though the  German  navy  consists  at  present  of 
only  twenty- three  vessels,  with  sixteen  gunboats 
and  six  torpedo  boats,  the  Mercantile  Marine 


ranks  next  to  those  of  England,  America  and 
France.  It  consists  of  219  steamers  of  105,178 
tons,  and  203  sailing  ships  of  1,143,810  tons. 
The  former  have  increased  since  1867  by  near- 
ly 50  and  the  latter  by  more  than  20  per  cent. 
It  has  nearly  reached  the  strength  of  France, 
which  has  316  steamers  of  240,275  tons  and 
4951  sailing  vessels  of  906,705  tons,  its  tonnage 
having  thus  already  exceeded  that  of  the 
French  Marine.  England  and  Us  colonies 
have  4343  steamers  of  1,041,000  tons  and  32,- 
461  sailing  ships  of  5,573,000  tons,  while 
America  has  3,625  steamers  of  1,048,205  tons 
and  17,049  sailing  ships  of  2,140,585  tons. 
Next  to  Germany  comes  Russia  with  185  steam- 
ers of  36,000  tons  and  3089  sailing  vessels  of 
771,292  tons.  Austria  has  ninety-seven  steam- 
ers of  52,005  tons  and  2692  sailing  vessels  of 
288,176  tons.  Sweden  has  406  steamers  of 
22,000  tons;  Italy,  118  steamers  of  37,810  tons, 
and  as  many  as  19,488  sailing  vessels  of  1,031,- 
907  tons;  and  Spain,  151  steamers,  mostly  colo- 
nial, of  45,514  tons  and  4363  sailing  ships  of 
345,186  tons.  The  merchant  navy  of  Germanv 
is  manned  by  90,000  sailors,  while  that  of 
France  has  96,000. — Iron. 
TPhe  Vienna  paper  Naval  News  gives  some 
JL  information  as  to  the  present  state  of  the 
Austro-Hungarian  navy.  The  iron-clad  fleet 
consists  of  four  casemate  ships,  the  Custozza, 
Lissa,  Erzherzog  Albrecht,  and  Kaiser,  each 
with  from  fourteen  to  sixteen  guns,  engines 
from  800  to  1000  horse-power,  and  a  tonnaffe 
of  from  6000  to  7000.  There  are  also  7  iron- 
clad frigates.  The  first-class,  comprising  the 
Erzherzog  Ferdinand  Max  and  the  Hapsburg, 
have  sixteen  guns,  engines  of  800  horse  power, 
and  a  tonnage  of  5200  ;  the  second,  consisting 
of  the  Kaiser  Max,  the  Don  Juan  d' Austria, 
and  the  Prinz  Eugen,  are  being  converted  into 
casemate  ships;  and  the  third,  the  Salamander 
and  Drache,  have  fourteen  guns,  engines  of 
500  horse-power,  and  a  tonnage  of  3120.  The 
unarmored  fleet  consists  of  three  frigates, 
eight  corvettes,  five  gunboats,  one  torpedo  ship 
five  schooners,  two  aviso  steamers,  two  yachts, 
two  Danube  monitors,  one  factory  ship,  and 
ten  training  ships.  The  above  shows  that  the 
number  of  ironclads  has  remained  unchanged 
since  1872 ;  of  the  unarmored  ships,  one  gun- 
boat and  two  steamers  have  been  placed  on 
the  non-effective  list,  and  two  corvettes  and 
two  schooners  have  been  added.  The  estab- 
lishment of  officers  now  consists  of  1  admiral, 
2  vice-admirals,  5  rear-admirals,  52  captains, 
117  lieutenants,  145  ensigns,  and  87  cadets. 
The  number  of  seamen  was  increased  in  1S74 
from  5702  to  5836,  3557  of  whom  on  the 
average  serve  on  board  ship.  The  health  of 
the  navy  is,  on  the  whole  satisfactory,  and 
great  progress  has  been  made  in  the  organiza- 
tion of  the  naval  schools. 


BOOK  NOTICES. 

Systems  of  Projectiles  and  Rifling,  with 
Practical    Suggestions  for  their  Im- 
provement, AS  EMBRACED  IN  A  REPORT  TO  THE 

Chief  of  Ordnance.  By  Capt.  John  G. 
Butler,  Ordnance  Corps,  United  States  Army. 
New  York  :  D.  Van  Nostrand.     Price  $7.50. 


2S6 


VAN   NOSTRAND'S   ENGINEERING   MAGAZINE. 


For  some  years  past  Capt.  John  G.  Butler, 
of  the  United  States  Ordnance  Corps,  has  given 
unremitting  attention  to  the  improvement  of 
projectiles,  and  rifled  cannon,  and  he  has  now 
embodied  the  result  of  his  investigation  and 
experience,  with  the  consent  of  the  Chief  of 
Ordnance,  in  a  handsome  volume,  which  will  be 
of  great  utility  to  his  brother  officers,  and  of 
very  general  interest.  In  dealing  with  the 
question  he  arranges  the  different  forms  of  ri- 
fling and  projectiles  under  three  general  sys- 
tems— the  expansive,  embracing  all  projec- 
tiles which  in  loading  are  inserted  in  the  gun 
without  respeect  to  the  rifling,  but  which  "  take 
the  grooves"  by  the  action  of  the  gases  of  dis- 
charge upon  a  device  or  feature  of  the  projec- 
tile which  is  readily  expanded  thereby  into  the 
grooves  of  the  gun  ;  the  compressive,  embrac- 
ing all  projectiles  which  are  loaded  in  a  cham- 
ber, and  then  forced  by  the  action  of  the  pow- 
der through  the  bore  of  the  gun,  the  diameter 
of  which  across  the  lands  is  less  than  the  supe- 
rior diameter  of  the  projectile  (all  projectiles 
for  breech-loading  guns  have  heretofore  been 
of  this  class) ;  and  the;  flanged  system  embrac- 
ing all  projectiles  upon  the  cylindrical  por- 
tions of  which  are  projections  which  in  load- 
ing are  intended  to  be  inserted  into  correspond- 
ing grooves  in  the  bore  of  the  gun.  These  pro- 
jections may  be  studs  or  buttons,  ribs  or  flanges, 
grooved  shot  being  nothing  more  than  flanged 
shot  with  wide  flanges. 

The  simplicity  of  the  expanding  system,  says 
Capt.  Butler,  strongly  recommends  it  for  muz- 
zle-loading guns,  and  especially  for  field  cali- 
bres, where  rapid  firing  is  a  desideratum.  Its 
advantages,  indeed,  are  numerous  and  well  ac- 
knowledged, but  the  defects  of  different  pro- 
jectiles of  this  class  have  been  so  many  and 
serious  as  to  more  than  counter-balance  in  the 
opinion  of  many  the  admitted  advantages  of 
the  system.  He  proposes  then  a  system  of 
rifling  and  projectiles  which  removes  these  ob- 
jections and  defects.  The  rotating  device  con- 
sists of  a  double-lipped  annular  band  or  sabot 
attached  to  the  base  of  the  projectile.  A  nar- 
row camelure  between  the  upper  and  lower  lips 
of  the  sabots  distributes  the  gases  of  discharge 
so  evenly  that  the  slightest  irregularity  in  the 
expansion  of  the  upper  lip  has  never  been  dis- 
covered ;  at  the  same  time  ballotting  is  almost 
entirely  prevented.  It  is  officially  recorded  that 
in  the  course  of  upwards  of  100  rounds  with 
the  proposed  projectile  suoh  a  thing  as  a  flut- 
tering or  in  the  slightest  degree  unsteady  flight 
was  never  discovered.  The  upper  lip  of  the 
grooved  ring  may  be  made  so  thin  as  to  almost 
entirely  check  windage,  and  yet  possess  suffici- 
ent strength  to  rotate  the  heaviest  shot.  It 
may  also  be  made  so  extremely  thin  as  to  close 
windage  while  the  projectile  is  getting  under 
way, but  through  sheer  lack  of  stiffness  ride  over 
the  lands  towards  the  muzzle.  The  behavior  of 
the  new  projectile  is  all  that  need  be  desired  ; 
it  gives  very  superior  accuracy,  great  steadi- 
ness and  smoothness  of  flight,  there  was  not  a 
single  case  of  stripping,  though  over  100  projec- 
tiles were  fired,  and  not  a  single  failure  to  take 
the  grooves. 

With  regard  to  projectiles  of  large  calibre 
and  maximum  weight,  Capt.  Butler  does  not 


deny  that  they  might  be  benefited  by  a  more 
substantial  centreing,  and  he  gives  the  diagram 
of  a  double  centred  shot,  but  it  is  found  that 
his  system  is  sufficiently  accurate  for  all  prac- 
tical purposes.  In  discussing  the  compressive 
system  he  follows  the  same  course,  first  points 
out  and  comments  upon  the  principal  defects, 
and  then  explains  the  methods  of  removing 
them.  He  adopts  the  same  principle — the 
double-lipped  annular  sabot — as  with  muzzle 
loaders,  and  explains  that  there  can  be  no  un- 
due strain  from  the  checking  of  windage.  The 
sabot  is  forced  no  more  deeply  into  the  grooves 
than  occurs  in  a  muzzle  loading  gun,  while 
the  slight  quantity  of  gas  which  escapes  is  dis- 
tributed evenly  about  the  projectile.  He  men- 
tions that  if  it  be  thought  desirable  in  the  use 
of  either  of  the  expansive  projectiles  described 
to  entirely  close  the  windage,  this  can  be  done 
very  readily  by  a  scft  lead  ring  in  front,  or  by 
a  thin  flange  on  the  base  of  the  projectile  ;  and 
on  the  other  hand,  if  windage  is  desired  in  the 
chamber  as  well  as  in  the  bore  it  can  easily  be 
effected  by  grooving  the  sabot  by  attaching  it 
in  segments,  by  grooving  the  chamber  longi- 
tudinally with  channels  too  narrow  to  admit 
of  the  sabot  being  forced  into  them,  or  by  three 
or  more  holes  running  diagonally  through  the 
base  of  the  projectile,  and  terminating  at  its 
cylindrical  portion,  but  he  considers  the  system 
better  as  it  is. 

Of  course  the  practical  value  of  a  system  can 
only  be  determined  by  actual  experience,  but 
it  cannot  be  questioned  that  that  advocated  by 
Capt.  John  Butler  is  scientifically  correct,  since 
it  secures  accuracy  of  aim,  perfect  rotation 
with  the  least  possible  fatigue  to  the  gun,  owing 
to  the  reduction  of  friction  to  the  minimum, 
absence  of  ballotting,  and,  probably  also  from 
the  rotation  being  secured  with  so  little  friction 
between  the  gun  and  the  projectile  uniform 
and  high  velocitites.  The  projectile  is  so 
thoroughly  strong  that  slight  carelessness  in 
manufacture  or  inferiority  of  materials  do  not 
seriously  affect  its  value,  whilst  it  can  be  rough- 
ly handled  both  in  storing  and  transportation, 
is  comparatively  inexpensive,  and  does  not  in- 
jure the  gun.  Capt.  Butler's  book  should  be 
read  by  every  officer  of  ordnance,  to  whatever 
country  he  may  belong. — London  Mining  Jour- 
nal. 

Science  Series.  Skew  Arches  :  Advant- 
ages and  Disadvantages  of  Different 
Methods  of  Construction.  ByE.  W.  Hyde, 
C.E.  New  York  :  Van  Nostrand.  Price  50  cts. 
The  combination  of  strength,  elegance,  and 
economy  in  the  designing  and  construction  of 
a  skew  arch  of  more  than  limited  span  is  a 
fair  test  of  the  ability  of  an  engineer  ;  and 
although  when  brick  is  the  material  used  there 
is  really  little  choice  in  the  matter,  it  is  pro- 
bable that  a  more  intimate  acquaintance  with 
the  principles  involved  would  lead  to  the  adop- 
tion of  stone  in  many  cases  where  it  is  now 
neglected.  To  facilitate  the  acquisition  of  the 
requisite  knowledge,  the  excellent  little  treat- 
ise of  Mr.  E.  W.  Hyde  will  be  found  very  use- 
ful, since  it  contains  the  result  of  the  author's 
careful  personal  investigation,  chiefly  with  a 
view  to  ascertain  the  relative  security  and  the 


MISCELLANEOUS. 


287 


relative  facility  of  construction,  and  descrip- 
tions of  the  manner  of  making  the  necessary 
draughts,  templets,  &c.  To  facilitate  the  sys- 
tematic consideration  of  the  subject  he  treats 
of  the  helicoidal,  the  logarithmic,  and  the 
corne  de  vache,  or  cow's  horn  methods  sepa- 
rately, explaining  that  the  first  two  named  are 
derived  from  the  nature  of  the  coursing  and 
heading  joint  surfaces  and  their  intersections 
with  the  soffit,  and  the  third  from  the  soffit 
itself,  which  is  a  warped  surface  that  has  been 
thus  named. 

Commencing  with  the  helicoidal  method,  he 
explains  the  mode  of  draughting  the  arch,  and 
then  investigates  the  security  of  an  arch,  con- 
structed according  to  this  method,  remarking 
that  in  order  that  there  may  be  no  tendency  in 
the  successive  courses  to  slide  upon  each  other 
it  is  evident  that  the  coursing  joint  surface 
must  be  at  every  point  normal  to  the  direction 
of  the  pressure  at  that  point.  It  is  probable 
that  the  direction  of  pressure  varies  somewhat 
with  reference  to  the  vertical  plane  in  differ- 
ent portions  of  the  arch,  especially  if  the 
crown  settles  to  any  extent  after  removal  of 
the  centre.  Still  it  must  be  approximately 
parallel  to  the  plane  to  the  face,  otherwise  por- 
tions would  be  left  unsupported  and  fall.  He 
assumes  that  it  must  be  parallel,  and  then  ex- 
plains the  nature  of  the  curves,  and  the  direc- 
tion of  their  tangents  at  the  point  of  piercing 
the  soffit,  subsequently  giving  an  analytical  in- 
vestigation of  the  curves. 

Similar  information  is  then  given  with  re- 
gard to  the  logarithmic,  and  the  Corne  de 
Vache  methods,  and  the  author  then  discusses 
the  relative  advantages  of  each.  There  is  one 
advantage,  he  remarks,  possessed  by  the  heli- 
coidal method  over  each  of  the  others — it  may 
be  constructed  of  brick.  This  is  owing  to  the 
fact  that  the  successive  coursing  joint  curves 
are  parallel,  so  that  the  voussoirs,  except  those 
at  the  end  of  the  courses,  are  all  exactly  alike, 
while  in  the  other  methods  each  stone  is  differ- 
ent from  the  next  one,  though  the  two  halves 
of  the  arch  on  each  side  of  the  keystone  are 
alike,  so  that  any  stone  cut  for  one  side  will 
fit  also  in  the  corresponding  place  in  the  other 
side.  The  fact  that  the  different  voussoirs  are 
alike  in  the  helicoidal  method  of  course  lessons 
the  labor  of  preparing  the  drawings,  and  of 
making  the  necessary  measurements.  As  re- 
regards  the  difficulty  of  cutting  the  stones, 
this  method  does  not  seem  to  have  any  serious 
advantage  over  the  others  even  when  the  ap- 
proximate method  is  adopted,  while  if  the 
coursing  and  heading  joint  faces  were  cut  with 
exactness  as  helicoids  the  difficulty  would  be 
fully  equal  if  not  greater  than  that  by  the 
other  methods.  It  may  be  considered  an  ad- 
vantage as  regards  appearance  that  the  quoin 
stones  should  be  all  alike,  or  rather  those  faces 
of  the  quoin  stones  which  coincide  with  the 
faces  of  the  arch.  This,  of  course,  is  the  case 
only  with  the  helicoidal  method.  He  thinks, 
however,  that  the  gradual  decrease  in  the  size 
of  these  faces  from  one  side  of  the  arch  to  the 
other  would  not  be  displeasing  to  the  eye 
when  taken  in  connection  with  the  direction 
of  the  coursing  joint  curves,  which  would 
make  the  reason  for  the  decrease  obvious. 


The  real  test,  however,  of  the  relative  value 
of  the  different  methods  would  appear  to  be 
that  of  security.     When  this  test  is  applied  the 
logarithmic  and  cow's  horns  methods  both  ex- 
ceed by  far  the  helicoidal.     In  the  last-men- 
tioned when  semi-circular  there  is  always  a 
tendency  to  sliding  on  the  coursing  joints  both 
above  and  below  a  certain  point ;  that  is,  the 
assumed    direction    of    pressure    is    nowhere 
normal  to  the  coursing  joint  except  at  a  certain 
height  above  the  spring  plane  equal  to  r  sin. 
39°  32'  23",  and  that  near  the  springing  plane 
this  tendency  tq  sliding  increases  rapidly  with 
the  obliquity  up  to  a=20°  (about);  while  in  the 
logarithmic  method  along  each  coursing  joint 
curve  this  tendency  is  zero — that  is,  the  as- 
sumed direction  of  pressure  is  normal  to  the 
coursing  joint  surface  in  any  of  the  coursing 
joint  curves,  and  in  the  cow's  horn  the  tend- 
ency is  small  as  compared  with  the  helicoidal. 
The  logarithmic  method,  therefore,  seems  to 
approximate  to    theoretical  perfection  as  re- 
gards security,  is  followed  closely  by  the  cow's 
horn,  and  at  a  great  distance  by  the  helicoidal. 
The  cow's  horn  soffit  admit  of  plane  coursing 
joints,  which  are  not  feasible  in  the  others, 
and  thus  possesses  an  advantage  over  them,  if 
such  an  approximate  construction  be  desirable. 
If  cheapness  be  an  important  item  to  be  con- 
sidered,   the    last-mentioned    method    would 
seem  to  present  most  advantages,  as  avoiding 
almost  entirely  the  use  of  curved  surfaces,  and 
at  the  same  time  reducing  the  sliding  tendency 
to  a  small  amount.     If  the  main  thing  to  be 
considered  is  security  the  logarithmic  method 
must  stand  first. 

From  the  manner  in  which  Mr.  Hyde  has 
handled  the  subject,  the  reader  will  have  no 
excuse  for  failing  to  comprehend  it  thoroughly, 
and  whether  he  desires  merely  to  understand 
the  scientific  bearing  of  the  question,  or  to 
make  the  necessary  drawings,  patterns,  &c. ,  to 
apply  his  knowledge  practically  the  volume, 
which  is  amply  illustrated,  will  give  him  all 
the  information  he  requires. — London  Mining 
Journal. 


MISCELLANEOUS. 

The  Steam  Magnet. — M.  Donato  Tommasi 
states  that,  if  a  current  of  steam  at  a 
pressure  of  5  to  6  atmospheres  is  passed 
through  a  copper  tube  of  0.08  to  0.12  inch  in 
diameter,  and  coiled  spirally  around  an  iron 
cylinder,  the  latter  is  magnetized  so  effectually 
that  an  iron  needle,  placed  at  the  distance  of 
some  inch  or  two  from  the  steam  magnet,  is 
strongly  attracted,  and  remains  magnetic  as 
long  as  the  steam  is  allowed  to  pass  through 
the  copper  tube. 

Artificial  Hardening  of  Sandstone. — 
Manfred  Lewin  has  tried  with  success  in 
his  quarries  at  Saxonia,  and  at  Neundorf,  near 
Pirna,  a  process  of  impregnating  sandstone. 
The  stone  there  quarried  is  porous  and  readily 
absorbs  water  to  a  certain  depth;  it  is  this 
fact  which  renders  it  possible  to  introduce  a 
solution  to  harden  the  surface.  Lewin  im- 
pregnates the  stone  with  solutions  of  an 
alkaline  silicate  and  of  alumina;  there  is  thus 


288 


TAN   NOSTRAND'S   ENGINEERING   MAGAZINE. 


formed  an  aluminum  silicate  within  its  pores, 
-which  gives  to  the  surface  considerable 
resistance.  The  solutions  employed  are  made 
with  soluble  glass  and  with  aluminum  sulphate. 
After  the  impregnation,  the  sandstone  may 
be  polished  like  marble,  which  it  then  resem- 
bles closely.  Heated  to  a  high  temperature, 
the  exterior  layer  vitrifies  and  thus  may  be 
colored  at  pleasure.  The  coloration  may 
even  be  obtained  simply  by  mixing  the 
desired  pigment  with  one  of  the  two  solutions 
used  for  the  impregnation. 

Cleopatra's  Needle. — The  fine  obelisk 
which  goes  by  this  name  was  offered  to 
the  British  Government  in  1820,  by  Mahomed 
Ali  Pasha,  but  has  never  been  removed  owing 
to  the  difficulty  of  transit  and  also  a  report  that 
it  was  much  defaced  towards  the  base.  A  short 
time  since  General  Alexander  wrote  to  say 
that  he  had  gone  to  Alexandria  for  the  pur- 
pose of  examining  the  prostrate  obelisk  and 
had  found  it,  with  its  hieroglyphic  inscription 
in  perfect  preservation.  On  the  authority  of 
experts  he  asserts  that  its  safe  transport  to 
England  is  quite  practicable,  and  proposes 
that  it  should  be  erected  on  the  Thames  Em- 
bankment. General  Alexander,  on  the  same 
authority,  states  the  cost  at  £10,000,  for  which 
he  suggests  a  Parliamentary  grant,  observing 
that  this  is  just  an  eighth  part  of  the  sum  ex- 
pended by  the  French  Government  in  the 
transport  and  erection  of  the  obelisk  of  the 
Place  de  la  Concorde.  There  cannot  be  two 
opinions  regarding  the  ornamental  effect  of 
this  fine  relic  on  the  Embankment — a  work  it- 
self in  extent  and  strength  worthy  of  ancient 
Egypt ;  and  in  the  present  state  of  engineering 
art  there  should  be  no  difficulty  in  bringing  it 
over  and  placing  it. 

White  Brass  Bearings. — In  the  case  of 
bearings  for  shafts  and  axles  the  value 
of  the  metal  alloy  used  can  only  be  ascertained 
by  actual  practical  experience,  a  circumstance 
which  prevents  many  inventors  of  really  useful 
alloys  from  even  getting  their  material  tested  ; 
it  would  seem,  however  that  at  the  presant  time 
this  causes  but  little  inconvenience,  since  the  i 
economy  and  durability  of  white  brass  really  ! 
leaves  nothing  to  be  desired.  Although  some-  J 
what  similar  in  color,  white  brass,  or  as  it  is 
more  commonly  called  Parsons'  white  brass, 
differs  essentially  from  what  is  generally  called 
white  metals,  and  should  not  be  classed  with  j 
them,  being  harder,  stronger,  and  sonorous  ; 
it  is,  in  fact,  as  its  name  implies,  a  species  of 
Drass,  and  behaves  like  it  under  the  tool  when  j 
bored  or  turned,  it  does  not  clog  the  file,  and 
is  susceptible  of  a  very  high  polisn  ;  at  the  same 
time,  it  fuses  at  a  lower  temperature  than  or- 
dinary brass,  and  can  be  melted  in  an  iron  pot 
or  ladle  over  an  ordinary  fire,  which  renders  it 
exceedingly  useful  for  fitting  up  engines  and 
machines  where  first  cost  is  an  object,  as  it  can 
be  run  into  the  plummer-blocks  or  framing  to 
form  the  bearings,  bushes,  sockets,  &c,  with- 
out the  expense  of  fitting  or  boring  them,  or  it 
can  be  cast  in  metal  moulds,  or,  like  ordinary 
brass  or  gun  metal,  in  sand  or  loam.  It  has 
now  been  in  use  for  many  years  for  railway  ' 


carriage  and  engine  bearings,  shafting,  rolling- 
mills,  fans,  and  the  wearing  parts  of  many  other 
kind  of  engines  and  machines. 

Except  when  used  as  carriage-axle  bearings 
it  is  difficult  to  obtain  a  reliable  comparative 
test  of  the  durability  of  bearing  metal,  owing 
to  the  impracticability  of  having  the  bearings 
in  competition  with  each  other,  working  sim- 
ultaneously, and  under  precisely  corresponding 
conditions  ;  fortunately,  however,  the  wear  of 
a  carriage  axle  bearing  so  accurately  represents 
the  varying  speeds,  pressure,  &c,  met  with  in 
one  or  other  class  of  industrial  machinery  that 
an  alloy  which  can  successfully  pass  through 
the  ordeal  of  continued  use  under  a  railway  car- 
riage is  accepted  with  every  confidence  as  ap- 
plicable wherever  bearings  are  employed.  The 
manner  in  which  Parsons'  White  Brass  passed 
through  this  ordeal  is  most  satisfactory.  Two 
white  brass  bearings  were  put  under  one  end 
of  a  Great  Northern  brake  van,  and  at  the  same 
time  two  ordinary  brass  bearings  were  put  un- 
der the  other  end,  and  the  van  was  run  19,200 
miles,  or  twenty-four  trips  to  Edinburgh  and 
back,  and  it  was  found  that  whilst  the  White 
Brass  had  diminished  in  weight  but  2  ozs. ,  the 
ordinary  brass  had  lost  no  less  than  2  lbs.  4  ozs. 
Under  two  third-class  passenger  carriages(same 
railway  and  conditions)  the  white  brass  lost  2$ 
ozs.,  against  1  lb.  6  ozs.  and  1  lb  12  ozs.  respec- 
tively of  ordinary  brass  during  20,000  miles 
running  ;  the  locomotive  engineer  remarking 
that  the  bearings  ran  perfectly  cool,  and  were 
lubricated  with  oil.  The  break-van  bearing, 
after  it  had  run  the  19,200  miles  and  weighed, 
was  replaced,  and  the  following  week  the  van 
was  again  put  in  a  train,  this  time  running 
24,956  miles,  or  31  trips  to  Edinburgh  and  back. 

As  the  van  then  required  varnishing  it  was 
in  the  shop  at  Doncaster  for  a  month,  when  it 
was  brought  into  use  again,  and  up  to  the  Sat- 
urday preceding  the  date  of  the  report  it  had 
done  another  20,556  miles,  making  64,712  miles 
in  all,  the  locomotive  engineer  then  writing — 
"  These  bearings  are  yet  in  very  good  order, 
and  but  little  worn." 

With  such  results  as  these  it  is  not  surprising 
that  the  manufacturers  assert  that  the  white 
Brass  has  been  found,  by  carefully  conducted 
experiments,  to  greatly  surpass  in  durability  all 
other  kinds  of  anti-friction  metal  against  which 
it  has  been  tested,  to  reduce  friction  to  a  min- 
imum, and  effectually  prevent  heating  of  the 
journals.  It  is  equally  effective  with  quick  as 
as  with  slow  speeds,  and  will  work  satisfactory 
under  the  heaviest  weights.  Some  recent  appli- 
cations also  show  that  it  can  be  used  with  suc- 
cess to  replace  worn  out  bearings  even  when 
the  journals  have  been  greatly  worn  and  scored 
from  long  continued  use,  without  the  necessity 
of  returning  them.  The  price  of  the  white  Brass 
being  less  than  that  of  gun  metal  or  ordinary 
brass,  and  its  durability  very  considerably  great- 
er, a  double  saving  is  effected  by  its  use — first, 
in  prime  cost,  and  secondly,  in  renewals  and 
repairs,  to  which,  in  the  case  of  railway  car- 
riages, heavy  shafts,  &c,  which  have  to  be 
lifted  to  replace  the  bearings,  should  be  added 
the  saving  in  the  cost  of  labor,  and  the  loss 
arising  from  stoppages. — London  Mining  Jour- 
nal. 


VAN     NOSTRAND'S 


ECLECTIC 


EMIKEEEIM    MAGAZINE. 


NO.  LXXXII  -OCTOBEE,  1875.-V0L.  XIII. 


ELEMENTARY    DISCUSSION"    OF    STRENGTH    OF    BEAMS 
UNDER    TRANSVERSE    LOADS. 

By  Prof.  W.  ALLAN. 

Written  for  Van  Nostrand's  Engineering  Magazine. 
III. 


DOUBLE  FLANGED  BEAMS. 

So  far  we  have  considered  beams  with 
rectangular  cross  sections,  and  beams  of 
uniform  strength  deduced  from  these. 
We  will  now  consider  beams  of  =■=  shape. 

It  is  evident  from  the  investigation  al- 
ready given  of  the  condition  of  stress 
in  transversely  loaded  beams,  that  those 
portions  of  the  beam  nearest  the  centre 
bear  but  a  small  proportion  of  the  stress, 
while  the  contrary  is  the  case  with  the 
outside  fibres.  Hence  we  would  gain 
strength  by  moving  a  considerable  por- 
tion of  that  about  the  neutral  axis  and 
placing  it  on  the  top  and  bottom. 

The  first  form  in  which  the  idea  was 
applied  was  in  the  T  or  _L  cast  iron  beam. 
The  fact  that  rectangular  cast-iron 
beam  always  broke  by  the  tearing  of  the 
fibres  on  the  side  subjected  to  tension, 
suggested  the  idea  of  reinforcing  that 
side  of  the  beam  with  a  flange.  The  re- 
sult of  this  is,  that  the  neutral  axis  still 
passing  through  the  centre  of  gravity  of 
the  cross  section,  the  extreme  fibres  sub- 
jected to  compression  are  farther  off 
than  those  subjected  to  tension,  and  con- 
sequently are  strained  more  nearly  to 
their  full  strength  before  fracture.  This 
form  of  beam  gives  a  large  increase  of 
strength  for  the  same  amount  of  iron. 
Vol.  XIII.— No.  4—19 


It  was  still  plain  that  the  fibres  in  that 
part  of  the  web  about  the  neutral  axis 
were  but  little  strained  as  compared  with 
the  fibres  on  the  outside,  and  it  was  pro- 
posed to  leave  as  little  material  there  as 
possible,  and  to  place  the  mass  of  it  in 
two  flanges  (=c),  one  above  and  the 
other  below,  giving  to  these  flanges  sizes 
inversely  proportional  to  the  tensile  and 
compressive  strength  of  the  material. 
The  question  then  was,  how  much  of  the 
material  should  be  left  in  the  iceb,  for 
plainly  all  could  not  be  taken.  The 
amount  to  be  left  is  determined  by  ex- 
periment. If  the  web  is  left  too  thin, 
the  beam  will  twist  and  break  under  the 
shearing  force,  and  in  some  cases,  from 
the  want  of  stiffness  in  the  compressed 
flange. 

To  simplify  the  calculations,  the  web 
is  considered  as  bearing  all  the  shearing- 
stress,  and  no  other,  and  the  flanges  as 
bearing  all  the  extension  and  compres- 
sion clue  to  the  bending  moment  ;  and 
these  parts  should  be  proportional  ac- 
cordingly with  due  reference  to  the  prac- 
tical difficulties  that  sometimes  occur. 
The  ordinary  formulas  for  the  streugth 
of  such  beams  are  gotten  by  the  follow- 
ing approximation :  We  first  neglect 
the  compressive  and  tensile  forces  of  the 


290 


VAN   NOSTRAND'S   ENGINEERING  MAGAZINE. 


web,  which  are  small  compared  with 
those  of  the  flanges,  and  consider  it  as 
bearing  only  the  shearing  stress.  Then 
as  the  depth  of  the  flanges  is  generally- 
small  as  compared  with  the  depth  of  the 


beam,  we  consider  all  the  fibres  in> 
each  flange  as  strained  alike,  and  as  bear- 
ing the  average  stress  that  is  brought  on 
that  flange.     (Fig.  60.) 

The   resultant  of  the  force  on  each 


C 


Fig.  60. 


flange,  then,  is  equal  to  the  stress  on  a 
unit  of  surface  (S)  multiplied  by  the 
flange  area  (A)  :  that  is  =  S  A. 


The  point  of  application  of  the  force 
will  be  at  the  middle  of  the  depth  of  the 
flanges  (at  O  and  0\  Fig.  61).     Fig.  61 


N 


If- 


w 


Fig.  61. 


shows  the  forces  we  have  to  deal  with 
in  the  Case  corresponding  to  Case  I. 
under  rectangular  beams. 

Let  O'  0=d. 

S'  =  stress  on  upper   flange   per 

unit  of  surface. 
S"  =  stress   on   lower   flange   per 

unit  of  surface. 
A"=  area  of  lower  flange. 
A'  ==  area  of  upper  flange. 

Then  if  we  take  O  (Fig.  61)  as  a  cen- 
tre of  moments  we  have  : 

-Ntf-N'.0.+Wa:=0     (ButN=S'A') 
.•.S'A'fcWu  (57) 

If  we  take  O'  as  the  centre  of  mo- 
ments we  will  get 

S"A"d=Wx  (58) 

The  formula  for  shearing  force  is  iden- 


tical with  that  under  Case  I.  of  rec- 
tangular beams  ;  that  is  : 

T=Wz  (59) 

If  A'=A",  then  plainly  S'=S"  (from 
equations  57  and  58),  or,  the  forces  of 
tension  and  compression  are  equal  (as  in 
rectangular  beams)  ;  but  if  A'  and  A" 
are  not  equal,  we  have  : 

•■■A'«r  A"d-A  ; A 

That  is,  the  unit  stresses  in  the  flanges 
are  inversely  as  the  areas.  Now,  to  have 
the  material  distributed  between  the 
flanges  most  efficiently  for  strength  the 
unit  stress  should  be  in  proportion  to 
the  ultimate  strength  of  the  material 
against  tension  and  compression,  and 
hence  the  areas  of  the  cross  sections  of 
the  flanges  should  be  inversely  as  the 
ultimate  strength. 


STRENGTH   OF   BEAMS   UNDER   TRANSVERSE   LOADS. 


291 


Thus,  if  A  D  (Fig.  62)  be  of  cast-iron, 
which  is  six  times  as  strong  against  com- 


pression   as   against    tension,    the    nnit 
stress  in  the  lower  flange  should  he  made 


A 


£ 


0? 


Fig.  62. 


six  times  as  great  as  in  the  upper,  and  to 
effect  this  the  area  of  the  lower  flange 
should  be  one-sixth  that  of  the  upper. 

The  Cases  under  i  beams  are  similar 
to  those  under  rectangular  beams. 

Cass  I. — Beams  fixed  at  one  end  and 
loaded  at  the  other. 

S'  A'  d=  W  x,  and  S"  A"  d=  W  x  (60) 

Case  II — Beams  fixed  at  one  end  and 
.     loaded  uniformly. 

S'  A'd=%w  x\  and  S"  A"  d  =  i  w  x2  (61) 

Case  III — Beams  supported  at  both 
ends  and  loaded  at  some  interme- 
diate point. 

(62) 

92/ 

W.j.x-W(x-m)=S'A'd,or,=8"A"d 

Case  IV. — Beams  supported  at  both 
ends  and  loaded  uniformly. 

S'  A'  d=i  w  x  (l-a-)=S»  A"  d    (63) 

Case  V — A  single  moving  load  over  a 
beam  supported  at  both  ends. 


S'A'tf: 


—-  (l-x)=S"A"d    (64) 

v 


Case  VI — A  distributed  moving  load 
may  be  considered  as  included  in 
Case  IV 

The  formulae  for  shearing  stress  are 
identical  with  those  in  rectangular 
beams. 

The  principles  of  the  uniform  strength 
of  teams  may  be  applied  to  flanged 
beams  as  they  were  to  rectangular  beams. 
The  discussion  is  analogous  to  that  al- 
ready given. 

MOMENT  OF  RESISTANCE  OF  BEAMS  DETER- 
MINED   GEOMETRICALLY. 

The  following  method  of  obtaining 
the  moment  of  resistance  of  beams  is  of 
easy  application,  and  in  many  cases  of 
unsymmetrical  cross  section  is  the  sim- 
plest that  can  be  used  : 

I.  For  illustration,  take  a  beam  of 
rectangular  cross  section.  Let  GP  (Fig. 
63)  be  the  cross  section  at  some  point  of 


Fig.  64. 


292 


VAN   NOSTRAND'  S   ENGINEERING  MAGAZINE. 


this  beam.  The  stresses  on  the  fibres, 
as  we  have  already  seen,  increase  just  in 
proportion  as  we  go  from  the  neutral 
axis  towards  the  upper  or  lower  surface 
of  the  beam,  and  may  for  any  vertical 
slice  (as  that  at  E  F)  be  represented  by 
the  ordinates  of  two  triangles,  as  shown 
in  Fig.  64,  where  EI  (=F  J)  represents 
the  stress  on  the  outside  fibre.  For  the 
cross  section  GP  (Fig.  63)  the  stresses 
will  be  represented  by  two  wedges,  the 
bases  of  which  are  G  M  and  M  R,  and 
the  elevations  of  which  are  the  triangles 
shown  in  Fig.  64.  The  volumes  of  these 
wedges  give  the  amount  of  compressive 
and  tensile  force  exerted  at  the  cross  sec- 
tion in  question,  and  the  points  in  G  P 
under  the  centre  of  gravity  of  the 
wedges  give  the  "  centres  of  resistance," 
or  the  points  of  application  of  the  re- 
sultants of  these  forces. 

As  a  geometrical  representation  of  the 
stresses  on  the  fibres,  these  wedges  are 
perfect,  for  the  perpendicular  ordinate 
of  the  wedge  gives  in  every  case  the 
stress  which  exists  in  the  fibre  over 
which  it  stands.  Thus  the  line  T'V 
(Fig.  64)  represents  the  stress  on  each 
fibre  in  the  row  TV  (Fig.  63). 

But  it  is  often  difficult  to  find  the 
centre  of  gravity  of  these  wedges  in  the 
case  of  curved  and  irregular  cross  sec- 
tions, and  yet  this  must  be  done  before 
We  can  know  the  lever-arms  of  the 
stresses.  To  render  this  easier  to  do  we 
may  represent  the  stresses,  not  by 
wedges,  but  by  prisms,  the  centres  of 
gravity  of  which  are  over  the  centres  of 
gravity  of  their  bases. 

Thus,  if  in  (Fig.  65)  we  draw  the  two 


Fig.  65. 

shaded  triangles,  and  conceive  prisms  of 
a  height  =  E  I  (the  stress  on  the  outside 


fibre,  Fig.  64),  to  be  constructed  on  them 
as  bases,  we  shall  have  a  geometrical 
representation  of  the  stress  on  the  sec- 
tion GP,  less  perfect  in  some  respects 
than  that  given  by  the  wedges  but  bet- 
ter suited  to  our  purpose. 
For,  note  that, 

1.  The  volume  of  the  prism  GOH 
(Fig.  65)  is  equal  to  that  of  the  wedge 
GM  (Fig.  63),  and  the  volume  of  any 
part  of  the  prism  cut  off  by  a  plane 
parallel  to  the  neutral  axis,  as  that  whose 
base  t'  O  v'  is  equal  in  volume  to  the 
corresponding  part  of  the  wedge  T  M, 
or  since  the  height  of  the  prism  is  con- 
stant, the  stress  on  the  surface  GM  as 
we  go  out  from  the  neutral  axis  varies 
as  the  area  of  the  triangle  which  forms 
the  base  of  the  prism. 

2.  The  vertical  slice  of  the  prism 
standing  on  any  line  t'  v'  represents  in 
amount  the  stress  on  the  line  of  fibres 
t  v,  for  this  stress  is  equal  to  the  corres- 
ponding one  in  the  wedge,  the  slice  of 
the  prism  being  as  much  higher  than 
that  of  the  wedge  as  tv  exceeds  tl  v'. 
Of  course  (except  in  the  case  of  the  out- 
side fibres  in  the  row  G  H)  each  ordinate 
in  the  slice  of  the  prism  no  longer  rep- 
resents the  stress  on  the  fibre  over  which 
it  stands,  as  was  the  case  in  the  Wedge. 

3.  The  moment  of  the  tensile  forces, 
for  instance,  will  equal  the  area  of  the 
prism  GOH  multiplied  by  its  height, 
(EI  =  stress  on  outside  fibre  =  S).  The 
centre  of  resistance  of  these  forces,  or 
the  centre  of  gravity  of  the  prism  is  at 
C  (Fig.  65),  the  centre  of  gravity  of  the 
base  GOH.  The  triangle  GOH  is 
sometimes  called  the  "  effective  area  "  of 


Fig.  66. 

the    surface    GM,    because    a    uniform 
stress  on  it  of  an  intensity  =  the  unit 


STRENGTH   QF   BEAMS   UNDER   TRANSVERSE   LOADS. 


293 


stress  at  G  H  gives  the  same  amount  of 
resistance,  as  that  on  the  whole  area  G  M, 
acted  on  as  the  latter  is  by  a  varying 
stress. 

Considering   the   stresses   represented 


by  the  two  prisms  whoso  bases  are 
GOH  and  ROP  (Fig.  65),  as  concen- 
trated at  the  centres  of  gravity  C  and  C" 
(Fig.  67)  of  these  bases,  and  taking  one 
of  these  points    (as  C,  Fig.  67)   as  the 


"W 


Fig.  67. 

centre  of  moments,  we  have  in  the  case 
represented  in  the  figure  : 

(Vol.  of  prism  GOH)  x  00'=  Wx 
or  if  b  =  breadth  and  d  =  depth  of  beam 


S  (J  bd).  §  <?=!  S  bd*=M= W  x 
as  before. 


(65) 


Corollary.    If    the   beam   be    square, 
b=d,  and 


M=-Sbs 
6 


(66) 


LT.  As  a  second  example,  take  a  square 
beam  so  placed  that  its  diagonal  will  be 
vertical.  Fig.  68  is  the  cross  section. 
Here  we  find  the  base  of  the  prism  of 


stress  by  points.  To  find  the  line  in  the 
base  of  the  prism  corresponding  to  the 
stress  in  any  row  of  fibres,  such  as  A  B, 
whose  distance  from  the  neutral  axis  is 
O  X,  proceed  as  follows  : 

We  see  that  if  the  cross  section  were 


the  square  of  which  HLMK  is  the 
half,  then  a'  b'  would  be  the  line  requir- 
ed, since  this  is  the  breadth  at  thai  point 
of  the  triangle  H  O  K,  which  would  in 
that  case  represent  the  base  of  the  prism 
of  stress.     Project  the  points  A  and  B 


294 


VAN   NOSTRAND'S   ENGINEERING   MAGAZINE. 


upon  H  K.  Then  the  actual  row  (A  B) 
of  fibres  is  as  much  shorter  than  the  cor- 
responding row  in  the  supposed  section 
HM,  as  R  T  is  less  than  ELK,  and  conse- 
quently to  obtain  the  proper  line  in  the 
base  of  the  true  prism  of  stress,  a'  b' 
must  be  shortened  in  this  proportion. 
Draw  lines  from  R  and  T  to  O.  These 
lines  intersect  the  row  of  fibres  at  a  and 
b.     Then 

HK:RT(=AB)::«'5':ai    (67) 

Hence  a  b  is  the  line  required,  and  a  and 
b  are  two  points  in  the  outline  of  the 
base  of  the  prism  of  stress.  Any  num- 
ber .of  lines  as  nv,  &c,  may  be  gotten 
similarly  and  the  curve  drawn  through 
the  points  a--?i--b--v,  &c,  will  give 
the  form  of  the  base  of  the  prism  of 
stress.  This  base  is  shaded  in  the  dia- 
gram. 

For  any  ordinate  of  the  curve  O  nG, 
as  a  X,  we  have 


OX  :  aX;\ 
But  AX  =  XG 


OG : RG=AX 


and 


<r 


making   60  =  - 
&  2 

and   putting   0X=^   and 

have 


x  :  y 


>/-- 


2 
2 


«X=y,    we 

<f-> 


(68) 


This  is  the  equation  of  a  parabola 
with  vertex  at  n,  half  way  between  H  K 
and  the  neutral  axis.  Hence  the  base  of 
each  prism  is  composed  of  parts  of  two 
symmetrical  parabolas. 

Areas  of  the  bases.  Since  the  ai'ea  of 
a  parabola  is  two-thirds  of  the  circum- 
scribing rectangle,  the  area  of  each  base 

=%(GOxnv) 

Butw«=JR'T'  andR'T'=iHK 


Area 


2  ' 


4      12 


The  centres  of  gravity  of  these  bases 
(and  consequently  of  the  prisms)  are  at 
C  and  C,  and  the  distance 

CC'=%d' 
Hence  the  moment  of  resistance  of  the 
fibres  about  C  or  C  is 


24 


(69) 


(S=height  of  prism  or  stress  on  external 
fibres  at  G  and  P.) 

Corollary.  To  compare  the  resistance 
of  the  beam  in  this  position  with  its  re- 
sistance when  lying  flat  : 

Let  J=side  of  the  square  as  L  G. 
Then  d'=d  ^/2  and  eq.  (69)  becomes 


X  — 


1 


6v^" 


Sd3 


(70) 


Comparing  this  with  eq.  (66),  we  see 
that  the  beam  offers  greater  resistance 
when  flat  in  the  proportion  of 
1  _      1 
6  '  6^/2 
In  solving  these  problems  with  diagon- 
ally placed  beams,  place  the  above  value 
of  M  equal  to  the  moment  of  the  weight 
as  before. 

III.  Let  us  apply  this  method  to  a  T 
beam.  Take  for  example  the  cast-iron 
_L  beam,  calculated  in  part  on  p.  257 
Rankine's  Civil  Engineering,  in  which 
the  area  of  the  flange  =  §  that  of  the 
web.  Assume  the  flange  to  be  6  inches 
by  1  inch,  and  the  web  to  be  5  inches  by 
.8  of  an  inch,  and  draw  a  figure  of  the 
cross  section  to  scale  (Fig.  69). 


t     v 
Scaled. 

Fig.  69. 

1.  As  the  top  and  bottom  of  this  sec- 
tion is  not  symmetrical,  it  is  necessary  to 
find  the  position  of  the  neutral  axis, 
which  is  no  longer  at  the  half-depth. 
This  may  be  done  by  calculation,  or  by 
a  simple  mechanical  process  as  follows  : 


STRENGTH   OF   BEAMS   UNDER  TRANSVERSE   LOADS. 


295 


The  centre  of  gravity  of  the  cross 
section,  since  this  last  is  symmetrical 
with  regard  to  the  vertical  line  through 
the  middle  of  the  web,  must  lie  on  this 
line.  Cut  accurately  the  figure  of  the 
cross  section  out  of  card  board,  or  tin, 
or  good  paper,  and  suspend  it  freely  by 
one  end  of  the  flange,  suspending  also 
from  the  same  point  a  plummet.  Mark 
the  line  of  the  plummet  on  the  card 
board,  and  the  "centre  of  gravity  being 
on  this  line  and  also  on  the  middle  line 
of  the  web,  will  be  at  their  intersection 
O.  By  measurement  this  point  was 
found  to  be  distant  from  A  B  four  and 
three-tenths  inches  (4  .  3"),  which  is  also 
the  value  by  calculations.  The  line  L  M 
drawn  through  this  point  is  the  neutral 
axis. 

2.  To  determine  the  bases  of  the 
prisms  of  stress.  On  the  upper  side  the 
base  is  the  triangle  O  A  B,  if  the  alti- 
•  tude  be  taken  equal  to  the  stress  on  the 
fibres  along  A  B.  For  if  1/  M'  H  G  were 
the  upper  half  section,  O  G  H  would  be 
the  base  of  the  prism  and  O  A  B  is  less 
than  O  G  H ,  in  the  same  proportion  that 
L  M  A  B,  the  real  half  section,  is  less 
than  L'  M'  H  G.  Hence  (if  the  upper  be 
the  compressed  side)  the  total  compres- 
sive force  is  equal  to  the  prism  erected 
on  A  O  B,  with  the  height  equal  to  the 
unit  stress  at  A  B. 

Below  the  axis  L  M. — For  convenience 
we  should  have  the  height  of  the  tension 
prism  equal  to  that  of  the  compression 
one,  and  the  base  must  be  determined 
under  this  condition.  Complete  the 
large  rectangle  G  H  Q  Y,  making  the 
distance  of  QY  below  0  =  4.3  inches. 
Draw  O  Q  and  O  Y  and  the  shaded 
trapezoid  J¥RZ  cut  out  on  the  flange 
by  these  lines,  will  evidently  be  the  por- 
tion of  the  base  due  to  the  flange.  Hav- 
ing prolonged  the  lines  of  the  web  to  T 
and  V,  draw  O  T  and  O  V,  and  then  the 
shaded  triangle  OKI  will  be  that  part 
of  the  base  due  to  the  portion  (L  Z)  of 
the  web  below  the  neutral  axis. 

The  total  tensile  and  compressive 
forces  being  always  equal,  and  the  height 
of  the  prisms  having  been  assumed,  each 
=S'=  stress  on  fibres  at  the  distance  of 
A  B  from  O,  the  bases  of  these  prisms 
must  be  equal  also.  This  necessary 
equality  between  the  area  of  O  A  B  and 
that  ofOKI  +  JNRZ,  affords  a  means 


of  testing  the  accuracy  of  our  work  in 
finding  the  position  of  O. 

3.  Area  of  base  O  A  B.     This  is, 

=  £(LAxAB)  =1(4.3X.8)  =  1.72  sq. 
inches. 

4.  To  determine  the  distance  C  C 
(Fig.  69)  between  the  centres  of  gravity 
of  the  prisms,  which  distance  is  the  lever- 
arm  to  be  used  when  one  of  these  points 
is  taken  as  the  centre  of  moments. 
These  centres  of  gravity  (C  and  C)  can 
be  readily  determined  by  means  similar 
to  those  employed  in  finding  the  centre 
of  gravity  of  the  cross-section  itself. 
Thus,  cut  the  shaded  areas  (Fig.  69)  out 
of  card  board  or  paper,  and  suspending 
each  of  them  from  two  points  in  succes- 
sion, draw  vertical  lines  through  the 
points  of  suspension.  The  intersection 
of  these  two  lines  gives  the  centre  of 
gravity.  In  the  present  case  they  may 
be  so  simply  obtained  by  calculation, 
that  we  adopt  that  method.  The  centre 
of  gravity  of  A  O  B  is  =  §  the  distance 
from  O  to  A  B  or  O  C=|  (4 .  3)  =  2  .  87 
inches.  As  to  the  shaded  part  below  O, 
by  using  the  ordinary  formula  for  the 
centre  of  gravity  and  taking  moments 
around  O,  we  find  the  distance 

0C'= 

0NRx|(1.7)-(0  JK  +  0IZ)f(.7)  ) 


0NR-2(0JK) 

2.2764  — .01388 


=  1.318  inch. 


2.0145  — .2975 

Hence  the  distance 

CC'=OC  +  OC'  =  2.87  +  1.318=4.1Sins. 

Hence,  since  S'  is  the  height  of  the 
prisms,  the  moment  of  resistance  of  the 
fibres  is 

M=4.18X1.72.  S'=7.19  S' 

If  it  be  desired  to  have  M,  not  in 
terms  of  S',  the  stress  along  AB,  but  of 
S"  the  stress  on  the  lowermost  fibres  (at 
F  P),  we  have  since  the  stresses  increase 
directly  with  the  distance  from  O, 

S'  :  S"::L'G  :L'F::4.3"  :  1.7" 
.-.  S'=2.S3.  S"  and  M=18.19.  S* 

IV.  As  an  illustration  of  the  great 
saving  of  labor  sometimes  effected  by 
this  process,  take  the  steel  rail  now 
widely  used  in  England,  the  cross  sec- 
tion   of    which    is    given    to    scale    in 


296 


VAN   NOSTRAND'S   ENGINEERING   MAGAZINE. 


(Fig.    70) .     The   determination   of    the 
moment  here  by  calculation  would  be 


long  and  tedious.    The  dimensions  of  the 
cross  section  are -given  on  the  figure. 


1.  The  centre  of  gravity  O  of  the  cross 
section  is  found  by  making  a  template 
as  in  the  last  case,  and  suspending  it 
freely  by  a  corner.  The  vertical  through 
the  point  of  suspension  intersects  AX 
at  O,  which  is  2.55  inches  below  A. 
Through  this  point  draw  L  M,  the  neu- 
tral axis. 

2.  The  bases  of  the  prisms  of  stress 
are  determined  by  points  as  in  example 

Layoff  OX— 2.55  inches.  Draw  the 
rectangle  GHQY.  Assume  the  height 
of  the  prisms  to  be  the  stress  in  the  fibre 
at  A.  Then  proceeding  as  in  example 
II.,  the  line  of  the  base  corresponding 
to  any  row  of  fibres,  as  BD,  is  b  d. 
Obtain  any  number  of  points  in  the 
same  way  as  b  and  d,  and  through  these 
points  draw  a  curve  bounding  the  shaded 
figure  A  b  O  d.  Similarly  below  the 
neutral  axis,  t  v  is  the  line  in  the  base  of 
the  stress  prism  corresponding  to  T  V, 
and  the  shaded  figure,  ONR,  is  that 
base  where  the  height  is  taken  equal  to 
the  unit  stress  at  A.  The  equality  of 
the  bases  in  area  is  the  test  of  accuracy. 

3.  To  determine  these  areas.  The 
simplest  plan  in  the  present  case  is  first 
to  find  the  area  of  the  cross  section  it- 
self. This  is  done  as  follows  :  The  rail 
in  question  weighed  84  lbs.  per  yard, 
and  the    steel,  of   which  it  was  made 


weighed,  .277  lb.  per  cubic  inch.     Hence 

if   A = area  of   cross  section   in   square 

inches 

(36.  A)  .277  =  84     .-.  A=8.4  sq.  inches. 

Now  cut  out  of  the  same  card  board, 
or  paper,  templates  of  the  two  shaded 
parts  in  the  diagram,  and  also  of  the 
cross  section  itself,  and  weigh  them.  The 
ratio  of  the  weights  will  equal  that  of 
the  areas. 

The  comparison  of  weights  may  be 
readily  made  by  means  of  a  suspended 
wire,  which  may  serve  as  a  temporary  bal- 
ance, the  templates  to  be  compared  being 
stuck  on  the  opposite  ends,  and  one  or 
both  moved  until  the  wire  is  evenly  bal- 
anced. The  weights  of  the  templates 
being  inversely  as  their  distances  from 
the  point  of  suspension  of  the  wire, 
their  areas  will  be  in  the  same  propor- 
tion. The  areas  of  the  prisms  in  the 
case  before  us  were  found  to  be  equal 
each  to  2.49  square  inches. 

4.  The  centres  of  gravity  of  these 
bases  are  found  in  the  same  way  as  those 
of  the  cross  section  itself.  The  point 
C  was  thus  found  to  be  1.84  inches  above.. 
O  and  C  to  be  1.66  inches  below  it. 
Hence  the  distance 

CC'  =  3.5  inches. 

Therefore,  finally,  if  S'= trait  stress  at 
A,  the  moment  of  resistance  is, 


STRENGTH   OF   BEAMS   UNDER   TRANSVERSE   LOADS. 


297 


M=2.49X3.5xS'=8.7l5.  S' 

If  we  desire  M  in  terms  of  S"  (stress 
at  F  P),  we  have 


s' :  s" : :  i.84 

.  S'=l.ll  s" 


1.66 

.  M=9.67S" 


V.  A  circular  cross  section  (Fig.  71  j. 
Here  the  neutral  axis  of  course =L  M, 
passing  through  the  centre.  Draw  the 
circumscribing  rectangle  G  Y  and  obtain 
the  points  t,  b,  v,  d,  &c,  in  the  curve 
bounding  the  base,as  heretofore.  Through 
the  points  so  found  draw  the  curves. 


7V7i7\R 


Determine  the  areas  of  the  bases  of 

the   stress   prisms   by  comparing   them 

with  the  half-square  G  L  M  H.     Thus,  if 

a  template  is  not  to  the  surface  of  one 

of    these  beams   it   will    just  equal   in 

weight  the  template  cut  to  the  surface 

A6LOi5A,   or,    in    other   words,    the 

shaded   surface    AbOdA  is   just   one- 

da     1 
third  of  the  rectangle  GM,or|.-=-  d*. 

The  centres  of  gravity  C  and  C  are 
found  as  before  by  means  of  templates. 
In  this  way  it  was  found  that 

O  C  =  0  C'=.587  (O  A)  =  .  587 .  - 

.'.   CC'  =  .587c7 

The  height  of  the  prisms  being  S 
(=  stress  at  A  or  F)  the  moment  of  re- 
sistance is, 

M=S.^-  (.587  d)  =  .0978  d>  S 
6 

(The   accurate   value   by  calculation   is 

M=.0982dsS.) 


JVbte. — The  curve  of  the  base  of  the 
prisms  is  a  lemniscate.  To  find  its  equa- 
tion we  have  in  the  triangles  O  b  X  and 
OB' A, 

bX'  :  AB'  (=BX')  :;OX':OA 

And  taking  the  vertical  axis  as  that  of 
X,  and  the  horizontal  one,  as  that  of  Y, 
the  origin  being  at  O,  and  calling  the  co- 
ordinates of  the  circle  x'  and  y',  and 
those  of  the  lemniscate  x  and  y  we  have: 

y  :  y'\  \x  :  R,  or  y  :  VR!-.r  I  \  *  =  R 
.-.  RV=«*  (Ra-ss). 


Preservation  of  Metallic  Sodium. 
— According  to  Bottger,  if  sodium  be 
placed  in  alchohol  until  its  surface  be- 
comes brilliant,  and  then  in  naphthalic 
ether  chemically  pure,,  and  finally  in  a 
concentrated  solution  of  naphthaline  in 
naphthalic  ether,  the  metal  may  be  pre- 
served unalterable  with  its  lustre  unim- 
paired, for  a  long  time. 


298 


VAN   NOSTRAND  S   ENGINEERING-   MAGAZINE. 


THE  CONVERTED  RODMAN  GUN. 

From  "Engineering." 


We  have  recently  referred  to  experi- 
ments soon  to  be  made  in  the  United 
States  with  some  new  forms  of  ordnance, 
anions;  them  being  a  cast-iron  Rodman 
gun  converted  upon  the  Palliser  system. 
Some  interesting  trials  with  this  gun  have 
been  already  carried  out,  and  their  re- 
sults are  so  encouraging  that  the  Ord- 
nance Board  have  recommended  that 
more  of  the  cast-iron  guns  now  forming 
the  United  States  heavy  armament  should 
be  converted  in  a  similar  manner. 

The  gun  with  which  the  experiments 
just  referred  to  were  carried  out  was  orig- 
inally a  10-in.  smooth  bore  cast-iron  piece. 
The  bore  was  enlarged  to  a  diameter  of 
13.5  in.  and  a  wrought-iron  tube  2.75  in. 
thick  was  introduced.  The  cast-iron  shell 
had  been  made  in  1866,  the  ultimate 
tensile  strength  of  the  metal  was  32,369 
lb.  per  inch,  and  the  initial  tension  on 
the  gun  was  12,000  lb.  The  iron  tube 
was  manufactured  by  Sir  William  Arm- 
strong &  Co.,  and  the  clearance  between 
the  outside  of  the  tube  and  the  shell  was 
about  Tooth  of.  an  inch. 

The  gun  had  originally  been  made 
without  preponderance,  and  by  its  con- 
version it  became  heavy  at  the  muzzle. 
This  would  be  the  case  with  all  the  simi- 
lar guns  so  converted,  and  it  is  proposed 
to  overcome  the  difficulty  by  reducing 
the  diameter  of  the  trunnion  from  10  in. 
to  8  in.,  removing  the  metal  eccentri- 
cally, and  then  shrinking  eccentric  rings 
over  the  trunnions  until  their  diameter 
is  restored,  and  the  centre  of  gravity  is 
brought  into  the  required  position.  A 
collar  at  the  muzzle  keeps  the  tube  in 
the  gun,  and  a  screwed  plug  prevents  it 
from  turning.  The  rifling  consists  of 
fifteen  grooves  of  equal  width  with  the 
lands,  the  rate  of  twist  being  1  in  40. 
The  powder  employed  was  that  known 
as  the  double  hexagonal  grain,  to  which 
we  referred  on  a  recent  occasion.  The 
specific  gravity  is  1.7511,  and  the  weight 
equals  80  grains  to  the  pound.  The  di- 
mensions of  the. grains  are  as  follows: 
Width  between  faces  of  cones  .7  in., 
width  over  all  .75  in.,  width  of  faces  at 
each  side  .32  in.,  thickness  of  parallel 
portion  between  bases  of  cones  .15  in. 


Two  classes  of  projectiles  were  em- 
ployed for  the  trial,  known  as  the  Butler 
and  Arrick  projectiles — to  the  former 
we  shall  refer  again  shortly  with  consid- 
erable detail — but  only  sixteen  rounds 
were  fired  with  the  latter  class. 

The  following  are  some  of  the  leading 
particulars  of  the  trial :  Five  rounds 
were  fired  with  charges  rising  from  20 
lbs.  to  25  lbs.,  and  weights  of  projectiles 
from  160  lbs.  to  175  lbs.  No  change  in 
the  tube  was  detected  after  these  firings. 

Seven  rounds  were  then  fired  with  35- 
lb.  battering  charges,  and  173-lb.  pro- 
jectiles. After  these  rounds  it  was  found 
that  the  tube  had  set  at  some  points 
hard  against  the  cast-iron  shell,  and  that 
at  the  point  of  maximum  pressure,  the 
diameter  had  increased  to  8.007  in. 

With  the  same  charge  38  further 
rounds  were  fired,  of  which  30  were  with 
projectiles  of  186  lb.  weight;  after  these 
the  greatest  enlargement  of  the  tube 
was  .002  in.  at  the  charge,  and  .003  at 
the  projectile.  Sixteen  rounds  were  then 
fired  with  a  different  class  of  projectile, 
weighing  165  lb. ;  these  gave  very  bad 
results,  and  were  discontinued.  They 
were  succeeded  by  50  rounds  with  35-lb. 
powder  charges,  and  174-lb.  projectiles, 
with  a  further  enlargement  of  .001  at  a 
position  from  36  in.  to  40  in.  from  the 
bottom  of  the  bore,  the  tube  at  this 
point  not  having  been  previously  ex- 
tended. Sixty-three  rounds  were  then 
fired,  of  which  50  were  with  projectiles 
weighing  187-lb.  No  further  enlarge- 
ment was  detected,  but  beyond  the  trun- 
nions the  tube  set  out  .002  in.  One 
hundred  additional  rounds  with  171-lb. 
projectiles  resulted  in  a  further  enlarge- 
ment of  .002  in.  at  a  point  24  in.  from 
the  bottom  of  the  bore.  These  were 
succeeded  by  another  100  rounds,  with 
similar  charges  and  projectiles,  and  the 
increased  enlargement  was  found  to  be 
.003  in.  One  hundred  and  forty-seven 
further  rounds  completed  the  total  of 
513,  to  which  the  gun  has  been  already 
subjected,  the  final  series  causing  an  en- 
largement of  .004  in.,  and  the  total  in- 
crease in  diameter  being  .018  in.,  count- 
in  g:   from  the   twelfth   round.     Of   the 


THE   FUSION   OF   STYLES. 


299 


above,  however,  sixteen  rounds  were 
fired  with  unsuitable  projectiles,  and  the 
effect  they  produced  may  be  fairly  de- 
ducted, so  that  on  484  rounds  fired  with 
battering  charges  the  enlargement  was 
.011  in. 

In  conducting  these  experiments  the 
velocities  were  measured  with  the  Le 
Boulenge  chronograph,  and  the  Rodman 
pressure  gauge  was  also  employed.  The 
maximum  muzzle  velocity  was  1,459  ft., 
the  mean  maximum  pressure  with  bat- 
tering charges  was  31,282  lb.,  and  the 
maximum  energy  of  projectile  per  inch 
of  shot's  circumference  was  220,346 
foot-pounds. 

The  results  thus  obtained  are,  it  will 
be  seen,  highly  satisfactory,  and  open  up 
an  effective  mode  for  the  improvement 
and  strengthening  of  the  United  States 
ordnance,  of  which  the  cast-iron  is  the 
best  in  the  world.  The  present  arma- 
ment of  the  United  States  for  coast  de- 


fence includes  1,294  ten-inch  Rodman 
guns,  and  in  their  report  the  Ordnance 
Committee  point  out  that  these  guns 
are  at  present  useless  for  purposes  of 
defence  against  armor-plated  vessels,  so 
that  the  casemates  and  batteries  con- 
structed at  an  enormous  outlay,  are  com- 
paratively useless,  and  must  remain  so, 
until  the  present  armament  shall  have 
been  replaced  by  new  guns,  or  the  pres- 
ent ones  are  converted  into  efficient 
rifles. 

They  consider  that  the  trials  al- 
ready carried  out  with  the  10-in.  con- 
verted Rodman,  are  sufficiently  encour- 
aging to  justify  the  expectation  that  by 
the  same  process  the  existing  cast-iron 
guns  can  be  converted  into  formidable 
weapons,  but  before  recommending  any 
extensive  change,  they  propose  to  carry 
out  further  trials  with  another  10-in.  and 
a  12-in.  calibre  Rodman,  similarly  con- 
verted. 


THE  FUSION  OF  STYLES. 


From  "The  Architect. 


From  being  the  rallying  points  of  two 
opposing  camps  in  the  ai-chitectural  pro- 
fession, the  forms  of  architectural  de- 
sign long  known  as  Classic  and  Gothic 
seem  to  be  gradually  entering  into  a 
strict  bond  of  amity,  and  on  the  way  to 
prove  to  the  unprejudiced  spectator  that 
they  are  "  not  so  very  different  after 
all."  The  time  has  at  least  gone  by 
when  the  critic  of  decided  leanings  to- 
wards one  or  other  school  could  arrange 
the  sheep  of  Classicism  on  one  hand,  and 
the  Gothic  goats  on  the  other.  We  are 
losing  these  sharp  distinctions.  Collec- 
tions of  architectural  drawings,  as  in 
competitions,  are  no  longer  to  be  divid- 
ed into  designs  with  columns  and  pedi- 
ments, and  those  with  buttresses  and 
pinnacles.  If  in  such  a  gathering  there 
is  found  a  set  of  drawings  of  which  the 
details  are  purely  Roman,  or  one  that 
can  be  safely  referred  to  a  particular 
quarter  of  the  thirteenth  and  fourteenth 
century  for  all  its  precedents,  it  is  com- 
monly noted  by  the  enlightened  observer 
as  "  tame,"  and  rewarded  with  faint 
praise  accordingly ;  while  his  warmer 
commendations  are  reserved  for  designs 


which,  spurning  these  trammels  of  a 
past  day,  present  a  union,  or  reunion,  of 
features  from  both  the  main  sources  of 
the  modern  architect's  inspiration;  some- 
times fortunately  combined,  sometimes 
reminding  one  of  Portia's  suitor  from 
England,  who  she  thought  had  bought 
"his  doublet  in  Spain,  his  round  hose  in 
France,  and  his  behavior  everywhere." 
It  would  be  natural  that  such  a  fusion  of 
recognized  styles  should  be  practiced  for 
some  time  by  architects  before  its  exist- 
ence began  to  be  observed  outside  the 
profession  ;  but  the  fact  is  penetrating 
the  non-professional  stratum  now  ;  and 
as  we  read  in  a  weekly  literary  contem- 
porary the  other  day  that  the  Queen 
Anne  designs  of  the  London  Board 
Schools  which  are  being  erected  are  "  in 
all  their  main  qualities  essentially  Goth- 
ic," it  is  time  to  look  about  us. 

And,  on  the  whole,  we  think  an  im- 
partial survey  of  the  average  buildings 
going  on  just  now  will  show  that  Gothic 
and  Classic  have  not  met  on  quite  equal 
terms,  and  that  the  latter  is  in  fact  hav- 
ing rather  the  worst  of  it,  and  is  more 
or  less  succumbing  to  the  Gothic.     It  is 


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true  we  have  still  a  large  proportion  of 
buildings  in  which  columns  and  archi- 
traves play  an  important  part,  and  win- 
dows are  adorned  with  little  pediments 
and  neat  consoles  ;  hut  the  change  is 
shown  in  these  by  the  increased  vivacity, 
variety,  and  relief  of  the  carved  decora- 
tion. JSTo  architect,  with  any  concern 
for  his  artistic  reputation,  is  content  to 
adorn  his  building  with  the  old  stereo- 
typed festoon  and  garland  kind  of  thing, 
with  no  novelty  of  idea  and  no  light 
and  shade  in  execution.  Gothic  detail 
has  overflowed  into  our  Classic  buildings, 
and  carving  is  found  on  these  which 
would  be  nearly  as  well  in  place  on  a 
building  of  manifestly  Gothic  type.  But 
the  converse  is  hardly  the  case.  We 
do  not  often  find  details  in  any  marked 
degree  Classic  in  character  introduced 
into  Gothic  buildings.  The  fluted  col- 
umn, and  the  facias  of  the  architrave, 
do  not  find  their  way  there,  and  would 
be  pretty  well  killed  if  they  did.  The 
nearest  approach  to  something  of  Classic 
feeling  in  our  modern  Gothic  buildings 
is  perhaps  the  use  of  the  heavy  square 
pillar,  with  carved  capital,  which  may  be 
regarded  as  a  kind  of  modification  of 
the  pilaster  ;  though,  in  fact,  it  is  found 
in  early  Gothic  building  in  the  North  of 
Europe  especially  ;  and  perhaps  Classic 
influence  may  be  recognized  also  in  the 
increased  dimensions  and  more  pro- 
nounced character  of  the  horizontal  cor- 
nice in  modern  Gothic  buildings.  It 
might  not  be  very  easy  to  say  whether 
the  leaning  towards  early  and  even 
Romanesque  Gothic  at  present  is  a  cause, 
or  a  consequence,  of  the  feeling  in  favor 
of  a  kind  of  fusion  of  Classic  and  Goth- 
ic ;  but  we  are  inclined  to  regard  it  as  a 
consequence,  and  as  arising  almost  un- 
consciously from  a  desire  to  secure  the 
dignity  of  expression  belonging  to 
Classic  architecture,  and  perhaps  the  fit- 
ness of  its  horizontal  composition  for 
practical  purposes,  without  losing  the 
variety  and  play  of  light  and  shadow  so 
characteristic  of  Gothic  work.  Thus,  in 
an  indirect  way,  the  Classic  has  influ- 
enced the  main  type  of  modem  Gothic; 
but  in  regard  to  the  direct  visible  effect 
of  the  one  style  on  the  other,  there  can 
be  little  doubt,  as  before  observed,  that 
Gothic  is  carrying  the  day,  and  is  over- 
running what  would  otherwise  be  Classic 
design  with  its  own  specialties  of  detail. 


This  fusion  of  Gothic  and  Classic  is 
what  has  been  preached  some  time  back 
by  certain  critics,  who  may  now  see 
their  ideas  carried  out  to  a  greater  ex- 
tent perhaps  than  they  ever  expected. 
And  perhaps  any  movement  which  gives 
us  something  in  place  of  mere  copyism 
deserves  to  be  called  a  gain.  But  as  we 
look  at  the  buildings  of  this  mixed  type 
of  architecture  springing  up  around  us 
we  cannot  say  that  it  is  clear  gain.  A 
much  greater  variety  of  manner,  a  (gen- 
erally) much  more  ornate  treatment 
we  do  see  than  under  the  old  "  pure 
style  "  method,  and  occasionally  a  really 
picturesque  combination  of  detail  result- 
ing in  a  satisfactory  and  homogeneous 
effect.  But  in  the  main  this  homogene- 
ous quality,  this  unity  of  treatment,  is 
just  what  we  miss  in  our  new  buildings; 
there  seems  a  want  of  totality,  of  relation 
of  parts,  in  them,  accompanied  too  often 
also  by  a  lamentable  want  of  that  refine- 
ment of  detail  which,  after  all,  intelligent 
reproduction  of  a  complete  and  uniform 
style  at  least  secured  to  us.  Our  new 
buildings  seem  full  of  details  that  are 
quarreling  with  each  other  ;  full  of  con- 
tradictory emphasis.  Carved  ornament 
is  crowded  on  more  abundantly  than 
thoughtfully  ;  granite  shafts  with  large 
spreading  capitals  are  put  wherever 
they  can  be  got  in  ;  archivolts  and  win- 
dow-heads are  bemoulded  and  recessed 
so  as  to  be  quite  over-heavy,  and  key- 
stones are  getting  to  such  a  size  as  to  be 
sometimes  double  the  length  of  the  ra- 
dius of  the  arch  in  which  they  are  in- 
serted. All  this  produces  a  certain 
novelty  of  effect,  and  the  appearance  of 
a  great  deal  of  elaboration  of  design  ; 
but  it  is,  in  one  word,  vulgar  ;  and  that 
is  just  the  character  of  a  great  propor- 
tion of  this  nondescript  architecturewhich 
is  being  produced  at  present.  Details 
properly  Classic  would  unquestionably 
look  hard  and  thin  if  transferred  to  a 
Gothic  building ;  but  the  converse  is 
equally  true,  that  details  which  would 
be  very  well  in  place  in  a  design  entirely 
and  unaffectedly  Gothic  look  large, 
coarse,  and  over-pronounced,  when  trans- 
ferred to  a  design  the  main  type  of 
which  is  Classic.  The  two  schools  of 
detail  will  not  really  harmonize  with  one 
another,  except  to  a  very  limited  extent. 
But  what  is  even  more  marked  in  the 
class  of  design  of  which  we   are  speak- 


SPONGY   IRON. 


301 


ing  is  the  loss  of  that  unity  and  homo- 
geneous structure  which  belongs  to  really- 
good  purely  Classic  or  Gothic  buildings. 
In  these  latter,  at  least,  everything 
seems  to  be  in  its  place,  and  to  have  a 
general  coherence  of  treatment  and 
style  ;  a  quality  the  value  of  which  can 
sccrcely  be  overrated.  And  it  is  the  evi- 
dent loss  of  this  in  recent  architecture 
which  tempts  one  to  doubt  whether  the 
escape  from  architectural  reproduction, 
upon  which  we  are  sometimes  felicitated, 
is  by  no  means  an  unmixed  gain.  Such 
a  building  as  Whitehall  may  be  consid- 
ered very  artificial  and  cold  in  style ;  no 
doubt  it  is,  but  it  has  proportion  and 
consistency  of  design,  and  is  in  perfect 
keeping  with  itself.  And  similar  praise 
may  be  bestowed  on  a  much  greater 
building  in  every  way,  the  Houses  of 
Parliament.  That  the  style  selected  for 
it  is  not  in  itself  one  of  the  best  phases 
of  Gothic  is  unquestionable ;  that  it 
might  have  been  treated  with  more  pow- 
er and  effect  one  may  be  at  liberty  to 
think.  But  at  all  events  there  is  a 
"  oneness "  about  it  ;  an  entire  keeping 
throughout,  which  we-  look  for  in  vain 
among  the  buildings  of  the  eclectic 
school.  It  is  possible  that  by  means  of 
this  experimental  medley  through  which 
we  are  passing  we  may  arrive  at  some- 
thing both  novel  and  coherent  in  the 
end  ;  but  it  must  be  confessed  there  is 
not  much  indication  of  that  at  present. 
Novelty,  no  doubt,  there  is,  plenty  of  it; 
but  the  old  dignity  of  architecture  seems 
to  suffer  sadly  in  the  interim.  And, 
with  every  wish  that  modern  architec- 


ture should  entirely  emerge  from  mere 
copying,  we  may  suggest  that  it  is  pay- 
ing too  dear  for  this  to  throw  aside  and 
ignore  that  coherency  of  style  and  de- 
sign which  has  characterized  all  that  we 
admire  most  in  the  architecture  of  the 
past  ;  and  that  possibly  a  truer  (though 
perhaps  slower  and  more  laborious)  road 
to  originality  would  be  found  in  master- 
ing the  feeling  and  constructive  princi- 
ples of  a  complete  style,  and  adapting 
that,  freely  and  unreservedly,  to  the 
practical  wants  of  the  day,  than  in  pick- 
ing details  out  of  different  styles,  in  the 
vain  hope  of  piecing  them  together  into 
a  new  and  "original"  one;  original  only 
in  the  sense  of  having  no  origin. 

One  thing  is  unquestionable  :  that  if 
this  fusion  of  styles  goes  on  at  the  rate 
which  it  seems  to  threaten,  the  business 
of  architectural  critics  will  become  seri- 
ously and  painfully  complicated.  It 
used  to  be  sufficient  to  describe  a  build- 
ing as  Greek,  Roman,  or  Gothic  ;  every- 
body knew  what  was  meant.  But  now 
the  varieties  of  combination  are  so  di- 
verse and  unexpected,  that  language 
fails  in  the  effort  to  describe  them  in 
any  concise  form.  The  newspaper  writ- 
ers have  been  hopelessly  bothered  for 
some  time  back,  and  do  not  know  what 
to  call  a  new  building  now  ;  and  the 
professed  architectural  critic  must  suc- 
cumb before  long,  and  must  either  in- 
vent a  new  and  very  extensive  vocabu- 
lary, or  call  upon  the  architect  in  each 
case  to  say  what  he  wishes  his  design 
to  be  considered. 


SPONGY  IRON. 


From  "Iron." 


At  a  recent  meeting  of  the  Newcastle- 
upon-Tyne  Chemical  Society,  held  in  the 
theatre  of  the  College  of  Physical 
Science,  Mr.  J.  Pattinson,  the  President, 
in  the  chair,  Mr.  Gibb  read  a  paper  on 
"  Spongy  Iron." 

Spongy  iron,  or  iron  sponge — the 
slightly  cohering  mass  resulting  when 
iron  ores  are  reduced  below  the  welding- 
heat  of  iron,  said  the  author — is  produced 
in  nearly  all  iron  smelting  processes,  al- 
though it  is  a  form  of  iron  but  little 
known  in  practice.    Many  proposals  have 


been  made  to  separate  iron  smelting  into 
the  two  distinct  operations  of  reduction 
to  sponge,  and  the  subsequent  welding 
or  melting  of  this  product  to  produce 
malleable  iron,  steel,  or  cast  iron.  The 
earliest  attempts  on  a  large  scale  were 
those  of  Clay,  under  patents  obtained  in 
1837  and  1840,  and  he  has  been  followed 
by  a  series  of  inventors,  of  whom  Chenot 
conducted  the  most  elaborate  recorded 
experiments.  Efforts  in  this  direction 
still  continue;  two  processes,  having  for 
object  respectively  the  manufacture   of 


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puddle  bar  and  steel,  being  now  carried 
on  on  a  somewhat  large  experimental 
scale  ;  and  lately  a  series  of  extensive 
experiments  were  made  by  Siemens  with 
specially  planned  furnaces  that  certainly 
reduced  the  ore  to  sponge,  and  melted 
the  latter  successfully  so  far  as  economy 
of  working  was  concerned.  But  iron  as 
sponge  is  in  a  most  favorable  condition 
for  absorbing  sulphur  from  the  reducing 
agent  and  from  furnace  gases — a  draw- 
back that  compelled  Siemens  to  abandon 
this  method  of  working. 

Although  the  separate  production  of 
spongy  iron,  for  the  manuf acture  of  iron 
does  not  give  workable  promise,  the  fine 
state  of  division  of  the  metal  in  the  iron 
sponge  renders  it  very  suitable  for  the 
precipitation  of  copper  from  solutions 
produced  in  the  extraction  of  copper 
from  its  ores  by  the  wet  method. 

For  the  use  of  spongy  iron,  in  the  re- 
duction of  sulphides,  &c„  in  the  dry  way 
Bronze  and  Deherrypon  obtained  a  patent 
in  1859,  and  later  in  the  same  year 
Gossage  patented  the  use  of  spongy  iron, 
reduced  from  burnt  pyrites  in  ovens  or 
muffle  furnaces,  for  the  precipitation  of 
copper  from  solution.  In  1862  Bischof 
patented  the  manufacture  and  applica- 
tion of  spongy  iron  for  copper  precipita- 
tion, his  process  and  raw  material  being 
essentially  the  same  as  those  described 
in  Gossage's  patent  three  years  earlier. 
In  1863  Bischof  patented  an  arrange- 
ment reverberatory  furnace  and  acces- 
sory apparatus,  for  the  production  of 
spongy  iron,  for  use  in  precipitation  and 
other  purposes.  Henderson  in  1863  and 
1867,  patented  a  variety  of  furnaces, 
and  in  1869  Snelus  patented  a  furnace 
similar  to  Gerstenhofer's  pyrites  kiln, 
for  the  production  of  spongy  iron,  but 
no  one  of  their  devices  has  been  adopted. 
Proposals  patented  later  than  Bischof's 
have  had,  for  main  object,  the  pro- 
duction of  sponge  for  the  manufacture 
of  iron  and  steel.  Most  of  these 
have  been  some  form  of  retort  or  muffle 
furnace  in  which  the  mixture  is  heated 
by  transmission  through  brickwork,  the 
retort  being  horizontal  or  vertical.  This 
method  is  slow  in  action,  and  the  wear 
and  tear  of  the  brickwork  has  proved  too 
great  in  practice.  Snelus'  furnace,  in 
which  the  finely-ground  material  falls 
from  one  series  of  bars  to  another  in  a 
reducing  atmosphere,  whilst  maintained 


at  a  red  heat,  appears  well  adapted  for 
the  production  of  sponge,  but  its  intro- 
duction being  proposed  for  the  manufac- 
ture of  steel,  the  liability  of  iron  in  this 
state  to  absorb  sulphur  from  furnace 
gases  would  probably  prevent  its  adoption. 
Siemen's  cylindrical  revolving  furnace, 
although  well  adapted  for  quick  and 
economical  reduction,  was  abandoned  for 
this  reason.  The  vertical  retort  furnace 
has  been  again  proposed  by  Blair,  who 
states  that  he  has  overcome  the  former 
difficulties  of  working  this  class  of  fur- 
nace. In  a  vertical  retort  externally 
heated,  unless  the  width  be  impracti- 
cably small,  an  excessive  time  is  required 
for  heating  the  mass  through.  Blair 
employs  a  shaft  about  4  feet  in  diameter, 
and  by  the  device  of  a  cylinder,  suspen- 
ded in  the  throat  and  leaving  an  annular 
space  only  three  or  four  inches  wide, 
and  heated  internally  by  gas  at  the  same 
time  that  the  external  shaft  is  kept  heat- 
ed, the  ore  enters  the  body  of  the  fur- 
nace at  a  red  heat,  which  is  then  readily 
maintainable  in  the  mass.  The  reduced 
iron,  passing  down  into  a  cooling  shaft, 
is  withdrawn  from  time  to  time  whilst 
fresh  ore  and  charcoal  are  charged  into 
the  annular  mouth. 

Only  one  form  of  furnace  is  now  em- 
ployed in  making  iron  for  precipitation. 
This  is  essentially  a  reverberatory  furnace 
30  feet  long,  with  provision  for  conveying 
the  flame  under  the  hearth  after  it  has 
passed  over  the  charge.  The  hearth  of 
the  furnace  is  23  feet  long  and  8  feet 
wide,  and  is  divided  into  three  working 
beds  by  bridges.  Each  bed  has  two  work- 
ing doors  on  one  side.  The  doors  slide 
in  grooves  and  close  air-tight.  The  fire 
is  4  feet  by  3  feet,  with  bars  4  feet  8 
inches  below  the  bridge,  thus  allowing 
for  a  considerable  depth  of  burning  fuel. 
The  fire  door  slides  in  grooves  like  the 
working  doors.  The  hearth  is  formed 
of  tiles  sustained  on  brickwork  partitions 
forming  flues  through  which  the  flame 
returns  after  passing  over  the  hearth. 
From  these  flues  the  flame  drops,  by  a 
vertical  flue  alongside  the  fire-bridge,  to 
an  underground  flue,  communicating 
with  a  chimney.  The  entrance  to  the 
latter  flue  is  provided  with  a  fire-tile 
damper,  which  is  closed  whenever  the 
working  or  fire  doors  of  the  furnace 
have  to  be  opened.  A  cast-iron  pan,  20 
feet  by  10  feet,  is  carried  by  short  column 


SPONGY    IRON. 


303 


and  girders  over  the  furnace  roof.  In 
this  pan  the  ore  is  dried  and  mixed  with 
coal,  and  from  it  is  charged  into  the 
hearth,  through  cast-iron  pipes,  built  in- 
to the  furnace  arch.  The  furnace  is  ele- 
vated on  brick  pillars,  to  allow  of  iron 
cases  running  under  it,  to  receive  the 
reduced  iron,  and  it  is  worked  from 
a  platform  of  cast-iron  plates.  A 
vertical  pipe,  6  inches  diameter  passes 
through  the  hearth  of  the  furnace  inside 
of  each  working  door,  and  through  these 
pipes  the  reduced  iron  is  discharged  into 
iron  cases  placed  beneath.  These  cases 
are  horizontally  rectangular  and  taper 
upwards  on  all  sides.  The  cover  is  fixed 
and  in  its  centre  is  a  hole  6  inches  di- 
ameter, with  a  flange  upwards,  which 
serves  to  connect  the  discharging  pipe. 
The  bottom  of  the  case  is  closed  by  a 
folding  door,  hinged  on  one  side,  and  se- 
cured by  bolts  and  cutters  on  the  other. 
The  case  is  fitted  with  four  wheels,  clear 
of  the  door,  and  is  covered  with  a  cast- 
iron  plate,  fitting  loosely  into  the  open- 
ing on  the  upper  side.  It  stands  four  feet 
eight  inches  high,  and  has  a  capacity  of 
twelve  cubic  feet. 

The  furnace  hearth  being  at  a  bright 
red  heat,  each  of  the  three  working  beds 
is  charged,  with  20  cwt.  dry  purple  ore 
and  6  cwt.  ground  coal,  from  the  cast- 
iron  pan  over  the  roof.  The  fire  and 
working  doors  are  closed,  and  the  only 
air  entering  is  that  through  the  fire,  in 
working  which  care  is  taken  to  prevent 
the  mass  of  burning  fuel  getting  hollow. 
The  charge  in  the  first  bed  from  the  fire- 
bridge is  reduced  hi  from  nine  to  twelve 
hours  ;  in  the  second,  in  eighteen  hours; 
and  in  the  third,  in  about  twenty-four 
hours.  Each  charge  is  stirred  over  two 
or  three  times  during  the  period  of  re- 
duction. Before  opening  any  door  the 
flue  damper  is  closed,  to  prevent  a  cur- 
rent of  air  entering  over  the  charge. 
On  the  complete  reduction  of  the  charge, 
on  any  working  bed,  two  cases  are  run 
under  the  bottom  pipe,  to  which  their 
mouths  are  luted  by  clay,  and  the  charge 
is  quickly  drawn  into  them,  by  rakes 
worked  through  the  doors.  The  cases 
are  then  removed  and  closed  with  cast- 
iron  plates.  In  about  forty-eight  hours 
the  iron  is  cooled  sufficiently  to  be  dis- 
charged, and  this  is  simply  done  by  rais- 
ing the  case  by  a  crane,  and  knocking 
out  the  cutters  fastening  the  hinged  door 


on  the  bottom,  when  from  the  tapering 
form  of  the  case  the  mass  of  reduced  iron 
falls  out  readily.  The  sponge  is  ground 
to  powder  under  a  pair  of  heavy  edge 
stones,  6  feet  in  diameter,  and  is  passed 
through  a  sieve  of  fifty  holes  per  lineal 
inch. 

For  the  manufacture  of  spongy  iron 
for  precipitation,  two  materials  have 
been  proposed,  viz.,  burnt  pyrites  and 
"  purple  ore."  The  following  are  analy- 
ses of  these  materials  : 

Burnt  Ore.  Purple  Ore. 

Ferric  Oxide 78.15  . .  95.10 

Iron 3.76  ..  — 

Copper 1.55  ..  .18 

Sulphur 3.63  ..  .07 

Cupric  Oxide 2.70  ..  — 

Zinz  Ozide 47  ..  — 

Lead  Oxide 84  ..  .96 

Calcium  Oxide 28  . .  .20 

Sodium  Oxide —  ..  .13 

Sulphuric  Acid 5.80  . .  .78 

Arsenic  Acid 25  .  — 

Silicious  residue 1.85  ..  2.13 

Total 99.27     ..     99.55 

Bischof  and  Gossage  both  proposed 
the  use  of  burnt  ore  on  the  ground  of  the 
obvious  economical  advantage  that  the 
copper  it  contains  is  obtained,  with  the 
precipitated  copper,  without  the  expense 
of  extraction.  But  burnt  ore  contains  a 
notable  portion  of  arsenic — .16  per  cent, 
in  above  analysis — and  this  metal  re- 
maining in  the  sponge,  is  left  mixed 
with  the  precipitated  copper,  and  seri- 
ously deteriorates  the  quality  of  the  re- 
fined copper  ultimately  made  from  it. 
Bischof  states  that,  "  should  the  ore  have 
contained  traces  of  metals,  such  as  ar- 
senic or  lead  they  will  be  volatalized  dur- 
ing the  process  of  reduction."  Whilst 
lead  is  reduced  and  in  a  great  measure 
volatalized  in  the  spongy  iron  furnace,, 
the  arsenic  in  such  ores  being  present 
mainly  as  arseniates  of  copper  and  iron, 
which  are  likely  to  be  reduced  to  fixed 
arsenes,  is  not  volatilized,  spongy  iron 
made  from  burnt  ores  containing  a  pro- 
portion of  arsenic  closely  agreeing  with 
that  in  the  ore.  "  Purple  ore,"  which  re- 
tains only  the  most  minute  trace  of  ar- 
senic, is  the  only  material  now  employed.. 
and  the  following  analysis  gives  the 
composition  of  spongy  iron,  made  from 
purple  ore  by  means  of  the  furnace  and 
method  described  above  : — Ferric  oxide, 
8.15  per  cent.;  ferrous  oxide,  2.40;  me- 
tallic iron,  70.40  ;  copper,  .24  ;  lead  .2  7  ; 


304 


VAN  nostrand's  engineering  magazine. 


carbon,  7.60;  sulphur,  1.07;  alumina,  .19; 
zinc,  .30  ;  silicious  residue,  9.00  ;  total, 
99.62  per  cent. 

In  using  spongy  iron  in  precipitating 
copper,  the  liquids  are  agitated  by  an  air 
blast  whilst  the  iron  is  gradually  added. 
By  this  means  a  very  perfect  mixture 
is  obtained,  and  a  copper  precipitate  can 
be  readily  produced,  containing  not 
more  than  1  per  cent,  of  metallic  iron. 
As  compared  with  precipitation  by  scrap 
iron,  the  economy  of  space  required  and 
facility  of  manipulation  are  very  great. 
On  the  side  of  spongy  iron  precipitation 
are  cheapness  of  material  and  economy 
of  application  ;  whilst  against  it  is  the 
presence  with  the  precipitated  copper  of 
the  unreduced  iron  oxides  and  excess  of 
carbon  from  the  reduction.  In  employ- 
ing spongy  iron,  the  copper  extractor  has 
the  production  of  the  precipitant  in  his 
own  hands,  and  avoids  the  troublesome 
handling  of  a  material  so  cumbrous  as 
scrap  iron. 

As  regards  the  chemistry  of  spongy 
iron  precipitation,  it  is,  of  course,  identi- 
cal with  that  of  scrap  iron  precipitation, 
and  although  it  is  stated  by  Bischof 
that,  "  some  substances,  such  as  arsenic 
especially,  are  only  precipitated  after 
the  iron  has  been  in  contact  with  the 
solutions  containing  copper  and  these 
substances  for  several  hours.  The  pre- 
cipitation of  the  copper  by  my  process 
being  finished  in  a  much  shorter  time, 
and  the  solutions  then  being  separated 
from  the  iron  powder,  the  above  sub- 
stances cannot  be  precipitated  or  mixed 
with  the  precipitated  copper,"  the  writer 
has  been  unable,  with  iron  in  any  form 
or  with  copper  solutions  in  any  state,  to 
completely  pi'ecipitate  copper  and  leave 
any,  even  the  smallest,  proportion  of 
arsenic  in  solution. 

The  president  says  that  a  paper  com- 
ing from  such  an  authority  as  Mr.  Gibb, 
was  very  valuable.  From  his  experience 
of  the  temperature  at  which  spongy  iron 
was  formed  from  oxide  of  iron,  he  wish- 
ed to  know  whether  it  could  be  formed 
below  a  red  heat,  or  was  a  continued  red 
heat  necessary  for  the  formation  of 
metallic  iron  ? 

Mr.  Gibb  replied  that  he  could  hardly 
say.  They  took  care  to  keep  their  fur- 
nace at  least  at  a  red  heat,  yet  it  was 
often  worked  at  a  very  dull  red  heat  at 
the  flue  end    of   the    furnace,    and  the 


best  iron  was  then  made  by  a  long 
way — the  best  iron  for  precipitation  pur- 
poses; but  it  was  simply  a  question  of 
time;  and  it  would  be  found  that  when 
the  furnace  went  down  to  such  a  heat  as 
that,  instead  of  coming  out  in  about 
twenty-four  hours  they  were  bringing  it 
out  in  about  sixty  or  sixty-two  hours, 
which  was  a  time  quite  inadmissible  in 
pratice.  But  at  a  very  dull  red  heat  the 
iron  was  reduced,  and  reduced  thorough- 
ly, to  a  metallic  state,  but  time  must  be 
given. 

Mr.  Scholefield  wished  to  know  whether 
it  was  stirred  much  during  that  period. 

Mr.  Gibb  :  Rarely  ;  now  and  again, 
but  not  very  often.  That  was  one  of 
the  things  experience  had  shown  should 
be  done  as  little  as  possible,  because  with 
all  the  precaution  of  dampers  and  close 
fires  and  everything  of  that  kind,  it 
could  not  be  stirred  without  ah'  getting 
in,  and  they  found  the  less  it  was  stirred 
the  better.  It  had  to  be  stirred  up  or  it 
would  cake,  particularly  over  the  bed. 

Mr.  Lomas  wished  to  know  the  thick- 
ness of  the  layers  in  those  beds;  if  they 
perfected  the  process  in  each  of  these 
three  divisions  without  removal  from 
one  end  to  the  other;  and  if  each  was 
perfect  by  itself  ? 

Mr.  Gibb,  in  reply,  said  that  the  thick- 
ness was  six  inches;  that  there  was  no 
removal,  as  there  was  a  partition  to  pre- 
vent that;  that  each  was  perfect  in  itself, 
and  that  was  why  he  said  the  bed  next 
the  bridge  was  completed  in  from  nine  to 
twelve  hours.  The  flue  bed  took  about 
twenty-four  hours,  and  the  others  some- 
thing between  the  two. 

The  President  said,  then  the  higher  the 
heat  the  more  rapid  the  formation  of 
spongy  iron. 

Mr.  Gibb  replied,  yes  ;  that  was  just 
the  reason  why,  without  having  much 
experience  in  iron  smelting,  he  doubted 
whether  spongy  iron  would  ever  be  made 
unless  in  such  a  great  structure  as  a  blast 
furnace,  where  no  doubt  spongy  iron  was 
made,  and  in  fact  no  doubt  all  iron  pass- 
ed through  that  state,  and  where  they 
had  the  quicker  action  of  a  reducing 
gaseous  current.  That  was  why  he 
doubted  altogether  that  spongy  iron  as 
a  manufacture  by  itself  would  ever  take 
its  stand  as  a  step  towards  another  pro- 
cess, either  smelting  or  puddling,  in  the 
manufacture  of  iron. 


THE   MEANS    OF   AVERTING   BRIDGE   ACCIDENTS. 


305 


ON  THE  MEANS  OF  AVERTING  BRIDGE  ACCIDENTS. 

Transactions  of  the  American  Society  of  Civil  Entjineers. 


Report  I. 

To  the  American  Society  of  Civil  En- 
gineers : 

The  Committee  appointed,  under  the 
resolution  of  May  21st,  1873,  *  to  inquire 
into  the  "  most  practicable  means  of 
averting  bridge  accidents,  begs  leave  to 
report  as  follows  : 

After  a  careful  examination  into  the 
■causes  of  the  most  disastrous  accidents 
•which  have  occurred  during  the  past  few 
years,  it  finds  that  they  can  readily  be  di- 
vided into  three  different  classes.  First, 
where  bridges  are  erected  by  incompe- 
tent or  corrupt  builders,  and  accepted 
by  incompetent  or  corrupt  railway  or 
municipal  officials.  Second,  where  bridges 
of  good  design  and  sufficient  material 
fail  from  absolute  neglect  on  the  part  of 
their  owners,  or  from  injury  to  the 
material  during  transportion  or  erection. 
Third,  where  bridges,  good  or  bad,  are 
"knocked  down  or  destroyed  by  derailed 
trains  moving  at  a  high  rate  of  speed, 
or  where  the  growth  of  a  neighborhood 
has  brought  a  class  of  traffic  on  a 
bridge,  which  it  was  not  originally  de- 
signed to  bear,  either  by  the  builders 
or  the  owners.  How  to  treat  each  of 
these  classes  of  causes  will  now  be  con- 
sidered in  the  order  above  stated. 

Accidents  occurring  from  the  first  class 
would  certainly  not  have  taken  place  had 
the  wrecked  structures  been  correctly 
designed  and  had  they  possessed  the  pro- 
per sectional  areas  in  their  different  parts 
— but  failure  from  faulty  design,  is  not 
nearly  so  frequent  as  failure  from  in- 
sufficient material.  One  great  difficulty 
in  the  way  of  protecting  the  public  from 
the  results  of  imperfect  design  or  scanty 

*  At  the  Fifth  Annual  Convention,  held  at  Louisville, 
Ky.,  May  21st  and  22d,  1873,  it  was  :— 

"Resolved  :  in  view  of  the  late  calamitous  disaster  of 
the  falling  of  the  bridge  at  Dixon,  III.,  and  other  casual- 
ties of  a  similar  character  that  have  occurred  and  are  con- 
stantly occurring,  that  a  committee  *  *  *  be  appointed  to 
Teport  at  the  next  Annual  Conventi  on  the  most  practicable 
means  of  averting  such  accidents." 

The  committee  appointed  consists  of  Messrs.  James  B. 
Eads  and  C  Shaler  Smith  of  St.  Louis.  Mo.,  I.M.  St.  John 
of  Quinnimont,  Va.,  Thomas  C.  Clarke  of  Philadelphia, 
Pa.,  James  Owen  of  Newark,  N.  J.,  Alfred  P.  Boiler, 
Octave  Chanute  and  Charles  Macdonald  of  New  York, 
Julius  W.  Adams  of  Brooklyn,  NY.,  and  Theodore  G. 
Ellis  of  Hartford,  Conn.  Mr.  Alfred  L.  Rives  of  Mobile, 
Ala.,  was  appointed  on  the  Committee  but  resigned. 

Vol.  X1H.— No.  4—20 


material  lies  in  the  absence  of  a  fixed 
legal  standard  of  loads  and  stresses  for 
all  classes  of  these  structures,  and  an- 
other is  the  negligence  of  those  controll- 
ing public  works  or  those  engaging  in 
their  construction,  in  securing  skillful 
professional  aid. 

It  would  seem,  therefore,  to  be  our 
duty  as  a  Society  to  establish  in  a  few 
general  terms— such  as  can  be  readily 
embodied  in  a  law — a  standard  of  maxi- 
mum stresses  and  a  table  of  least  loads 
for  which  bridges  should  be  designed, 
and  to  add  thereto  a  practicable  sugges- 
tion as  to  the  necessary  legislation  re- 
quired to  give'  the  public  that  protection 
which  an  adherence  to  this  standard 
would  afford.  First,  as  to  the  standards 
for  the  least  live  loads  to  be  used  in  pro- 
portioning bridges ;  a  law  which  would 
provide  that  all  railroad  bridges  should 
be  built  to  carry  not  less  than  the  follow- 
ing loads,  would  be  well  within  the  mark 
of  safety. 

For  highway  and  street  bridges  the 
standard  loads  should  not  be  less  than 
as  in  first  table  on  next  page;  for  city 
and  suburban  bridges  and  those  over 
large  rivers  where  great  concentration 
of  weight  is  possible,  as  in  column  A; 
for  highway  bridges  in  manufacturing 
districts,  or  on  level,  well  ballasted  roads 
as  in  column  _Z?,  and  for  country  road 
bridges,  where  the  roads  are  unballasted 
and  the  loads  hauled  are  consequently 
liofht,  as  in  column  G 


Pounds  per  square  foot. 

Spans. 

A. 

B. 

c. 

60  feet  and  under. . . 

100 

100 

70 

60  to  100  feet 

90 

75 

60 

100  to  200  feet 

75 

60 

50 

200  to  400  feet. 

60 

50 

40 

With  the  highway  bridge  the  floor- 
beam  strength  is  especially  important, 
because  of  the  great  concentration  of 
weight  which  may  be  carried  on  a  sin- 
gle pair  of  wheels,   therefore   the  floor 


306 


VAN   NOSTRAND'S   ENGINEERING   MAGAZINE. 


system  of  each  class  of  bridge  should  be 
— per  floor-beam  for  each  wagon-way — 


for  city  bridges,  6  tons;  turnpike  bridges 
5  tons,  and  county  bridges,  4  tons. 


Span  or  Panel. 

Pounds  per  Lineal 
Foot  of  Track. 

Span  or  Panel. 

Pounds  per  Lineal 
Foot  of  Track. 

Under  12  feet. 
Under  15  feet. 
Under  20  feet. 
Under  25  feet. 
Under  30  feet. 
Under  50  feet. 

6,000 
5,500 
5,000 
4,500 
4,000 
3,250 

Under  75  feet. 
Under  100  feet. 
Under  150  feet. 
150  to  175  feet. 
175  to  200  feet. 
200  to  300  feet. 

3,000 
2,750 
2,500 
2,500 
2,400 
2,250 

The  panel  weights  for  railroad  bridges  I  ceding  the  standard  span  load.  The 
are  obtained  by  using  the  standard  proposed  law  should  also  provide  that 
weight  per  foot  for  short  spans.  In  com-  with  the  foregoing  loads,  the  stresses  or 
puting  all  web  members,  one  panel  of  materials  shall  not  exceed  the  f ollow- 
panel  weight  is  to  be  considered  as  pre- 1  ing  : 

For  wrought-iron  in  tension,  long  bars  or  rods 10,000  pounds  per  square  inch. 

For  wrought-iron  in  tension,  short  links  (for  floor  beams) 8,000  pounds  per  square  inch.. 

For  wrought-iron  against  shearing  force 7,500  pounds  per  square  inch. 

And  for  wrought-iron  in  compression,  as  in  this  table  : 


Diameters. 

Pounds  per 

Square  Inch. 

Diameters. 

Pounds  per 

Square  Inch. 

Square  Ends. 

Round  Ends. 

Square  Ends. 

Round  Ends. 

10 
10  to  15 
15  to  20 
20  to  25 
25  to  30 

10,000 
9,000 
8,000 
7,500 
6,800 

7,000 
6,500 
6,000 
5,500 
5,000 

30  to  35 
35  to  40 
40  to  50 
50  to  60 

6,000 
5,000 
3,800 
3,000 

4,000 
3,500 
2,500 
2,000 

Where  one  end  is  square  and  the  other 
end  is  rounded,  a  mean  is  to  be  taken  be- 
tween the  two. 

Cast-iron  to  be  used  in  compression 
only,  in  lengths  not  exceeding  22  diam- 
eters, and  at  the  same  stresses  as  those 
prescribed  for  wrought  iron. 

The  shapes  under  compression  in  the 
above  are  assumed  to  be  hollow  struts 
either  square  or  cylindrical  in  section; 
other  shapes  than  these  to  have  the 
stresses  varied  as  actual  experiment  may 
dictate.* 

For  wood  the  greatest  allowable 
strains  shall  be  as  follows  : 

.1  200  lbs.  per  square  in., 
.1000    "     "         "        " 


For  oak  in  flexture. 
"    pine  "        ". . . 


*  Further  experiments  can  alone  determine  the  values 
to  be  used  for  other  than  square  or  cylindrical  cross 
sections.— A.  P.  B. 


and  in  compression  as  in  this  table  : 


Diameters. 

Pounds  per 

Square  Inch. 

Oak. 

Pine. 

10 
10  to  20 
20  to  30 
30  to  40 

1,000 
800 
600 
400 

900 
700 
500 
300 

The  above  standard  should  be  changed 
or  elaborated  more  fully,  from  time  to 
time,  as  future  experience  and  experi- 
ments on  material  suggest. 

In  order  to  secure  to  the  public  the 
full  measure  of  benefit  from  the  adop- 
tion of  this  standard,  the  law  in  question 


THE   MEANS    OF   AVERTING   BRIDGE   ACCIDENT-. 


3<  >7- 


should  provide  for  the  appointment  by 
the  governor  of  each  state,  of  an  expert 
whose   duties   would   consist  in  having 
cognizance    of     the     construction     and 
maintenance  of   every  bridge   intended 
for  public  travel  in  the  state  or  states 
for  which  he  was  appointed.     The  law 
should  also  make  it  imperative  that  the 
expert  so  fppointed  shall  pass  an  exam- 
ination   as    to    his    mathematical     and 
mechanical  competency,  which  it  is  sug- 
gested,   should  be   by  a  standing  com- 
mittee of  this  Society,  regularly  consti- 
tuted  for   the   purpose,    and   that     the 
appointment  of   any   such   expert   who 
fails  to  receive  the  endorsement  of  this 
committee  shall  be  null  and  void.     Un- 
der the  proposed  law  it  should  be  the 
duty  of  all  railroad,  city,  county  or  state 
officials  having  charge  of  the  letting  or 
construction  of  bridges  to  call  upon  this 
expert — first,  to  examine  the  strain-sheet 
of  the   proposed  structure  before  work 
has  been  commenced,   to  certify  to  its 
correctness  if  correct,  or  to  make  such 
alterations  as  may  be  necessary  if  it  is 
faulty   in   design  or   scant   in   material 
according  to  the  legal  standard  ;  next, 
to  be  present  on  the  completion  of  the 
bridge,   and  then  and  there  to  make  a 
critical  examination  of  the  work  in  all  its 
details,    comparing    and    verifying    the 
sections  on  the  strain  sheet  with  those  of 
the  actual  structure,  and  if  these  last  are 
insufiicient,  to  forbid  the  use  of  the  work 
until  the  law  is  fully  complied  with  ;  and 
lastly,  if  the  bridge  is  up  to  the  standard 
in  all  its  parts,  to  obtain  from  him  a  cer- 
tificate to  that  effect,  copies   of  which 
certificate  shall  always  be  given  to  the 
builder,  and  filed  on  record  in  the  pro- 
per department  of  the  state  government. 
This  officer  shall  also  see  that  a  tablet 
or  plate  is  placed  on  a  conspicuous  part 
of  the  bridge,  bearing  the  names  of  the 
builders,  his  own  name,  and  that  of  the 
officer  of  the  railway  or  corporation  who 
accepts    the   work,    together  with   the 
strength  of  the  bridge  as  designed,  and 
the  year  of  its  erection. 

Accidents  arising  from  the  first  class 
of  causes  would  be  nearly,  if  not  quite 
prevented  by  the  general  enforcement 
of  the  foregoing  provisions.  Against 
accidents  occurring  from  causes  of  the 
second  class,  the  law  should  further  pro- 
vide that  all  railway  or  other  corporate 
bodies,  when  having  a  bridge  built,  to 


be  used  for  public  travel,  shiall  be  com- 
pelled during  the  erection  of  the  work, 
to  keep  on  the  spot  a  competent  inspec- 
tor, who  shall  have  the  power  to  reject 
any  piece  of  material  which  may  have 
been  injured  in  transportation  or  while- 
being  placed  in  position.  Also  that  all 
railroad  and  city  bridges  shall  be  in  spected 
once  every  month  by  a  competent  per- 
son in  the  employ  of  the  corporation 
owning  the  bridge,  for  the  purpose  of 
seeing  that  all  iron  parts  are  in  order, 
all  nuts  screwed  home,  that  there  are  no 
loose  rivets,  that  the  iron  rails  are  in  line 
and  without  wide  joints,  and  that  all 
wooden  parts  of  the  structure  are  sound 
and  in  proper  condition. 

It  should  also  be  the  duty  of  the  state 
officer  before  mentioned,  upon  any  bridge 
being  reported  as  in  a  neglected  condi- 
tion— whether  the  report  be  an  official 
one  or  made  by  one  not  connected  with 
the  corporation — to  proceed  to  the  spot 
and  examine  for  himself,  and  if  he  finds 
the  bridge  in  a  neglected  or  dangerous 
condition,  he  should  cause  the  owners 
to  put  it  in  safe  order  without  delay. 

In  relation  to  the  third  class  of  causes 
— destruction   by   derailed   trains,   high 
winds,    or    by    concentration  of  living 
weight  owing  to  the  growth  of  cities  or 
neighborhoods — prevention  is  less  easy, 
but  much  can  be  done  by  carefully  de- 
signing the  structure.     In  most  of  our 
railroad  bridges  the  floor  system  is   the 
weak  point.     The    cross-ties    are    short, 
the  stringers  are  proportioned  for  a  train 
on,  not  off  the  rails;  and  the  guard-tim- 
bers are  too  low,  and  are  insufficiently 
bolted.     A   derailed   engine  on   such   a 
floor  as  this,  plunges  off  the  end  of  the 
cross-ties  into  the  open   space   between 
the  stringers  and  the  chords,  and  gener- 
ally wrecks  the  bridge.     To  obviate  this, 
the    law    should    provide  that,  first, — 
all  cross-ties  shall  extend  from  truss  to 
truss,  they  shall  be  placed  so   close  to 
each  other  that  if  supported  at  the    pro- 
per intervals  it  will  be  impossible  for  a 
derailed    engine  to  cut    through    them, 
and  the  stringers  shall  be  so  spaced  as 
to  give  them  this  support.     Next,   the 
guard-timbers  shall  be  scantlins  not  less 
than  9  X  10  inches,  and  they  shall  be 
strongly  bolted  or  spiked  to  at  least  each 
alternate  cross-tie.    And  lastly,  the  clear 
width  between  the  trusses  on  through 
bridges  shall  be  so  great  that  the  wheels 


308 


YAN   NOSTRAND  S   ENGINEERING   MAGAZINE. 


of  a  derailed  train  will  be  arrested  by 
the  guard-rail  before  the  side  of  the 
widest  car  can  strike  the  truss.  Where 
switches  are  placed  at  the  end  of  a 
bridge,  the  Wharton  or  some  other 
form  of  safety  switch  should  be  used. 

Against  the  majority  of  accidents  from 
high  winds,  a  provision  in  the  law  re- 
quiring that  all  lateral  bracing  shall  be 
sufficient  to  resist  a  pressure  of  30  pounds 
per  square  foot  of  truss  and  train,  will 
be  sufficient.  Lateral  bracing  can  be 
proportioned  at  15,000  pounds  per  sqnare 
inch  against  this  particular  strain,  as  it 
is  of  very  rare  occurrence. 

The  last  case  in  the  third  class  of 
causes  of  accidents  is  where  a  bridge 
built  originally  for  a  neighborhood  or 
country  road  becomes  too  weak  for  the 
requirements  of  a  growing  community  or 
possiby  of  a  newly  established  manu- 
factory; also  where  a  railroad  bridge, 
intended  only  for  that  class  of  traffic, 
has  a  highway  floor  subsequently  added 
to  it.  Against  the  first  contingency, 
the  vigilance  of  the  state  official  and  a 
chance  that  some  of  the  users  of  the 
bridge  may  occasionally  notice  the  tab- 
let setting  forth  its  strength,  would 
seem  to  be  about  the  only  safeguard; 
but  in  the  second  case  the  law  should 
provide  that — except  by  permission  of 
the  state  officer  in  charge  of  bridges — 
no  corporation  or  other  bridge  owner 
shall  add  to  the  dead  weight  on  a  bridge 
without  at  the  same  time  making  the 
proper  addition  to  its  strength. 

The  foregoing  provisions,  if  embodied 
in  a  law,  will  afford  the  public  about  all 
the  protection  which  is  readily  obtainable 
in  the  case. 

No  mention  is  here  made  of  the 
quality  of  the  material,  as  the  proposed 
officials  engaged  in  carrying  out  the  law 
will  be  men  who  have  been  passed  on  by 
the  Society,  and  the  very  fact  of  their  sur- 
veillance will  be  apt  to  produce  care  in 
this  regard.  In  addition  to  this,  the 
standard  stresses  have  been  placed  so 
low  that  the  use,  whether  accidental  or 
fraudulent,  of  low  grades  of  iron  will 
hardly  endanger  the  work.  A  provision 
in  the  law  that  all  bridge  details  shall 
possess  the  proper  proportional  strength 
to  that  of  the  main  members  of  the 
bridge,  and  a  series  of  instructions  from 
the  examining  committee  of  the  Society 
to  those  who  pass  their  examinations  for 


appointments  under  this  law  in  reference 
to  these  proper  proportions,  will  protect 
the  purchasers  of  bridges  from  insecure 
details  of  construction. 

In  addition  to  his  duties,  as  above  de- 
fined, the  state  officer  in  charge  of  brid- 
ges should  also  visit  the  scene  of  any 
accident  in  his  district  as  sogn  as  possi- 
ble after  the  occurrence,  and  remain  dur- 
ing the  removal  of  the  wreck,  or  until 
he  is  able  to  ascertain  the  true  cause  of 
the  failure.  The  facts  in  the  case 
should  then  be  reported  by  him  to  the 
examining  committee  of  the  Society. 

In  conclusion,  it  is  here  advised  that 
a  committee  be  appointed  to  draft  such 
a  law  as  is  outlined  in  this  report;  that 
a  resolution  be  passed  by  the  Society  re- 
commending the  adoption  of  this  law  by 
the  different  state  legislatures,  and  that 
printed  copies  of  this  report,  the  pro- 
posed laws  and  the  accompanying  resolu- 
tions, be  sent  to  the  members  of  the 
Society  with  a  request  that  they  move 
actively,  each  in  his  own  state,-  towards 
procuring  the  passage  of  the  specified 
law  by  the  various  state  legislatures 
during  the  coming  winter. 

Jas.  B.  Eads,  Chairman. 
Oct.  30th,  1874.  C.  Shaler  Smith.  * 

*  In  advocating  the  views  presented  in  the  foregoing 
report,  the  undersigned  is  actuated  by  the  following  rea- 
sons. 

First -the  resolution  under  which  the  Committee  is 
acting  requires  from  it  "  the  most  practicable  means  of 
averting — i.  c,  preventing  bridge  accidents,"  rather  than 
the  mode  of  sitting  in  judgment  on  them  after  they  occur. 

Second — as  the  national  legislature  has  for  some  time 
been  passing  laws  for  the  protection  of  life  on  navigable 
waters  of  the  United  States,  prescribing  qualifications 
and  standards  for  engineers  and  pilots,  the  proportions  of 
safety  valves,  &c,  lor  boilers,  and  appointing  examiners 
and  inspectors  under  these  laws,  so,  sooner  or  later  will 
the  question  of  the  proper  construction  of  railways  be 
taken  up  and  legislated  upon. 

Third — many  mistakes  have  been  made  in  these  laws, 
owing  to  ignorance  en  the  part  of  those  passing  them, 
and  the  undue  influence  of  interested  inventors  and 
manufacturers,  and  each  succeeding  Congress  has  had 
amendments  to  make  in  order  to  repair  some  injustice 
or  supply  some  omission. 

Lastly— as  laws  regulating  the  construction  of  railroads 
and  bridges  will  certainly  be  enacted,  and  official  posi- 
tions will  assuredly  be  created  by  them,  it  is  far  better 
that  this  Society  should  take  time  by  the  forelock,  dic- 
tate a  law 'which  will  be  just  and  eqaitable,  and  hold  con- 
trol of  the  appointment  under  it,  than  that  it  should 
stand  in  the  background,  until  an  aroused  public  opinion 
compels  legislation  which  may  be  injuri  .us  to  the  pro- 
fession, especially  if  enforced  by  political  appointees 
who  may  be  utterly  unfit  to  fill  such  positions.  All  laws 
are  written  by  some  one,  and  the  greater  the  knowledge 
of  the  subject  matter  on  the  part  of  that  person  is,  the 
more  probable  the  production  of  a  good  and  wise  statute. 

Hence  the  undersigned  believes  that  the  fixing  of  the 
standards  as  proposed,  the  preparation  of  such  a  law  as 
suggested,  and  the  professional  surveillance  of  the 
appointees  under  it,  are  eminently  the  province  of  this 
association,  and  that  all  legislation  on  the  subject  should 
be  both  inspired  and  dictated  by  the  most  prominent 
authority  in  the  premises— the  American  Society  of  Civil 
Engineers. 

April  18, 1ST5.  C.  Shaler  Smith. 


THE   MEANS   OF  AVERTING  BRIDGE   ACCIDENTS. 


309 


Report  II. 

The  undersigned  differ  from  the  views 
expressed  in  the  foregoing  report,  and 
present  the  following  as  Nan  expression 
of  their  own  : 

1. — They  agree  with  the  report,  that 
it  is  desirable  the  American  Society  of 
Civil  Engineers  should  publicly  declare 
what  it  considers  to  be  a  standard  bridge, 
anything  below  which  is  not  to  be  deem- 
ed as  a  safe  and  durable  construction. 
But  they  do  not  think  it  is  desirable  to 
go  much  into  detail,  as  they  believe  it 
to  be  impossible  to  construct  a  specifica- 
tion that  will  meet  all  cases.  Incompe- 
tent engineers  cannot  be  prevented  from 
building  bad  bridges  by  any  specifica- 
tion however  elaborate;  they  therefore 
are  content  with  laying  down  general 
principles,  leaving  the  application  to 
others,  and  offer  the  following  standard 
specification  for  bridges  of  iron  and  wood : 


Spans — Feet. 


100  and  under. 
100  to  200 
200  to  300 


Pounds. 


100 
80 
70 


Spans — Feet 


300  to  400 
Over  400 


Pounds. 


60 
50 


1.  Every  highway  bridge  shall  be 
capable  of  carrying,  in  addition  to  its 
weight,  a  moving  load  per  square  foot 
of  roadway  and  sidewalks  as  follows  : 

2.  Every  railroad  bridge  shall  be 
capable  of  carrying  on  each  track  in 
addition  to  its  own  weight,  2  locomotives 
coupled,  weighing  30  tons  on  drivers  in 
space  of  12  feet,  and  whose  total  weight, 
including  loaded  tenders,  is  65  tons  each; 
said  locomotives  to  be  followed  by  so 
many  loaded  coal  cars  weighing  one  ton 
per  lineal  foot,  as  will  cover  the  remain- 
der of  the  span. 

3.  Bridges  shall  be  so  proportioned 
that  the  above  loads  shall  not  strain 
any  part  of  the  material  over  one-fifth 
of  its  ultimate  strength. 

II. — The  signers  of  the  foregoing  re- 
port, propose  to  cause  future  bridges  to 
come  up  to  the  standard  by  a  system  of 
inspection,  the  inspectors  to  be  passed 
by  the  Society  before  being  appointed. 
The  undersigned  believe  that  in  the  pre- 
sent state  of  public  opinion  this  is  im- 
practicable. If  any  inspectors  are 
appointed,  it  will  be  by  political  influ- 


ence, and  the  results  will  be  worse  than 
at  present,  as  the  inspection  will  be  in- 
sufficient, and  yet,  to  a  great  extent,  re- 
lieve the  owners  of  bad  bridges  from 
legal  responsibility. 

The  undersigned  consider  that  the 
most  the  Society  can  hope  to  do,  is  to 
provide  means  in  case  of  the  fall  of  a 
bridge,  by  which  the  responsibility  of 
imperfect  construction  (if  this  was  the 
cause  of  the  accident)  may  be  fixed  on 
designers  and  builders,  and  iron  manu- 
facturers. 

It  is  therefore  recommended  that  the 
Society  prepare  and  present  to  the  state 
legislatures,  a  petition  embodying  the 
following  data: 

1.  That  the  standard  of  the  Ameri- 
can Society  of  Civil  Engineers  shall  be 
the  legal  standard,  and  in  case  it  should  be 
found  that  any  bridge  is  of  less  strength 
than  this,  it  shall  be  taken  as  'prima  facie 
evidence  of  neglect  on  the  part  of  its 
owners. 

2.  That  no  bridge  shall  be  opened 
for  public  traffic  until  a  plan,  giving  the 
maximum  loads  it  was  designed  to  carry, 
the  resulting  strains,  and  the  dimensions 
of  all  the  parts,  sworn  to  by  the  design- 
ers and  makers,  and  attested  by  the  sig- 
nature of  the  proper  officer  representing 
the  municipality  or  corporation  by  whom 
it  is  owned,  be  deposited  in  the  archives 
of  the  Society,  and  that  the  principal 
pieces  of  iron  in  the  bridge  be  stamped 
with  name  of  maker,  place  of  manufac- 
ture and  date. 

The  result  of  this  will  be,  that  in  case 
of  the  fall  of  a  bridge,  the  responsibility 
can  be  directly  and  easily  traced  to  the 
right  party,  which  at  present  cannot  be 
done,  and  the  Society  should  willingly 
aid  to  such  a  purpose.  This,  it  is  recom- 
mended, should  thus  be  done:  the  Society 
to  appoint  a  committee — with  compen- 
sation to  be  fixed  by  law — which,  upon 
the  call  of  the  executive  of  any  state, 
should  visit  and  report  upon  any  fallen 
bridge,  care  being  taken  that  no  parties 
interested  in  the  construction  of  the 
bridge  be  upon  the  committee. 

It  is  believed  by  the  undersigned,  that 
the  knowledge  all  bridge  builders  would 
have  that  their  misdeeds,  if  any.  could, 
by  this  process,  be  traced  home  to  them- 
selves, would  make  them  very  careful 
in  the  future,  and  eliminate  all  failures 
of  imperfect  design  or  material. 


310 


VAN  nostrand's  engineering  magazine. 


As  to  the  inspection  of  existing  struc- 
tures; if  the  society  assumed  the  first  duty, 
this  would  soon  fall  under  its  jurisdic- 
tion, and  if  it  would  volunteer  the  duty — 
in  case  any  plan  was  deposited  obviously 
unsafe — to  protest  against  it,  that  also 
would  be  well;  such  would  have  pre- 
vented the  fall  of  the  Dixon  bridge,  and 
the  lamentable  loss  of  life  and  limbs 
there  occurring. 

Thos.  C.  Clarke. 
Feb.  1st,  1875.         Julius  W.  Adams. 

Report  III. 
The     undersigned     differ    from    the 
views    expressed    in    the  foregoing  re- 
ports,   and     respectfully     present    the 
following  : 

1.  The  members  of  the  committee 
agree  that  it  is  meet  and  proper  the 
American  Society  of  Civil  Engineers 
should  determine  the  standard  strength 
for  all  bridges  to  be  built  in  this  country, 
and  they  further  agree  in  the  main,  what 
this  standard  should  be.  The  differences 
in  opinions  grow  out  of  the  methods  for 
incorporating  this  standard  in  the  every- 
day practice  of  the  country.  Two 
general  modes  present  themselves  for  so 
doing;  the  one  legislative  and  compul- 
sory, and  the  other  looking  forward  to 
directing  public  sentiment  to  right  con- 
clusions by  a  thorough  dissemination  of 
the  adopted  standard. 

2.  The  undersigned  advocate  the 
latter  method  as  the  true  policy  of  the 
Society,  believing  that  any  attempt  to 
influence  the  enactment  of  laws  that 
would  be  so  far-reaching  as  the  ones 
proposed,  is  impracticable,  if  not  con- 
trary to  the  genius  of  the  Society  itself. 
They  further  believe  that  when  once 
public  sentiment  is  aroused  by  the   pub- 


licity which  should  be  given  to  the 
adopted  standard,  it  will  compel  the 
passage  of  laws  covering  the  question. 

3.  The  undersigned  therefore  suggest 
that  the  report  to  be  accepted  be  simply 
one  covering  a  standard  strength  for  all 
bridges,  in  as  general  terms  as  possible, 
with  a  recommendation  that  such  stand- 
ard be  widely  disseminated  by  circular 
and  the  public  prints,  and  that  copies 
be  distributed  among  the  legislative 
bodies  of  the  several  states. 

The  following  standard,  culled  from 
the  foregoing  reports,  is  proposed  for 
adoption  : 

4.  For  highway  bridges,  as  submitted 
in  Report  I. 

5.  For  railroad  bridges:* — the  struc- 
ture shall  be  at  least  capable  of  carrying 
on  each  track,  in  addition  to  its  own 
weight,  2  locomotives  coupled,  weighing 
30  tons  on  drivers  in  space  of  12  feet, 
and  whose  total  load,  including  tender, 
is  65  tons  each.  Said  locomotives  to  be 
followed  by  as  many  loaded  coal  cars, 
weighing  one  ton  per  lineal  foot,  as  will 
cover  the  remainder  of  the  span. 

Bridges  to  be  so  proportioned  that  the 
above  described  loads  shall  not  strain  the 
several  parts  in  excess  of  one-fifth  or  one- 
sixth  of  the  ultimate  strength.  In  de- 
termining the  strains  produced  by  the 
above  standard,  it  is  to  be  understood 
that  the  chord  system  is  to  be  computed 
for  a  uniform  loading,  while  the  web 
strains  must  be  based  upon  the  irregular- 
ly distributed  or  concentrated  loads  pro- 
duced by  the  above  described  train,  in 
its  passage  from  one  end  to  the  other. 

The  following  table  represents  the 
uniform  distributed  moving  load  for 
different  spans  : 

*  Being  the  same  as  submitted  in  Report  II,  page  129. 


Span  or  Panel. 

Pounds  per  Lineal 
Foot  of  Track. 

Span  or  Panel. 

Pounds  per  Lineal 
Foot  of  Track. 

12  feet. 
15  feet. 
20  feet. 
25  feet. 
30  feet. 
50  feet. 

5,250 
5,250 
5,000 
4,500 
4,200 
3,250 

75  feet. 
100  feet. 
150  feet. 
175  feet. 
200  feet. 
200  to  300  feet. 

3,000 
2,750 
2,500 
2,400 
2,300 
2,250 

THE  MEANS   OF   AVERTING-   BRIDGE  ACCIDENTS. 


311 


The  extreme  panel  weight  for  all  spans 
as  obtained  by  using  the  standard  weight 
per  foot  for  short  spans. 

6.  Under  the  standard  loading,  as  ex- 
pressed in  above  table,  materials  should 
not  be  strained  in  excess  of  what  is  sub- 
mitted in  Report  I. 

All  of  which  is  respectfully  submitted. 


March  1st,  1875. 


Alfred  P.  Bollee. 
Chas.  Macdonald. 


Report  IV. 

While  agreeing  in  many  important 
particulars  with  the  report  of  the  Chair- 
man of  this  Committee,  the  undersigned 
holds  the  views  expressed  by  some  of  the 
other  members  regarding  the  expediency 
of  compulsory  legislation  on  the  subject. 
It  is  believed  that  the  opinions  of  the 
Society  as  a  body,  advanced  for  its  in- 
terest and  benefit  and  that  of  those  who 
should  choose  to  be  governed  by  them, 
would  have  more  weight  and  influence 
than  though  the  Society  should  assert 
itself  as  a  competent  authority  upon 
bridge  construction.  If  this  Society 
adopts  a  well  defined  standard  of 
strength  for  bridges,  it  is  believed  that 
the  public  generally  will  wish  to  con- 
form to  it,  and  engineers  even  who  are 
not  members  will  be  glad  to  avail  them- 
selves of  the  united  opinion  of  so  many 
of  the  profession. 

There  seems  to  be  a  unanimity  of  opin- 
ion among  the  members  of  the  Com- 
mittee as  to  what  constitutes  the  ordin- 
ary load  upon  a  railway  bridge,  and  but 
a  slight  difference  of  opinion  as  to  its 
amount. 

From  an  examination  of  the  weights 
carried  upon  many  of  the  principal  rail- 


ways in  the  United  States,  it  is  found 
that  the  heaviest  engines  weigh  about 
2,830  pounds  per  foot ;  and  that  three, 
and  sometimes  four,  are  coupled.  The 
heaviest  weight  on  one  pair  of  drivers 
is  from  21,000  to  24,000  pounds,  and  the 
weight  on  all  the  drivers,  generally  not 
exceeding  12  feet  wheel-base,  is  from 
72,000  to  84,000  pounds.  The  heaviest 
trains  may  be  assumed  to  weigh  2,250 
pounds  to  the  running  foot,  exclusive  of 
the  engines.  As  the  coupling  of  more 
than  two  engines  is  mainly  upon  snow 
roads,  it  is  not  believed  they  should  be 
included  in  a  general  rule  for  proportion- 
ing bridges,  but  should  be  classed  anions 
those  exceptional  cases  for  which  a  gen- 
eral provision  cannot  be  made. 

In  view  of  the  above,  it  is  believed 
that  all  railway  bridges  should  be  pro- 
portioned for  a  rolling  load  of  3,000 
pounds  to  the  foot  for  the  total  engine 
length,  and  for  2,250  pounds  to  the  foot 
for  the  remainder  of  the  bridge  ;  that 
bracing  on  each  system  should  be  pro- 
portioned to  sustain  84,000  pounds  on 
any  12  feet  of  track,  and  that  any  point 
on  the  track  should  sustain  24,000 
pounds. 

It  is  not  believed  that  the  system  of 
expressing  the  loads  that  a  bridge  should 
carry,  by  so  much  per  foot  with  a  vary- 
ing amount  for  each  length  of  span,  is 
the  best ;  but  if  such  a  standard  is  to 
be  adopted,  the  table  in  the  report  of  the 
Chairman  is  believed  to  be  the  best  of 
those  given,  although  it  is  somewhat  be- 
low the  loads  actually  carried  by  many 
roads  in  this  country. 

The  floor-beams  of  railway  bridges 
should  be  proportioned  for  not  less  than 
the  following-  loads  : 


Spaces. 

Pounds. 

Spaces. 

Pounds. 

4  feet  apart,  or  less. 

6  feet  apart,  or  less. 

8  feet  apart,  or  less. 

10  feet  apart,  or  less. 

28,000 
31,500 
35,000 
38,500 

12  feet  apart,  or  less. 
15  feet  apart,  or  less. 

More  than  15  feet  apart 

42,000 
45,000 
i  3,000 
( to  the  foot. 

The  following  table  is  offered  as  em- 
bracing the  foregoing  loads  when  reduced 
to  so  much  per  lineal  foot : 

For  intermediate  lengths  of  span  the 
proportional  number  of  pounds  per  foot 
should  be  taken. 


These  loads  do  not  include  the  extra- 
ordinary weights  that  are  sometimes 
drawn  over  railways  in  this  country  ; 
such  as  heavy  pieces  of  machinery, 
blocks  of  stone,  or  a  locomotive  of  differ- 
ent gauge  on  a  truck  car,  nor  more  than 


312 


VAN   NOSTRAND  S   ENGINEERING   MAGAZINE. 


Span  or  Panel . 

Pounds  per  Lineal 
Foot  of  Track. 

Span  or  Panel. 

Pounds  per  Lineal 
Foot  of  Track. 

12  feet  and  under. 

15  feet. 

20  feet. 

25  feet. 

30  feet. 

40  feet.     • 

7,000 
6,000 
4,800 
4,000 
3,600 
3,200 

50  feet. 
100  feet. 
200  feet. 
300  feet. 
400  feet. 
500  or  over. 

3,000 
2,800 
2,600 
2,500 
2,450 
2,400 

two  engines  coupled.  These  are  ex- 
ceptional cases  which  can  be  provided 
for  when  they  may  be  expected  to  occur, 
and  the  weight  can  ordinarily  be  dis- 
tributed so  to  cover  a  sufficient  length 
of  track  as  not  to  exceed  the  loads  above 
given. 

For  the  effect  of  wind,  the  maximum 
strain  is  believed  to  be  about  40  pounds 
per  square  foot  horizontal,  and  about  20 
pounds  per  square  foot  vertical. 

For  highway  bridges,  the  following 
table  is  offered  as  a  substitute  for  that 
given  in  the  report  of  the  Chairman  for 
the  three  classes  of  bridges  named  : 


Spans. 

Pounds 

per  Square  Foot. 

(Intermediate 
lengths  in 

proportion.) 

A. 

B. 

C. 

100  feet  and  under. 

100 

75 

60 

200  feet. 

80 

60 

50 

300  feet. 

70 

50 

50 

400  feet. 

60 

50 

50 

500  feet  and  over. 

50 

50 

50 

The  floor-beams  and  flooring  should  be 
of  sufficient  strength  to  sustain  the  fol- 
lowing loads  on  four  wheels  : — Class  A, 
24 — B,  16 — and  C,  8  tons  respectively. 
These  do  not  include  the  extraordinary 
loads  sometimes  taken  over  highways. 
They  are  exceptional  cases  and  the 
weight  can  generally  be  divided. 

With  regard  to  the  factors  of  safety 
to  be  used,  it  is  believed  that  a  less  fac- 
tor is  required  for  the  permanent  and 
unchanging  dead  load,  than  for  the  vi- 
brating and  uncertain  live  load,  which 
may,  by  accident,  be  increased  beyond 
the  limit  for  which  it  was  computed. 
This,  together  with  the  fact  that  a  larger 
factor  for  the  dead  load  gives  no  addi- 
tional strength  to  the  bracing  near  the 
middle  of  the  span,  but  only  at  the  ends, 


leads  to  the  following  substitution  for 
the  factor  offered  in  the  rej^ort  of  the 
Chairman. 

For  wrought-iron  and  steel  in  both 
compression  and  extension — for  the  dead 
load  including  snow,  \ — for  the  live  load 
including  wind,  i  the  ultimate  strength. 

For  cast-iron  in  compression  only,  and 
for  lengths  of  not  more  than  20  diame- 
ters— for  the  dead  load  i,  and  for  the 
live  load,  tV  the  ultimate  strength.  For 
large  masses,  as  in  arches,  a  factor  of 
£  the  ultimate  strength  may  be  adopt- 
ed. 

Bridges  should  be  tested  with  the 
maximum  loads  which  they  are  intended 
to  sustain  A  less  load  would  seem  to 
be  of  but  little  use,  and  a  much  greater 
one  might  unnecessarily  strain  the  struc- 
ture. The  load  should  be  applied  grad- 
ually, and  the  moment  any  undue  deflec- 
tion or  crippling  is  observed,  or  the 
slightest  diminution  in  the  transverse 
section  of  any  bar  is  occasioned,  the 
load  should  be  immediately  removed  and 
never  repeated.  If  no  actual  rupture 
occurs,  the  bridge  will  probably  be  safe 
with  0.4  of  the  test  applied.  The  ac- 
ceptance of  all  bridges,  after  being  con- 
structed with  proper  proportions  for  the 
material  used,  should  be  subject  to  such 
a  practical  test. 

Theodore  G.  Ellis. 
April  20th,  1875. 


An  Egyptian  Railway.  —  A  great 
railway  in  Egypt,  from.  Cairo  to  Khar- 
toum, is  progressing  rapidly  ;  it  is  pro- 
posed to  extend  it  westward  to  Darfur. 
Plans  have  been  prepared  for  a  line 
from  Khartoum  to  the  frontier  of  Abys- 
sinia, the  acquisition  of  that  country  by 
the  Egyptian  Government  being  regard- 
ed as  only  a  question  of  time. 

— Engineering. 


THE    "DIRECT  PROCESS"    IN   IRON   MANUFACTURE. 


313 


THE  "DIRECT  PROCESS"  IN  IRON  MANUFACTURE. 

By  THOMAS  S.  BLAIK,  Pittsbubgh,  Pa. 
Transactions  of  American  Institute  of  Mining  Engineers. 


I  peel  a  certain  sense  of  responsibility 
in  bringing  before  you  the  subject  of  the 
direct  process  in  iron  manufacture.  I  am 
aware  that,  in  such  a  body  as  I  have  the 
honor  of  addressing,  there  are  few  who 
are  not  already  so  well  informed  upon 
its  past  history  that  it  would  be  a  weari- 
ness to  them  to  listen  to  anything  else 
than  an  account  of  practical  success. 
Yet,  to  claim  that  success  involves  so 
much  that,  if  I  do  not  make  good  my 
claim,  I  deservedly  expose  myself  to 
severe  criticism. 

The  whole  literature  of  the  art,  so  far 
as  it  relates  to  the  direct  process,  is,  up 
to  this  time,  but  a  history  of  failure.  It 
is  safe  to  say  that  more  money,  time, 
and  talent  have  been  fruitlessly  spent  in 
the  pursuit  of  this  object  than  in  all  the 
other  unsuccessful  efforts  in  the  whole 
line  of  iron  metallurgy.  A  distinguished 
authority  in  patent  law  has  remarked 
that  "  the  invention  records  of  the  United 
States  and  of  foreign  countries  are  filled 
with  the  waifs  and  abandoned  relics  of 
these  abortive  struggles." 

Dr.  Percy,  whose  great  work  may  be 
taken  as  an  epitome  of  all  that  was 
worth  mention,  whether  useful  or  curious 
in  pig-iron  metallurgy,  up  to  the  date  of 
its  publication  (1864),  after  giving  ela- 
borate accounts  of  various  attempts  at 
the  direct  process,  condenses  his  own 
opinion  of  all  that  had  been  then  effected, 
into  a  brief  but  summary  comment  upon 
a  pamphlet  of  one  of  the  sanguine  in- 
ventors who  had  said:  "  It  is  evident 
that  the  present  mode  of  working  iron 
ores,  whether  rich  or  poor,  is  not  the 
most  rational  or  economic  one,  although 
almost  the  only  one  in  general  use. 
They  convert  iron  already  malleable  into 
cast  iron,  to  be  reconverted  at  much 
labor  and  cost,  into  malleable  iron 
again." 

To  this  Dr.  Percy  rejoins  :  "  These 
questions  are  extremely  obvious.  They 
have  been  repeatedly  proposed  before, 
but  never  yet  satisfactorily  answered." 
Elsewhere  he  speaks  of  Cheno,t  (who 
came  so  near  success  that  the  jury  of 
the  French  Exposition  of  1855  thought 


he  had  attained  it,  awarding  to  him  one 
of  the  great  gold  medals;  and  Le  Play 
pronounced  his  invention  "  The  greatest 
metallurgical  discovery  of  the  age")  as 
"  poor  Chenot,"  and  ridicules  the  claims 
set  up  for  him. 

Gruner  in  his  "  Steel  and  its  manufac- 
ture," 1867,  translated  by  Lenox  Smith, 
1872,  says:  "  Several  metallurgists  have 
thought  that  instead  of  smelting  ores  in 
a  blast-furnace,  it  would  be  better  to 
simply  reduce  them  to  the  condition  of 
soft  or  carburized  sponge.  They  hoped 
to  obtain  purer  products  and  consume 
less  fuel  by  operating  at  a  lower  tem- 
perature. They  were  completely  de- 
ceived. When  the  sponges  are  made, 
instead  of  cast-iron  we  have  blooms  of 
less  purity,  since  they  contain,  besides 
the  usual  cinder,  the  earthy  substances 
in  the  ore.  And  if  the  sponges  are  melted 
in  crucibles  insteadof  forging  them  direct- 
ly in  the  form  of  blooms,  we  shall  have  a 
homogeneous  product,  but  it  will  be  iron 
or  crude  steel  of  inferior  quality,  unless 
the  iron  sponge  undergoes  fining  like 
pig-metal.  In  the  direct  methods  whose 
object  is  the  abolition  of  blast-furnaces, 
the  addition  of  carbon  mixed  with  the 
ore  cannot  be  avoided ;  and  it  is  this 
which  destroys  all  profit  in  the  processes 
invented  by  Chenot  in  France,  Renton 
in  America,  Gurlt  in  Germany,"  etc. 

Bauerman  who  comes  later  than  Percy 
(1868),  gives  but  slight  attention  to  the 
direct  process.  Speaking  of  the  various 
processes  for  the  direct  production  of 
wrought  iron  from  the  ore,  he  says: 
"  As  these  methods  are  only  applicable 
to  the  treatment  of  easily  reducible  ores 
and  are  essentially  slow  in  work,  giving 
only  a  small  production  from  a  plant  of 
considerable  extent,  as  compared  with 
the  open  fire  (Catalan  forge),  they  have 
not  as  yet  been  found  to  possess  suffi- 
cient advantages  to  be  generally  adopted 
on  a  large  scale. 

Crooks  and  Rohrig's  work  (I860),, 
adapted  from  Professor  Kerl's  Metal- 
lurgy gives  small  encouragement.  In  the 
volume  on  iron  they  say.  in  their  difini- 
tion  of  wrought   iron  :     "  It   is   usually 


314 


VAN   NOSTRAND'S   ENGINEERING   MAGAZINE. 


produced  by  the  conversion  of  pig-iron, 
and,  in  rare  cases  is  obtained  direct  from 
the  ore."  And  again,  under  the  caption, 
"  Methods  for  Making  Wrought  Iron 
Direct  from  the  Ore:"  "At  present  this 
process  is  seldom  nsed  on  account  of  its 
numerous  disadvantages.  It  requires 
pure,  rich,  and  easily  fusible  ores,  and  is 
performed  in  interrupted  operations; 
much  iron  is  scorified,  the  consumption  of 
fuel  is  very  large;  and  lastly  the  product 
is  seldom  uniform,  and  is  mixed  with 
slag,  which  can  only  be  removed  by  re- 
peated welding."  After  describing  the 
Catalan  forge,  etc.,  they  proceed  as 
follows:  "  Gersdorff  roasts  sparry  iron 
ore  in  reverberatory  furnaces,  and  heats 
the  roasted  ore,  together  with  coal,  in 
crucibles.  Clay  heats  ore  and  coal  in  a 
retort,  and  treats  the  reduced  iron  in  a 
puddling  furnace.  Renton  reduces  the 
iron  ores  in  vertical,  slightly  heated 
tubes,  by  means  of  carbonic  oxyde  gas, 
and  forms  the  reduced  iron  into  balls  in 
a  puddling  furnace.  Chenot  submits  the 
ores  to  a  reducing  roasting,  to  transform 
them  into  magnetic  oxyde,  which  he 
finally  crushes,  and  by  means  of  an 
electro-magnetic  apparatus,  extracts  the 
magnetic  components;  he  then  reduces 
the  ore  with  carbonic  oxyde  gas,  grinds 
the  resulting  spongy  iron,  mixes  it  with 
soda,  presses  into  cylindrical  shape, 
and  at  a  suitable  temperature  draws 
it  out  into  bars.  Roger  heats  the  iron, 
together  with  coal,  in  a  rotating  cylin- 
der, and  forms  the  balls  in  a  puddling 
furnace.  None  of  these  methods  seem 
to  have  met  with  any  practical  success." 
In  their  volume  on  steel  they  say, 
under  the  heading,  "  Steel  Direct  from 
the  Ore:"  "  Gurlt  proposes  to  treat  rich, 
pure  iron  ore  in  cupola  furnaces  by 
means  of  carbonizing  and  reducing  gases, 
and  to  melt  the  resulting  product  in  a 
gas  reverberatory  furnace,  but  this 
method  has  not  proved  successful  when 
carried  out  on  a  large  scale.  By  Chenot's 
method,  rich,  pure,  ores  are  reduced  in 
cupola  furnaces  by  interstratified  layers 
of  charcoal;  the  resulting  spongy  pro- 
ducts containing  various  amounts  of 
carbon,  are  sorted  and  ground  in  mills, 
and  the  mass  is  pressed  into  cylinders 
and  melted  in  crucibles,  sometimes  to- 
gether with  coal  and  a  purifying  and 
scorifying  flux  of  manganese.  This 
method  has  been  tried  in  Belo-ium  with- 


out economical  success,  and  it  does  not 
permit  the  production  of  cast  steel  con- 
taining a  fixed  proportion  of  carbon. 

The  newest  and  most  promising  way 
of  producing  steel  direct  from  the  ore  is 
Mr.  Siemens'  method  with  the  regenera- 
tive gas  furnace.  This  is  the  method  des- 
cribed by  Mr.  Siemens  before  the  Chem- 
ical Society  of  Great  Britain,  May  7th, 
1868.  The  main  feature  is  the  vertical 
hoppers  in  which  the  ore  was  to  be  re- 
duced, and  the  product  dropped  thence 
into  the  bath  of  an  open-hearth  furnace. 
(Further  on  we  shall  see  that  Mr.  Sie- 
mens states  that  it  has  been  abandoned.) 
Neither  Kohn  nor  Fairbairn  appear  to 
have  thought  the  subject  worthy  of  seri- 
ous notice. 

Under  the  date  of  February  27th,  1869, 
we  have  the  record  of  the  opinion  of  a 
metallurgical  chemist,  known  to  you  all 
as  an  eminent  authority.  I  allude  to 
Mr.  Geo.  J.  Snelus.  I  quote  from  an  Eng- 
lish patent  granted  to  him,  of  the  date 
just  mentioned:  "In  the  ordinary  pro- 
cess of  making  iron,  the  ore  is  reduced 
under  such  conditions  that  it  immediately 
takes  up  carbon  and  is  converted  into 
cast  iron.  Several  attempts  have  been 
made  to  produce  wrought  iron  direct 
from  the  ore,  but  either  owing  to  the 
process  not  being  continuous,  or  its  re- 
quiring too  much  time  and  fuel,  or  its 
inapplicability  to  the  treatment  of  fine 
ore,  and  the  incomplete  reduction  of  the 
ore,  none  of  these  attempts  have  yet  been 
successful  in  such  a  degree  as  to  afford 
the  means  of  making  iron  or  steel  so 
economically  as  can  be  done  by  first 
forming  pig-iron  in  the  blast-furnace." 

On  this  side  of  the  Atlantic,  with  one 
notable  exception,  the  direct  process  re- 
ceived little  attention  in  the  literature 
of  iron  metallurgy.  The  exception  I  re- 
fer to  is  the  report  of  Dr.  T.  Sterry 
Hunt,  addressed  to  Sir  W.  Logan,  Di- 
rector of  the  Geological  Survey  of 
Canada,  1869.  In  this  report  the  author 
says:  "In  accordance  with  the  well- 
known  fact  that  the  reduction  of  oxyde 
of  iron  takes  place  at  a  temperature  very 
much  below  that  required  for  subsequent 
carburization  and  fusion,  it  has  been 
shown  that  the  charge  of  ore  in  the 
blast-furnace  is  converted  to  the  metallic 
state  some  time  before  it  descends  to  the 
zone  in  which  melting  takes  place.  It 
foims,  when   reduced,    a   spongy  mass, 


THE    "DIRECT   PROCESS'      IN   IRON   MANUFACTURE. 


315 


readily  oxydized,  which,  by  proper  man- 
agement, can  be  co-repressed  and  made 
to  yield  malleable  iron,  or  by  appropri- 
ate modes  of  treatment,  may  be  con- 
verted into  steel.  This  fact  has  been 
the  starting-point  of  a  great  number  of 
plans  designed  to  obtain  malleable  iron 
and  steel  without  the  production  of  cast 
iron  and  the  employment  of  the  process- 
es of  puddling  and  cementation.  This, 
it  is  true,  is  attained  in  the  Catalan  and 
blooming  forges,  but  the  attention  of 
many  inventors  has  been,  and  still  is,  di- 
rected to  the  discovery  of  simpler,  or  at 
least  more  economical,  methods  of 
obtaining  similar  results." 

Dr.  Hunt  then  proceeds  to  sketch  all 
the  direct  process,  in  this  country  and 
abroad,  worthy  of  mention,  up  to  the 
date  at  which  he  wrote,  pointing  out  in 
each  case  the  difficulty  or  drawback  de- 
veloped in  practical  working.  It  is  a 
brief  but  comprehensive  history  of  the 
subject,  and  tells  the  same  story  in 
every  case, — failure  to  reach  any  large 
results. 

The  British  Iron  and  Steel  Institute 
may  certainly  be  taken  as  embodyidg  the 
latest  and  most  advanced  ideas  in  every- 
thing that  relates  to  iron  metallurgy. 
At  its  meeting  in  London,  March  19th, 
1872,  the  discussion  which  arose  respect- 
ing the  Danks  puddling  furnace,  brought 
out  incidentally  an  expression  of  opinion 
on  the  direct  process  from  some  of  its 
most  eminent  members.  Mr.  Edward 
Riley  said :  "  As  regarded  making 
wrought  iron  direct  from  the  ore,  he  be- 
lieved there  was  certainly  very  little 
hope  of  that  being  carried  out  practically 
or  profitably.  He  thought  no  one  could 
conceive  any  method  more  simple  than 
the  present  process  of  throwing  mate- 
rials into  the  blast-furnace  for  the  pur- 
pose of  reducing  them,  and  he  was  sure 
that  all  improvements  in  iron  should 
commence  with  the  pig-iron.  They 
could  make  it  in  any  quantity,  and  they 
ough  to  start  there.  He  could  not  con- 
ceive of  any  other  process  of  making 
iron  cheaper." 

Mr.  Isaac  Lowthian  Bell  "  thought 
that  a  certain  amount  of  disrespect  had 
been  shown,"  in  a  previous  part  of  the 
discussion,  "  with  regard  to  the  blast- 
furnace, in  speaking  of  it  as  a  roundabout 
way  of  doing  the  work  which  was  per- 
formed by  it.     There  was  no  doubt  that 


they  combined  the  iron  with  the  carbon 
or  silicon  in  the  smelting  process,  which 
had  subsequently  to  be  dispersed  ;  but 
they  must  remember  that  the  blast-fur- 
nace, at  the  same  time,  got  rid  of  earthy 
impurities  generally  found  associated 
with  iron  ores.  He  therefore  quite 
agreed  with  Mr.  Riley  that,  although  it 
might  be  a  roundabout  way  in  the  first 
instance,  they  could  not  conceive  any 
means  so  simple  for  getting  rid  of  a 
large  amount  of  extraneous  matter  as 
blast-furnaces." 

These  views  appear  to  have  been  acqui- 
esced in  by  the  members  generally.  At 
their  meeting  in  April,  1873,  Dr.  C.  W. 
Siemens  read  a  paper  which,  from  the 
distinguished  position  of  its  author,  and 
the  character  of  its  reception  by  his  as- 
sociates, may  reasonably  be  supposed  to 
represent  the  condition  at  that  date  of 
the  art  of  iron  making  in  Great  Britain, 
so  far  as  relates  to  the  direct  process. 
After  describing  the  various  attempts 
made  by  him  to  bring  the  direct  process 
into  practice,  and  explaining  the  reasons 
which  induced  him  to  abandon  them, 
one  after  the  other, he  uses  these  words: 
"  These  experiments  convinced  me  that 
the  successful  application  of  reduced 
ores  could  not  be  accomplished  through 
their  conversion  into  spongy  metal,  and 
fully  explained  to  me  the  want  of  suc- 
cess which  has  attended  the  previous  ef- 
forts of  Clay,  Chenot,  Yates,  and  others, 
to  produce  iron  direct  from  the  ore."  He 
then  describes  a  new  method  and  appa- 
ratus wherein  he  begins  by  abandoning 
one  of  the  cardinal  features  of  a  truly 
direct  process,  a  feature  pointed  out  by 
Dr.  Hunt  in  the  extract  I  have  already 
quoted,  viz.,  that  the  reduction  of  the 
oxyde  of  iron  can  be  obtained  at  a  heat 
much  below  that  required  for  its  conse- 
quent combustion  and  fusion.  Dr.  Sie- 
mens, despairing  of  realizing  this  feature, 
begins,  in  his  new  process,  by  fusing  the 
oxyde. 

Such,  I  think,  may  be  called  a  fair 
statement  of  the  literature  of  the  sub- 
ject up  to  the  present  time.  Further- 
more, its  uniform  and  consistent  record 
of  failure  is  borne  out  by  the  facts.  It 
would  have  been,  for  example,  impossible 
for  a  metallurgist  so  intelligent  and  de- 
servedly esteemed  as  Gruner  is.  to  com- 
mit himself  to  the  statements  I  have 
quoted,  if,  at  the  time    he   made    them, 


316 


VAN  NOSTRAND'S   ENGINEERING   MAGAZINE. 


there  had  been  in  existence,  as  an  article 
of  manufacture  on  a  large  scale,  a  true 
iron  sponge.  He  speaks  of  the  "  earthy 
substances"  as  causing  "impurity,"  and 
says  that  the  sponge  when  melted  will, 
it  is  true,  give  a  homogenous  product, 
but  of  inferior  quality,  "  unless  the  iron 
sponge  undergoes  fining  like  pig-metal." 
Had  he  been  acquainted  with  iron  sponge 
whose  only  "  impurities  "  (in  quantities 
sufficient  to  be  objectionable)  were  silica 
and  alumina,  could  he  have  fallen  into 
the  error  of  stating  that  the  impurities 
could  not  be  removed  by  the  state  of 
fusion,  but  only  "  when  the  iron  sponge 
undergoes  fining  like  pig-metal  ?  " 

So  with  his  statement  that  the  neces- 
sity of  adding  carbon  in  the  direct  pro- 
cess "  destroys  all  profit "  in  it.  Had 
he  been  acquainted,  I  say,  with  true  iron 
sponge,  and  familiar  with  its  manufac- 
ture into  iron  and  steel,  he  would  have 
recognized  the  fact  that  in  iron  sponge 
we  have  the  least  possible  affinity  be- 
tween the  earthy  substances  and  the 
metal.  And  he  undoubtedly  would  have 
been  thus  informed  had  such  practice 
been  known  in  the  art. 

But  setting  aside  all  these,  I  come 
down  to  the  present  hour  and  present 
place,  and  our  own  country,  and  I  ask 
you  here  present,  who  are  familiar  with 
all  the  industries  of  the  nation,  whether 
you  have  knowledge  of  any  direct  pro- 
cess for  the  production  alike  of  iron  and 
steel,  now  carried  on  upon  a  working 
scale,  as  a  successful  rival  of  the  ordin- 
ary indirect  methods  ?  " 

When  one  considei's  that  the  immense 
results  which  must  flow  from  the  success- 
ful achievement  of  the  direct  process  are 
understood  by  all  scientific  men,  and 
have  been  by  them  so  understood  for 
years  past,  it  seems  like  presumption  to 
attempt  to  carry  off  a  prize  which  all 
have  hitherto  either  despaired  of,  or, 
seeking,  have  failed  to  win.  It  seems  so 
plain,  so  easy,  yet  has  still  remained,  as 
it  were,  just  out  of  reach.  There  must 
be,  one  would  say,  some  hidden  but  in- 
superable difficulty,  else  the  problem 
had  long  since  been  solved.  Consider 
for  a  moment  how  inviting  a  field  it  is. 
Nature  provides  us  with  the  metal  we 
want,  chemically  combined  with  oxygen, 
and  mechanically  mingled  with  other 
substances.  Let  us  withdraw  this 
oxygen  from  the  iron  only,  leaving  the 


rest  as  compounds,  it  alone  being  ele- 
mentary. Now  let  us  melt  the  product, 
so  that  the  iron  shall,  simply  by  differ- 
ence of  gravity,  be  separated  from  the 
dross,  and  then  poured  into  proper 
moulds.  Here  we  have  but  two  steps, 
each  of  great  apparent  simplicity — first, 
reduction  ;  second,  fusion.  Such  is  the 
ideal,  which  by  contrast  makes  the 
old  system  appear  so  crude,  unscientific, 
and  roundabout,  that  the  term  "  direct" 
applied  to  the  new  method  sounds  like 
the  promise  of  a  great  and  beneficent 
revolution. 

We  know  that  carbon  at  a  certain 
heat  will  dissociate  the  iron  and  the 
oxygen,  yet  leave  the  other  mineral 
matter  of  the  ore  unreduced,  giving 
metallic  iron — wrought  iron — as  the 
result.  We  know  further,  that  we  have 
at  command  furnaces  in  which  the  pro- 
duct can  be  melted  down  in  a  bath  of 
cast  iron,  and  so  treated  that  it  shall  re- 
sult in  ingots  of  any  desired  degree  of 
carburation.  We  know  that  if  the  reduc- 
tion of  the  ore"  can  be  effected  the  ele- 
ments of  cost  in  fuel,  labor,  etc.,  will  make 
the  product  cheaper  than  pig-iron,  and 
also  that  the  melting  process  is  less  cost- 
ly than  puddling,  whereas  its  product  is  of 
far  greater  value.  Why  is  it,  then,  that 
while  the  whole  iron  industry  of  the 
world  is  struggling  by  small  economies 
to  realize  a  return  upon  its  capital,  this 
most  plain,  most  prominent  of  all  econo- 
mies remains  unpractised  ? 

There  has  been  a  link  missing — with- 
out it,  all  is  naught.  There  has  been  no 
thorough,  uniform,  economical  process 
of  reduction.  The  missing  link  is  true 
iron  sponge.  It  is  that  which  I  come 
hereto  exhibit  to-day;  to  tell  you  how 
it  is  obtained,  and  to  show  you  that,  by 
the  means  I  shall  describe,  it  is  within 
the  reach  of  all.  Let  me  be  your  guide 
while  Ave  travel  together,  ( in  thought, 
from  the  point  at  which  I  started  to  the 
final  point  of  success.  It  shall  not  be  the 
path  I  traveled.  This  time  we  will  take 
the  smoothest  and  shortest  way. 

We  are  in  a  chemical  laboratory.  We 
take  a  small  porcelain  tube  and  fill  it 
with  a  mixture  of  pulverized  peroxyde 
of  iron  and  charcoal;  next  we  seal  the 
ends  of  the  tube  hermetically,  then  ex- 
pose it  to  heat,  by  immersing  it  in  a 
bath  of  brightly  red-hot  sand  for  a 
certain  time  (varying  with  the  character 


THE  "direct  process"  in  iron  manufacture. 


317 


of  the  ore),  then  take  it  out,  cool  it,  and, 
after  cooling,  break  it  open,  and  pour 
out  the  contents.  Carefully  separating 
and  testing  them,  we  find  that  we  have 
obtained  particles  of  metallic  iron.  Now 
what  condition  did  we  observe  to  get 
this  result  ? 

First.  There  was  contact  of  the  iron 
oxyde  with  carbon. 

Second.  There  was  isolation  from  the 
free  oxygen  of  the  atmosphere. 

Third.  There  was  the  heat  of  bright 
redness. 

Fourth.  There  was  a  certain  duration 
of  time. 

Fifth.  There  was  continued  isolation 
from  the  air  until  cold. 

Hence,  we  have  established  the  fact 
that  if  a  peroxyde  of  iron  be  brought  in- 
to contact  with  a  sufficient  quantity  of 
carbon,  with  perfect  isolation  from  the 
atmosphere  while  exposed  for  a  sufficient 
length  of  time  to  a  sufficient  heat,  and 
then  cooled  down  to  a  sufficient  degree 
while  still  isolated  from  the  air,  the 
oxygen  and  the  iron  will  be  dissociated, 
the  oxygen  passing  off  in  a  gaseous  form, 
leaving  the  iron  behind.  Now,  chemis- 
try supplies  all  the  data  for  filling  up 
with  absolute  figures  the  blanks  in  this 
statement,  and  we  have  in  consequence 
a  formula  by  which,  if  strictly  carried  out, 
we  can  achieve  the  first  of  our  two  great 
steps  in  the  direct  process — we  can  gain 
the  metallic  iron  directly  from  the  ore. 
Hence  the  chemistry  of  the  operation  is 
clear,  and  it  becomes  simply  an  engin- 
eering question  how  to  meet  all  the 
necessary  conditions,  so  as  to  conduct  it 
on  the  large  scale. 

First,  we  investigate  previous  attempts, 
striving  to  detect  what  is  defective, 
recognizing  what  is  correct,  and  supply- 
ing what  yet  is  wanting.  Proceeding 
in  our  course  of  elimination  we  first  re- 
ject all  those  methods  in  which  it  is 
sought  to  yoke  the  production  of  the 
iron  sponge  directly  with  a  method  of 
treating  it;  those,  for  example,  which 
are  meant  to  reduce  the  ore  in  one  cham- 
ber and  pass  it  as  fast  as  reduced  (or 
supposed  to  be  reduced)  into  another 
chamber  for  after-treatment — welding, 
melting,  etc.  The  operations  cannot  be 
made  synchronous.  One  or  the  other 
must  be  disarranged  in  order  to  accom- 
modate its  fellow. 

Confining   ourselves,  therefore,  to  the 


simple  question  of  reduction,  we  finally 
give  the  preference,  among  the  multi- 
tude of  contrivances  and  appliances,  to 
the  vertical  chamber,  to  be  filled  at  top, 
and  drawn  at  bottom,  and  working  con- 
tinuously. But  in  all  these  we  discover 
one  fatal  defect;  there  is  no  adequate- 
provision  for  the  isolation  of  the  mater- 
ial, either  while  under  treatment,  or  cool- 
ing, or  both. 

We  experiment  ourselves,  and  despair 
of  obtaining  the  desired  result  by  any 
arrangement  of  valves,  or  slides,  or  the 
like  contrivances.  The  dilemma  is  this  : 
we  want  an  apparatus  that,  as  I  have 
said,  shall  work  continuously,  and  on  a 
scale  of  considerable  magnitude,  taking 
in  and  discharging  material  at  short  in- 
tervals, yet  always  closed  to  the  entrance 
of  free  oxygen.  Or,  otherwise  stated, 
we  must  have  a  chamber  so  open  at  top 
and  bottom  that  we  can  dump  in  a  cart- 
load of  crude  material  above  and  draw 
out  a  cartload  of  finished  product  below, 
yet  be  all  the  time  hermetically  sealed 
against  admission  of  air.  Now  this 
chamber — assuming  that  we  have  settled 
upon  the  plan  of  filling  it  with  ore  and 
solid  carbonaceous  matter,  and  heating 
them  through  its  walls — must  be  sur- 
rounded by  heat  for  a  certain  distance 
down  and  by  a  cooling  medium  below 
that,  because  we  intend  to  reduce  and 
then  cool  down.  Well,  we  find  that  our 
difficulty  as  regards  the  keeping  out  of 
air  at  top,  takes  care  of  itself.  The  solid 
oxygen  and  solid  carbon,  down  in  the 
zone  of  reduction,  are  combining  as  car- 
bonic oxyde,  and,  by  virtue  of  their 
great  expansion,  forcing  their  way  up- 
ward and  out  so  that  they  arrest  every 
particle  of  free  oxygen  before  it  can 
penetrate  downward.  As  to  the  bottom, 
however,  we  have  not  this  resource,  and 
must  find  another.  We  get  it  by  giving 
to  our  chamber  such  proportions  that 
there  shall  always  be  above  the  place  of 
egress  a  column  of  material,  so  cool  it- 
self as  to  be  proof  against  the  influence 
of  oxygen,  and  of  such  a  height  as  to 
form  a  packing,  which  shall  seal  up  all 
that  material  above  it  which  has  not  yet 
reached  the  safe  degree  of  cooling. 

By  this  device,  which,  surely,  is  as 
simple  as  anything  in  metallurgical  en- 
gineering, our  dilemma  is  answered. 
We  are  now  operating,  in  regular  prac- 
tice, at  Glenwood,  cylinders  of  three  feet 


318 


VAN  nostrand's  engineering  magazine. 


internal  diameter,  and  forty  feet  in 
height,  whch  are  open  tubes,  so  far  as 
relates  to  the  taking  in  and  discharging 
of  their  contents,  but  as  relates  to  access 
of  air  in  their  working  zones,  are  sealed 
retorts;  the  seal  above  being  the  ingoing 
material  itself  and  the  gases  percolating 
upward  through  it  ;  and  the  seal  below, 
the  material  which,  by  cooling,  has  be- 
come indifferent  to  exposure.  For  the 
first  time,  then,  in  the  history  *>f  attempts 
at  the  direct  process  we  have  at  our 
command  complete  isolation,  yet  con- 
tinuous working. 

Let  us  next  take  up  the  question  of 
imparting  and  maintaining  the  necessary 
heat.  Here  at  once  another  difficulty 
confronts  us.  We  must  work  upon  a 
scale  of  considerable  magnitude,  and  our 
reducing  chambers  must,  therefore,  be 
of  considerable  area.  But  their  contents 
are  very  poor  conductors  of  heat,  and  a 
little  experience  will  convince  us  of  the 
impracticability  of  getting  an  evenly- 
distributed  temperature  by- conduction 
from  the  outside  through  a  mass  of,  say, 
three  feet  diameter.  Now,  we  must 
have  uniformity  of  temperature  to  get 
uniformity  of  result,  and  the  system  we 
have  adopted  obliges  us  to  impart  the 
heat  by  conduction.  We  could  conduct 
it,  we  will  say,  through  three  inches  of 
the  materials,  in  time  enough  to  answer 
all  practical  purposes,  but  not  through 
three  feet. 

Let  us  see,  therefore,  if  we  cannot 
bring  every  particle  of  the  material  with- 
in three  inches  of  a  sufficiently  heated 
surface.  Thus  stated,  you  will  probably 
guess  at  the  solution  of  the  problem.  It 
is  this  :  When  charging  your  material 
into  your  cylinder,  cause  it  to  pass  be- 
tween heated  surfaces  in  streams  whose 
greatest  distance,  in  any  part,  from  a 
sufficiently  heated  surface,  shall  not  ex- 
ceed your  limit  of  three  inches. 

This,  you  will  readily  perceive,  may 
be  done  in  many  ways.  Let  me  describe 
to  you  one  of  the  arrangements  which  I 
employ.  It  accomplishes  very  economi- 
cally the  purpose  just  explained,  and 
performs  another  function  which  I  will 
refer  to  directly. 

In  the  top  or  mouth  of  the  reducing 
cylinder,  I  suspend  an  inner  cylinder  or 
thimble  of  cast  iron,  with  walls,  say  one 
inch  thick,  and  having  an  outside  diame- 
ter of  twenty-eight  inches. 


Now,  the  reducing  cylinder  has  an  in- 
side diameter  of  thirty-six  inches;  hence 
there  is  left  an  open  space  or  annulus 
between  the  two  of  four  inches  across. 

I  charge  my  materials  into  this  annu- 
lus only,  so  that  all  have  to  pass  down- 
ward through  it,  and  none  can  be  more 
distant  than  two  inches  from  the  heated 
surface,  either  of  the  cylinder  or  of  the 
thimble.  I  make  the  thimble  long 
enough — say  six  feet — to  insure  that  all 
the  materials  shall  have  acquired  the 
temperature  desired  before  they  descend 
below  the  annulus. 

This  "initial  heating,"  as  I  call  it,  es- 
tablishes one  of  the  primary  conditions 
with  which  we  started  out — the  impart- 
ing of  the  necessary  degree  of  heat — the 
only  duty  required  of  that  portion  of  the 
heating  chamber  which  surrounds  the 
cylinders  below  the  level  of  the  bottom 
of  the  thimble  being  to  prevent  the 
escape  of  the  heat  thus  imparted.  You 
will  observe  that  this  device  completely 
meets  the  whole  difficulty  as  to  the  con- 
duction of  the  heat,  so  that — whatever 
the  diameter  of  the  reducing  cylinder — 
it  is  only  a  question  of  what  diameter 
and  length  you  will  give  the  thimble,  in 
order  to  impart  your  materials  the  tem- 
perature you  wish. 

We  have  now  got  thus  far.  Our  re- 
ducing furnace  shall  consist  of  one  or 
more  cylinders  (adopting  the  cylinder  as 
the  preferable  form  of  chamber),  which 
shall  be  heated  externally  for  a  certain 
distance  from  the  top  down,  then  cooled 
the  rest  of  the  distance  downward  to  the 
base,  excepting  the  room  required  at 
bottom  for  raising  the  telescopic  sleeve 
for  the  discharge  of  material. 

At  its  top  is  the  thimble  for  initial 
heating. 

Let  us  now  revert  to  our  original  state- 
ment of  the  conditions  to  be  met,  and  see 
if  we  have  fulfilled  them. 

First.  We  provide  the  contact  of 
iron  ore  and  carbonaceous  matter  by 
mingling  them  before  discharging  into 
our  cylinder. 

Second.  We  isolate  these  materials 
from  free  oxygen  while  in  the  zone  of 
reduction. 

Third.  We  conduct  the  required 
degree  of  heat  through  the  mass. 

Fourth.  Our  apparatus  enables  us  to- 
hold  it  under  treatment  for  any  length 
of  time  desired. 


THE    "DIRECT   PROCESS"    IN   IRON   MANUFACTURE. 


319 


Fifth.  We  have  continued  the  isola- 
tion until  the  product  was  too  cool  to 
be  oxydized  on  exposure  to  the  air. 

Thus  we  have  realized,  upon  a  work- 
ing scale  commensurate  with  the  require- 
ments of  the  art,  the  laboratory  experi- 
ment of  the  sealed  tube,  and  the  manu- 
facture of  iron  sponge  becomes  as  simple 
as  any  of  the  ordinary  operations  in  the 
art  of  iron  making. 

From  the  general  principles  above 
laid  down,  it  will  be  easy  to  plan  a  good 
working  reducing  furnace;  but  there  are 
a  number  of  details,  both  of  construction 
and  management,  which  I  think  may  in- 
terest you. 

I  have  already  alluded  to  the  thimble 
arrangement  for  the  "  initial  heating," 
as  having  another  recommendation  be- 
yond its  convenient  form.  What  I  re- 
ferred to  is  this :  When  the  carbon 
dissociates  the  oxygen  from  the  iron, 
carbonic  oxyde  is  formed,  and  this,  rising 
as  I  have  said,  passes  outward  by  way 
of  the  interior  of  the  thimble,  as  furnish- 
ing a  line  of  less  resistance  than  the 
annulus,  packed  as  the  latter  is  with  the 
ingoing  materials.  As  it  ascends  through 
the  thimble  it  is  met  by  the  air,  which, 
in  virtue  of  its  greater  weight  (being 
colder),  and  from  the  tendency  to  trans- 
fusion in  gaseous  bodies,  descends  into 
the  thimble,  and  a  perfect  combustion  of 
the  carbonic  oxyde  is  kept  up. 

Thus  the  carbon,  which  had  served  as 
a  chemical  agent  in  the  reduction  of  the 
ore,  is  made  to  do  duty  once  more,  as  a 
fuel. 

Speaking  of  fuel,  I  would  say  that  my 
method  of  heating  the  cylinders  is  to 
place  the  portion  of  them  to  be  heated 
in  a  chamber  of  brick,  which  is  supported 
on  iron  pillars ;  thus  leaving  the  cooling 
zone  accessible  below.  This  chamber  is 
heated  by  letting  into  it  streams  of  gas 
at  different  levels,  with  an  air  inlet  adja- 
cent to  each  inlet  of  gas.  All,  of  course, 
are  arranged  so  as  to  have  the  gas  supply 
under  convenient  control.  Aside  from 
the  economy  of  gaseous,  as  compared 
with  solid  fuel,  it  is  incomparably  easier 
to  keep  a  chamber  such  as  this  at  a  uni- 
form temperature  with  gas  than  to  heat 
it  by  burning  coal  or  wood  on  grates. 

While  on  this  subject  of  fuel,  I  may 
say  that  I  am  tired  of  the  ordinary  form 
of  gas-producer.  It  is  certainly  a  clumsy 
affair. 


I  hope  to  have  something  interesting 
to  say,  upon  a  future  occasion,  as  to  a 
better  form  throughout.  Meantime  I 
would  suggest  to  others  who  find  the 
clinkering  to  be  as  much  of  an  annoy- 
ance as  I  do,  to  try — as  I  shall  soon — in 
the  present  form  of  producer,  a  water- 
tox  all  round,  as  high  up  as  clinkers 
borm,  and  water-bars  like  those  seme- 
mes used  under  boilers. 

I  not  only  introduce  the  gas  into  the 
heating  chamber,  but  also  carry  a  pipe 
into  and  project  it  downward  nearly  to 
the  bottom  of  the  thimble.  By  this 
means,  whenever  the  gases  developed  in 
the  cylinders,  as  before  explained,  do  not 
suffice  to  keep  the  heat  of  the  interior  of 
the  thimble  up  to  the  point  desired,  I 
turn  on  other  gas  enough  to  make  up 
the  deficiency. 

Thus  I  secure  perfect  control  of  the 
heat  of  the  thimble,  and  make  sure  that 
the  material  in  the  annulus  will  always 
be  hot  enough  to  be  ready  for  dropping 
when  a  charge  is  drawn  from  below.  In 
this  way  the  output'  of  the  furnace  is 
limited  to  but  one  consideration,  to  wit  : 
what  duration  of  exposure  to  a  red  heat 
is  necessary  to  perfect  the  conversion. 
The  amount  of  fuel  required  for  heating 
is  about  one-third  of  a  ton  of  iron  in  the 
sponge  turned  out.  Any  description  of 
fuel  commonly  used  in  gas  producers 
will  answer.  As  to  the  cooling,  the  re- 
ducing cylinders  underneath  the  heating 
chamber  are  prolonged  simplyin  wrought 
iron  of  one-fourth  inch  thickness,  and 
each  is  surrounded  by  a  jacket,  which  is 
kept  full  of  water  continually  changed. 
The  wrought  iron  cylinder  ends  about 
eighteen  inches  above  the  floor,  and  a 
sleeve,  working  telescope  fashion,  closes 
the  remainder  of  the  connection  when 
let  fully  down.  By  raising  the  sleeve 
more  or  less,  as  required,  the  material 
gushes  out  underneath,  and  as  it  does  so- 
the  whole  column  of  material  in  the 
cylinder  descends,  leaving  a  space  at  the 
top  of  the  annulus,  which  is  immediately 
filled  up  with  fresh  material. 

I  do  not  find  that  the  size  of  the  ore 
makes  any  practical  difference,  whether 
it  is,  say,  two  inches  through,  or  any 
smaller.  This  fact  has  been  observed 
in  experimental  work  heretofore,  but  I 
have  never  seen,  nor  been  able  to  frame 
for  myself,  any  explanation  that  is  quite 
satisfactory.     I  suggest  it  as  an  interest- 


320 


VAN  nostrand's  engineering  magazine. 


ing  subject   for  our   fellow-members  of 
the  chemical  profession. 

It  has  been  stated  iu  the  books  that 
the  sesquioxyde  of  iron  in  the  process  of 
reduction  first  becomes  magnetic  oxyde, 
then  protoxyde,  then  metallic.  This  ap- 
pears to  be  demonstrated  by  the  fact 
which  may  often  (if  not  always)  be  ob- 
served in  pieces  too  large  to  be  "  done 
through"  (as  the  workmen  phrase  it),  in 
the  time  during  which  they  were  under 
treatment. 

If  the  size  of  the  piece  is  large,  say 
four  inches,  and  the  core  is  still  quite 
raw,  but  the  outside  completely  reduced, 
the  concentric  layer  next  to  the  core  will 
"be  protoxyde,  the  next  magnetic  oxyde, 
and  the  next  the  iron  sponge.  Not  that 
these  layers  are  distinctly  defined,  but 
merge  into  each  other  at  the  points  of 
contact.  But  if  the  size  is  kept  within 
the  limit  named,  there  is  usually  no  dis- 
tinction to  be  observed,  and  the  pieces, 
if  anything  near  raw  at  the  core,  will 
usually  show  signs  of  protoxyde  on  the 
surface. 

I  must,  however,  qualify  my  remark 
as  to  the  comparative  time  required  for 
the  reduction  of  pieces  of  different  sizes. 
I  did  not  mean  to  include  ore  in  fine  par- 
ticles. This  does  appear  to  be  more 
rapidly  reduced  than  that  which  is 
coarser,  but  as  it  is  cheaper  to  break  the 
ore  only  to  a  moderately  small  size,  and 
the  fine  powder  is  hence  an  insignificant 
fraction,  I  have  not  observed  it  closely 
in  this  particular. 

"With  respect  to  the  time  required  for 
treatment,  it  varies  according  to  two  sets 
of  conditions. 

The  first  is  that  of  chemical  composi- 
tion. The  sesquioxydes  are  more  easily 
reduced  than  the  magnetic,  and  the  lat- 
ter than  the  protoxydes.  Hence,  hasty 
reasoners,  who  might  argue  that  because 
the  sesquioxyde  had  to  pass  through  the 
stages  of  magnetic  and  protoxyde  before 
becoming  metallic,  it  must,  therefore,  be 
the  hardest  to  reduce,  would  find  them- 
selves in  direct  opposition  to  the  fact. 
The  explanation,  I  suppose,  is  this  : 
Where  the  oxygen  most  abounds,  reduc- 
tion is  easiest  to  commence,  and  once  on 
the  move,  the  operation  proceeds  rapidly. 

The  second  set  of  conditions  are  those 
of  mechanical  structure.  The  massive 
materials  are,  as  one  would  naturally 
suppose,  harder   to  operate   upon   than 


those  which  are  loose  and  open.  The 
brown  hematites  are  capital  subjects  for 
the  reducing  furnace.  As  soon  as  they 
reach  a  red  heat,  the  water  of  combina- 
tion is  driven  off,  leaving  an  open,  sponge 
like  structure,  and  being  also  sesqui- 
oxydes, we  have  both  the  chemical  and 
mechanical  conditions  for  speedy  reduc- 
tion. The  compact  hematites,  such  as 
the  Iron  Mountain  ore  of  Missouri,  and 
the  red  specular  of  Lake  Superior, 
though  sesquioxydes,  have  no  combined 
water,  and  are  of  a  dense  structure.  In 
consequence  they  require  a  much  longer 
treatment.  The  magnetic  oxydes,  such 
as  those  of  Lake  Champlain  and  the  iron 
sands  of  the  St.  Lawrence,  being  both 
very  compact,  and  leaner  in  oxygen,  re- 
quire a  longer  time  still  than  the  com- 
pact hematites ;  while  the  protoxydes, 
when  in  such  a  shape  as,  for  example, 
the  dense  tap  cinder  from  the  puddling 
furnace,  are  extremely  obstinate  under 
treatment. 

Among  the  curiosities  of  the  reduction 
of  iron  oxydes,  is  the  fact  that  the  in- 
tensity of  action  bears  but  slight  rela- 
tion, within  certain  limitations,  to  the 
degree  of  heat  employed.  This  is  a  fact 
noted  by  Mr.  I.  Lowthian  Bell,  in  his  ex- 
periments with  the  blast  furnace.  It 
suffices  for  our  present  purposes  to  state, 
as  relates  to  it,  that  there  would  be  no 
particular  acceleration  of  the  process 
gained  by  pushing  the  heat  to  a  degree 
that  involves  danger  of  welding  the 
material  together  while  under  treatment. 
But  I  am  able  to  announce  to  you 
another  very  important  fact,  and  one  not 
to  be  found  in  the  books,  namely,  that 
at  the  temperature  of  reduction — say  a 
fairly  bright  red  heat,  and  with  carbon 
alone  as  the  reducing  agent — no  carbon 
whatever  is  taken  up  by  the  iron.  I 
think  it  sufficiently  indicates  the  state  of 
the  art  of  iron-sponge  making  as  it  has 
been  hitherto,  when  I  tell  you  that  I 
asked  this  question  direct  of  one  of  the 
most  distinguished  and  most  practical  of 
the  foreign  authors  I  have  already  quot- 
ed, and  the  answer  was  that,  to  the  best 
of  his  knowledge,  the  point  had  never 
been  settled.  Now,  if  you  will  consider 
for  a  moment  the  immense  importance 
of  this  question — the  question  whether 
your  product  is  to  be  wrought  iron  alpne 
— a  product  which  you  can  employ  as 
iron  or  carburize  with  precision  to  the 


THE    "DIRECT   PROCESS"    IN   IRON   MANUFACTURE. 


321 


temper  desired,  or  whether  it  is  to  be- 
come an  unsettled  and  uncertain  carbide 
of  iron,  to  be  sampled  and  analyzed, 
every  lot,  before  using,  and  from  which 
carbon  must  be  removed  if  wrought  iron 
is  to  be  made  from  it ;  when  I  say,  you 
consider  the  magnitude  of  this  question 
and  the  fact  that  neither  the  man  of  sci- 
ence nor  the  practical  manufacturer  had 
any  answer  for  it,  you  will  agree  with 
me  that  the  art  had  not  yet  made  much 
progress. 

But  at  all  events,  the  question  is  now 
set  at  rest.  I  have  had  frequent  analyses 
made  of  iron  sponge,  produced  from 
various  descriptions  of  ore,  and  in  no 
case  has  combined  carbon  been  found. 
The  iron  sponge,  sensitive  as  it  is  to 
many  chemical  reactions,  only  takes  up 
carbon  '(when  presented  unaccompanied 
by  an  accelerating  agent)  as  other 
wrought  iron  does,  to  wit  :  at  the  recog- 
nized heat  of  comentation,  a  heat  far 
higher  than  we  need  to  (or  ought  to) 
employ  in  the  reducing  furnace. 

With  respect  to  the  carbonaceous 
matter  used  as  the  reducing  agent,  I 
would  state  that,  in  regular  practice,  we 
have,  up  to  the  present  time,  made  use 
of  charcoal.  We  have  tried  both  coke 
and  anthracite,  but  merely  in  an  experi- 
.  mental  way.  We  have  not  been  pre- 
pared to  remove  the  sulphur  from  either, 
and — having  so  many  other  things  to 
get  into  working  order — have  preferred 
to  run  no  risks  in  this  particular.  Our 
experiments  have  been  conclusive,  how- 
ever, as  to  the  reducing  power  of 
these  substances,  and  we  shall,  early 
in  the  spring,  take  measures  to  use  coke 
from  washed  coal.  We  have  experi- 
mented with  a  Bradford  separator,  and 
find  that  the  fine  "  slack "  of  the  Pitts* 
burgh  coal  can  be  so  freed  from  sulphur 
that  even,  if  none  were  driven  off  in  cok- 
ing, and  the  whole  of  it  absorbed  by  the 
iron  in  the  reducing  cylinder,  there 
would  not  be  over  0.08  per  cent,  in  the 
iron.  For  the  country  east  of  the  Alle- 
ghenies,  the  anthracite  culm  should  fur- 
nish an  exceedingly  cheap  reducing 
agent.  I  am  informed  that  there  is  no 
difficulty  in  removing  the  sulphur  by 
treatment  with  steam  charged  with 
alkaline  vapors,  and  at  moderate  cost. 
I  have  not  yet  had  any  practical  experi- 
ence, however,  in  this  matter. 

The  estimate  of  quantity  required  per 
Vol.  XUL— No.  4—21 


ton  of  iron  produced  is  very  easily  made. 
For  brevity's  sake  we  will  consider  only 
the  sesquioxydes,  as  they  require  the 
largest  ratio  of  carbon.  They  carry  70 
per  cent,  of  iron  to  30  per  cent,  of  oxy- 
gen. Now,  every  30  parts,  by  weight, 
of  oxygen  take  up  22^  parts  of  carbon, 
so  that  we  employ  22^  parts  of  carbon 
for  every  70  parts  of  iron,  or  32.14  parts 
of  carbon  to  the  100  of  iron  ;  in  round 
numbers,  one-third  ton  of  carbon  to  the 
ton  of  iron  in  the  sponge.  It  may  occur 
to  you  that  this  is  the  theoretical  quan- 
tity, and  that  in  practice  it  must  require 
more.  But  such  is  not  the  case — at  least 
to  any  appreciable  extent.  No  carbon 
is  used  in  the  reducing  cylinder  except 
what  is  taken  up  by  the  chemical  opera- 
tion referred  to  above.  None  of  the 
other  oxydes  of  which  the  ore  is  com- 
posed are  reduced,  and  there  is  no  free 
oxygen  present  to  consume  any  carbon. 
Whatever  excess,  beyond  the  amount 
absolutely  required,  we  may  mix  in  with 
the  ore,  to  secure  a  sufficiency  through- 
out the  mass,  is  regained  at  the  bottom 
of  the  cylinder. 

I  would  now  ask  your  attention  to  the 
fact  that,  in  my  statements  respecting 
reduction,  I  have  hitherto  confined  my- 
self to  the  case  of  reduction  by  carbon 
only.  You  are  aware,  however,  that 
there  are  certain  substances,  such  as 
cyanogen,  hydrogen,  etc.,  which,  when 
present  with  carbon,  exert  a  singular 
power  in  accelerating  its  combination 
with  iron.  Some  of  these  substances, 
as,  for  example,  hydrogen,  are  also  in 
themselves  powerful  reducing  agents. 
You  will  see  at  once  how  the  employ- 
ment of  these  may  vary  the  results. 
The  hydrocarbons,  for  example,  will 
produce  reduction  at  a  lower  tempera- 
ture or  with  great  saving  of  time,  but 
Avill  yield  an  irregularly  carburized 
sponge.  The  field  is  too  large  to  enter 
upon  hei'e,  and  must  be  passed  over  with 
this  brief  notice,  to  be  reverted  to,  how- 
ever, for  a  moment  when  I  come  to 
speak  of  the  second  branch  of  the  direct 
process,  viz.,  fusion. 

There  is  another  feature  of  the  reduc- 
ing operation  which  has  been  remarked, 
upon  by  some  accurate  observers,  such 
as  Mr.  I.  Lowthian  Bell,  but  which  ap- 
pears to  have  been  unsuspected  by  the 
generality  of  those  who  have  attempted 
to  make  iron-sponge.     It  is  this,  that  the 


322 


VAN   NOSTRAND'S   ENGINEERING   MAGAZINE. 


resistance  of  the  oxygen  against  its  dis- 
sociation from  the  iron  increases  in  inverse 
ratio  to  the  quantity  remaining.  Thus, 
to  get  out  fifty  per  cent,  of  it,  for  in- 
stance, is  a  very  easy  and  a  very  short 
operation  ;  to  get  out  the  next  twenty- 
five  per  cent,  may  perhaps  not  take 
much  longer  additional  time  than  to  ab- 
stract the  first  fifty  per  cent. ;  but  the 
refractory  quality  in  the  oxygen  keeps 
rapidly  rising  until  it  becomes  practically 
almost  a  matter  of  impossibility  to  get 
out  the  last  remnant  of  it.  Ignorance  of 
this  simple  law  has  kept  many  a  sanguine 
inventor  pursuing  an  ignis  fatutis,  and 
at  its  door  must  be  laid  the  corpse  of 
many  a  once  cherished,  but  now  lifeless 
"process." 

From  it  arises  the  talk,  sometimes  so 
freely  indulged  in,  about  iron-sponge  as 
a  well-known  article,  quite  at  command 
if  wanted. 

As  a  curiosity  in  this  line,  let  me  quote 
from  an  English  patent  of  lS^O,  taken 
out  by  a  practical  manufacturer,  a  man- 
ager of  steel  works  :  "  The  reduction 
of  the  ore  to  the  condition  of  spongy 
metallic  iron  is  a  matter  of  comparatively 
little  difficulty,  and  may  be  effected  in 
various  ways,"  etc. 

These  so-called  iron-sponges  carrying, 
say  ten  per  cent,  of  the  iron  as  protoxide, 
are  not  the  materials  with  which  to  ob- 
tain a  victory  over  the  old,  well-estab- 
lished, indirect  process.  They  will  give 
too  poor  an  account  in  yield,  however 
used,  and  they  are  especially  objection- 
able for  open-hearth  practice.  Dr.  Sie- 
mens covers  the  whole  ground  in  a  few 
words,  in  his  American  patent  of  April 
11th,  1871  :  "The  metallic  oxide  cor- 
rodes the  banks  of  the  metal  bath." 

Let  us  turn  now  to  the  second  step  in 
the  direct  process,  the  fusion  of  the  iron- 
sponge.  I  will  pass  by  all  other  meth- 
ods of  treatment  and  confine  myself  to 
this,  the  most  important.  The  open- 
hearth  gas-furnace  enables  us  to  produce 
a  homogenous  product  cast  into  ingots. 
We  will  not  stop  here  to  discuss  the  vari- 
ous definitions  of  "  steel"  as  distinguished 
from  "  iron."  For  present  purposes  we 
will  adopt  the  popular  conception,  and 
apply  the  term  steel  to  what  a  black- 
smith would  call  steel,  that  is,  whatever 
will  "  take  a  temper,"  and  iron  shall 
mean  what  the  blacksmith  would  call 
iron:  that  is,  what  will  stand  the  same 


heat  and  weld  the  same  way  as  that 
which  he  has  always  called  iron,  and 
which  will  not  take  a  temper. 

These  ingots  of  iron  or  steel  (accord- 
ing to  the  ratio  of  carbon  contained)  are 
produced  by  melting  wrought  iron  in 
cast  iron.  Here  then  is  an  operation  for 
which  the  sponge  is  especially  adapted. 

It  is  more  fusible  than  any  other  form 
of  wrought  iron,  and  its  mineral  portion 
will  be  separated  by  the  act  of  fusion 
without  any  special  treatment  whatever. 

I  had  no  other  idea  than  to  use  the 
"  Siemens"  regenerative  gas-furnace 
(that  being  the  one  invariably  employed 
heretofore  in  open-hearth  practice)  until 
I  came  to  arrange  for  a  license,  when  I 
was  informed  by  the  agents  in  this  coun- 
try of  Dr.  Siemens,  that  my  license  must 
contain  the  stipulation  that  I  could  only 
employ  in  the  furnace  such  materials  as 
he  (Dr.  Siemens)  would  permit  me  to  use  ; 
and  my  iron-sponge  was  not  embraced 
in  the  list.  After  repeated  efforts  I 
found  it  impossible  to  shake  his  deter- 
mination that  his  furnace  should  not  be 
employed  for  any  other  direct  process 
than  his  own.  I  was,  therefore,  obliged 
to  look  elsewhere,  and,  happily,  found 
what  I  sought  in  the  gas-furnace  of  Mr. 
H.  Frank,  of  Pittsburg. 

This  furnace  works  on  a  system  of 
"continuous  regeneration,"  the  waste 
gases  passing  continuously  in  one  direc- 
tion outward,  and  the  air  and  gas  supply 
passing  continuously  in  one  direction  in- 
ward. I  regret  that  the  length  of  this 
paper  compels  me  to  omit  a  detailed  de- 
scription of  this  most  satisfactory  fur- 
nace. It  gives  all  the  heat  that  can  be 
used  (the  endurance  of  the  structure 
being  the  limit),  and  works  with  the 
greatest  steadiness.  All  clogging  of 
the  regenerators  by  tar  and  soot  is 
avoided  by  the  simple  expedient  of  al- 
ternating the  currents  of  gas  and  air  so 
that  the  air  is  made  to  pass  through  the 
chamber  where  the  gas  had  previously 
been,  thus  burning  out  all  those  deposits, 
while  the  gas  finds  a  clear  passage  in 
the  other  chamber  where  the  air  had 
been  flowing.  It  is  only  neccessary  to 
make  this  alternation  between  heats,  so 
that,  from  the  time  of  charging  until  the 
cast  is  made,  the  only  manipulation 
called  for  is  the  adjustment  of  the  inlet- 
valves  for  gas  and  air,  and  of  the  damp- 
er of  the  stack. 


THE    "DIRECT  PROCESS"    IN   IRON   MANUFACTURE. 


323 


Our  present  practice  at  Glenwood  is 
to  take  the  iron-sponge  and  press  it, 
while  cold,  into  blooms  of  six  inches  di- 
ameter and  about  twelve  to  eighteen 
inches  in  length.  A  specimen  of  these  is 
exhibited  here.  The  pressing  is  per- 
formed by  hydraulic  machinery,  and 
the  force  exerted  is  about  30,000  pounds 
to  the  square  inch,  or  about  900,000  on 
the  bloom.  Thus  prepared,  we  charge 
them  into  an  auxiliary  heating-furnace, 
where  they  are  brought  to  a  bright-red 
heat,  and  then  thrown  into  the  bath  of 
the  melting-furnace.  We  use  no  other 
form  of  wrought  iron  whatever.  Other- 
wise there  is  nothing  peculiar  in  our 
operations,  and  everything  goes  on  just 
as  if  we  were  melting  ordinary  blooms, 
except  that  the  fusion  is  much  more 
rapid.  We  have  no  difficulty  whatever 
with  the  lining  of  the  furnace,  owing  to 
the  small  amount  of  protoxide  left  in  the 
sponge,  there  being  decidedly  less  than 
is  usually  found  in  puddle-bar.  It  is 
here  that  the  perfection  of  the  reduction 
tells. 

We  have  operated  hitherto  with  ores 
so  rich — Iron  Mountain  of  Missouri,  and 
Red  Specular  of  Lake  Superior — that  we 
have  no  excess  of  slag.  On  the  contrary, 
Ave  generally  find  it  expedient  to  throw 
in  a  little  cinder  from  a  previous  cast. 
When  using  ores  which  carry  so  much 
earthy  matter  that  the  slag  would  be  in 
excess,  we  shall  "  bleed"  it  away,  to  the 
extent  desired,  from  a  cinder-notch  which 
we  have  provided  in  the  wall  of  the  fur- 
nace. 

I  propose  to  do  away  with  pig-iron,  at 
first  in  part,  finally  altogether.  There 
are  two  ways  of  doing  this,  both  of  which 
I  shall  practice  long  enough  to  deter- 
mine which  seems  preferable,  and  hope 
to  have  the  pleasure,  on  some  future  oc- 
casion, of  reporting  the  results  to  you. 

In  the  first  method  I  avail  myself  of 
the  system  of  rapid  carburization  prac- 
ticed in  "case-hardening"  and  in  the 
melting  of  wrought  iron  in  crucibles, 
viz.,  the  employment  of  an  accelerating 
agent,  such  as  cyanogen,  along  with  com- 
mon carbonaceous  material.  Mixing  one 
or  more  of  these  agents  with  charcoal- 
dust,  and  the  resultant  mixture  again 
with  sponge  before  pressing,  I  have  a 
bloom  which  holds  the  carburizing  ma- 
terials in  intimate  contact  with  the 
particles  of  iron,  and  it  is  a  question  to 


be  developed  by  experience  what  amount 
of  carbon  can  be  imparted  to  the  iron 
up  to  the  time  of  its  fusion. 

In  the  second  method  I  take  up  Gurlt's 
idea  of  the  carburization  of  sponge  by 
hydrocarbon  vapors,  and  apply  it  to  my 
reducing  furnace  in  this  way  :  I  have 
tapped  a  gas-pipe  into  one  of  the  cylin- 
ders, so  as  to  furnish  an  inlet  by  which 
I  can  force  gas  into  and  among  the  con- 
tents of  the  cylinder.  This  inlet  is 
placed  just  above  the  cooler,  so  that  the 
gas  will  enter  when  the  material  is  yet 
hot,  but  has  passed  below  the  zone  of 
reduction.  I  generate  gas  from  benzine, 
in  an  apparatus  placed  at  such  a  distance 
from  the  building  as  to  be  safe,  and 
under  pressure  sufficient  to  overcome  the 
resistance  in  the  cylinder.  I  shall  thus 
get  the  carburizing  action  without  any 
other  extra  expenditure  of  fuel  than  the 
small  amount  required  for  generating 
the  benzine  gas.  The  apparatus  is  now 
just  ready  to  go  into  operation,  and  I  ex- 
pect to  impart  such  a  quantity  of  carbon 
to  the  sponge  as  to  render  it  readily  fus- 
ible without  the  aid  of  a  bath  of  cast 
iron. 

I  consider  it  a  very  desirable  step  in 
the  perfecting  of  the  direct  process, 
that  we  should  dispense  with  cast  iron 
in  the  open  hearth  for  two  cogent  reas- 
ons :  first,  because  we  have  now  turned 
the  tables,  and  wrought  iron  is  cheaper 
than  pig  ;  and  second,  because  the  less 
pig  we  use  the  better  the  quality  of  the 
product.  Dr.  Siemens,  in  the  paper  from 
which  I  have  already  quoted,  puts  this 
matter  in  a  very  clear  light.  Speaking 
of  the  desirability  of  a  direct  process, 
as  regards  the  question  of  quality,  and 
referring  to  one  of  Mr.  I.  Lowthian  BelPs 
diagrams  of  a  blast-furnace,  he  says  : 

"It  shows  that  the  reduction  of  the 
metallic  oxydes  to  spongy  iron  is  accom- 
plished within  the  first  twenty  feet  in 
their  descent  in  the  furnace,  and  at  a 
comparatively  low  temperature.  This 
upper  zone  is  followed  by  one  where  the 
limestone  is  decomposed  and  the  carbon- 
ization of  the  spongy  metal  is  com- 
menced. Between  this  second  zone  and 
the  zone  of  fusion  in  the  boshes  of  the 
furnace,  one  of  great  magnitude  inter- 
venes, where  apparently  no  other  change 
is  effected  than  an  increase  of  tempera- 
ture of  (the)  spongy  metal,  but  where  in 
reality  a  very  powerful  reducing  action 


324 


VAN   NOSTRAND'S   ENGINEERING   MAGAZINE. 


is  accomplished  of  substances  which  had 
much  better  not  be  joined  to  the  iron. 
It  is  well  known  that  almost  all  the 
phosphorus  contained  in  the  ironstone 
and  the  coke  is  here  incorporated  with 
the  spongy  iron.  The  silica  is  reduced 
to  silicon,  and,  together  with  arsenic  and 
other  bases  which  may  be  present,  com- 
bines with  the  iron.  The  final  action  in 
the  blast-furnace  only  consists  in  fusing 
those  reduced  substances  and  forming  the 
slags  which  envelop  and  protect  the 
fused  metal." 

On  the  other  hand,  as  I  have  already 
explained,  the  low  temperature  at  which 
the  reduction  of  the  iron  oxyde  takes 
place  in  the  direct  process  gives  no 
opportunity  for  reduction  of  the  other 
oxydes  accompanying  it.  Hence,  though 
the  mechanical  union  remains,  there  is 
no  chemical  affinity,  and  as  we,  in  our 
second  step,  produce  the  fusion  under 
conditions  which  do  not  allow  time  for 
the  reduction  of  the  other  substances, 
we  get  away  our  iron  uncontaminated. 

Here,  again,  I  have  to  regret  that  time 
and  your  endurance  do  not  allow  me  to 
do  more  than  refer  to  some  exceptions 
to  this,  in  the  case  of  sulphur  and  phos- 
phorus. As  to  the  former,  it  is  perhaps 
unnecessary  for  me  to  explain  how  the 
difficulty  can  be  overcome.  As  to  the 
latter,  I  will  say,  speaking  from  absolute 
experience,  that  no  difficulty  arises  where 
the  phosphorus  exists — as  in  the  Lake 
Champlain  ores — in  the  condition  of 
phosphate  of  lime.  With  respect  to 
other  phosphorus-bearing  ores,  I  hope  to 
make  a  special  report  to  you,  when  I  can 
enter  into  details  which  are  inadmissible 
here,  and  after  I  have  more  extended 
experience.  I  must  also  defer  anything 
beyond  a  mere  casual  reference 'to  tit- 
anium, which  gives  no  trouble  in  the  di- 
rect process. 

Dismissing  these  interesting  topics,  I 
close  my  explanatory  statements,  trust- 
ing that  nothing  further  is  needed  to 
satisfy  you  that  you  have  now  presented 
to  you  a  perfectly  practical  and  tho- 
roughly direct  process  for  obtaining  the 
ingot  of  cast  steel  or  homogeneous  iron. 

Little  need  be  said  as  to  the  value  of 
this  product.  Open-hearth  practice  has 
already  established  the  fact  that  steel  fit 
for  all  purposes  short  of  edge  tools  can 
be  produced  (even  when  using  the  sys- 
tem of  melting  wrought  into  cast  iron), 


and  that  the  homogeneous  metal  is  the 
type  of  all  perfection  in  wrought  iron. 
With  respect  to  the  results  which  will 
follow  the  introduction  of  the  direct 
process  into  the  field  of  iron  metallurgy, 
I  do  not  venture  any  prediction  as  to 
how  speedy  or  how  slow  may  be  the 
revolution.  Some  time  must  elapse,  dur- 
ing which  the  old  system  will  regulate 
the  market  price,  while  the  new  system 
will  (for  those  employing  it)  regulate 
the  cost.  But  with  such  data  as  I  will 
now  very  briefly  call  your  attention  to, 
it  is  easy  to  see  that  the  old  system 
must  either  be  greatly  cheapened,  or  it 
must,  sooner  or  later,  be  overgrown  by 
the  new. 

The  direct  process  demands  so  much 
smaller  an  amount  of  fuel  that  the 
proper  plan  for  realizing  the  most  profit- 
able results  in  practicing  it  will  be  to  go 
to  the  mines,  and  there  produce  the 
sponge  at  least  ;  in  many  cases  the  in- 
got also.  The  extreme  simplicity  of  the 
plant  required,  and  the  ease  with  which 
the  process  can  be  conducted  on  a  small 
scale,  if  desirable,  also  point  to  the  mine 
as  the-  proper  locality  for  the  works,  up 
to,-  as  I  say,  the  sponge  always,  the  in- 
got often. 

Take,  now,  such  a  locality,  where  ore 
of  50  per  cent,  metallic  iron  is  worth  $4 
per  ton,  and  charcoal  is  worth  6  cents 
per  bushel,     We  have  : 

2  tons  ore  at  $4 $8  00 

40  bushels  charcoal,  at  6  cts . . .  2  40 
Gas  producing  fuel  (wood)  say.  1  00 
Wages,  say 3  00 

1  ton  iron  in  sponge. .....  $14  40 

Let  us  add  |5.60  per  ton  for  trans- 
portation to  a  manufacturing  centre, 
making  the  cost  of  the  sponge,  say  $20, 
delivered.  Add  $2  per  ton  for  cold 
pressing. 

One  ton  of  ingots  will  cost  about  as 
follows  : 

f  ton  cold-pressed  blooms,  $22.  $16  50 

15  per  cent,  waste  on  the  same .  2  48 

^  ton  Bessemer  pig,  at  $45 11  25 

7i  per  cent,  waste  on  the  same .  84 

Wages,  per  ton 5  00 

Maintenance  of  furnace,  &c . .  2  50 
Spiegeleisen,   ^Vth  ton,  at  $70 

per  ton , 3  50 

f  ton  fuel  for  producers,  at  $5 

per  ton 3  75 

Cost  of  2,240  lb.  ingots, . .  $45  82 


THE    "DIRECT   PROCESS5'    IN   IRON   MANUFACTURE. 


325 


Assuming  that  we  shall  be  able  to 
substitute  carburized  sponge  for  the 
Bessemer  pig,  we  reduce  this  to  about 
$38.50. 

The  figures  must  be  varied  to  suit 
every  different  locality,  and  in  those 
where  ore  is  a  high-priced  commodity 
and  fuel  cheap,  there  will  not  be  as  great 
a  difference  in  favor  of  the  direct  process 
as  where  those  conditions  are  reversed  ; 
but  there  will  always  be  enough  to  give 
it  an  advantage  that  must  tell  eventually. 

Finally,  there  is  one  aspect,  at  least, 
of  this  branch  of  the  subject  that  must 
be  gratifying  to  all.  I  refer  to  the 
humanitarian  view.  The  word  "pud- 
dling" finds  no  place  in  the  direct  pro- 
cess. No  such  exhausting,  overtaxing 
labor  is  demanded  in  any  of  its  opera- 
tions, and,  as  it  is  the  truly  scientific 
method  of  iron  metallurgy,  so  does  it, 
in  common  with  all  true  science,  point  to 
the  ultimate  reconcilement  of  capital  and 
labor. 

I  desire,  before  closing,  to  take  this 
opportunity  to  acknowledge  my  in- 
debtedness to  my  associate  and  cola- 
borer,  Mr.  Morrison  Foster,  of  Pitts- 
burgh, whose  assistance,  from  the  first 
inception  of  my  experiments  up  to  the 
present  time,  has  been  of  the  greatest 
value  to  me. 

Prop  Egleston  desired  to  know  how 
complete  the  reduction  was,  how  much 
oxygen  remained  in  the  sponge,  and  how 
the  impurities  common  to  iron  ores  were 
eliminated.  He  said  that  in  the  paper 
just  read  there  were  some  severe  remarks 
on  the  crude  condition  of  iron  metallurgy, 
especially  the  blast-furnace  process.  He 
desired  to  say  that  the  blame  did  not  lie 
at  the  doors  of  scientific  metallurgists  in 
this  country.  It  must  be  remembered 
that  most  of  the  experiments  abroad  had 
government  aid  for  their  experiments, 
and  government  furnaces  at  their  dis- 
posal to  practice  on.  For  the  last 
thirteen  or  fourteen  years  he  had  en- 
deavored to  make  experiments  on  blast- 
furnace gases,  but  had  never  been  able 
to  overcome  the  prejudice  of  furnace- 
men  to  having  holes  made  in  the  stack 
of  the  furnace.  Prof.  Egleston  spoke  of 
some  investigations  made  by  Director 
Jiingst,  of  Gleiwitz,  on  the  temperatures 
at  which  ores  begin  to  lose  oxygen  in 
the  blast-furnace,  and  the  temperatures 
at  which   reduction  is   complete.      The 


temperature  of  incipient  reduction  is 
stated  by  Jungst  to  be  much  lower  than 
is  generally  supposed.  Regarding  the 
elimination  of  sulphur  from  coal  by 
washing  and  coking,  Prof.  Egleston 
spoke  of  the  works  of  the  Orleans  Rail- 
way, at  Aubin,  in  the  South  of  France, 
which  he  had  studied,  where  a  refuse 
coal  containing  12  per  cent,  of  ash  and 
iron  pyrites  in  large  quantities,  in  lumps 
from  the  size  of  a  hickory-nut  to  fine 
grains,  was  worked  so  as  to  contain  only 
3  per  cent,  of  ash  and  0.5  per  cent  of 
sulphur. 

Mr.  Blair  :  We  find  95  to  98  per 
cent,  of  the  iron  reduced.  The  impuri- 
ties in  the  ore,  as  silica,  alumina,  lime, 
etc.,  are  all  contained  in  the  sponge  ; 
but  when  the  sponge  is  introduced  into 
the  bath  of  molten  pig  metal,  the  earthy 
ingredients  melt  and  rise  to  the  surface 
in  the  form  of  slag.  In  rich  ores  the 
amount  of  slag  is  not  enough  to  cover 
the  molten  metal,  and  slag  is  added  as 
such.  In  poor  ores  the  amount  of  slag 
may  be  too  large,  and  provision  is  made 
in  the  cinder-notch  for  tapping  it  off. 
The  height  of  this  notch  is  raised  or 
lowered  by  means  of  fire-brick,  accord- 
ing to  the  height  of  metal  in  the  furnace. 

Mr.  F.  Firmstone  asked  Mr.  Blair 
what  became  of  the  phosphorus  in  the 
ore  in  his  process. 

Mr.  Blair  :  We  have  made  steel  in 
crucibles  from  sponge  made  from  Lake 
Champlain  ores,  which  contained  a  large 
amount  of  apatite,  and  found  no  phos- 
phorus in  the  steel.  The  case  might  be 
different  where  the  phosphorus  was  com- 
bined with  the  iron  in  the  ore. 

Mr.  Raymond  remarked  that  it  might 
make  considerable  difference  if  the  phos- 
phorus was  combined  with  manganese 
in  the  ore.  He  had  heard  of  a  case  re- 
cently, in  which  Bessemer  pig  was  said 
to  have  been  made  from  an  ore  con- 
taining 0.58  per  cent,  of  phosphorus,  and 
at  the  same  time  considerable  manganese. 
It  may  be  that  phosphate  of  manganese 
is  reduced  with  great  difficuly,  or  that 
manganese  will  tend  to  carry  off  the 
phosphorus  in  the  slag.  He  would  like 
to  ask  Mr.  Blair  what  became  of  the  car- 
bonic oxyde  escaping  from  his  cylin- 
ders. 

Mr.  Blair  :  It  is  burned  within  the 
thimble  to  carbonic  acid,  and  exerts  no 
injurious  influence  on  the  workmen.     He 


326 


VAN   NOSTRAND'S   ENGINEERING   MAGAZINE. 


had  had  a  few  quite  serious  cases  of 
poisoning  with  carbonic  oxyde  arising 
from  his  gas-producers,  and  had  invaria- 
bly found  ammonia  (spirits  of  harts- 
horn), applied  to  the  nostrils,  a  prompt 
and  efficient  redemy.  When  nausea  is 
produced  by  inhaling  carbonic  oxyde, 
a  few  drops  of  the  aromatic  spirits  of 
ammonia  give  relief. 

Peof.  B.  Silliman  said  that  the  ques- 
tion of  the  influence  of  manganese  in 
smelting  ores  containing  phosphorus  was 
an  interesting,  and,  to  a  considerable 
extent,  an  unexplored  field.  He  had  in 
mind  a  case  where  a  spiegeleisen,  con- 
taining 11  per  cent,  of  manganese,  and 
•0.1  per  cent,  of  phosphorus,  was  said  to 
be  made  from  a  spathic  ore  containing 
but  0.5  per  cent,  manganese,  and  0.6  per 
cent,  phosphorus.  He  thought  that  this 
could  only  be  explained  by  the  addition 
of  manganese  in  some  form  to  the  charge, 
and  in  this  connection  the  unexpectedly 
small  amount  of  phosphorus  in  the 
spiegel  was  suggestive. 

Me.  E.  B.  Coxe:  The  subject  of  poison- 
ing by  carbonic  oxyde  is  one  of  such 
great  importance  that  I  think  that  all 
possible  publicity  should  be  given  to  the 
antidotal  effect  of  ammonia  mentioned 
by  Mr.  Blair.  I  think  it  very  probable 
that  the  "  white  damp"*of  the  mines  is 
carbonic  oxyde,  and  its  fatal  effects  are 
well  known  to  miners. 

Me.  E.  C,  Pechin  :  I  have  listened  to 
the  very  able  paper  read  by  Mr.  Blair 
with  melancholy  pleasure.  As  a  human- 
itarian I  am  delighted,  as  a  pig-metal 
manufacturer  I  am  in  the  depths  of  des- 
pair. I  am  placed  in  a  position  which 
must  appeal  powerfully  to  your  sym- 
pathies. A  few  weeks  since  I  was  blown 
up  by  physical  force — to-day  I  am  blown 
away  by  scientific  investigation.  All 
my  beautiful  plans  for  new  furnaces 
must  be  stowed  away  with  the  inscrip- 
tion, "  What  might  have  been  if  it  had'nt 
been  for  Blair."  In  behalf  of  the  pig- 
iron  makers  of  the  United  States,  I  ap- 
peal to  Mr.  Blair  to  follow  the  example 
of  Dr.  Siemens,  to  surround  his  process 
with  such  restrictions,  and  to  charge 
such  excessive  royalties,  that  we  may 
for  this  generation,  at  least,  rather  die 
by  slow  combustion  than  meet  a  violent 
and  hasty  death  by  carbonic  oxyde. 

Me.  Blaie  reminded  Mr.  Pechin  that 
he  had  used  the  expression  that  the  old 


process  will  be  overgrown,  not  over- 
thrown. 

Db.  Hunt  expressed  his  pleasure  at 
the  results  obtained  by  Mr.  Blair,  whose 
works  near  Pittsburg  he  had  an  oppor- 
tunity of  visiting  in  November  last.  He 
felt  a  great  interest  in  the  question  of 
iron-sponge,  from  the  fact  that  he  had 
been  the  friend  of  Adrian  Chenot,  who 
had,  in  1855,  works  in  operation  on  a 
considerable  scale  at  Clichy-la-Garenne, 
near  Paris,  and  had  assisted  him  in  some 
of  his  exj)eriments  just  before  his  sudden 
and  accidental  death  at  the  end  of  that 
year.  Chenot  died  with  many  of  his 
plans  unrealized,  leaving  behind  him 
no  one  fully  competent  to  carry  on  his 
work.  Dr.  Hunt  testified  that,  notwith- 
standing the  difficulties  encountered, 
Chenot  did  succeed,  at  least  with  the 
readily  reducible  and  porus  Spanish  ores, 
in  obtaining  a  complete  reduction,  as  the 
regular  daily  manufacture  from  the 
sponge  of  cast  steel,  which  he  had  per- 
sonally overlooked  and  followed,  suffi- 
ciently showed.  The  apparatus  of 
Chenot  was  essentially  that  of  Mr.  Blair, 
but  there  were  practical  difficulties  in 
the  way  of  heating  the  column  which 
have  been  overcome  by  the  latter  by 
means  of  his  simple  and  ingenious  initial 
heater,  in  which  the  gas  wasted  from 
the  top  of  Chenot's  furnace  performs  the 
work  of  heating  the  ore  in  the  upper 
part  of  the  cylinder  ;  while  by  the  happy 
device  of  using  a  mixture  of  charcoal  in 
powder,  instead  of  in  lumps,  the  diffi- 
culty of  preserving  the  reduced  ore  from 
the  influence  of  the  air  below  is  resolved. 
By  these  additions  to  the  furnace  of 
Chenot,  Blair  has  continued  and  perfect- 
ed his  work. 

But  the  ready  production  of  iron- 
sponge  was  but  one  part  of  the  problem  ; 
its  utilization  was  still  more  difficult. 
The  conversion  of  the  sponge  into  cast 
steel  by  cementation  with  oil,  and  fusion 
in  a  crucible,  as  practised  at  Clichy  by 
Chenot,  was,  at  best,  but  a  slow  and 
troublesome  method  ;  and  the  attempt 
to  weld  the  sponge  into  blooms,  as  tried 
at  Clichy,  and  afterwards  practiced  at 
Baracaldo,  in  Spain,  was  an  expedient 
not  easy  of  execution,  and  applicable 
only  to  very  pure  ores.  The  work  of 
Chenot,  of  Gurlt,  and  of  others,  in  mak- 
ing iron-sponge,  was  in  vain  ;  the  time 
had  not  yet  come  for  its  economic  utili- 


INDUCTIVE   MAGNETISM   IN   SOFT   IRON. 


327 


zation,  nor  was  it  until  the  brothers 
Martin,  with  the  aid  of  the  Siemens  gas- 
furnace,  succeeded  in  producing  steel  on 
a  large  scale  in  the  open  hearth  from 
the  fusion  of  soft  iron  with  cast 
iron,  that  the  true  use  of  the  sponge, 
as  a  substitute  for  puddled  iron,  was 
found. 

This  new  process  again  turned  the  at- 
tention of  inventors  to  the  production  of 
iron-sponge,  and  three  or  four  years 
since  a  reduction-furnace,  erected  for  the 
purpose  at  Westport,  on  Lake  Cham- 
plain,  succeeded  in  producing  sponge 
which,  at  the  Bay  State  Works,  at  South 
Boston,  gave  in  the  Siemens-Martin  pro- 
cess a  soft  steel,  with  excellent  results. 
This  reduction-furnace,  which  the  speaker 
had  examined,  seemed,  however,  but  in- 
differently fitted  for  its  work,  and  was 
soon  abandoned.  The  simple,  cheap, 
and  efficient  apparatus  of  Chenot  has,  in 
the  hands  of  Mr.  Blair,  received  such  im- 
provements as  made  it,  in  the  speaker's 
opinion,  admirably  fitted  for  the  purpose 
of  reducing  iron  ores  to  sponge.  He  re- 
gretted exceedingly  that  the  beautiful 


and  ingenious  reduction-furnace  con- 
structed by  Mr.  Edward  Cooper,  at 
Trenton,  which  many  of  the  member-  of 
the  Institute  had  an  opportunity  of  in- 
specting in  October  last,  was  not  already 
in  operation,  so  that  we  might  be  en- 
abled to  judge  of  its  practical  efficiency. 
For  the  rest,  the  speaker  entertained  no 
doubt  that  the  economic  production  of 
iron-sponge,  and  its  utilization  in  the 
open  hearth,  in  accordance  with  the  Sie- 
mens-Martin plan,  was  destined  to  be 
one  of  the  great  metallurgical  problems 
of  the  future.  One  of  the  most  impor- 
tant advantages  of  this  process  is  the 
fact  pointed  out  by  Mr.  Blair,  that  the 
mechanical  impurities  of  the  reduced 
ore  are  readily  and  completely  elimina- 
ted by  the  process  of  dissolving  it  in 
a  bath  of  molten  metal.  The  iron  is  re- 
duced to  the  metallic  state  without  the 
reduction  of  phosphorus  and  silicon,  and 
the  compounds  of  these  are  not  attacked 
by  the  metallic  bath,  which  takes  up  the 
reduced  Iron  as  mercury  takes  up  the 
precious  metals  in  the  process  of  amalga- 
mation. 


EFFECTS  OF  STRESS  ON  INDUCTIVE  MAGNETISM  IN  SOFT 

IRON. 

By  Prop.  Sir  WILLIAM  THOMSON,  F.  R.  S. 
Proceedings  of  the  Royal  Society. 


1.  At  the  last  ordinary  meeting  of  the 
Royal  Society  (May  27),  after  fully  des- 
cribing experiments  by  which  I  had 
found  certain  remarkable  effects  of  stress 
on  inductive  and  retained  magnetism  in 
steel  and  soft  iron,  I  briefly  referred  to 
seeming  anomalies  presented  by  soft 
iron  which  had  much  perplexed  me  since 
the  23d  of  December.  Differences  pre- 
sented by  the  different  specimens  of  soft 
iron  wire  which  I  tried  complicated  the 
question  very  much  ;  but  one  of  them, 
the  softest  of  all,  a  wire  specially  made 
by  Messrs.  Richard  Johnson  &  Nephew, 
of  Manchester,  for  this  investigation, 
through  the  kindness  of  Mr.  William  H. 
Johnson,  gave  a  result  standing  clearly 
out  from  the  general  confusion,  and 
pointing  the  way  to  further  experiments, 
by  which,  within  the  fortnight  which 
has  intervened  since  my  former  com- 
munication, I  have  arrived  at  a  complete 


explanation  of  all  that  had  formerly 
seemed  anomalous.  These  experiments 
have  been  performed  in  the  Physical 
Laboratory  of  the  University  of  Glas- 
gow by  Mr.  Andrew  Gray  and  Mr. 
Thomas  Gray,  according  to  instructions 
which,  in  my  absence,  I  have  sent  from 
day  to  day  by  post  and  telegraph. 

2.  The  guiding  result  (described  near 
the  end  of  my  former  paper,  and  referred 
to  in  the  last  paragraph  but  one  of  the 
Abstract  in  Proceedings  of  the  Royal 
Society  for  May  27)  was,  that  the  soft- 
est wire,  tried  with  weights  on  and  off 
repeatedly,  after  it  had  been  magnetized 
in  either  direction  by  making  the  cur- 
rent, in  the  positive  or  negative  direc- 
tion, and  stopping  it,  gave  effects  on  the 
ballistic  galvanometer  which  proved  a 
shaking  out  of  residual  magnetism  by 
the  first  two  or  three  ons  and  offs,  and  a 
gradual   settlement  into  a  condition  in 


328 


'VAN  NOSTRAND's  ENGINEERING   MAGAZINE. 


which  the  effect  of  "  on "  was  an  aug- 
mentation^ and  the  effect  of  "off"  a 
diminution,  of  the  inductive  magnetiza- 
tion due  to  the  vertical  component  of 
the  earth's  magnetizing  force.  When  a 
fresh  piece  of  the  same  wire  was  put 
into  the  apparatus  and  tested  with 
weights  on  and  off  it  gave  this  same  ef- 
fect. If  the  wire  had  been  turned  upper 
end  down  and  tried  again  in  the  course 
of  any  of  the  experiments,  still  this  same 
effect  would  have  been  shown.  It  seem- 
ed perfectly  clear  that  in  these  experi- 
ments there  was  no  other  efficient  dipolar 
quality  of  the  apparatus  by  which  the 
positive  throw  of  the  ballistic  galvan- 
ometer could  be  given  by  putting  on  the 
weight,  and  the  negative  throw  by  tak- 
ing it  off,  than  the  vertical  component 
of  the  earth's  magnetic  force. 

3.  Yet  I  did  not  consider  that  I  had 
explained  the  result  by  the  terrestrial  in- 
fluence, because,  for  all  the  specimens  of 
steel  and  soft  iron,  the  effect  of  weights 
on  had  been  uniformly  to  diminish,  and 
of  weights  off  to  augment  the  magnet- 
ism when  the  magnetizing  current  was 
kept  flowing.  And  I  was,  moreover, 
perplexed  by  the  magnitude  of  the  re- 
sult— the  effects  of  weights  on  and  off 
shown  by  the  very  soft  iron  wire,  under 
only  the  feeble  magnetizing  influence  of 
the  earth,  being  many  times  (from  three 
times  to  nine  or  ten  times)  as  great  as 
the  effects  which  the  same  weights  on 
and  off  produced  in  the  same  wires  when 
under  vastly  greater  magnetizing  forces 
of  the  currents  through  the  helix. 

4.  But  by  reducing  the  strength  of 
the  magnetizing  current  gradually,  it 
was  clear  that  the  small  positive  effect 
of  the  "on"  with  the  positive  current 
flowing  and  the  small  negative  effect 
with  the  negative  current  must  be  gradu- 
ally brought  to  approximate  more  and 
more  nearly  to  the  large  positive  effect 
of  the  "  on  "  when  there  is  no  current  at 
all.  Immediately  after  my  former  com- 
munication I  therefore  arranged  to  have 
experiments  made  with  different  measur- 
ed strengths  of  current,  feebler  and 
feebler,  until  the  law  of  the  continuity 
thus  pointed  out  should  be  ascertained  ; 
and  so  speedily  arrived  at  the  following 
astonishing  cenclusions  : 

5.  (1)  When  the  magnetizing  force 
does  not  exceed  a  certain  critical  value 
the  alternate  effects  of  pull  and  relaxa- 


tion are  respectively  to  augment  and  di- 
minish the  induced  magnetization. 

(2)  When  the  magnetizing  force 
exceeds  the  critical  value  the  effects  are 
— pull  diminishes,  relaxation  augments, 
the  induced  magnetization. 

(3)  The  critical  value  of  the  mag- 
netizing force  for  the  annealed  Johnson 
soft  iron  wire,  with  14  lbs.  on  and  off,  is 
about  J  V  or  18,  if  (for  a  moment)  we 
take  as  unity  the  vertical  component  of 
the  terrestrial  magnetic  force  at  Glas- 
gow. 

(4)  The  maximum  positive  effect  of 
the  pull  on  the  inductive  magnetism  is 
obtained  when  the  magnetizing  force  is 
about  4. 

(5)  The  positive  effect  of  the  pull 
when  the  magnetizing  force  is  3  is  about 
eight  or  nine  times  the  amount  of  the 
negative  effect  when  the  magnetizing 
force  is  25. 

6.  The  actual  results  of  the  experi- 
ments which  proved  these  conclusions 
are  exhibited  graphically  in  the  accom- 
panying diagram.  The  hotizontal  scale 
(abscissas)  shows  the  numbers  of  divi- 
sions of  the  scale  of  the  steady  current 
galvanometer  (called  for  brevity  the 
"  battery-galvanometer  ")  used  to  meas- 
ure the  strengths  of  the  current  through 
the  helix.  The  scale  of  ordinates  shows 
the  numbers  of  divisions  of  the  scale  of 
the  ballistic  galvanometer  by  which  the 
sudden  changes  of  the  magnetism  of  the 
wire  produced  by  14  lbs.  "on"  and  14 
lbs.  "off"  were  measured.  The  ordin- 
ates are  drawn  in  the  positive  direction 
when  the  effect  of  "on"  is  to  increase 
and  of  "off  "  to  diminish  the  magnet- 
ism. The  simple  round  spots  show  the 
results  of  observations  with  currents  in 
the  direction  called  negative  (being  those 
which  gave  negative  deflections  of  the 
battery -galvanometer).  The  spots  in  the 
centre  of  signs  (  +  )  show  results  obtain- 
ed with  currents  in  the  direction  called 
positive.  The  star  (*)  at  the  position  64 
on  the  line  of  ordinates  through  the  zero 
of  abscissas  shows  the  mean  effect  of 
many  ons  and  offs  with  no  current  flow- 
ing— that  is  to  say,  when  the  sole  mag- 
netizing force  is  the  vertical  component 
of  the  earth's  magnetic  force.  The 
curves  are  drawn  as  smoothly  as  may  be 
by  hand,  one  of  them  to  pass  as  nearly 
as  it  can  (without  intolerable  roughness) 
through  all  the  crossed  (plus)  dots  and 


INDUCTIVE   MAGNETISM   IN   SOFT   IRON. 


329 


the  star  at  64,  the  other  through  all  the 
plain  dots.  The  latter  curve  cuts  the  line 
of  abscissas  at  8,  this  being  the  result 
(telegraphed  to  me  this  evening)  of 
special  experiments  made  to-day  for  the 
purpose  of  finding  accurately  the  amount 


of  the  negative  current  which,  by  neu- 
tralizing the  vertical  force  of  the  earth 
or  the  wire,  gives  an  accurate  zero  effect 
for  the  "off"  and  "on."  The  dotted 
prolongation  of  the  curve  through  the 
plus's,  to  cut  the  line  of  abscissas  on  its 


negative  side,  is  ideal,  and  is  inserted  to 
illustrate  the  relation  of  this  curve  to 
the  other.  By  the  two  curves  cutting 
the  line  of  abscissas  at  +  8  and  —  8,  we 
see  that  8  is  the  strength  of  the  current, 
measured  on  the  scale  of  the  battery- 
galvanometer,  which  gives   a  magnetic 


force  in  the  axis  of  the  helix  equal  to  the 
vertical  component  of  the  terrestrial 
magnetic  force. 

7.  Next  a  series  of  experiments  to  test 
the  inductive  effects  of  repeatedly  mak- 
ing the  current  always  in  one  direction, 
and  stopping  it,  with  the  weight  of  14 


330 


VAN   NOSTRAND'S   ENGINEERING   MAGAZINE. 


lbs.  always  on,  and  again  with  the 
weight  off,  and  this  with  various  degrees 
of  current,  feebler  than  those  used  in 
the  earlier  experiments.  The  results 
with  all  the  different  intensities  of  mag- 
netizing force  thus  applied  were  the  same 
in  kind  as  that  which  I  found  on  the  23d 
of  December,  operating  with  a  much 
stronger  magnetizing  force  on  the  first 
soft  iron  wire  tried  ;  that  is  to  say  (con- 
trarily  to  what  I  had  found  in  the  steel 
wires),  the  change  of  magnetization  pro- 
duced by  repeated  applications  and  an- 


nxdings  of  the  magnetizing  force  of  the 
helix  was  greater  icith  the  xoeight  off  than 
on. 

[JVote  on  Diagram,  added  July  2, 1S75. 
— A  continuation  of  the  experiments 
with  higher  and  higher  magnetizing 
powers,  since  the  communication  of  this 
paper,  disproves  the  negative  minimum 
indicated  by  the  curves  on  the  diagram, 
and  proves  an  asymptotic  approach  to  a 
value  approximately  —  12,  of  ordinates 
for  infinitely  great  positive  values  of  the 
abscissas.] 


THE  HYDRAULIC  DOUBLE  FLOAT. 

By  HENRY  L.  ABBOT,  Major  of  Engineers,  Brevet  Brigadier  General. 
Written  for  Van  Nostrand's  Magazine. 


In  the  August  number  of  this  Maga- 
zine appeared  an  article  by  Prof.  S.  W. 
Robinson,  on  River  Gauging  and  the 
Double  Float. 

As  he  refers  therein  to  some  observ- 
ations made  with  the  latter  upon  the 
Mississippi  Delta  Survey,  I  will  very 
briefly  correct  a  few  misapprehensions 
into  which  he  has  fallen. 

Some  are  of  little  importance  ;  as,  for 
instance,  when  he  states  that  the  double 
float  was  used  upon  "  the  Mississippi, 
previous  to  the  Delta  Survey,  by  Mr. 
Chas.  Ellet.  This  is  an  entire  mistake, 
as  Mr.  Ellet's  first  trial  of  them  was 
made  after  they  had  come  into  regular 
daily  use  by  the  parties  of  the  Delta 
Survey. 

Prof.  Robinson  argues  that  the  cur- 
rent meter  in  some  form  must  be  supe- 
rior to  the  double  float,  because  it  has 
been  adopted  more  generally  by  hy- 
draulic engineers  —  and  he  establishes 
the  fact  of  more  general  use  by  citing 
the  names  of  many  engineers  whose  ob- 
servations were  made  with  it.  If  the 
dates  of  most  of  the  measurements  had 
been  given,  it  would  have  been  at  once 
apparent,  that,  although  suggested  long 
ago,  the  double  float  as  now  used  is 
really  the  more  modern  instrument  of 
the  two.  The  flint  lock  musket  has  been 
employed  far  more  in  great  battles  than 
the  modern  breech  loader,  but  its  supe- 
riority is  not  established  thereby. 

It  would  seem  that  the  fairer  criterion 


of  the  merits  of  the  two  instruments, 
would  be  the  practical  results  obtained 
from  their  use.  Now,  it  is  certain  that, 
although  many  careful  observers  em- 
ployed time  and  money,  and  displayed 
great  scientific  ability  in  endeavoring  to 
discover  the  law  of  change  in  velocity 
from  surface  to  bottom  by  the  use  of 
meters,  they  utterly  failed  to  detect  the 
form  of  the  curve.  Whereas,  on  the 
very  first  serious  attempt  with  the 
double  float,  a  law  was  revealed  which 
has  since  received  many  confirmations, 
and  which  has  greatly  simplified  the 
operation  of  the  practical  gauging  of 
rivers  by  showing,  first  algebraically  and 
afterward  by  actual  trial,  that  the  ratio 
of  the  mid  depth  to  the  mean  velocity  is 
practically  constant,  and  is  even  unaf- 
fected by  the  wind.  The  scientific  En- 
gineer Corps  of  India  has  recognized  the 
value  of  the  modern  form  of  the  instru- 
ment, and  is  now  extensively  applying  it 
in  their  operations  upon  the  great  rivers 
of  that  country.  The  latest  and  most 
accurate  work  in  river  gauging  done  in 
this  co\mtry  since  the  date  of  the 
Delta  Survey — I  refer  to  the  unpub- 
lished material  of  the  Connecticut  River 
Survey  conducted  by  General  Ellis, 
which  will  appear  in  the  forthcom- 
ing report  of  the  Chief  of  Engineers  U. 
S.  Army — establishes  the  facts  that  the 
double  float  and  meter,  properly  used, 
give  sensibly  the  same  result ;  and  that 
the  fundamental  law  respecting  flowing 


THE  HYDKAULTC  DOUBLE  FLOAT. 


331 


water  announced  in  the  Delta  Report  for 
the  Mississippi  River,  is  true  also  for  the 
Connecticut.  So  far  then  as  the  useful 
record  of  the  two  classes  of  instruments 
is  concerned,  the  double  float  is  no  whit 
behind. 

Prof.  Robinson  fails  to  touch  upon 
the  great  practical  objection  to  meters — 
namely  the  uncertainty  which  attends 
the  determination  of  the  coefficient  for 
translating  their  revolutions  into  feet  per 
second.  Bo  long  as  it  remains  impossi- 
ble to  exactly  reproduce  the  same  iden- 
tical conditions  in  deducing  this  coeffi- 
cient, which  are  to  affect  the  observa- 
tions themselves,  so  long  will  there  be 
grounds  for  doubt  and  uncertainty  in 
this  vitally  important  point.  Therefore, 
without  disputing  the  value  of  the  in- 
strument for  certain  kinds  of  work,  its 
superiority  to  the  double  float  for  detect- 
ing slight  changes  in  velocity  may  well 
be  doubted. 

Without  following  Prof.  Robinson  in 
his  application  of  the  higher  mathemat- 
ics to  the  theoretical  solution  of  the 
problem  of  the  mutual  influence  of  the 
several  parts  of  the  double  float  upon 
each  other  ;  I  would  like  to  suggest  one 
or  two  ideas. 

He  treats  the  problem  upon  the  as- 
sumption that  the  curve  of  velocity  from 
the  surface  to  the  bottom  of  a  river,  is 
unvarying.  Now  all  observations  show 
that  a  continual  irregular  pulsation  is 
going  on  ;  and  that  the  mean  curve  is 
only  to  be  deduced  from  many  observa- 
tions. Hence  the  different  parts  of  the 
double  float  are  acted  upon  by  varying 
forces  ;  and  thus  their  masses  cannot  be 
neglected,  as  he  has  done,  in  treating  the 
subject.  In  other  words,  there  is  a  con- 
tinual gain  or  loss  of  living  force  in  the 
several  parts  which  will  prevent  the 
large  and  heavy  sub-float  from  being  af- 
fected as  his  equations  indicate. 

Whatever  may  be  the  value  of  these 
equations  for  other  rivers,  we  are  not 
left  in  doubt  as  to  their  entire  inapplica- 
bility to  the  Mississippi  River,  at  least 
as  he  has  applied  them.  This  truth  does 
not  rest  upon  any  theory,  but  upon  a 
fact  observed  again  and  again,  and  rec- 
orded in  the  note  books  of  the  Survey. 
To  make  this  clear  a  few  words  are  nec- 
essary. 

No  matter  how  deep  the  river,  we 
found  that,  if   the  lower  float  touched 


bottom,  the  sudden  check  in  velocity 
gave  an  unmistakable  oscillation  to  the 
surface  float.  The  points  of  crossing 
the  transit  lines,  two  hundred  feet  apart, 
were  both  fixed  accurately  by  triangula- 
tion  ;  and  the  telescope  of  one  or  other 
of  the  observers  was  kept  on  the  little 
flag  during  the  whole  of  the  critical 
period  of  its  motion.  The  exact  sound- 
ings in  the  vicinity,  and  the  daily  gauge 
records,  rendered  it  possible  to  know 
precisely  the  depth  of  water  in  ever} 
part  of  the  path  of  the  float.  Now  it 
was  sometimes  the  case  that  a  float 
would  diverge  a  little,  laterally,  into 
water  too  shoal  for  its  length  of  line — 
and  in  such  cases  it  at  once  revealed  the 
fact  by  the  bobbing  of  the  flag — which 
was  duly  noted  in  the  record  book.  We 
have,  therefore,  certain  knowledge  that 
in  many  cases,  and  probably  in  all,  our 
deep  floats  preserved  the  depths  at 
which  they  are  reported.  Prof.  Robin- 
son's diagrams  and  imputations,  there- 
fore, evidently  do  not  apply  to  the  work 
of  the  Delta  Survey. 

I  have  only  one  more  remark  to  add  ; 
Prof.  Robinson  lays  much  stress  on  our 
neglect  to  reduce  the  size  of  the  connect- 
ing cord — and  suggests,  in  its  place,  a 
wire  filament,  a  hundredth  of  an  inch  in 
diameter.  The  importance  of  using 
cords  of  the  minimum  size  was  perfectly 
appreciated  ;  and,  on  the  only  occasion 
during  the  Survey  when  it  was  practica- 
ble to  use  a  fine  wire  to  advantage,  viz. 
on  the  Little  Falls  Feeder  of  the  C.  and 
O.  Canal,  reported  on  page  252  of  the 
report,  such  a  wire  was  actually  used — 
probably  for  the  first  time  in  the  history 
of  the  double  float.  The  reason  why, 
in  our  deep  measurements  on  the  Missis- 
sippi, we  used  so  large  a  cord,  was  be- 
cause it  was  found  by  experience  to  be 
necessary.  The  cord,  in  raising  the  float, 
had  at  times  to  sustain  severe  strains, 
amounting  to  fifty  or  more  pounds  ;  and 
smaller  cords  had  not  the  requisite 
strength.  The  operation  of  gauging 
the  Mississippi  in  flood  was  a  struggle — 
not  a  delicate  laboratory  task.  The 
whirl  of  the  waters,  which  six  oars 
vigorously  plied  in  a  light  skiff  could 
hardly  stem ;  the  rushing  drift-logs, 
which  at  the  peril  of  life  must  be  avoid- 
ed ;  the  passing  steamers  that  often 
seemed  to  enjoy  interrupting  our  work  ; 
and,  lastly,  the  importance  of  multiply- 


332 


VAN  nostrand's  engineering  magazine. 


ing  observations  as  rapidly  as  possible, 
in  order  to  keep  tbe  finger  firmly  upon 
the  pulse  of  the  great  river — all  compel- 
led the  use  of  apparatus  which  would 
endure  rough  handling  without  breaking. 
In  conclusion,  I  would  express  the 
hope  that  nothing  in  the  foregoing  com- 
munication may  seem  to  imply  any  de- 


sire on  my  part  to  undervalue  the  inter- 
esting article  of  Prof.  Robinson,  which 
opens  a  new  subject  for  analytical  in- 
vestigation. I  only  wish  to  show  that, 
in  applying  his  formulas  to  the  Missis- 
sippi Delta  Survey  observations,  he  was 
not  informed  as  to  all  the  circumstances 
in  the  case. 


ON"  THE   THEORY   OF  VENTILATION— AN  ATTEMPT   TO   ES- 
TABLISH A  POSITIVE  BASIS  FOR  THE  CALCULATION  OF 
THE  AMOUNT  OF  FRESH  AIR  REQUIRED  FOR  AN 
INHABITED   AIR   SPACE. 

By  Surgeon-Major  F.  DE  CHAUMONT,  M.  D. 
Prom  the  Proceedings  of  the  Koyal  Society. 


The  question  of  ventilation,  and  the 
amount  of  fresh  air  required  to  keep  an 
inhabited  air-space  in  a  sweet  and  healthy 
condition,  has  been  much  discussed  of 
late  years,  and  very  fully  treated  of  by 
various  writers  ;  but  there  was  a  good 
deal  of  vagueness  and  want  of  precision 
in  the  manner  of  treatment  previous  to 
the  Report  of  the  Committee  on  Metro- 
politan Workhouse  Infirmaries  in  1867. 
In  a  paper  in  the  '  Lancet'  in  1866  I  at- 
tempted to  show  that  a  more  scientific 
method  might  be  employed,  and  suggest- 
ed some  formulae,  which  we  quoted  by 
Dr.  Parkes  in  a  paper  appended  to  the 
Report  above  mentioned.  Professor 
Donkin  also  investigated  the  question 
there,  and  in  a  short  but  exhaustive 
paper  showed  that,  general  diffusion  in 
an  air-space  being  admitted,  the  same 
amount  of  air  was  required  to  ventilate 
it,  whatever  its  size  might  be.  In  an- 
other paper,  published  in  the  '  Edin- 
burgh Medical  Journal'  in  May  1867,  I 
went  into  the  subject  with  the  view  of 
pointing  out  that  we  might,  with  exist- 
ing data,  establish  a  basis,  which  should 
be  both  scientific  and  practical,  for  es- 
timating the  amount  of  air  required  ; 
and  I  adduced  some  results  to  show  that 
the  evidence  of  the  senses  might  be  em- 
ployed (if  used  with  proper  care  and 
precautions)  as  the  ground-work  of  a 
scale,  and  gave  a  short  table  of  the 
amounts  of  respiratory  impurity  (esti- 
mated as  C02)  which  corresponded  to 
certain  conditions  noted  as  affecting  the 


sense  of  smell.  This  paper  attracted 
the  attention  of  General  Morin,  who 
made  it  the  text  of  a  short  article  in  the 
Journal  of  the  Conservatoire  des  Arts  et 
Metires  during  last  year.  Since  the 
publication  of  my  paper  in  1867  I  have 
accumulated  more  data  ;  and  the  number 
of  observations  being  now  sufficient  to 
give  at  least  a  fair  approximation  to  the 
truth,  I  beg  to  call  attention  to  the  re- 
sults. 

It  is  generally  admitted  that  it  is  or- 
ganic matter,  either  suspended  or  in  the 
form  of  vapor,  that  is  the  poison  in  air 
rendered  impure  by  the  products  of  res- 
piration. It  is  also  admitted  that  it  is 
the  same  substance  that  gives  the  disa- 
greeable sensation  described  as  "  close- 
ness" in  an  ill-ventilated  air-space.  Al- 
though the  nature  of  the  organic  matter 
may  vary  to  a  certain  extent,  it  will  be 
allowed  that  a  condition  of  good  ven- 
tilation may  be  established  if  we  dilute 
the  air  sufficiently  with  fresh  air,  so  that 
the  amount  of  organic  matter  shall  not 
vary  sensibly  from  that  of  the  external 
air.  Unfortunately  all  the  methods  de- 
vised for  the  determination  of  organic 
matter  in  air  are  both  difficult  and  un- 
satisfactory, so  much  so  that  they  are 
almost  practically  impossible  in  a  ven- 
tilation inquiry.  Observations,  however, 
as  far  as  they  have  gone,  seems  to  show 
that  the  amount  of  organic  impurity 
bears  a  fairly  regular  proportion  to  the 
amount  of  carbonic  acid  evolved  by  the 
inhabitant  in  an  air-space  ;  and  as  the 


THE  THEORY   OF   VENTILATION. 


333 


latter  can  be  easily  and  certainly  deter- 
mined, we  may  take  it  as  a  measure  of 
the  condition  of  the  air-space.  This 
being  accepted,  and  general  diffusion 
being  admitted,  we  can  easily  calculate 
the  amount  of  fresh  air  required  to  bring 
down  the  C02  to  some  fixed  standard, 
adopting  as  a  datum  the  ascertained 
average  amount  of  C02  evolved  by  an 
adult  in  a  given  time.  If,  now,  we 
adopt  as  our  standard  the  point  at  which 
there  is  no  sensible  difference  between 
the  air  of  an  inhabited  space  and  the  ex- 
ternal air,  and  agree  that  this  shall  be 
determined  by  the  effects  on  the  sense 
of  smell,  our  next  step  is  to  ascertain 
from  experiment  what  is  the  average 
amount  of  C02  in  such  an  air-space,  from 
which  we  can  then  calculate  the  amount 
of  air  required  to  keep  it  in  that  con- 
dition. The  sense  of  smell  is  very 
quickly  dulled,  so  that,  in  order  to  keep 
it  acute,  each  air-space  to  be  examined 
ought  to  be  entered  directly  from  the 
open  air.  For  this  reason  I  have  not  in- 
cluded in  the  present  paper  any  of  the 
observations  made  in  prisons,  as  it  is  al- 
most impossible,  from  their  construction, 
to  enter  the  cells  directly  from  the  open 
air.  All  the  results,  therefore,  have 
been  obtained  in  buildings  where  this 
could  be  done,  viz.  barracks  and  hospit- 
als, and  several  were  examined. 

The  plan  followed  in  all  was  to  take 
the  observations  chiefly  at  night,  when 
the  rooms  or  wards  were  occupied,  and 
when  fires  and  lights  (except  the  lamp 
or  candle  used  for  the  observation)  were 
out.  In  this  way  all  disturbing  sources 
of  C02  were  avoided,  except  in  the  oc- 
casional rare  instances  of  a  man  smoking 
in  bed  or  the  like.  On  first  entering  the 
room  from  the  outer  air  the  sensation 
was  noted  and  recorded  just  as  it  oc- 
curred to  the  observer,  such  terms  as 
"fresh,"  "fair,"  "not  close,"  "close," 
"  very  close,  "  extremely  close,"  &c. 
being  employed.*  Most  of  these  notes 
were  made  by  myself  ;  but  a  good  many 
were  also  made  by  my  assistants,  Sergt. 
(now  Lieut.)  Sylvester  in  the  eariler,  and 
Sergt.  H.Turner  in  the  latter  experiments. 
The  air  was  then  collected  (generally  in 
two  jars  or  bottles,  for  controlling  ex- 
periments), and  set  aside  with  lime-water 
for  subsequent    analysis,  and  the  tem- 

•    N.  B .    The  terms  used  in  the  Tables  are  exactly 
those  noted  down  at  the  time  of  observation. 


peratures  of  the  wet-  and  dry -bulb  ther- 
mometers noted.  About  the  same  time 
samples  of  the  external  air  were  also 
taken,  and  the  thermometers  read.  In 
this  way  any  unintentional  bias  in  the 
record  of  sensations  was  avoided,  and 
this  source  of  fallacy  fairly  well  elimin- 
ated. 

In  some  of  the  earlier  observations  the 
C02  in  the  external  air  was  not  observed 
as  constantly  in  connection  with  the  in- 
ternal observations,  partly  because  the 
importance  of  .  this  was  not  so  clearly 
perceived  then,  and  partly  from  want  of 
apparatus,  the  jars  used  being  very 
bulky  and  not  easy  of  carriage.  It 
might  therefore  be  argued  that  the  com- 
bination-weights of  the  earlier  experi- 
ments should  be  less  in  calculating  the 
averages.  I  do  not  think,  however,  that 
this  would  amount  to  any  sensible  dif- 
ference in  the  result,  as  the  external  C02 
ratios  adopted  from  single  experiments 
accord  fairly  with  the  mean  ratio  of  the 
outer  air*.  In  each  case  the  C02  has 
been  corrected  for  temperature,  but  not 
for  barometric  pressure,  and  in  some 
cases  the  reading  of  the  barometer  was 
not  taken  ;  the  difference,  however, 
would  not  exceed  on  an  average  1  per 
cent.  The  vapor  and  humidity  were 
calculated  from  Glaisher's  Tables. 

Although  the  records  of  sensation  are 
various  in  terms,  I  have  thought  that 
they  might  be  advantageously  reduced 
to  five  orders  or  classes,  as  follows  : 

No.  1.  Including  such  expressions  as 
"  fresh,"  "  fair,"  "  not  close,"  "  no 
unpleasant  smell,"  &c,  indicating 
a  condition  giving  no  appreciably 
different  sensation  from  the  outer 
air. 

No.  2.  Including  such  expressions  as 
"rather  close,"  "a  little  close," 
"  not  very  foul,"  "  a  little  smell," 
&c.j  indicating  the  point  at  which 
organic  matter  begins  to  be  ap- 
preciated by  the  sense  of  smell. 

No.  3.  "  Close,"  indicating  the  point 
at  which  organic  matter  begins  to 
be  decidedly  disagreeable  to  the 
sense  of  smell. 

No.  4.  "Very  close,"  "bad,"  &c,  in- 
dicating the  point   at  which  or- 


*  Mean  ratio  of  the  whole  series  .372 ;  omitting  those 
at  Portsmouth  Garrison  Hospital,  which  were  exception- 
ally low,  413. 


334 


VAN  NOSTRAND's  ENGINEERING    MAGAZINE. 


ganic  matter  begins  to  be  offen- 
sive and  oppressive  to  the  senses. 
No.  5.  "Extremely  close,"  "very bad," 
&c,  indicating  the  point  at  which 
the  maximum  point  of  differentia- 
tion by  the  senses  is  reached. 

Where  there  was  a  slight  smell  of  to- 
bacco no  change  in  the  record  was  made; 
but  where  the  smell  of  tobacco  was  strong, 
the  observation  was  generally  referred 
to  the  next  order,  both  because  the  pres- 
ence of  the  tobacco-smoke  indicated  slow 
change  of  atmosphere,  and  also  because 
the  sense  of  closeness  must  have  been 
considerable  to  make  itself  felt  along 
with  the  tobacco.  Hence  such  a  remark 
as  "  rather  close,"  which  properly  be- 
longs to  No.  2,  is  referred  to  No.  3, 
"close,"  if  accompanied  with  a  strong 
smell  of  tobacco. 

The  total  number  of  observations  for 
the  temperature,  vapor,  and  humidity  in 
the  inhabited  spaces  amounts  to  247*, 
and  of  carbonic-acid  analyses  to  473. 
Where  the  latter  are  in  pairs  they  are 
linked  by  a  bracket.  In  each  case  the 
external  and  internal  observations  and 
their  differences  are  given,  and  the  arith- 
metical means  of  all  are  taken.  In  the 
differences  which  represent  the  quantities 
due  to  respiratory  impurity,  the  mean 
error,  error  of  mean  square,  and  probable 
error  (both  of  a  single  measure  and  of 
the  result)  are  calculated,  and  the  limits 
shown  between  which  the  range  would 
lie  in  each  case.  The  values  are  also 
given  as  the  reciprocals  of  the  squares  of 
mean  error  and  of  probable  error  of  re- 
sult, and  their  ratios  to  No.  1  as  unity. 
The  modulus  is  also  calculated  from  the 
mean  error  and  error  of  mean  square,  and 
the  ratio  of  the  two  resuls  thus  obtained 
shown  as  another  means  of  estimating 
the  value  of  the  series. 

Analyses  of  the  different  Orders. 

No.  1,  "Fresh,"  &c.  :  a  condition  of 
atmosphere  not  sensibly  different 
from  the  external  air. 
1.      Temperature. — The     experiments 
were  made  during  both  winter  and  sum- 
mer, so  that  there  is  a  good  deal  of  vari- 
ation in  the  external  temperature,  and  the 
mean  is  some   degrees  above  the  mean 

•  It  has  been  thought  unnecessary  to  give  these  in  de- 
tail as  taking  up  too  much  space,but  the  means  are  given 
at  the  end  of  the  Table  of  Carbonic  Acid. 


annual  temperature  of  this  country 
(southern  part  of  it),  viz.  57°. 47.  The 
mean  in  the  inhabited  air-spaces  is  62°.- 
85,  or  5°. 38  higher.  This  is  a  moderate 
difference,  and  shows  a  good  average 
temperature  for  dwelling-rooms.  The 
maximum  range  is  10°  (5 7°. 89  to  67°.- 
81),  calculated  from  the  error  of  mean 
square,  the  actual  extremes  being  77° 
and  53°. 

2.  Vapor  and  Humidity. — As  the  ex- 
ternal temperature  varied  considerably, 
so  also  did  the  amount  of  vapor,  the 
mean  being  4.285,  equal  to  about  80  per 
cent,  of  humidity.  The  internal  obser- 
vations showed  a  mean  of  4.629,  or  73 
per  cent,  of  humidity,  being  an  excess  of 
vapor  of  0.344  of  a  grain,  and  a  lowering 
of  relative  humidity  equal  to  7  per  cent. 

3.  Carbonic  Acid.—  The  mean  exter- 
nal carbonic  acid  was  0.4168,  a  little 
above  the  usual  amount.  The  mean  in 
the  inhabited  air-spaces  was  0.5998,  or 
an  excess  of  0.1830,  the  mean  error  being 
0.0910.  The  probable  error  of  a  single 
observation  is  0.0831,  so  that  the  truth 
would  lie  between  0.2661  and  0.0999  ; 
whilst  the  probable  error  of  the  result  is 
only  0.0078,  the  range  being  between 
0.1908  and  0.1752  ;  we  are  therefore  en- 
titled to  say  that  the  limit  of  impurity, 
imperceptible  to  the  sense  of  smell,  lies 
at  or  within  0.2000  volume  of  C02  per 
1000  as  a  mean.  From  these  data,  then, 
we  may  lay  down  as  conditions  of  good 
ventilation  the  following  : 

Temperature  about  63°  Fahrenheit. 

Vapor  shall  not  exceed  4.7  grains  per 
cubic  foot. 

Carbonic  acid  shall  not  exceed  the 
amount  in  the  outer  air  by  more 
than  0.2000  per  1000  volumes. 

No.  2.  "Rather  close"  &c. :  a  con- 
dition of  atmosphere  in  which 
the  organic  matter  begins  to  be 
appreciated  by  the  senses. 

1.  Temperature. — In  this  series  the  ex- 
ternal temperature  (although  still  above 
the  mean  temperature  of  this  climate) 
was  rather  lower  than  in  the  previous 
one,  viz.  54°. 85,  whilst  the  internal  ob- 
servations gave  a  mean  of  62°. 85  (the 
same  as  in  No.  1),  or  a  difference  of  8°. 

2.  Vapor  and  Humidity. — Although 
the  temperature  was  the  same  as  in  No. 
1,  the  amount  of  vapor  in  the  inhabited 
air-spaces  was  greater,  both  actually  and 


THE  THEORY    OF   VENTILATION. 


335 


relatively,  the  excess  being  0.687  of  a 
grain  and  the  lowering  of  humidity 
being  about  7.6  per  cent. 

3.  Carbonic  Acid. — The  mean  amount 
in  the  outer  was  0.4110  per  1000  volumes, 
in  the  inhabited  air-spaces  0.8004,  or  a 
mean  difference  (respiratory  impurity) 
of  0.3894.  The  range  for  the  probable 
error  of  result  lies  between  0.4057  and 
0.3731. 

"We  may  therefore  say  that  ventilation 
ceases  to  be  good  when  the  following 
conditions  are  present  : 

Vapor  in  the  air  exceeds  4.7  grains 

per  cubic  foot. 
C04    in  excess   over  outer   air,   ratio 

reaching  0.4000  per  1000  volumes. 

No.  3.  "  Close"  &c. :  the  point  at 
which  the  organic  matter  begins 
to  be  decidedly  disagreeable  to 
the  senses. 

1.  Temperature. — The  temperature  in 
this  series  was  more  near  the  mean  of 
our  climate,  viz.  51°. 28.  The  mean  in 
the  inhabited  air-space  was  64°. 67,  or  a 
mean  excess  of  12°. 91. 

2.  Vapor  and  Humidity. — The  vapor 
in  the  outer  air  was  3.837,  and  in  the  in- 
habited air-space  4.909,  a  mean  differ- 
ence of  1.072  grain  per  cubic  foot.  The 
drying  of  the  air  amounted  to  a  lower- 
ing of  the  humidity  by  11.56  per  cent. 

3.  Carbonic  Acid. — The  carbonic  acid 
in  the  outer  air  was  0.3705  per  1000 
volumes,  rather  below  the  average.  In 
the  inhabited  air-spaces  it  was  1.0027, 
or  a  mean  difference  of  0.6332  due  to 
respiratory  impurity,  the  range  for  the 
probable  error  of  result  being  between 
0.647  and  0.617. 

We  may  therefore  say  that  ventilation 
begins  to  be  decidedly  bad  when  the 
following  conditions  are  reached  : 

Vapor  reaches  4.9  grains   per   cubic 

foot. 
Carbonic  acid  in  excess  over  outer  air 

to  the  amount  of  0.6000  per  1000 

volumes. 

No.  4.  "  Very  close,"  &c.  :  the  point 
at  which  the  organic  matter  be- 
gins to  be  offensive  and  oppressive 
to  the  senses. 


temperature  was  51°. 28,  and  the  internal 
65°. 15,  or  a  mean  difference  of  13°. 87. 

2.  Vapor  and  Humidity. — The  mean 
vapor  in  the  outer  air  was  3.678  grains, 
and  in  the  inhabited  air-spaces  5.078,  or 
a  mean  difference  of  1.400  grain  per 
cubic  foot.  This  corresponds  to  a  low- 
ering of  the  humidity  by  8°.58  per  cent. 

3.  Carbonic  Acid. — The  mean  amount 
in  the  outer  air  was  0.3903  per  1000  vol- 
umes, pretty  near  the  usual  average.  In 
the  inhabited  air-spaces  it  was  1.2335,  or 
a  mean  difference  due  to  respiratory  im- 
purity of  0.8432,  the  range  for  probable 
error  of  result  being  between  0.8640  and 
0.8224. 

We  may  say  that  ventilation  is  very 
bad  when  : 

Vapor  reaches  5  grains  per  cubic  foot. 
Carbonic  acid  in  excess  over  outer  air 
reaches  0.8000  per  1000  volumes. 

No.  5.  "  Extremely  close,"  &c.  :  the 
maximum  point  of  differentiation 
by  the  senses. 

1.  Temperature. — The  temperature  in 
the  outer  air  was  51°. 86,  and  in  the  in- 
habited air-spaces  65°.05,  giving  a  mean 
difference  of  13°,  19. 

2.  Vapor  and  Humidity. — The  mean 
vapor  in  the  outer  air  was  3.875,  and  in 
the  inhabited  air-spaces  5.194,  showing 
an  excess  of  1.319  grain,  corresponding 
to  a  lowering  of  relative  humidity  of 
9.88  per  cent. 

3.  Carbonic  Acid. — The  mean  amount 
in  the  outer  air  was  0.4001,  or  exactly 
the  average  amount.  In  the  inhabited 
air-spaces  it  was  1.2818,  showing  an  ex- 
cess due  to  respiratory  impurity  of  0.8817 
per  1000  volumes,  the  range  for  the 
probable  error  of  result  being  between 
0.9202  and  0.8432. 

The  extreme  point  of  differentiation 
by  the  senses  is  thus  reached  when  the 
following  conditions  are  found  : 

Vapor  5.100  grains  per  cubic  feet. 

Carbonic  acid  in  excess  over  the 
amount  in  the  outer  air  beyond 
0.8500  per  1000  volumes. 

It  will  at  once  be  seen  that  the  figures 
in  No.  5  differ  but  little  from  those  in 
Mo.  4,  and  that  the  probable  limit  of  dif- 
ferentiation by  the  senses  is  reached  in 
No.  4.     The  number  of  recorded  observ- 


1.   Temperature. — The   mean  external   ations  in  No.  5  is  also  very  few  compara- 


336 


VAN   NOSTRAND's   ENGINEERING   MAGAZINE. 


lively;  and  I  think  it  would  therefore  be 
better  to  group  the  two  together,  as  be- 
low. 

Nos.  4  and  5  combined,  being  the 
probable  limit  of  possible  differ- 
entiation by  the  senses. 

1.  Temperature.  —  In  the  outer  air 
51°. 43,  in  the  inhabited  air-spaces  65°. 12, 
or  a  mean  difference  of  13°. 69. 

2.  Vapor  and  Humidity. — The  vapor 
in  the  outer  air  was  3.729,  inside  5.108, 
or  a  mean  difference  of  1.379  grain,  cor- 
responding to  a  lowering  of  relative  hu- 
midity of  8.92  per  cent. 


3.  Carbonic  Acid. — In  the  outer  air 
0.3928,  in  the  inhabited  air-spaces  1.2461, 
or  a  mean  difference  to  respiratory  im- 
purity of  .0.8533,  the  range  for  probable 
error  of  result  being  between  0.8717 
and  0.8349. 

We  may  therefore,  I  think,  say  that 
when  the  vapor*  reaches  5.100  grains 
per  cubic  foot,  and  the  C02  in  excess 
0.8000  volume  per  1000,  the  maximum 
point  of  differentiation  by  the  senses  is 
reached. 

By  referring  to  the  Tables  it  will  be 
seen  that  there  is  a  regular  progression 
as  we  pass  from  one  order  to  another. 
The  following  abstract  shows  this  : 


Temperature. 

Vapor. 

Carbonic  Acid. 

No. 

In  air-space. 

Excess 

over 

outer  air. 

In  air-space. 

Excess 

over 

outer  air. 

In  air-space. 

Excess 

over 

outer  air. 

1 
2 
3 
4 
5 

62.85 
62.85 
64.67 
65.15 
65.05 

5.38 

8.00 

12.91 

13.87 

13.19 

4.629 
4.823 
4.909 

5.078 
5.194 

0.344 
0.687 
1.072 
1.400 
1.319 

0.5999 
0.8004 
1.0027 
1.2335 
1.2818 

0.1830 
0.3894 
0.6322 

0.8432 
0.8817 

The  progression  is  complete  in  the 
carbonic  acid,  although  there  are  slight 
retrogressions  in  the  temperature  and 
vapor  of  No.  5.  Taking  the  last  two 
combined,  we  have 


65°.12  13°69  5.108 

1.2461  0.8533 


1.379 


We  have  now  the  progression  com- 
plete throughout.  Adopting  four  orders, 
then,  we  shall  find  the  regularity  of  pro- 
gression sufficiently  note-worthy  in  the 
vapor  and  carbonic  acid,  the  two  pro- 
ducts of  respiration.  It  is  less  regular 
in  the  temperature,  as  might  indeed  be 
expected,  from  the  varying  condition  of 
the  external  air. 


Table  of  Differences  of  Temperature,  Vapor,  and  C02 


Temperature. 

Vapor. 

Carbonic  Acid. 

No. 

Actual  ex- 
cess over 
outer  air. 

Progressive 
difference. 

Actual  ex- 
cess over 
outer  air. 

Progressive 
difference. 

Actual  ex- 
cess over 
outer  air. 

Progressive 
difference. 

1 

2 

3 

4  and  5 

(combined). 

5.38 

8.00 

12.91 

13.69 

2^62 
4.91 
0.78 

0.344 
0.687 
1.072 
1.379 

0.343 
0.385 
0.307 

0.1830 
0.3894 
0.6322 
0.8533 

0.2064 
0.2428 
0.2211 

*  It  is  to  be  understood  that  the  amounts  of  vapor 
stated  in  these  cases  are  in  reference  to  a  mean  tempera- 
twre  of  about  63°  F. 


In  each  observation  there  is  a  culmin- 
ation at  No.  3,  and  a  decline  at  the  next 


THE   THEORY   OF   VENTILATION. 


337 


order.     The  average  rates  of  progression 
(including  the  actual  excess  in  No.  1)  are  : 


Temperature. 
3°.  42 


Vapor. 
0.345 


Carbonic  Acid. 
0.2133 


Here  the  amount  of  vapor  is  exactly  the 
actual  excess  in  No.  1,  and  the  amount 
of  carbonic  acid  somewhat  in  excess  ; 
the  mean,  however,  between  this  amount 
and  the  actual  recorded  excess  in  No.  1 
is  as  follows  : 

Actual  excess  over  outer  air  in  No.  1 ...  0. 1830 
Mean  of  progressive  increase,  as  above.  0.2133 


Sum 2)0.3963 


Mean 0.1982 

This  is  sufficiently  close  to  0.2000  to 
furnish  some  additional  reason  for 
adopting  this  latter  number  as  the  limit 


of    respiratory    impurity   admissible   in 
good  ventilation. 

Values  of  the  several  series,  considered 
relatively  to  each  other. 
The  values  are  important  as  a  guide 
to  the  more  or  less  trustworthy  character 
of  the  series.  They  have  been  calculated 
out  in  three  ways  : 

1.  As  the  reciprocal  of  the  square  of 

mean  error. 

2.  As  the  reciprocal  of  the  square  of 

probable  error  of  result. 

3.  As  the  ratio  between  the  modulus 

calculated  from  the  mean  error 
and  the  modulus  calculated  from 
the  error  of  mean  square  of  a 
single  measure. 

The  following  Table  gives  the  values 
from  the  first  method,  viz.  as  reciprocal 
of  the  square  of  mean  error  : 


No. 

Temperature. 

Vapor. 

Humidity.            Carbonic  Acid. 

1 
2 
3 
4 
5 
4  &  5  combined 

0.0821 
0.0625 
0.0403 
0.0543 
0.0664 
0.0610 

6.1300 
3.1300 
2.6500 
2.7700 
1.3700 
2.2900 

0.0190 
0.0140 
0.0110 
0.0120 
0.0090 
0.0010 

122.0000 
34.0000 
21.8000 
17.0000 
14.1000 
16.5000 

And  the  ratios,  taking  No.  1  as  1000,  are 


No. 

Temperature. 

Vapor. 

Humidity. 

Carbonic  Acid. 

1 

.     1000 

1000 

1000 

1000 

2 

760 

510 

735 

277 

3 

492 

431 

575 

178 

4 

662 

450 

630 

139 

5 

810 

224 

473 

115 

4  &  5  combined 

745- 

374 

526 

135 

Here  we  see  that  there  is  a  diminution 
of  value  pretty  regular  up  to  No.  3, 
when  there  is  a  rise  in  No.  4  and  No.  5 
in  the  temperature,  a  rise  in  No.  4  and  a 
fall  in  No  5  in  the  vapor  and  humidity, 
whilst  the  fall  is  progressive  throughout 
in  the  carbonic  acid. 

In  each  case  the  result  of  the  combin- 
Vol.  XIII.— No.  4—22 


ation  of  4  and  5  gives  a  number  which 
takes  its  proper  place  after  No  3,  except 
in  the  temperature. 

The  following  Table  give  the  values 
according  to  the  second  method,  viz.  as 
reciprocal  of  the  square  of  the  probable 
error  of  the  result  : 


338 


VAN   NOSTRAND'S   ENGINEERING   MAGAZINE. 


No. 

Temperature.               Vapor.                  Humidity. 

Carbonic  Acid. 

1 
2 
3 
4 
5 
4  &  5  combined 

5.2716 
4.1165 
3.7470 
3.7100 
1.5839 
5.3171 

293.93000 
324.2300 
281.3300 
170.000 
34.2770 
195.8300 

1.2656 
0.5318 
1.0966 
0.5439 
0.1986 
0.7708 

16378.2000 
3750.4000 
4148.1000 
2307. 500O 
674.3000 
2957.5100 

And  the  ratios,  taking  No.  1  as  1000,  are  : 


No. 

Temperature. 

Vapor. 

Humidity. 

Carbonic  Acid. 

1 

1000 

1000 

1000 

1000 

2 

781 

1103* 

420 

229 

3 

711 

957 

867 

253 

4 

704 

578 

432 

141 

5 

302 

117 

157. 

41 

4  &  5  combined 

1008* 

667 

609 

181 

Here  we  see  much  the  same  order  pre- 
served, except  that  in  two  cases  marked  * 
(iVos.  4  and  5,  temperature,  and  No.  2, 
vapor)  the  amounts  exceed  No.  1.  It  is 
also  observable  that  in  the  vapor,  humid- 
ity, and  carbonic  acid  No.  3.  is  superior 
to  No.  2.  In  every  case  the  combined  4 
and  5  series  is  superior  to  the  two  singly, 
being  nearly  their  sum.  In  all  the 
Tables  it  may  be  observed  that  the 
humidity  is  somewhat  irregular  in  rela- 
tion to  the  amount  of  vapor.  This  may 
be  understood  from  the  fact  that  it  is  a 
complex  quantity,  depending  partly  on 
the  amount  of  vapor,  and  partly  on  the 
temperature. 

If  we  now  seek  to  get  a  general  ex- 
pression of  the  relative  values  of  all  the 
observations  in  each  order,  we  may  take 
the  product  of  their  values  by  the 
different  methods. 

Table  showing  the  Products  of  the  Values 
op  each  order,  calculated  from  the 
Reciprocals  op  the  Squares  op  Mean 
Errors. 


Table  showing  the  same  from  Probable 
Error  of  Result. 


No.  of  Order... 

Product. 

Ratio. 

1 

1 . 1720 

1000 

2 

0.0931 

794 

3 

0.0256 

218 

4 

0.0307 

262 

5 

0.0115 

98 

4&5 

0.0230 

196 

Product. 


32139057 

2661995 

4794655 

791570 

7254 

2373680 


Ratio. 


1000.00 

83.00 

149.00 

25.00 

0.23 

74.00 


HerG  we  see  a  greater  irregularity,. 
No.  3.  showing  a  superiority  over  No.  2, 
due  probably  to  the  greater  number  of 
individual   observations    in    the   former 


case. 


Taking  the  mean  of  the  ratios  by  the 
two  methods,  we  have  : 


No. 
1 


No. 


1000 
439 
184 


4      = 

144 

5       = 

49 

4  &  5  = 

135 

But  the  discrepancy  in  the  ratios  of 
the  values  from  the  probable  error,  where 
No.  3  exceeds  No.  2,  is  due  to  the  irregu- 
larity in  the  humidity  column  ;  and  as 
this  is  not  an  independent  quantity,  but 
dependent  on  the  temperature  and  vapor, 
we  may  legitimately  omit  it.  We  shall 
then  have  the  products  as  follows  : 


THE  THEORY   OF   VENTILATION. 


339 


Values  from  Mean  Error. 


No. 

Value. 

Ratio. 

1 

61.40 

1000 

2 

6.65 

108 

3 

2.33 

38 

4 

2.56 

41 

5 

1.28 

21 

4&5 

2.30 

38 

Values  from 

Probable  Error  of  Result. 

No. 

Value . 

Ratio. 

1 
2 
3 

4 
5 

4&5 

25382435 

5005632 
4372692 
1455360 
36526 
3079500 

1000.00 

197.00 

172.00 

57.00 

1.44 

121.00 

And  the  mean  of  the  two  valuer?  will  he : 


No.  1. 
No.  2. 


.1000 
.  153 


No.  i 
Nos. 


!  108 

4&5...  80 


It  will  be  seen  that  in  the  calculation 
from  mean  error  there  is  a  rise  at  No.  4 
in  both  instances,  i.  e.  with  and  without 
the  humidity.  There  is  a  fall  at  No.  5, 
whilst  the  combined  series  4  and  5  gives 
a  result  which  follows  naturally  'after 
No.  3.  We  may  now  reject  Nos.  4  and 
5  as  separate  orders,  and  consider  them 
in  combination,  when  we  shall  have  the 
following  relative  values  : 


■  No. 

From 

Mean  Error. 

From  probable 
Error  of  Result. 

1 

2 

3 

4&5 

1000 

108 

38 

38 

1000 
197 

172 
121 

We  have  now  a  series  of  ratios  which 
follow  a  regularly  descending  scale,  very 
much  in  the  order  we  might  have  expect- 
ed a  priori,  seeing  that  the  sense  of 
smell  is  naturally  less  acute  as  the  or- 
ganic matter  increases  in  amount.  But 
it  is  of  less  consequence  to  determine  the 
position  of  the  higher  orders  in  the  scale, 
except  as  a  measure  of  the  general  value 
of  the  observations  throughout  the  in- 
quiry, the  really  important  point  being 
the  very  great  superiority  of  the  first 
order,  particularly  as  regards  the  car- 
bonic acid.  This  is  an  additional  argu- 
ment for  its  adoption  as  the  limit  of  ad- 
missible impurity  in  good  ventilation. 

The  amount  of  fresh  air  necessary  to 
keep  the  impurity  down  to  the  particular 
limit  would  be  according  to  the  follow- 
ing formula, 


ch 


where  cl  is  the  delivery  of  fresh  air  in 
cubic  feet  per  head  per  hour,  e  the 
amount  of  carbonic  acid  expired  per 
hour  by  one  inmate,  and  q  the  limit  of 
respiratory  impurity  taken  as  carbonic 
acid  per  cubic  foot.  If  we  take  e  to  be 
the  0.6  of  a  cubic  foot  in  a  state  of  com- 
plete repose,  such  as  during  sleep,  we  are 
rather  under  Pettenkofer's  estimate,  but 
considerably  above  Angus  Smith's.  The 
following  Table  gives  the  amounts  neces- 
sary for  the  three  estimates  : 


• 

Limit  of 

respiratory 

impurity 

per  cubic  feet. 

Cubic  feet  of  air  per  head  per  hour  calculated  from 

No.  of  order. 

Angus  Smith's 
estimate, 
e  =  0.450. 

Proposed  estimate 

as  adopted  by 

Dr.  Parkes, 

e  =  0.600. 

Pettenkofer's 
estimate, 
e  =  0.705. 

1 

2 

3 

4&5 

0.0001831 
0.0003894 
0.0006322 
0.0008533 

2460 

1155 

710 

530 

32S0 

1540 

950 

700 

3850 

1810 

1115 

825 

I  think  that  the  general  opinion  is  that 
Angus   Smith's  results  give  too  low  an 


estimate,  *,nd   that   0.600   is   really  the 
lowest  that  can  be  with  safety  admitted. 


340 


VAN   NOSTRAND'S   ENGINEERING   MAGAZINE. 


The  existing  Army  Regulations  con- 
template a  delivery  of  1200  cubic  feet 
per  head  per  hour  in  barracks;  but  prac- 
tical inquiry  has  shown  that  this  amount 
is  generally  fallen  short  of.  The  result 
is  that  the  life  of  the  soldier,  at  least 
during  his  sleeping-hours,  is  passed  in  a 
~No.  3  air-space,  or  one  in  which  the  or- 
ganic impurity  is  decidedly  disagreeable 
to  the  senses.  Previous  to  1858  he  did 
not  even  get  this  moderate  amount  of 
air  ;  so  that  his  life  was  spent  in  an  air- 
space in  which  the  organic  matter  was 
offensive  and  oppressive  to  the  senses.  If 
we  adopt  (as  proposed  already)  0.2000 
per  1000  of  CO„  as  the  limit  of  impurity, 
then  3000  cubic  feet  per  head  per  hour 
is  the  amount  which  must  be  delivered, 
on  the  supposition  that  e= 0.600,  or  3525 
if  e=0.705. 

We  may  say,  in  conclusion,  that  the 
experimental  data  already  quoted  fairly 
justify  the  adoption  of  the  following 
conditions  : 

Conditions  as  to  the  Standard  of  good 
Ventilation. 

Temperature  (dry  bulb)  63°  to  65°  F. 
(wet  bulb)  58°  to  61°  F. 

N.  B. — The  temperature  should  never 
be  very  much  below  60°,  but  it  may  be 
found  difficult  to  prevent  its  rising  in 
hot  weather.  In  any  case  the  difference 
between  the  two  thermometers  ought 
not  to  be  less  than  4°,  and  ought  not  to 
exceed  5°. 

Vapor  ought  not  to  exceed  4.7  grains 
per  cubic  foot  at  a  temperature  of  63  F., 
or  5  grains  at  a  temperature  of  65°  F. 

Humidity  (per  cent.)  ought  not  to  ex- 
ceed 73  to  75. 

Carbonic  Acid. — Respiratory  impurity 
ought  not  to  exceed  0.0002  per  foot,  or 
0.2000  per  1000  volumes. 

Taking  the  mean  external  air  ratio  at 
0.4000  per  10*00,  this  would  give  a  mean 
internal  air  ratio  of  0.6000  per  1000 
volumes. 

By  considering  separately  the  condi- 
tions found  in  barracks  and  in  hospitals, 
or  among  healthy  and  among  sick  men, 
a  point  of  some  interest  and  importance 
seems  to  be  indicated — namely,  that 
more  air  is  required  for  the  latter  than 
for  the  former  to  keep  the  air-space  pure 
to  the  senses.  This  is  due  either  to  the 
greater  quantity  of  organic  matter  or  to 


a  difference  in  its  quality  and    nature. 

The  following  results  are  found  from  the 

data  in  the  Tables  : 

Barracks.  Hospitals. 

Mean  amount  of  carbonic  acid 
per  1000  volumes  as  respira- 
tory impurity  found  when  the 
air  was  noted  as  "  fresh, "&c, 
the  impurity  not  being  appre- 
ciable to  the  senses 0.196      0.157 

Number  of  analyses  in  each 
group 75  38 

Assuming  the  average  carbonic  acid 
per  head  to  be  0.6  of  a  cubic  foot,  these 
amounts  indicate  a  supply  of  air  as  fol- 
lows : 

Barracks.  Hospitals. 
Amount   of    air    supplied    per 

head  per  hour  in  cubic  feet. .     3062        3822 

Stated  in  round  numbers,  therefore, 
we  may  say  that  while  a  barrack-room 
may  be  kept  sweet  with  3000  cubic  feet, 
it  will  take  4000  to  keep  a  hospital  ward 
containing  ordinary  cases  in  the  same 
condition.  Much  more  would,  of  course, 
be  required  during  times  of  epidemic  or 
the  like. 

There  is  less  regularity  in  the  higher 
orders  ;  but  if  the  whole  of  the  observ- 
ations, other  than  No.  1,  are  taken  to- 
gether, we  find  a  similar  indication  : 

Barracks.  Hospitals. 
Mean  amount  of  carbonic  acid 
per  1000  volumes,  as  respi- 
ratory impurity,  in  all  the 
observations,  when  the  or- 
ganic matter  was  apprecia- 
ble by  the  senses 0.601        0.580 

Calculating  the  amount  of  air  supplied 
as  above,  we  have  : 

Barracks.  Hospitals. 
Amount  of  air  supplied  per 

head  per  hour  in  cubic  feet        998  1034 

A  comparison  may  also  be  made  by 
attaching  a  numerical  value  to  each 
order,  which  we  may  do'  by  making  the 
mean  carbonic  acid  of  ISTo.  1  uuity,  and 
finding  its  ratio  to  the  others  thus  : 


No.  of 
Order. 


3 

4&5 


Mean  respi- 
ratory im- 
purity as 
CO*. 


0.1830 
0.3894 
0.6322 
0.8533 


Ratio,  No. 
1  being- 
unity. 


Differ- 
ences. 


1.00 
2.13 
3.46 
4.66 


1.13 
1.33 
1.20 


THE   NEW   METHOD    OF   GRAPHICAL   STATICS. 


341 


The  progression  is  pretty  regular,  and 
the  mean  difference  is  1.22,  which  differs 
but  little  from  the  individual  terms. 

Adopting  the  above  numbers  as  the 
respective  numerical  values  of  each  order, 
we  have  for  barracks  : 


No.  of  obser-  Value 
No.  of  order,  vations.  of  order. 

2        89     x     2.13     : 

3  ....     88     x     3.46     : 
4&5     ....     97     x     4.66     = 

Sums..  274 

giving  a  mean  of  3.45. 

For  hospitals,  we  have  : 


Total. 
189.57 
304.48 
452.02 

946.07 


2 

..     20 

X 

2.13 

= 

42.60 

3 

..     46 

X 

3.40 

= 

159.16 

&-5     .. 

..     20 

X 

4.46 

= 

93  20 

Sums..    86  294.96 

giving  a  mean  of  3.43. 

Here  we  find  the  same  numerical  value 
(signifying  close)  applied  to  0.580  in 
hospitals  and  0.601  in  barracks.  There 
is  thus,  even  in  this  comparatively  limit- 
ed number  of  observations,  a  confirma- 
tion of  the  opinion  that  more  air  is  nec- 
essary to  keep  an  air-space  sweet  in 
disease  than  in  health.  It  is,  however, 
right  to  point  out  that  in  the  one  case 
the  occupation  was  continuous,  and  in 
the  other  chiefly  at  night  only. 


THE  NEW  METHOD  OF  GRAPHICAL   STATICS. 
APPLICATION  OF  THE  GRAPHIC  METHOD  TO  THE  APvCH. 

Bt  A.  J.  DU  BOIS,  C.  E  ,  Ph.  D. 

Written  for  Van  Nostrand's  Engineering  Magazine. 


One  of  the  most  important  applica- 
tions of  Graphical  Statics  in  point  of 
ease  of  solution  and  saving  of  labor,  is 
to  the  arch,  both  the  stone  and  braced 
iron  arch.  We  shall  consider  here  only 
the  first  or  stone  arch.  The  method  en- 
ables us  to  find  easily  and  accurately 
both  the  thrust  at  crown  and  proper  di- 
mensions for  stability  for  any  form  of 
arch  and  surcharge,  without  the  aid  of 
tables  or  the  use  of  formula?.  Indeed, 
this  is  the  principal  advantage  of  the 
graphical  method,  that  its  solutions  are 
general  and  independent  of  particular 
assumptions.  We  are  in  the  present 
case  not  restricted  by  any  special  limita- 
tions, but  take  the  arch  just  as  it  is  in 
the  case  considered,  and  investigate  it 
under  the  actual  conditions  to  which  it 
is  subjected. 

LINE    OE    PRESSURES    IN    THE    ARCH. 

We  have  already  indicated  (Art.  28, 
Fig.  16)  the  manner  in  ivhich  a  number 
of  successive  forces  are  resisted  by  an 
arch.  We  see  from  the  force  polygon 
in  that  figure  that  the  horizontal  press- 
ure is  the  same  at  every  point,  and  that 
the  vertical  pressure  is  equal  to  the  sum 
of  the  weights  between  the  crown  and 
any  point.     The  pressure  line  is  thus  an 


equilibrium  polygon  formed  by  laying 
off  the  weights,  choosing  a  pole  and 
drawing  lines  from  the  pole,  etc.,  as 
described  in  our  previous  articles.  If 
the  weights  are  small  and  their  number 
great,  the  equilibrium  polygon  becomes 
a  curve.  This  curve  for  equilibrium 
should  never  pass  outside  the  limits  of 
the  arch.  More  than  this,  this  curve 
must  under  all  circumstances  lie  within 
the  middle  third  of  the  arch — all  its  pos- 
sible positions  must  be  included  between 
two  curves  parallel  to  extrados  and  in- 
trados  respectively  and  distant  ^  of  the 
depth  from  each.  The  proof  of  this 
condition  is  simple  and  to  be  found  in 
any  treatise  upon  the  arch.  It  is  unnec- 
essary to  give  it  here,  and  sufficient  to 
remark  that  if  from  any  cause  the  curve 
of  pressure  passes  beyond  these  limits 
the  neutral  axis  enters  the  cross  section. 
That  is  while  on  one  side  of  the  neutral 
axis  there  is  compression,  on  the  other 
side  there  is  tension.  But  as  the  mortar 
is  neglected,  the  joints  open  freely  under 
the  influence  of  tensile  strain,  all  the 
material  upon  the  tensile  side  of  the 
axis  is  not  brought  into  play  at  an.  and 
might  be  removed  without  affecting  the 
pressure  upon  the  other  side.  To  obtain 
the    entire   effecth*e    resistance    of    the 


342 


VAX    NOSTRAND'S    ENGINEERING    MAGAZINE. 


given    cross  section    then,    the   pressure 
curve  must  lie  between  the  above  limits. 

CONDITIONS    FOE    STABILITY. 

The  arch  may  fail  either  by  rotation 
about  one  or  several  joints,  or  by  the 
sliding  of  the  joints  upon  each  other. 
The  first  is  effectually  prevented  if  the 
pressure  curve  lies  between  the  limits 
just  prescribed.  The  second  can  never 
take  place  if  the  angle  between  every 
joint  and  the  direction  of  the  pressure 
at  that  joint  is  well  within  the  angle  of 
repose.  The  curve  of  pressure  being 
known  in  any  case,  it  is  easy  to  so  dispose 
the  joints  that  this  shall  be  the  case. 
The  whole  problem  then  is  simply  to  de- 
termine the  pressure  curve.  The  arch 
is  stable  if  the  joints  can  not  slide,  and 
if  it  is  possible  in  any  two  joints  to 
take  two  reactions,  such  that  with  the 
weight  of  the  intervening  portion  of  the 
arch  and  its  load,  the  resulting  pressure 
line  shall  lie  so  far  within. the  arch  that 
rotation  about  an  edge  cannot  take 
place.  If  the  arch  is  so*  light  and  the 
resistance  of  the  material  so  slight  that 
only  one  assumption  of  the  reactions  can 
be  made,  and  only  one  such  pressure 
curve  drawn,  this  is  evidently  the  true 
pressure  curve  for  stability,  and  by  it 
the  reactions  or  pressures  at  every  joint 
are  determined. 

If,  however,  the  arch  is  so  deep  and 
the  resistance  of  the  material  so  great, 
that  several  pressure  curves  may  be 
drawn,  none  of  which  cause  rotation 
about  and  edge,  which  of  all  these  curves 
is  the  true  pressure  curve  ? 

We  assert  :  that  is  the  true  pressure 
carve  which  approaches  nearest  the  axis, 
so  that  the  pressure  in  the  most  compressed 
joint  edge  is  a  minimum. 

If  we  assume  the  material  so  soft  that 
the  pressure  line  approaches  the  axis  so 
closely  that  only  one  curve  is  possible, 
then  this  is  evidently  the  true  curve.  If 
now  the  material  hardens  without  alter- 
ing any  of  its  other  properties,  such  as 
its  specific  weight  or  modulus  of  elastic- 
ity, then  the  position  of  the  pressure 
curve  is  not  changed.  As  there  is  no 
reason  for  supposing  the  pressure  line 
different  in  an  arch  built  of  hard  mate- 
rial from  that  in  one  originally  soft 
which  has  afterwards  gradually  harden- 
ed, it  follows  that  the  pressure  line  in  all 
arches  of  same  form  and  loading  has  the 


same  position  which  it  would  have  had 
if  the  arch  had  been  originally  of  the 
softest  material  ;  that  is  the  position 
which  makes  the  pressure  in  the  most 
compressed  joint  edge  a  minimum. 

We  have  then  in  any  case  to  ascertain 
whether  it  is  possible  to  draw  a  pressure 
line,  whose  sides  cut  the  joint  areas 
within  the  inner  third,  for  then  since  we 
know  that  there  can  be  a  still  more  fav- 
orable position,  there  is  no  danger  of 
rotation.* 

DIMENSIONS    OF    THE  ARCH STABILITY  01' 

ABUTMENTS. 

The  object  of  the  construction  of  the 
pressure  curve  in  the  arch  is  to  determine 
also  the  stability  of  the  abutments. 
When  the  live  load  of  the  arch  can  be 
neglected  with  respect  to  its  own  weight 
and  when  the  material  of  the  arch 
presses  the  usual  strength  and  the  press- 
ure line  lies  within  the.  inner  third,  then 
the  lower  point  of  rupture  lies  so  low 
that  the  rear  masonry  completely  en- 
closes it.  There  is  therefore  nothing  ar- 
bitrary when  the  form  of  the  arch  is 
given  except  the  depth.  Since  in  an 
arch  of  less  depth  than  is  allowable  in 
practice  a  pressure  line  can  still  be  in- 
scribed, the  graphical  method  is  unable 
to  determine  the  proper  depth.  This 
must  be  determined  by  practice,  empiri- 
cal formulae,  and  regulated  by  the 
strength  of  the  material,  etc.  We  must 
assume  that  not  only  the  form  of  the 
arch,  but  also  its  proper  depth  as  well 
as  its  surcharge  are  given.  It  is  requir- 
ed then  to  determine  the  stability  of  the 
abutments. 

We  may  regard  the  abutment  simply 
as  a  continuation  of  the  arch — so  that 
the  arch  is  continued  as  such,  clear  to  the 
foundation  ;  or  we  may  regard  it  as  a 
wall  whose  moment  about  the  joint  of 
rupture  resists  the  rotation  about  this 
joint  due  to  the  thrust.  Both  views  are 
identical,  as  the  entire  theory  of  the 
pressure  curve  rests  upon  the  investiga- 
tion of  the  rotation.  They  differ  only 
in  the  method  of  expressing  the  safety 
of  the  abutments. 

If  the  arch  is  continued  to  the  founda- 
tion, and  the  space  between  it  and  the 
road  line  filled  up  with  masonry,  or  if 
the  thickness  of  the  abutment  increases 


Colmann-Die  graphische  Statik.    Zurich,  1866. 


THE   NEW   METHOD    OE   GRAPHICAL    STATICS. 


343 


from  above  as  the  pressure  curve  re- 
quires ;  or  if  the  abutment  consists  of 
partitions  and  hollow  spaces ;  still  in 
every  case  the  abutment  is  not  to  be  dis- 
tinguished from  the  arch  proper — it  is 
stable  when  the  pressure  line  lies  in  the 
interior.  If  the  prolonged  is  separated 
entirely  from  the  adjacent  masonry, 
there  is  no  reason  for  not  giving  the  axis 
of  the  prolongation  the  form  of  the 
pressure  curve  itself.  If,  on  the  other 
hand,  there  is  no  separation  of  the  arch 
and  abutment,  it  is  sufficient  that  the 
pressure  line  lie  within  the  inner  third, 
and  the  abutment  is  certainly  stable. 

The  supposition  that  the  resistance  of 
the  mortar  is  sufficient  to  unite  the  whole 
abutment  as  a  single  block  which  turns 
about  its  under  edge,  gives  dimensions 
too  small.  To  insure  safety  it  is  assum- 
ed that  equilibrium  exists  with  reference 
to  rotation  about  the  lower  edge  when 
the  thrust  of  the  arch  is  1.5  greater  than 
the  actual.  Investigations  of  French 
engineers  have  showed  that  this  coeffi- 
cient of  safety  for  very  light  arches  is 
not  less  than  1.4.  The  table  of  Petit 
give  1.9.     We  assume  it  therefore  at  2. 

If  therefore  the  double  thrust  of  the 
arch  at  the  lower  point  of  rupture  is 
united  with  the  weight  of  the  abutment, 
the  resultant  should  still  fall  within  the 
base.  Since  it  is  indifferent  in  what 
order  the  elements  of  the  abutment  are 
resolved,  it  is  best  to  divide  it  into  ver- 
tical slices,  and  unite  the  weight  of  these 
with  the  double  thrust.  The  equilibrium 
polygon  thus  obtained  should  cut  the 
foundation  base  within  the  edge  of  the 
abutment. 

When  the  thickness  of  the  abutment 
is  thus  determined,  we  must  construct 
the  actual  pressure  line  by  more  than 
the  angle  of  repose.  Finally  the  press- 
ure line  itself  must  lie  within  the  inner 
third.  A  single  example  will  illustrate 
and  apply  all  the  above  remarks,  and 
will  enable  the  reader  to  determine  read- 
ily the  dimensions,  thrust,  joint  of  rup- 
ture, etc.,  in  any  case. 

CONSTRUCTION  OF    THE    PRESSURE    LINE 

EXAMPLE. 

Thus,  in  the  accompanying  Fig.  1,  we 
are  supposed  to  have  drawn  a  given  arch 
to  scale.  We  must  first  divide  the  arch 
into  vertical  slices  and  determine  the 
weight  of    each.     If   the  surcharge  has 


vacant  spaces,  or  is  generally  of  differ- 
ent specific  weight  from  the  material  of 
the  arch  itself,  it  must  first  be  reduced. 
Thus  if  the  surcharge  (spandrel  filling, 
etc.)  weighs,  for  instance,  only  fds  as 
much  as  an  aqual  area  of  masonry  in  tin- 
arch,  we  must  diminish  the  vertical 
height  by£.  We  thus  obtain  the  dotted 
line  given  in  the  figure  which  forms  the 
limit  of  the  reduced  laminae,  and  we  can 
treat  the  areas  bounded  by  this  line,  by 
the  vertical  lines  of  division  and  by  the 
intrados,  as  homogeneous.  We  have 
next  to  determine  the  centres  of  gravity 
of  the  various  laminae,  according  to  the 
construction  for  finding  the  centre  of 
gravity  of  a  trapezoid  (art.  33)  and  sup- 
pose at  these  points  the  weights,  which 
are  of  course  proportional  to  the  reduced 
areas  of  the  several  trapezoids,  to  act. 
[All  trapezoids  must  be  reduced  to  equiva- 
lent rectangles  of  common  base,  the 
heights  of  these  rectangles  are  then  pro- 
portional to  their  weights,  art.  33.] 

Laying  off  then  these  weights  in  their 

order  we  have  the  force  line  0  1  2  3 

11,  Fig.  2.  The  weights  of  the  abut- 
ment laminae  9  10  and  11,  are  laid  off  to 
same  scale  as  the  others,  one  half  of  their 
proper  length.  The  reason  will  soon  ap- 
pear. 

1st.  To  determine  the  thrust  H  at  crourn, 
and  also  the  joint  of  rupture. 

We  first  sketch  in  a  pressure  curve  by 
the  eye,  and  assume  the  point  of  the  in- 
trados to  which  this  curve  most  nearly 
approaches  as  the  edge  of  the  joint  of 
rupture.  Draw  now  from  the  corres- 
ponding force  of  the  force  line,  a  line 
parallel  to  the  direction  of  the  assumed 
pressure  curve  at  this  point.  This  line 
will  cut  off  from  the  horizontal  through 
the  beginning  of  the  force  line,  our  first 
approximate  value  for  FL 

Thus,  suppose  we  have  inscribed  by 
eye  the  pressure  curve  12  3  4,  etc.,  which 
gives  us  the  point  a  for  the  position  of 
the  joint  of  rupture.  This  point  a  be- 
longs to  force  5.  Then  a  line  drawn 
from  5  on  the  force  line  parallel  to  the 
side  45  of  the  drawn  pressure  curve  cuts 
off  o  O  in  Fig.  2,  our  first  value  for  H. 

Now,  assume  this  value  of  H  as  cor- 
rect, erase  the  pressure  curve  by  which 
we  have  just  obtained  it,  and  with  this 
value  of  H  and  the  forces  12  3  4,  etc., 
construct  the  corresponding  equilibrium 


344 


VAN   NOSTRAND'S   ENGINEERING   MAGAZINE. 


/y-1- 


polygon.  If  this  polygon  lies  always 
within  the  middle  third  of  the  arch,  it 
may  be  taken  as  the  proper  pressure  line 
and  H  as  the  true  thrust.  In  general, 
however,  this  will  not  be  the  case.  The 
polygon  thus  obtained  may  even  pass  en- 
tirely outside  the  arch. 

We  then  determine  another  point 
of  rupture,  viz.  the  point  of  exit,  or 
the  point  of  the  intrados  to  which  the 
polygon  most  nearly  approaches,  and 
produce  the  side  of  the  polygon  at  this 
point  bach  to  intersection  with  H  pro- 
longed through  the  crown.  From  this 
point  of  intersection  draw  a  line  which 
does  lie  within  the  middle  third  at  the 
point  of  rupture,  and  then  parallel  to  this 
line  draw  a  line  in  Fig  2  from  the  end  of 
the   proper  force,  and  we  thus  obtain  a 


second  and  more  accurate  value  of  H. 
Erase  now  the  preceding  polygon,  and 
with  the  new  value  of  H  and  the  given 
forces  proceed  as  before,  and  we  shall 
have  in  general  a  pressure  line  lying 
everywhere  within  the  middle  third.  If 
not,  another  approximation  may  easily 
be  made.  .We  thus  find  by  successive 
approximation,  the  position  of  the  joint 
of  rupture  and  the  thrust  at  crown. 

2d.    Width  of  Abutment. 

Since  we  have  laid  off  the  arch  weights 
to  scale  in  their  true  value,  the  pressure . 
line  thus  obtained  is  the  pressure  curve 
for  the  arch.  But  we  have  laid  off  the 
abutment  laminae  9  10  and  11,  one  half 
their  true  value,   and  the  pressure  line 


THE   NEW    METHOD    OF   GRAPHICAL   STATICS. 


34; 


thus  obtained  with  the  same  thrust  and 
and  pole  O,  is  the  same  as  if  we  had 
taken  their  true  value  and  twice  the 
value  of  H.  Its  intersection  with  the 
foundation  gives  us  then  the  proper 
width  of  the  abutment  for  stability,  ac- 
cording to  our  assumption  of  2  for  the' 
coefficient  of  stability. 

3d.-  The  pressure  line  being  thus  known 
we  can  easily  dispose  the  joints  so  as 
to  avoid  sliding. 

Thus,  by  an  easy  construction,  we  can 
determine  for  any  given  case  of  arch  and 
surcharge,  the  horizontal  thrust,  the 
proper  width  of  abutments,  and  the  dis- 
position of  the  joints.  If  the  dimen- 
sions of  the  arch,  as  given,  are  not  such 
as  to  be  stable  for  the  load,  it  will  be 
found  impossible  to  inscribe  as  above  a 
pressure  line  which  shall  lie  within  the 
middle  thirds  and  the  curve  of  the  ex- 
trados  or  intrados,  or  both  will  have  to 
be  altered  so  that  this  shall  be  possible. 

The  pressure'  line  thus  obtained  does 
not  indeed  exactly  correspond  with  the 
true  one,  as  it  is  still  possible  to  inscribe 
another  which  shall  deviate  less  from  it. 
We  have  also  taken  the  double  thrust 
for  the  abutment  laminae  alone,  instead 
of  from  the  joint  of  rupture.  Both 
deviations  render  the  construction  more 
easy  and  rapid.  It  would  be  found 
very  tedious  to  take  first  the  force  poly- 
gon (Fig.  2)  up  to  about  the  estimated 
joint  of  rupture,  then  by  long  trial  find 
the  innermost  pressure  line,  and,  finally, 
after  the  joint  of  rupture  is  by  this  last 
line  determined,  to  layoff  the  remainder 
of  the  force  polygon  and  prolong  the 
pressure  line  through  the  abutment. 

It  is  far  simpler  to  proceed  as  above, 
by  assuming  the  point  of  application  of 
the  horizontal  thrust,  as  also  temporarily 
the  joint  of  rupture.  We  obtain  thus  a 
somewhat  smaller  value  for  the  width  of 
abutment,-  but,  on  the  other  hand,  we 
have  for  this  reason  taken  the  coefficient 
of  stability  at  2,  instead  of  1.9,  as  as- 
sumed in  Peng's  Tables. 

Moreover,  the  widths  of  abutment 
thus  obtained  are  greater  than  those  ob- 
tained by  the  tables,  as  it  is  assumed  in 
them  that  the  point  of  application  of 
the  horizontal  thrust  is  at  the  upper  edge 
of  the  abutment.  Thus,  in  every  respect, 


the  construction  gives  results  reliable 
;iik1  even  more  accurate  than  the  tables, 
as  we  take  the  arch  as  it  really  is,  while 
in  the  tables  suppositions  are  made  with 
reference  to  surcharge,  etc.,  which  do 
not  hold  good  for  every  ease. 

PROPER    THICKNESS    OF    ARCH    AT    CROWN. 

For  this,  as  has  been  remarked,  we 
must  refer  to  practical  experimental  for- 
mulae and  the  circumstances  of  tin-  case. 
The  proper  depth  depends  not  only  upon 
the  rise  and  span,  but  also  upon  the  toad. 
The  pressure  at  the  extrados  at  -the  key, 
which  is  in  general  the  most  exposed 
part  of  joint,  should  not,  according  to* 
the  best  authorities,  exceed  hth  of  the 
ultimate  resisting  power  of  the  material. 
If  P  is  the  pressure-  per  unit  of  surface, 
lithe  thrust,  and  c/  the  depth  of  key- 
stone joint,  then 

<>  TT 
d 

since  on  the  assumption  that  the  curve 
of  pressure  does  not  pass  beyond  the 
middle   third,  the  wiaximum  pressure  is 

twice  the  mean  pressure  — .      1  his  mean 

a 

pressure  then  should  not  exceed  ^oth  the 
ultimate  resisting  power  of  the  material. 
"In  the  best  works  of  Rennie  and  Stev- 
enson, the  thickness  of  key  varies  from 
3!d  to  3ls  the  span,  and  from  its  to  30,  the  ra- 
dius of  the  intrados.  The  augmentation 
of  thickness  at  the  springing  line  is  made 
by  the  Stevenson's  from  20  to  30  per 
cent.,  by  the  Rennie's  at  about  100  per 
cent.  Perronet  gives  for  the  depth  at 
crown  the  empirical  formula  d=  0.0694 
r  +  0.325  metres,  in  which  r  is  the  great- 
est length  in  metres  of  the  radius  of  cur- 
vature of  the  intrados.  For  arches 
with  radius  exceeding  15  metres  this 
gives  too  great  a  thieknes.  According 
to  Rankine  d  =  0.346 ^/r  for  circular 
arches,  and  ^=0.412A/^7,  where  r  is  the 
radius  of  curvature  of  the  intrados  at 
the  curve." 

"The  London  Bridge  is  in  its  plan  and 
workmanship,  perhaps,  the  most  perfect 
work  of  fts  kind.  The  intrados  is  an 
ellipse,  the  span  152  feet,  the  rise  £  as 
much,  the  depth  of  key  x'oth  the  span. 
The  crown  settled  only  two  inches  upon 
removal  of  the  centres." — [Woodbury — 
Theory  of  the  arch?] 


346 


VAN   NOSTRAND  S   ENGINEERING   MAGAZINE. 


In  general,  we  must  first  assume  the 
depth  at  key  in  view  of  the  strength  of 
the  material,  the  character  of  the  work- 
manship, the  load,  etc.  Then  the  thrust 
being  found  as  above,  we  find  the  mean 
pressure  per  unit  of  area.  If  this  ex- 
ceeds soth  the  ultimate  resisting  power 
of  the  material,  Ave  must  make  a  new 
supposition,  increase  the  thickness,  find 
the  thrust  and  pressure  anew,  and  so  on 
till  the  results  are  satisfactory.  The 
ultimate  resisting  power  of  Granite  may 
be  taken  at  6,000  lbs.  ;  Brick,  1,200  ; 
Sandstone,  4,000  ;  Limestone,  7,000  lbs. 
per  square  foot.  These  values  are,  of 
course,  very  general,  and  subject  to  con- 
siderable variations,  according  to  the  kind 
and  quality  of  the  material.  The 
strength  of  the  material  to  be  used  must 
for  any  particular  case  be  determined  by 
actual  experiment. 

The  weight  of  a  cubic  foot  of  stone 
may  be  assumed  for  preliminary  investi- 
gations at  160  lbs. — brick  masonry  at  125 
lbs. 

INCREASE  OP  THICKNESS  DUE  TO  CHANGE 
OF  FORM. 

Having  obtained  a  thickness  which 
satisfies  all  the  conditions,  we  must,  if 


the  arch  be  very  light,  make  some  fur- 
ther provision  for  the  change  of  form, 
which  is  sure  to  take  place  after  the  re- 
moval of  the  centre.  By  this  change  of 
form  the  pressure  line  is  altered  and  the 
thickness  must  be  increased.  In  general 
we  need  only  to  increase  the  depth  from 
the  key  to  the  springing.  This  increase 
need  not  exceed  50  per  cent,  at  the  joint 
of  rupture  and  weakest  intermediate 
joint. — [  Woodbury — Theory  of  the  Arch.'] 

Thus  Ave  have  all  the  datanecessary 
for  the  investigation  of  any  given  case, 
and  can  determine  by  a  simple  and  rapid 
construction  the  thrust,  joint  of  rupture 
and  proper  thickness  of  the  abutments, 
Avithout  the  aid  of  tables  or  the  intricate 
formula?  usually  employed.  There  is  no 
difficulty  in  laying  down  upon  paper 
and  verifying  all  the  elements  of  the 
most  complex  case.  The  method  is  en- 
tirely independent  of  all  particular  as- 
sumptions, and  is  therefore  especially 
valuable  when  irregularities  of  outline 
or  construction  place  the  arch  almost  be- 
yond the  reach  of  calculation.  It  is  gen- 
eral, and  may  be  applied  with  equal  ease 
to  loaded  and  unloaded,  full  circle,  seg- 
mental or  elliptical  arches  Avith  any  form 
of  surcharge. 


MECHANICAL  CHANGES  IN"  BESSEMER  STEEL. 

By  ARCHIBALD  MACMARTIN,  M.  E. 
Transactions  of  American  Institute  of  Mining  Engineers. 


The  Konigin-Marien-Hutte  is  the  only 
Avorks  in  Germany  where  the  Bessemer 
process  is  carried  on  by  the  direct 
method.  The  Bessemer  plant  there,  is 
arranged  after  the  true  English  type, 
and  the  only  resemblance  to  the  Swedish 
mode  of  procedure  is  the  dispensing  with 
the  use  of  spiegeleisen  at  the  end  of  the 
"  blow" 

In  a  neAv  department  of  the  establish- 
ment, started  Avithin  three  years,  each 
of  the  converters  is  turned  by  means  of 
a  A7ery  neat  and  compact  reversible'  en- 
gine, the  steel  shaft  of  which  is  an  end- 
less screw,  which  turns  against  the  ob- 
lique cogs  of  a  large  wheel  attached  to 
the  shaft  of  the  ATessel.     An  advantage 


which  this  arrangement  possesses  over 
the  ordinary  English  hydraulic  arrange- 
ment, is  the  fact  that  the  endless  screw 
suffices  to  turn  the  vessel,  in  either  direc- 
tion any  number  of  complete  revolutions  / 
Avhile  even  the  latest  American  improve- 
ments, so  clearly  explained  to  us  by  Mr. 
Holley  at  the  •  opening  session  of  this, 
meeting,  do  not  secure  eA'en  one  complete 
revolution  without  changing  the  angle 
of  inclination  of  the  hydraulic  piston. 

In  the  endless  screw  arrangement, 
there  being  no  limit  to  the  working  of 
the  motor  in  either  direction  (no  return- 
stroke  necessary),  the  vessel  can  always, 
unless  outside  reasons  demand  the  con- 
trary, be  turned  around  to  any  desired 


MECHANICAL   CHANGES    IN    BESSEMER   STEEL. 


347 


position  by  the  shortest  cut,  whether 
backwards  or  forwards.  Also,  the  di- 
ameter of  the  cog-wheel  attached  to  the 
vessel  can  be  made  sufficiently  great  to 
avoid  all  unevenness  of  motion.  In  the 
old  department  the  motive-power  still 
continues  to  be  hydraulic. 

If  reports  be  true,  the  new  department 
produces  spiegelized  steel,  for  the  manu- 
facture of  all-steel  rails.  But  the  old 
department  is  still,  as  from  the  begin- 
ning, devoted  to  the  production  by  the 
direct  method  of  steel  for  steel-headed 
rails.  The  most  remarkable  fact  con- 
nected with  this  direct  steel  is  the  ease 
with  which  it  welds  to  the  iron  of  the 
rail-packets,  although  no  borax  or  other 
fluxing  agent  is  used  to  facilitate  the 
welding.  It  is  very  rarely  that  an  ex- 
ception occurs,  and  an  ingot  or  a  charge 
is  discarded  by  the  rail-mill. 

The  mixture  of  pig-iron  used  for  the 
production  of  this  steel  is  inelted  in 
cupolas  of  very  interesting  construction 
(not  to  be  described  here),  and  consists 
generally  of  gray  "  Konigin-Marien- 
Hutte,"  two  grades  of  gray  "  Georg-Ma- 
rien-Hutte,"  of  Osnabruck,  "  Charlotten- 
Hutte,"  and  "  Schmalkaldner-eisen." 
The  last  is  rich  in  manganese  and  re- 
sembles spiegeleisen,  although  its  silver- 
white  crystals  are,  as  a  rule,  much  smaller 
than  those  of  spiegeleisen.  It  is  prob- 
ably due  to  a  high  percentage  of  man- 
ganese in  this  mixture  of  iron  employed, 
that  it  is  possible  in  Zwickau  to  do  what 
has  been  tried  in  vain  in  England, 
namely,  to  dispense  with  the  use  of 
spiegeleisen  at  the  end  of  the  blow. 

The  five  tons  of  molten  iron  are  blown, 
till  the  conductor  of  the  operation  is 
warned  by  the  spectroscope  that  the 
charge  has  come  to  the  condition  of 
steel.  Then  the  vessel  is  turned  over, 
back  downwards,  and  the  blast  cut  off. 
In  more  than  ninety  cases  out  of  a  hun- 
dred, nothing  further  would  be  necessary. 
But,  to  make  assurance  doubly  sure,  a 
mechanical  test  is  applied.  No  extra 
time  is  lost  by  this  ;  for  it  is  always  well 
to  let  the  finished  charge  rest  in  the  ves- 
sel a  short  period  previous  to  pouring  it 
into  the  ladle.  This  second  test  is  called 
the  "  globule-test."  Three  or  four  long 
iron  rods  are  plunged  into  the  metal- 
bath,  at  the  mouth  of  the  converter,  and 
drawn  out  very  rapidly.  The  slag  ad- 
hering contains  minute  globules  of  metal, 


of  the  same   degree  of  decarburization 

represented  by  the  whole  bath.  These, 
after  the  rods  have  been  plunged  into 
cold  water  and  the  slag  thus  disen- 
tegrated,  are  collected  together  and 
hammered.  Those  globules  which  cooled 
on  the  outer  surface  of  the  slag,  are  apt 
to  be,  in  part,  superficially  oxydized,  and 
are  always  discarded,  because  they  are 
almost  sure  to  crack  on  the  edges  when 
hammered.  But  any  wholly  bright 
globule,  even  slightly  irregular  in  shape, 
is  suitable  for  the  test  in  question.  A 
number  of  the  chosen  globules  are  ham- 
mered upon  an  anvil  with  a  hand-ham- 
mer. If  the  steel  be  too  soft  (which  al- 
most never  occurs),  the  globule  will 
hammer  down  very  flat  and  with  un- 
broken edges  ;  but  the  experienced 
hand  can  readily  feel  that  the  resistance 
offered  to  the  hammer  is  too  slight.  If 
the  steel  be  too  hard,  the  globules  will 
crack  on  the  edges  when  hammered  ;  or 
their  too  great  resistance  to  the  ham- 
mer can  just  as  easily  be  felt,  as  can  the 
opposite  in  the  former  case. 

When  the  steel  possesses  the  desired 
degree  of  hardness,  no  cracks  are  seen  on 
the  edges  of  the  hammered  globules  ; 
but  yet  a  perceptible  (though  not  too 
great)  resistance  is  offered  to  the  ham- 
mer But,  if  any  globule  that  is  partially 
coated  with  oxyde,  or  any  wholly  bright 
globule  larger  than  W™*  in  diameter, 
hammers  out  without  cracking  on  the 
edges,  it  is  a  sign  that  the  steel  is  too 
soft.  There  is  a  limit,  then,  to  the  size 
of  the  globules  taken. 

When  the  steel  is  shown  by  the  test 
to  have  the  right  hardness,  it  is  allowed 
to  remain  as  much  longer  in  the  convert- 
er as  ma}r  be  necessary  to  cool  it,  or  to 
get  rid  of  contained  gases,  etc. ;  after 
which  it  is  poured  into  the  ladle  and  east 
into  ingots,  as  in  the  English  method. 

When  the  hammered  globules  show 
too  great  hardness,  the  blast  engine  is 
started  again,  and  the  vessel  again 
brought  to  the  upright  position,  for 
extra  blowing.  But,  so  nearly  accurate 
is  the  original  indication  of  the  spectro- 
scope, that  it  is  rarely  necessary,  in  cases 
of  insufficient  previous  blowing,  to  do 
more  than  merely  turn  the  vessel  up  and 
then  immediately  down  again,  in  order 
to  make  up  the  deficiency  ;  as  will  be 
shown  by  making  a  new  globule-test. 

But,  when  the  very  rare  ease  occurs. 


348 


VAN   NOSTRANDS   ENGINEERING   MAGAZINE. 


that  the  metal  has  been  blown  too  far, 
all  that  can  be  done  (unless,  indeed,  it 
is  possible  and  convenient  to  finish  up 
in  true  English  style)  is  to  add  a  small 
quantity  of  manganiferous  white  iron 
(generally  "  Schmalkaldner")  cold,  and 
then  blow  a  little  more,  till  the  spectro- 
scope warns  again  to  stop. 

The  use  of  the  spectroscope  in  the 
Zwickau  process  is  one  of  the  most 
beautiful  expedients  in  metallurgy, 
One  never  tires  watching  the  brilliant 
changes  in  the  spectrum,  blow  after 
blow.  The  specific  causes  of  these 
changes  have  been  the  subject  of  much 
dispute  and  unsatisfactory  investigation. 
But  all  are  agreed  that  carbon  has  some- 
thing to  do  with  them,  whether  as  such 
or  in  gaseous  form  in  such. nitrogenous 
compounds  as  cyanogen.  Whatever  be 
their  cause,  these  changes  takes  place, 
and  that  so  regularly  that  an  experi- 
enced eye  can  place  full  dependence 
upon  them  as  indicators  of  the  state  of 
preparation  of  the  metal-bath.  The 
spectrum  at  first  appears  without  lines  ; 
but,  as  soon  as  the  "  spark-period"  be- 
gins to  give  place  to  its  successor,  and 
the  clear  flame  to  extend  out  of  the 
mouth  of  the  converter,  the  bright 
orange-yellow  sodium-line  quickly  makes 
its  appearance,  and  remains  clearly  visi- 
ble till  the  blast  is  turned  off.  After  the 
sodium-line  appear  the  red  lines,  which 
represent  calcium  and  lithium  ;  and 
then  a  beautiful  series  of  perfectly 
graded  green  lines  in  the  green,  and 
pale-blue  lines  in  the  blue  section  of  the 
spectrum,  manifest  themselves,  one  after 
another,  each  in  its  series,  until,  at  the 
climax  of  the  operation,  when  the  great- 
est heat  is  attained,  the  spectrum  rivals 
that  of  chloride  of  copper  in  beauty  and 
brilliancy.  *A  very  experienced  eye  can 
also  sometimes  see  a  beautiful  violet  line 
in  the  violet  section  at  this  point. 

But  the  characteristic  lines  of  the 
Bessemer  spectrum  are  the  beautiful 
band-like,  graduated  series,  in  the  blue 
and  especially  in  the  green  section.  In 
the  inverse  order  to  that  in  which  they 
arose  to  their  climax,  these  lines  grad- 
ually diminish  in  brilliancy,  and  at  last 
vanish.  But  some  of  the  green  lines 
still  remain  after  the  blue  series  has  en- 
tirely vanished  ;  and  at  this  point  noth- 
ing must  be  allowed  to  distract  the  con- 
ductor   of    the    operation   from   closely 


watching  the  spectrum  ;  for  the  only  in- 
dex (though  a  perfect  one)  of  the  exact 
end  of  the  operation,  is  the  degree  of 
brilliancy  or  certain  green  lines,  which 
remain  when  the  charge  has  arrived  at 
the  point  of  desired  decarburization. 
For  different  mixtures  of  pig-iron,  a 
slight  difference  in  the  appearance  of  the 
indicating  green  lines  is  noticable  at 
this  point  ;  and  to  secure,  with  the  same 
mixture,  a  desired  slight  difference  in  the 
grade  of  steel  produced  in  two  different 
blows,  proper  allowance  must  be  made, 
on  one  or  other  side  of  a  certain  degree 
of  brilliancy  of  the  green  lines.  This  is 
merely  a  matter  of  experience,  and  any 
liability  to  risks,  in  producing  either  the 
same  grade  of  steel  with  different  mix- 
tures of  iron,  or  different  grades  with 
the  same  mixture,  is  always  counteracted 
by  the  subsequent  globule-test,  if  only 
the  conductor  of  the  operation  be  sure, 
when  making  either  of  the  above 
changes,  to  blow  his  charge  rather  too 
little  than  too  much. 

With  one  pair  of  five-ton  vessels  and 
three  cupolas,  the  ordinary  production 
in  Zwickau  is  twelve  to  fourteen  blows 
in  twenty-four  hours. 

The  ingots,  as  soon  as  they  shrink 
enough  to  be  removed  from  the  moulds, 
are  evenly  heated  in  a  gas  or  air-furnace, 
preparatory  to  being  hammered  by  a 
1 7^-ton  steam  hammer,  which  removes 
their  bevel,  and  reduces  them  to  a 
uniform  cross-section,  a  little  less  than 
the  size  of  their  original  smaller  end. 
There  is  no  doubt  that,  if  hammering 
previous  to  rolling  is  advantageous,  the 
tremandous  blows  of  that  massive  ham- 
mer are  of  great  advantage  to  these  in- 
gots. Each  bloom  is  weighed  and 
wheeled  to  the  rail- mill,  where,  after  re- 
heating, it  is  rolled  out  into  what  is 
called  a  "  platina."  One  platina  corres- 
ponds to  the  steel  heads  of  several  rails,, 
and  must  be  cut  up  into  a  corresponding 
number  of  pieces,  of  proper  length  for  a 
rail-packet.  The  platina  is  a  plate 
about  eight  and  a  half  inches  wide,  and 
one  inch  and  a  half  thick,  with  a  longi- 
tudinal central-flange  on  its  upper  sur- 
face of  a  little  more  than  one  square 
inch  cross-section.  Each  piece  of  platina 
constitutes  the  bottom  of  a  rail-packet 
(the  flange  lying  uppermost),  and  granu- 
lar iron,  flat  rolled  pieces  of  old  steel- 
headed   rails,   etc.,   and   piled  upon,  it, 


MECHANICAL   CHANGES    IN   BESSEMER   STEEL. 


349 


on  each  side  of  its  flange  ;  and  lastly  a 
fibrous  iron  platina  without  a  flange, 
makes  a  top  for  the  packet  and  secures 
a  tough  bottom  for  the  rail.  The  pack- 
ets are  brought  to  a  bright  welding 
heat,  in  ordinary  reheating-furnaces,  and 
then  rolled,  in  two  heats,  into  rails, 
there  being  twelve  passes  in  the  final 
.heat.  The  welding  is  perfect,  and  the 
fracture  of  a  finished  rail  shows  a  head 
completely  of  steel  resting  on  two 
shoulders  of  granular  iron,  while  a 
tongue  of  steel,  corresponding  to  the 
platina  flange,  extends  from  the  head 
one-third  of  the  way  down  the  upright 
of  the  rail,  penetrating  it  like  a  wedge. 
But  the  bottom  of  the  rail  shows  a 
beautiful  fibrous  fracture. 

The  use  of  crop-ends  of  steel-headed 
rails  and  pieces  of  broken-up  old  rails  of 
the  same  kind,  as  components  of  the 
rail-packets,  is  worthy  of  notice.  These 
jneces  are  first  rolled  out  as  flat  as  the 
case  requires,  and  two  lengths  are  usually 
employed  in  each  packet.  But,  as  the 
steel  will  not  weld  to  itself,  care  is  taken 
to- lay  these  pieces  so  that  the  head  of 
one  piece  lies  against  the  fibrous  iron 
bottom  of  the  other,  while  a  layer  of 
granular  iron  always  separates  the 
platina  from  all  parts  of  these  old  rail- 
sections.  The  crop-ends  of  the  platinas, 
and  those  rail  crop-ends  not  long  enough 
for  convenient  use  in  the  rail-packets, 
are  generally  rolled  into  rail-straps 
{"  laschen"),  or,  if  they  are  very  small, 
they  are  used  cold,  as  occasion  requires, 
to  cool  down  the  metal,  in  too  hot  blows, 
previous  to  casting. 

This  utilization  of  old  rails  and  crop- 
ends  enables  the  managers  to  dispense 
with,  the  use  of  a  Siemens-furnace  for 
working  up  their  steel-scrap  ;  although 
this  was  contemplated,  and  an  agreement 
made  with  Mr.  Siemens,  by  which  Mr. 
Jones,  of  Wales,  was  sent  to  Zwickau, 
to  assist  in  the  arrangement  and  take 
charge  of  the  starting  of  a  gas-furnace 
for  the  manufactui-e  of  Siemens-Martin 
.  steel.  The  plan  was,  for  the  time,  given 
up,  and  Mr.  Jones  (who  has  since,  with 
me,  constructed  and  is  now  running  a 
'Siemens-furnace,  with  the  latest  improve- 
ments, near  Providence,  R.  I.)  was, 
while  the  matter  was  in  abeyance,  given 
-charge  of  the  furnaces  where  the  steel 
ingots  are  heated  for  the  hammer.  I 
was    at   that    time    (1871),  through  the 


kmdness  of  Herr  von  Lilienstern,  the 
general  superintendent,  allowed  the  free 
run  of  the  works  as  a  "  volunteer  ;"  and 
thus  Mr.  Jones  and  I  were*enabled  to 
try  experiments  with  the  steel,  aided  by 
such  useful  auxiliaries  as  some  very  hot- 
air  furnaces  and  a  IV^-ton  steam-ham- 
mer. 

The  experiments  to  be  here  recorded 
had  to  do  with  an  investigation  into  the 
effects  of  heat  upon  hammered  steel. 

We  found  that  the  thoroughness  of 
the  hammerinof  had  nothing  to  do  with 
the  coarseness  or  fineness  of  the  grain  of 
steel,  provided  the  hammered  piece  were 
subsequently  exposed,  for  any  protracted 
period,  to  a  very  high  heat.  I  was,  at 
the  time,  preparing  a  Zwickau  collection 
for  the  metallurgical  cabinet  of  the  Xew 
York  School  of  Mines,  and  it  occurred 
to  me  to  illustrate  this  property  of  steel 
by  a  series  of  samples.  We  took  a 
small  test-ingot,  and,  after  heating  it  as 
high  as  the  ingots  are  usually  heated 
for  hammering,  hammered  it  out  from 
its  original  size  of  3  inches  square  into  a 
bar  about  l^  inches  square.  The  grain 
was  then  very  fine  throughout,  just  as 
in  the  ordinary  hammered  samples  taken 
from  every  blow.  The  bar  was  then 
put  into  the  furnace  again  and  left  from 
two  to  three  hours  exposed  to  a  heat 
not  quite  as  high  as  that  at  which  the 
steel-headed  rail-packets  are  rolled.  It 
was  then  taken  out  of  the  furnace,  and, 
as  its  outside  now  shows,  was  hammered 
for  only  one-half  of  its  length  and  then 
bent  up  into  a  horseshoe-shape,  so  that 
its  two  ends  could  be  viewed  side  by 
side.  There  were  only  four  blows  of  the 
hammer  given  to  it — one  on  each  side  ; 
and  yet,  when  enough  of  each  end  was 
broken  off  to  show  the  interior  structure 
of  the  two  halves,  a  most  astounding 
contrast  presented  itself.  The  end  not 
hammered  since  reheating  had  a  much 
coarser  and  much  more  distinctly  crys- 
talline structure  than  even  the  coarsest 
of  large  unhammered  Bessemer  ingots. 
while  the  rehammered  end  was  just  as 
fine  in  grain  as  the  whole  hammered  bar 
had  been  before  reheating.  The  fracture 
of  the  unrehammered  part  resembled, 
indeed,  more  than  anything  else,  that  of 
galena  of  the  same  degree  of  coarseness. 
This  specimen,  with  its  two  contiguous 
fractured-ends,  can  be  seen  at  any  time 
in    the' ,  metallurgical    cabinet    of     the 


350 


van  nostrand\s  engineering  magazine. 


School  of  Mines,  together  with  samples 
of  hammered  and  unhammered  ingots 
(with  which  to  compare  it,  as  to  grain), 
a  section  of  platina,  and  one  piece  of  a 
steel-headed  rail,  from  Zwickau,  beauti- 
fully showing  by  fracture  the  interior 
structure,  with  the  wedge-like  penetra- 
tion of  the  steel-head  into  the  iron  body 
of  the  rail,  and  the  exceedingly  fibrous 
quality  of  the  rail-bottom.  The  practi- 
cal bearing  of  the  facts  proved  by  these 
samples  is  of  more  importance  than  may 
at  first  appear. 

If  we  apply  them  to  the  rail  manu- 
facture at  Zwickau,  the  question  imme- 
diately arises  :  "Of  what  real  benefit  is 
the  use  of  a  steam-hammer  there  for 
blooming  the  steel  ingots  ?"  As  every- 
body knows,  they  could  be  brought 
down  to  shape  at  much  less  expense  by 
a  pair  of  rolls,  as  in  many  other  works 
in  this  country  and  abroad.  But  assum- 
ing that,  of  a  hammered  and  a  rolled 
bloom,  drawn  down  to  the  same  size  and 
shape  from  two  similar  steel  ingots,  the 
former  has  a  much  more  compact  struc- 
ture than  the  other,  it  does  not  by  any 
means  surely  follow  that  the  same  or  an 
analogous  difference  will  exist,  after  the 
two  blooms  have  been  similarly  heated, 
till  they  are  soft  enough  to  roll  out  into 
platinas. 

But,  even  if  experiment  should 
prove  such  a  difference,  can  it  be  sup- 
posed that  its  effects  would  be  in  any 
measure    apparent    in    the    final    steel- 


headed  rails  made  from  these  two  differ- 
ent platinas?  It  seems  to  me  that  each 
of  the  two  platinas  would,  just  before 
the  rolling  of  the  rail-packet,  have  the 
same  coarse  structure  that  we  see  in  the 
unrehammered  section  of  our  horseshoe- 
shaped  sample,  however  great  the  differ- 
ence in  grain  may  have  been  previous  to 
their  exposure  to  the  welding-heat. 
This  can  fairly  be  assumed  from  the 
fact  that  the  specimen  referred  to  was 
not  exposed  to  a  greater  than  a  welding 
heat. 

The  application  of  this  subject  to  the 
manufacture  of  all-steel  rails  can  be 
satisfactorily  determined  only  by  still 
further  experiment  ;  because  the  tem- 
perature at  which  these  are  rolled  is  less 
then  a  welding-heat,  and  also  the  thick- 
ness of  the  blooms,  when  they  last,  leave 
the  reheating-furnace,  is  much  greater 
than  that  of  the  platinas  at  Zwickau, 
and  this  would  probably  partly  counter- 
act the  crystallizing  effect  of  the  heat. 
Such  further  experimentation  would  do 
much  to  throw  light  upon  the  discussion 
so  ably  carried  on  before  the  Institute, 
about  a  year  ago,  by  Messrs.  Holley  and 
Pearse,  upon  this  same  subject  of 
"  Hammer  or  No  Hammer  ?"  These 
gentlemen  have  it  in  their  power  to  seek, 
in  a  comparatively  untried  field,  for  a 
ratifying  test  of  the  correctness  of  their 
theories  on  this  subject,  and  it  is  sin- 
cerely to  be  hoped  that  such  a  course 
will  be  pursued. 


THE  CONSUMPTION  OF  IRON  PER  CAPITA. 

From  the  Bulletin  Iron  and  Steel  Association. 


Bv  the  phrase,  "  consumption  of  iron," 
is  meant  the  utilization  of  iron  in  its  raw 
or  unworked  state,  as  pig  iron,  blooms 
made  direct  from  the  ore,  castings  direct 
from  the  blast  furnace,  and  scrap  iron. 
"We  include  scrap  iron  (by  which  phrase 
we  mean  all  old  iron)  because  whenever 
used  it  displaces  at  least  its  own  weight 
of  pig  iron  or  blooms.  If  it  were  not 
used,  these  would  be.  Correctly  speak- 
ing, iron  is  never  consumed.  Its  quan- 
tity may  be  slightly  diminished  by  wear 
and  tear  and  by  the  action  of  the  ele- 
ments, but  it  is  never  wholly  lost.  It 
can  not  be  eaten  like  bread,  nor  burned 


like  wood.  In  consuming  or  utilizing 
iron,  therefore,  after  its  conversion  from 
the  ore,  we  merely  change  its  form.  In 
an  inquiry  into  the  consumption  of  iron 
by  a  nation,  the  object  should  be  to  as- 
certain how  much  pig  iron  or  its  equiva- 
lent is  required  to  meet  the  industrial 
wants  of  that  nation.  If  we  aim  to  as- 
certain the  annual  consumption  of  iron 
by  that  nation,  evidently  the  quantity  of 
iron  actually  consumed  in  any  year  can 
not  be  decreased  upon  the  pretext  that 
a  portion  of  it  had  been  used  ten  or 
twenty  years  before  and  cast  aside  after 
it  ceased  to  be  of  service.     The  accept- 


THE   CONSUMPTION    OF   IRON   PER   CAPITA. 


351 


ance  of  this  proposition  would  not  lead 
to  correct  results. 

In  the  able  and  exhaustive  report  on 
The  Production  of  Iron  and  Steel,  by 
the  Hon.  Abram  S.  Hewitt,  United 
States  Commissioner  to  the  Paris  Uni- 
versal Exposition  of  1867,  there  occurs 
the  following  estimate  of  the  consump- 
tion of  iron  per  capita  in  all  countries  at 
that  time  : 

"  Allowing  for  the  production  in  bar- 
barous countries,  and  something  for  the 
use  of  scrap  iron,  it  may  be  stated  in 
round  numbers  that  the  production,  and 
consequently  the  consumption  of  the 
world,  has  reached  9,500,000  tons  of 
2,240  pounds  each,  or  21,280  millions  of 
pounds  ;  so  that  if  the  population  of 
the  world  has  reached  1,000  millions  the 
consumption  is  a  little  over  20  pounds  of 
iron  per  head.  A  careful  calculation, 
after  allowing  for  the  iron  exported, 
shows  that  the  consumption  per  head  in 
England  is  189  pounds  of  iron.  The 
consumption  in  Belgium  has  reached 
about  the  same  limits.  The  consumption 
in  France  is  69|.  pounds  per  head,  and  in 
the  United  States  not  far  from  100 
pounds  per  head.  If  the  industry  of  the 
whole  world  were  as  thoroughly  devel- 
oped as  in  Great  Britain,  the  consumption 
of  iron  would  reach  nearly  90,000,000 
tons  per  annum.  If  brought  to  the 
standard  of  the  United  States,  a  little 
less  than  50,000,000  tons  per  annum 
would  answer  ;  or  if  to  that  of  France, 
a  little  over  30,000,000  tons  would  be 
required  ;  figures  to  be  increased  further 
by  the  steady  increase  of  population  in 
the  world." 

Since  this  estimate  was  made,  statistics 
show  that  the  world's  annual  production 
of  iron  has  increased  from  9,500,000 
gross  tons  in  1867  (Mr.  Hewitt's  figures) 
to  15,000,000  tons  in  1874.  Theincrease 
of  the  population  of  the  globe  has  cer- 
tainly not  kept  pace  with  this  increase 
in  production  ;  consequently  the  con- 
sumption per  capita  has  increased.  It 
was  probably  over  30  pounds  in  1874, 
against  21  pounds  in  1867,  as  estimated 
by  Mr.  Hewitt.  Making  no  allowance 
for  the  use  of  scrap  iron,  an  estimated 
population  of  1,100  millions  in  1874  will 
give  in  the  total  product  of  cast  or  pig 
iron  in  that  year  exactly  30A  pounds 
consumption  per  capita.  This  increased 
consumption  is  easly  explained  by  the 


increased  demand  during  the  past  few 
years  for  iron  for  railways,  iron  ship-, 
iron  bridges,  iron  buildings,  iron  pipe, 
and  other  comparatively  new  uses  of 
iron.  This  stimulus  to  the  consumption 
of  iron  has,  however,  been  sensibly  weak- 
ened in  most  countries  since  the  autumn 
of  1873,  when  the  American  panic  oc- 
curred, and  it  is  not  at  all  an  open  ques- 
tion whether  the  world's  consumption  of 
iron  will  increase  in  the  same  proportion 
during  the  decade  which  began  with  1874 
as  during  the  decade  which  then  ended. 
It  will  not.  The  depressing  effects  of 
the  financial  revulsion  which  has  affect- 
ed many  countries  besides  our  own  will 
restrict  this  consumption  for  some  time 
to  come,  particularly  in  the  interruption 
to  the  building  of  railways.  The  exten- 
sive substitution  of  steel  rails  for  less 
durable  iron  rails,  and  the  strong  tend- 
ency to  substitute  steel  for  iron  in  many 
other  forms,  will  necessarily  lessen  the 
demand  for  pig  iron.  The  increased  at- 
tention now  given  to  the  reworking  of 
scrap  iron,  especially  in  this  country, 
while  not  in  a  strict  sense  affecting  the 
consunqHion  of  iron,  will  also  reduce 
the  demand  for  pig  iron.  Finally,  the 
occurrence  of  great  wars  is  one  of  the 
most  powerful  influences  in  stimulating" 
the  use  of  iron,  and  it  is  scarcely  pos- 
sible that  Europe  and  America  can  be 
convulsed  during  the  decade  upon  which 
we  have  just  entered  by  such  violent 
and  destructive  struggles  as  the  past  few 
years  have  witnessed. 

The  consumption  of  iron  per  capita 
in  the  United  States  is  placed  by  Mr. 
Hewitt  at  100  pounds  in  1867.  Without 
inquiring  into  the  basis  of  Mr.  Hewitt** 
calculation,  we  proceed  to  inquire  wheth- 
er the  per  capita  consumption  of  iron  by 
this  country  has  since  advanced  beyond 
his  estimate,  and  if  so,  how  much.  We 
will  first  take  the  census  year  IS 70.  for 
which  more  detailed  and  reliable  data 
exist  than  for  any  subsequent  year. 
From  the  census  report  and  the  statistics 
of  the  Treasury  Department  we  have 
compiled  the  following  table,  showing 
the  quantity  of  pig  iron  or  its  equivalent 
which  was  actually  used  in  the  census 
year  : 

Net  tons. 
Production  of  pitr  iron  in  the  census 

year  1809-70. .. 3,052,831 

Consumption  of  domestic  and   im- 
ported scrap  iron,  in  the  census 


352 


VAN   NOSTRANDS    ENGINEERING   MAGAZINE. 


year,  in  the  manufacture  of 
1,350,663  tons  of  rolled  iron, 
1,115,000  tons  of  castings,  103,288 
tons  of  forgings,  110,808  tons  of 
blooms,  and  30,354  tons  of  steel. .        630,442 

Importation  of  pig  iron  in  the  fiscal 
year  1869-70,  corresponding  very 
closely  to  the  census  year 171,677 

Importation  of  419,924  net  tons  of 
rails,  bar  iron,  castings,  and  forg- 
ings, in  the  fiscal  year  1869-70, 
in  approximate  tons  of  pig  iron. .       493,685 


Total  quantity  of  iron  made  in  the 
United  States  and  imported  in  the 
census  year  1869-70 3,348,625 

Deduct  1,557  tons  of  pig  iron  ex- 
ported from  the  United  States  in 
the  fiscal  year  1869-70,  and  5,500 
tons  of  pig  iron  worked  into  fin- 
ished iron,  exported  in  same  year  7,057 

Quantity  of  iron  actually  used  in  the 

United  States  in  the  census  year 
1869-70,  the  quantity  held  in  stock 
at  the  close  of  the  year  being  esti- 
mated as  equal  to  that  carried 
over  from  the  preceding  year 3,341,568 


The  3,341,568  net  tons  of  iron  con- 
tained 6,683,136,000  pounds,  which,  if 
divided  by  38,925,598,  the  total  popu- 
lation of  the  United  States  in  the  census 
year,  give  171  pounds  as  the  per  capita 
consumption  in  that  year.  This  result 
is  so  much  more  gratifying  to  our 
national  pride  than  that  reached  by  Mr. 
Hewitt  only  four  years  before  the  taking 
of  our  last  census,  that  we  were  ourselves 
astonished  by  it,  and  we  therefore  give 
in  entire  frankness  in  the  above  table 
the  process  by  which  it  was  reached. 

The  year  1872  was  probably  the  year 
of  greatest  activity  in  the  consumption 
of  iron  in  this  country.  It  was  the  year 
of  the  iron  famine,  when  production  and 
consumption  were  both  stimulated  to 
the  utmost.  In  the  following  statement 
we  have  endeavored  to  ascertain  the 
quantity  of  raw  and  scrap  iron  used  in 
that  year.  The  elements  of  the  calcula- 
tion are  the  same  as  those  which  were 
employed  in  ascertaining  the  consump- 
tion in  the  census  year,  but  some  of  the 
data  are  necessarily  estimated.  In  the 
certain  data  we  have  the  production  for 
the  year  of  pig  iron,  blooms,  and  steel, 
and  the  imports  and  exports  of  iron  of 
all  kinds  ;  while  in  the  estimated  data 
we  have  the  stocks  of  pig  iron  on  hand 
at  the  beginning  and  end  of  the  year, 
the  quantity  of  cast  iron  produced  by 
the  foundries,  the  quantiy  of  scrap  iron 
used,  and  the  production  of  rolled  and 


forged  iron  except  rails.  The  quantity 
of  cast  iron  and  other  estimated  iron 
products  is  obtained  by  assuming  that 
the  output  of  the  foundries,  bar  mills, 
etc.,  had  increased  from  1870  to  1872  in 
the  same  proportion  as  that  of  the  rail 
mills,  which  is  definitely  known.  To  as- 
certain the  quantity  of  scrap  iron  con- 
sumed in  obtaining  all  these  products, 
including  rails,  we  have  assumed  that 
in  1872  the  proportion  of  scrap  to  each 
of  these  products  was  the  same  as  in 
1870.  According  to  the  census  returns, 
one-third  of  all  the  iron  forged  and 
rolled  in  the  census  year,  one-eighth  of 
the  pig  and  scrap  blooms,  one-eighth  of 
the  castings,  and  one-fourth  of  the  cast 
steel  were  made  of  scrap  iron.  With 
these  explanations  we  submit  the  state- 
ment of  aggregate  consumption  in  1872  : 

Net  tons. 
Production  of  pig  iron  in  1872.  . . .  2,854,558 
Consumption  of  domestic  and  im- 
ported scrap  iron  in  the  manufac- 
ture of  1,941,922  tons  of  rolled 
and  forged  iron,  28,000  tons  of  pig 
and  scrap  blooms,  1,800,000  tons 
of  castings,  and  35,000  ton  of  cast 

steel  in  1872 - 884,581 

Production  of  blooms  from  ore  in 

1872 ' 30,000 

Importation  of  pig  iron  in  1872 295,967 

Importation  of  643,639  tons  of  rails 
and  other  rolled  iron,  5,875  tons 
of  forging,  and  407  tons  of  cast- 
ings in  1872,  in  approximate  tons 
of  pig  iron 764,197 

Total  pig  and  scrap  iron  made  and 
imported  in  1872 ■  4,829,303 

Deduct  1,477  tons  of  pig  iron,  and 
5,203  tons  of  pig  iron  worked 
into  finished  iron,  exported  in 
1872 6,680 

Deduct  the  estimated  excess 
of  production  of  pig  iron 
over  consumption  in  1872   300,000       306,680 

Total  consumption  of  pig  and  scrap 
iron  and  blooms  by  the  United 
States  in  1872 4,522,623 


The  above  4,522,623  net  tons  of  iron 
contained  9,045,246,000  pounds.  The 
population  of  the  United  States  in  1872 
we  estimate  at  40,500,000.  These  fig- 
ures give  us  223  pounds  as  the  per  capita 
consumption  of  iron  in  the  United  States 
in  1872.  The  increase  in  our  consump- 
tion of  iron  per  capita  from  1870  to  1872 
was  the  difference  between  171  and  223 
pounds,  namely,  52  pounds,  or  over  30 
per  cent.     This  increase  in  two  years  is 


WATER   SUPPLY   AND   DRAINAGE. 


353 


marvelous,  but  it  must  be  remembered 
that  1871  and  1872  were  themselves 
marvelous  years.  If  our  premises  in  the 
two  calculations  we  have  made  be  ac- 
cepted, no  other  results  than  those 
reached  are  possible. 

The  consumption  of  iron  per  capita 
in  the  United  Kingdom  of  Great  Britain 
and  Ireland  is  stated  by  Mr.  Hewitt  to 
have  been  189  pounds  in  1867.  It  has 
since  increased.  Without  making  any 
allowance  for  the  large  consumption  of 
scrap  iron  in  that  country,  which  has 
never  been  definitely  ascertained,  and 
which  it  is  impossible  accurately  to  es- 
timate, we  obtain  from  the  production 
of  pig  iron  alone,  as  will  be  seen  by  the 
following  itemized  statement,  a  larger 
per  capita  consumption  in  1872  than  in 
1867. 

Gross  tons. 

Production  of  pig  iron  in  1872 6,741,929 

Deduct  1,332,726  gross  tons  of  pig 
iron,  296,575  tons  of  castings,  and 
1.974,236  tons  of  rolled  and  forg- 
ed iron  and  steel,  exported  to 
other  countries,  in  approximate 
tons  of  pig  iron , .    3,603,537 


Left  for  home  consumption  3, 138,392 

These  3,138,393  gross  tons  of  pig  iron 
give  us  7,029,998,080  pounds,  which,  di- 
vided by  31,817,108,  the  population  of 
the  United  Kingdom  in  1871,  show  a 
product  of  220  pounds  as  the  per  capita 


consumption  of  iron  in  1872.  We  have 
not  taken  into  consideration  the  incon- 
siderable imports  of  iron  in  that  year, 
which  would  add  very  slightly  to  the 
consumption.  The  scrap  iron  consum- 
ed would  largely  increase  it. 

The  figures  given  and  the  facts  which 
we  have  made  no  attempt  to  reduce  to 
figures  point  to  a  much  larger  per  capita 
consumption  of  iron  in  Great  Britain  in 
1872  than  in  this  country.  But  we  are 
not  prepared  to  accept  this  conclusion. 
A  very  large  portion  of  the  iron  retained 
in  Great  Britain  for  home  consumption 
is  converted  into  iron  ships,  machinery, 
hardware,  cutlery,  etc.,  for  sale  to  other 
countries.  These  iron  and  steel  pro- 
ducts should  properly  not  be  confounded 
with  like  products  which  are  permanent- 
ly retained  in  the  country.  In  the  Unit- 
ed States,  however,  so  comparatively 
small  are  our  exports  of  machinery,  etc., 
and  so  nearly  are  they  balanced  by  our 
imports  of  similar  commodities,  that  it 
is  fair  to  assume  that  all  of  the  iron 
nominally  retained  here  is  actually  con- 
sumed by  our  own  people. 

We  shall  never  know  the  exact  facts 
of  per  capita  consumption  of  iron  in  any 
country.  The  foregoing  calculations 
and  deductions  are  submitted  as  the  re- 
result  of  a  careful  inquiry  into  the  prob- 
able consumption  by  the  world,  the 
United  States  and  Great  Britain. 


WATER  SUPPLY  AND  DRAINAGE.* 

By  W.  A.  CORFIELD,  Esq.,  M.A.,  M.D. 
III. 


SEWERS    AND    SEWERAGE    SYSTEMS. 


The  water  is  brought  into  the  town  to 
be  soiled,  and  it  must  be  removed  ;  and 
besides  this  dirty  water  which  has  to  be 
removed,  there  is  the  surface  water,  and 
the  subsoil  water  that  have  to  be  re- 
moved also  ;  together  with  a  quantity  of 
refuse  of  all  sorts,  with  various  impuri- 
ties from  manufactories,  from  slaughter- 
houses, from  animal  sheds,  together  with 
slops  from  private  houses,  and  so  on. 
This  impure  water  is  carried  away  from 
towns  by  means  of  pipes,  known  as  sew- 


*  Abstract  of  lectures  delivered  before  the  School  of 
Military  Engineering  at  Chatham. 

Vol.  XIII.— No.  4—23 


ers,  and  I  want  at  once  to  explain  to  you 
in  a  few  words,  the  difference  that  is  to 
be  kept  in  sight  between  a  sewer  and  a 
drain.  A  sewer  is  a  pipe  for  removing 
impure  water,  water  that  has  been 
fouled  ;  a  drain,  as  Mr.  Bailey  Denton 
said  in  a  letter  to  the  Times,  is  meant  to 
take  the  wetness  out  of  soil  ;  it  is  meant 
to  dry  the  soil — it  is  not  meant  to  carry 
away  impure  water. 

As  these  sewers  are  to  carry  away  im- 
pure water,  it  is  perfectly  plain  they 
must  be  impervious  to  water,  or  they 
may,   on  certain   occasions,   let    it   leak 


354 


VAN  NOSTRAND'S   ENGINEERING  MAGAZINE. 


out  into  the  subsoil  of  the  town  under- 
neath the  houses,  and  also  into  the  wells, 
if  there  are  any.  If  they  are  impervious, 
the  water  of  the  soil,  the  subsoil  water 
at  any  rate,  won't  get  into  them  and  so 
they  will  not  act  as  drains.  Now  you 
will  see  directly  why  it  is  necessary  to 
drain  the  subsoil  underneath  the  streets 
and  houses.  That  it  is  necessary  I  can 
show  you  in  a  half  a  minute. 

It  has  been  perfectly  clearly  shown 
by  Dr.  Buchanan,  from  statistics  of  the 
death-rate  of  certain  towns  that  have 
been  sewered,  that  in  those  towns  which 
have  had  sewers  so  constructed  that  the 
subsoil  water  of  the  town  has  been 
lowered,  the  death-rate  from  consump- 
tion has  increased  in  a  most  extraordi- 
nary manner.  In  the  case  of  certain 
towns  the  death-rate  from  consumption 
has  been  reduced  by  half  the  total  num- 
ber of  deaths,  by  50  per  cent,  by  the 
lowering  of  the  subsoil  water  consequent 
upon  sewering  the  town  as  it  is  called. 
But  these  sewers  were  so  .constructed 
that  they  acted  as  drains  as  well. 
Towns  which  have  been  sewered  with 
impervious  pipes  throughout,  so  that  no 
reduction  of  the  subsoil  water  had  been 
effected  have  shown  no  decrease  in  the 
death  rate  from  consumption,  and  some 
have  shown  an  increase.  So  that  shows 
you  that  it  is  necessary  to  drain  the  sub- 
soil. 

Then  from  the  incompatibility  of  hav- 
ing pipes  which  both  drain  the  subsoil 
and  are  impervious,  so  as  not  to  allow  of 
the  sewage  to  escape  from  them,  it  has 
been  suggested  to  have  two  systems — to 
have  drains  and  sewers.  Mr.  Menzies 
has  been  the  great  advocate  of  having 
what  is  called  the  separate  system.  His 
plan  was  to  have  deep  sewers,,  pipe  sew- 
ers., which  are  impervious,  and  then 
rather  superficial  drains  to  carry  off  the 
flood  waters.  This  plan  would  not  pro- 
vide for  actually  draining  the  subsoil 
unless  some  special  provision  were  made 
for  it.  The  usual  plan  that  is  practised 
is  to  build  sewers  large  enough  to  con- 
tain all  the  drainage  water  and  any 
reasonable  amount  of  storm  water  that 
may  fall  upon  the  land  which  is  sewered, 
but  it  is  perfectly  ridiculous  to  use  them 
for  intercepting  natural  watercourses,  as 
is  done  in  so  many  cases. 

Some  sewers  in  the  South  of  London 
actually    collect     water     from    natural 


watercourses  which  ought  to  be  allowed 
to  run  straight  into  the  Thames.  The 
argument  for  admitting  this  extra 
amount  of  water  into  sewers  is  that  they 
will  be  kept  cleaner,  and  that  they  will 
flush  themselves  naturally,  as  it  were. 
But  against  this  is  to  be  placed  the  diffi- 
culty of  dealing  with  the  increased 
amount  of  water  at  the  outfall.  I  may 
speak  to  you  of  that,  however,  bye  and 
bye. 

Now  for  laying  main  sewers  you  must 
have  accurate  plans  of  the  places,  with 
the  levels  of  the  surface  along  the  roads 
and  the  streets,  and  the  levels  of  the 
deepest  cellars,  so  that  the  sewer  of  the 
street  may  always  be  below  the  level  of 
the  lowest  cellers.  You  must  also  know 
the  levels  of  high  and  low  tides,  if  near 
to  the  sea.  The  general  plan,  according 
to  Mr.  Rawlinson,  ought  to  be  made  on 
a  scale  of  two  feet  to  a  mile,  and  the  de- 
tailed plan  on  one  of  ten  feet  to  a  mile. 

I  am  now  going  to  refer  you  to  an 
important  discussion  that  took  place  be- 
fore the  Institution  of  Civil  Engineers  in 
1862  and  1863.  You  will  find  it  in  Vol. 
22  of  the  Proceedings  of  the  Institution 
of  Civil  Engineers.  I  shall  have  to  refer 
to  this  discussion  several  times.  The 
first  point  to  be  attended  to  in  laying 
out  main  sewers  is  that  they  shall  be 
straight  from  point  to  point.  There  is 
no  reason  that  they  should  follow  ex- 
actly the  middle  of  the  streets  where 
they  are  not  straight,  but  they  should 
be  made  straight  from  one  point  to  the 
next.  The  curves  should  be  gentle,  not 
greater  than  22^  degrees,  for  instance. 
The  junctions  should  be,  as  in  the  case 
of  the  main  water  pipes,  curved.  Ran- 
kin e  tells  us  that  main  sewers  should  not 
be  less  than  two  feet  broad,  and  that 
the  velocity  in  them  should  not  be  less 
than  one  foot  in  a  second,  for  fear  of 
choking  up,  nor  greater  than  four  feet 
and  a  half  in  a  second,  because  with  a 
greater  velocity  than  this  you  have  too 
much  scouring.  The  usual  plan,  then, 
is  to  make  these  drain  sewers,  as  I  call 
them,  sewers  which  are  capable  to  a  cer- 
tain extent  of  acting  as  drains  also. 
That  end  is  often  realized  by  setting 
the  bricks  of  the  invert,  as  it  is  termed, 
in  cement,  and  setting  the  others  with 
mortar.  The  bricks  of  sewers  ought  al- 
ways to  be  set  in  hydraulic  mortar  or 
in  cement.     These  drain  sewers,  I  should 


WATER   SUPPLY   AND   DRAINAGE. 


355 


tell  yon,  are  on  the  plan  of  the  oldest 
sewer  we  know  of,  namely  the  Cloaca 
Maxima  in  Rome.  That  Cloaca  Maxima 
was  not  constructed  as  a  sewer  :  it  was 
originally  a  drain.  A  great  deal  of 
blame  has  been  thrown  upon  the  Romans 
because  the  Cloaca  Maxima  was  not 
made  impervious  ;  but  we  must  remem- 
ber it  was  originally  constructed  as  a 
drain.  It  was  formed  to  drain  off  the 
water  about  the  Forum,  and  it  did 
so,  -  and  does  so  to  this  day.  It  only 
came  afterwards  to  be  used  as  a  sewer, 
that  is  to  say,  to  have  refuse  matter 
thrown  into  it,  and  that  is  no  doubt  how 
Ave  have  got  our  system  of  drain  sewers, 
and  there  is  no  doubt  that  the  sewers  in 
many  towns  in  England  were  originally 
built  as  drains. 

The  first  thing  to  mention  is  the 
trench.  Mr.  Rawlinson  tells  us,  in  a 
paper  that  I  have  already  quoted  to  you, 
and  which  is  entitled  "  Suggestions  as  to 
plans  for  main  sewerage  and  drainage," 
that  the  most  difficult  earth  to  deal  with 
is  quicksand,  and  as  a  rule  it  should  only 
be  opened  in  short  lengths.  The  trench 
may  require  to  be  close  timbered  ;  and 
in  all  cases  the  greatest  care  should  be 
exercised  in  taking  the  timbers  from  the 
sides  of  the  trenches  so  that  none  of  the 
side  earth  may  fall  down  upon  the  sew- 
ers. 

With  regard  to  the  depth  of  the 
trenches,  of  course  this  must  vary  very 
much  in  different  places.  The  only  con- 
dition is  that  they  require  to  be  placed 
deep  enough  to  drain  all  the  cellars.  I 
may  mention,  as  an  example,  that  at 
Stratford-on-Avon  the  sewers  are  con- 
structed from  16  feet  deep  down  to  4  or 
5  feet  in  many  other  parts.  At  Rugby 
they  average  11  feet  in  depth,  but  they 
vary  from  7  to  25  feet.  One  of  those 
papers  that  I  quoted  to  you  from  the 
Proceedings  of  the  Institution  of  Civil 
Engineers  (Vol.  xxii.,  p.  265),  says,  that 
the  average  depth  is  12  feet,  but  that 
the  depths  vary  much.  Tunneling  may 
be  required,  as  practised  now  in  the 
large  outfall  sewer  being  constructed  at 
Brighton.  Tunneling,  however,  should 
never  be  resorted  to  when  it  can  be 
helped,  because  much  better  supervision 
can  be  exercised  over  the  construction 
of  a  sewer  when  you  have  a  trench  than 
if  you  have  a  tunnel.  This  is  perfectly 
clear,    and   also   for   the    same    reason, 


night  work  should  not  be  encouraged  : 
the  men  should  work  in  the  day  time. 

Now  as  to  the  incline.  The  incline, 
we  are  generally  told,  should  not  be  less 
than  1  in  600.  Sometimes,  of  course, 
that  cannot  be  got.  The  incline  must 
vary  very  much  with  the  natural  incline 
of  the  soil.  If  possible,  you  should 
have  it  about  1  in  600  in  mains,  and  a 
greater  incline  in  the  smaller  sewers,  and 
the  greatest  incline  in  the  house  sewers. 
The  incline  of  the  pipe-sewers  that  come 
from  the  houses  should  not  be  less  than 
1  in  60.  Where  sewers  are  joined  the 
incline  should  be  greater.  Where  a 
small  sewer  enters  into  a  large  one  there 
should  be  a  quicker  incline  for  some  little 
distance. 

Another  point  is  this — that  a  larger 
sewer  should  never  open  into  a  smaller 
one  ;  neither  should  a  sewer  open  into 
one  of  the  same  size,  but  always  a  small- 
er one  into  a  larger  one.  The  inverts 
should  not  be  level.  The  invert  of  a 
smaller  one  should  be  higher  up  than 
that  of  the  larger  one,  so  that  there  may 
be  a  fall.  "  Main  sewers  and  drains 
should  be  adapted,"  as  Mr.  Rawlinson 
says,  "  to  the  town  area,  length  of  streets, 
number  of  houses,  surface  area  of  house 
yards  and  roofs,  number  of  street  gullies, 
and  volume  of  water  supply," 

With  regard  to  the  size  and  shape  of 
the  main  sewers.  The  size  is,  of  course, 
very  variable  indeed.  I  told  you  that 
Professor  Rankine  said  they  should  not 
be  less  than  2  feet  broad.  They  are 
often  made  less  than  two  feet  broad. 
Perhaps  the  best  thing  is  to  give  you  an 
example.  It  is  taken  from  a  discussion 
in  the  volume  of  the  Proceedings  of  the 
Institution  of  Civil  Engineers,  which  I 
referred  to  a  few  moments  back.  Mr. 
Newton  said  that  "In  purely  urban  dis- 
tricts a  rainfall  of  one  inch  in  half  an 
hour  ought  to  be  provided  for  ;  thus,  on 
the  29th  July,  1857,  he  registered  at 
Preston  three  quarters  of  an  inch  of  rain 
in  35  minutes,  and  on  the  Sth  October, 
1861,  nearly  the  same  depth  in  30  min- 
utes. On  the  latter  occasion  an  egg- 
shaped  brick  sewer,  -t  feet  9  inches  high 
by  3  feet  2  inches  wide,  and  300  yards 
in  length,  with  a  fall  of  1  in  156,  carried 
away  this  water  from  a  closely  built  and 
densely  populated  district  containing  117 
acres.  In  another  part  of  the  town. 
which  was  also  built  upon,   and  which 


356 


VAN   NOSTRAND'S   ENGINEERING   MAGAZINE. 


•contained  85  acres,  a  sewer  3  feet  6  inches 
liigh  by  2  feet  4  inches  wide,  with  a  fall 
of  1  in  75,  carried  off  these  storms  with- 
out causing  any  damage,  and  without 
the  water  rising  in  the  cellars,  which 
were  generally  from  1  foot  to  2  feet  be- 
low the  soffit  of  the  arches.  In  both 
oases,  however,  the  sewers  were  under 
pressure,  and  on  the  first  occasion  the 
water  rose  18  inches,  and  in  the  other 
oase  1  foot,  in  the  man-hole  shafts." 
(Vol.  xxii.,  p.  295.) 

"  The  London  main  sewers  vary  from 
4  feet  in  diameter,  to  9  feet  6  inches  by 
12  feet  in  some  cases.  The  three  north- 
ern outfall  sewers  are  each  9  feet  by  9 
feet  with  vertical  sides,  the  southern  out- 
fall sewer  11  feet  6  inches  in  diameter." 
It  is  a  good  plan  to  make  what  are  called 
intercepting  sewers  if  there  are  consider- 
ably different  levels  in  the  town,  or  if 
the  sewage  has  to  be  pumped  at  the  out- 
fall. This  you  know  is  done  with  the 
sewage  of  London  on  both  sides  of  the 
river.  There  are  two  intercepting  sew- 
ers in  the  south  of  London,  and  the  sew- 
age runs  by  gravitation,  in  the  high  level 
sewer,  right  away  to  the  outfall  at  Cross- 
ness, and  by  the  southern  sewer,  it  runs 
also  by  gravitation,  as  far  as  Greenwich, 
where  it  is  all  pumped  up  into  the  out- 
fall sewer,  and  then  runs  away  to  Cross- 
ness, where  it  is  all  pumped  up  into  the 
Thames. 

On  the  north  side  of  London,  there 
are  three,  and  the  sewage  of  the  two 
lower  ones  is  pumped  up  into  the  highest 
at  Abbey  Mills,  and  thence  flows  on  to 
the  outfall  at  Barking  Creek. 

Now  for  the  shape.  The  best  shape 
has  been  decided  to  be  the  egg  shaped 
section.  There  are  plenty  of  shapes  in 
use.  The  rectangular  section  is  evident- 
ly bad.  The  amount  of  friction  is  very 
great  and  likewise  such  sewers  become 
choked  up  with  deposit.  A  flat  top  has 
been  used,  but  it  is  obviously  bad.  It  is 
not  so  strong  ;  and  even  the  Romans,  as 
in  the  Cloaca  Maxima,  used  an  arch. 
The  best  shape  is  an  oval  section  with 
the  smaller  end  downwards.  Another 
advantage  of  this  is  that  there  is  a  sav- 
ing of  a  material.  Sewers  less  than  2 
feet  in  diameter  are  better  made  circu- 
lar. There  was,  for  a  long  time,  a  dis- 
pute as  to  the  different  advantages  of 
brick  and  pipe  sewers.  You  will  find  in 
the  12th  Vol.  of  the  Proceedings  of  the 


Institution  of  Civil  Engineers  a  paper,  a 
very  important  paper,  by  Mr.  Rawlinson, 
in  which  he  supported  very  strongly  the 
use  of  pipes.  You  will  find  that  there 
was  a  great  deal  of  dispute  as  to  their 
efficacy.  Mr.  Rawlinson  laid  down  three 
propositions  that  he  thought  should  be 
borne  in  mind  in  laying  out  the  sewerage 
of  a  town.  In  the  first  place,  the  sewers 
cannot  receive  the  excessive  flood  water 
even  of  the  urban  portion  of  the  site. 
That  is  perfectly  true  ;  they  have  in 
certain  places  been  made  large  enough 
to  do  that.  In  the  second  place,  accord- 
ing to  Mr.  Rawlinson,  they  ought  not  to 
be  combined  with  the  natural  water- 
courses which  drain  large  areas  of  the 
suburban  land  previous  to  entering  the 
urban  portion.  No  doubt  sewers  are 
frequently  combined  with  watercourses 
which  ought  to  go  directly  into  the  riv- 
ers. In  the  third  place,  they  should  be 
adapted  exclusively  to  carry  the  liquid 
and  solid  refuse  from  the  houses  in  such 
a  manner  as  to  cause  the  least  possible 
nuisance  to  the  inhabitants.  These  con- 
clusions were  then  very  much  disputed, 
as  also  was  the  conclusion  that  sewers 
should  be  as  small  as  possible  and  im- 
pervious.— The  opponents,  no  doubt,  who 
disputed  these  statements,  did  so  from 
the  fact  that  they  did  not  sufficiently  ap- 
preciate the  antagonism  that  exists  be- 
tween sewers  and  drains.  Mr.  Robert 
Stephenson,  on  that  occasion,  expressed 
his  "  conviction  that  for  certain  localities, 
if  pipe-drains  were  sufficiently  strong  to 
resist  fracture,  and  sufficiently  large  to 
avoid  being  choked  up,  they  might  be 
advantageously  employed  to  form  the 
connections  of  houses,  courts,  and  other 
small  localities,  with  the  main  sewers, 
which  should  be  constructed  of  brick,  of 
such  dimensions  as  to  admit  of  easy  in- 
ternal inspection  and  repair,  and  be  of 
form  (except  where  the  flow  of  water  was 
at  all  times  considerable)  that  the  radius 
of  the  curved  bottom  should  be  able  to 
gather  a  small  supply  of  water  into  a 
sectional  area  affording  the  same  hy- 
draulic mean  depth  as  in  a  pipe-drain  of 
a  diameter  merely  adapted  to  discharge 
the  minimum  flow."  So  that  after  all 
this  discussion  the  result  which  was  come 
to  was  this :  that  impervious  pipes — 
glazed  earthenware  pipes — were,  on  the 
whole,  the  best  for  house  drains,  small 
streets,   courts  and  places  of  that  sort, 


WATER   SUPPLY   AND   DRAINAGE. 


357 


but  that  they  were  not  advantageously 
to  be  used  over  12, 15,  or  at  the  most  18 
inches  in  diameter.  Certainly,  when 
above  18  inches  in  diameter,  it  is  cheap- 
er to  make  a  brick  sewer  of  oval  section 
than  to  lay  pipes. 

In  very  wet  soil,  Mr.  Rawlinson  has 
used  iron  inverts  to  prevent  the  subsoil 
water  coming  into  the  sewer  and  keep- 
ing it  continually  full  up  to  a  certain 
height.  Mr.  Simpson  has  described  iron 
pipes  to  be  used  for  sewers  where  there 
are  bad  foundations,  as  in  running  sand  ; 
there  is  a  plan  for  preventing  subsoil 
water  from  getting  into  sewers  without 
using  cast-iron  pipes,  which  is  described 
by  Messrs,  Reid  and  Goddison,  of  Liver- 
pool, in  the  British  Association  Report 
for  1870.  They  have  introduced  a  sub- 
soil drain  and  pipe  rest  to  be  placed  be- 
neath the  pipes.  It  has  got  a  section 
like  the  letter  D.  Q  The  pipe  sewer 
is  laid  upon  it,  and  it  acts  as  a  drain  to 
keep  the  subsoil  water  below  the  sewer. 

With  regard  to  the  outfalls — the  out- 
falls ought,  if  possible,  to  be  quite  free. 
The  first  thing  that  you  have  to  do  is  to 
choose  the  best  place  for  the  outfall. 
For  that  there  are  no  general  rules 
whatever,  and  you  must  be  guided  en- 
tirely by  the  nature  of  the  locality. 
Most  sewers  having  been  originally  con- 
structed as  drains,  it  is  perfectly  plain 
that  their  only  outfail  is  into  the  sea  or 
into  a  river,  and  so  most  of-  the  outfalls 
are  built  into  the  sea  or  into  rivers,  and 
the  sewage  is  thrown  away.  We  shall 
in  the  next  lectures  consider  some  other 
methods  of  dealing  with  sewage. 

If  possible  the  outlet  should  be  free. 
If  it  cannot  be  free  there  must  be  some 
means  adopted  for  preventing  the  sew- 
age getting  backed  up  in  the  sewers, 
especially  when  the  rivers  are  high,  or 
at  high  tide  in  the  sea.  If  the  sewage  is 
allowed  to  get  back  in  the  sewers  you 
may  get  the  cellars  flooded,  and  you 
will  certainly  get  sewer  air  forced  up 
into  the  town.  One  way  of  preventing 
this  is  by  causing  the  outfall  to  open 
into  a  large  tank  out  of  which  the  sew- 
age is  continually  pumped.  Another 
plan  is  simply  to  have  a  flap  to  the 
mouth  of  the  sewer — a  flap  which  shuts 
and  keeps  it  full  of  sewage.  In  that 
case  the  outfall  has  to  be  made  large 
enough  to  contain  an  enormous  quantity 
of  sewage.     Then  it  should  certainly  not 


be  taken — that  is  if  you  drain  into  a 
river — into  a  river  near  the  town,  and! 
certainly  not  above  one.  The  better 
method  is  perhaps  to  have  a  large  tank, 
if  the  outfall  sewer  must  be  below  the 
surface  of  the  water.  Where  you  have 
rivers  with  considerable  difference  in  the 
level,  a  plan  has  been  adopted  for  dis- 
charging the  sewage  in  summer  when: 
the  river  is  very  low  by  means  of  a  sub- 
sidiary pipe.  This  cast-iron  pipe  is 
taken  at  a  lower  level  into  the  river. 
There  is  a  valve  capable  of  being  raised 
by  a  windlass,  which  valve  prevents  the 
sewage  coming  out  by  the  main  outfall. 
The  ordinary  sewage  of  the  town  can 
then  run  away  by  this  cast-iron  pipe, 
and  get  off  into  the  river  at  a  lower 
level.  This  plan  has  been  put  into 
operation  at  Windsor  by  Mr.  Rawlinson  j 
so  that  the  ordinary  amount  of  sewage- 
need  not  run  out  by  the  main  outfall 
high  up  when  the  river  is  low,  in  which 
case  it  would  run  down  the  banks  caus- 
ing a  nuisance.  When  there  is  an  enor- 
mous amount  of  sewage  and  a  flood  in 
the  river,  and  of  course  the  river  is  high, 
then  it  is  allowed  to  come  out  by  the 
main  outfall.  When  there  are  steep 
gradients  in  sewers  there  ought  to  be 
steps  made,  and  flaps  placed  at  the 
upper  parts,  and  at  such  places  also  there 
ought  to  be  ventilators.  Ventilators  are 
best  constructed  to  open  at  the  level  of 
the  street,  and  are  best  made  in  connec- 
tion with  man-holes.  In  the  first  place 
I  ought  to  tell  you  that  it  is  absolutely- 
necessary  to  ventilate  sewers.  It  is  per- 
fectly certain  that  a  certain  amount  of 
sewer  air,  as  it  is  called,  is  contained  in 
all  sewers,  and  is  given  out  from  sewers, 
and  is  given  out  from  sewage  whether 
there  is  much  stagnation  or  not.  Where 
there  is  great  stagnation  the  more  is 
evolved.  The  strongest  argument  for 
ventilating  sewers  is  the  argument  used 
by  those  who  say  they  should  not  be 
ventilated.  They  say  they  should  not 
be  ventilated  because  they  can  be 
securely  trapped,  and  the  small  amount 
of  gas  that  does  accumulate  in  them  can 
be  prevented  from  coming  into  the 
houses.  Now  this  fact  that  sewers  need 
to  be  trapped  is  the  best  argument  to 
show  that  it  is  neccessary  to  ventilate 
them.  I  should  tell  you  that  all  water 
traps  are,  essentially,  bends  in  pipes 
which   will   hold   water.      Water  traps 


358 


VAN   NOSTRAND'S   ENGINEERING   MAGAZINE. 


are  of  very  little  use  against  sewer  air. 
I  do  not  mean  to  say  that  the  air  will 
often  actually  force  them,  though  it  will 
do  that  sometimes  ;  but  what  I  mean  is 
that  most  of  the  dangerous  elements 
which  are  the  constituents  of  sewer  air 
are  soluble  in  water  and  are  evaporated 
and  given  out,  so  that  it  is  very  little 
use  to  rely  on  water  traps,  especially  if 
they  are  placed  under  pressure.  There- 
fore ventilation  must  be  provided. 

Now  this  ventilation  has  been  carried 
out  in  very  various  ways.  The  simplest 
way,  of  course,  is  to  allow  a  certain 
number  of  the  openings  into  the  sewers 
in  the  streets  to  be  untrapped,  and  then 
the  sewer  air  escapes  into  the  streets. 

That  was  the  plan  condemned  some 
years  ago,  because  it  allowed  the  sewer 
air  to  come  out  straight  into  the  streets, 
and  to  become  disagreeable  to  persons 
walking.  That  plan,  however,  is  cer- 
tainly very  much  better  than  letting  it 
remain  in  the  sewers,  from  which  it  will 
get  into  the  houses,  as  it  is  certain  to  do, 
through  weak  points. 

Another  plan  was  to  have  special  ven- 
tilating pipes  carried  up  to  the  top  of 
high  buildings.  These  are  very  well  in 
their  way,  but  they  are  certainly  not 
sufficient.  Sometimes  at  the  top  of  these 
pipes,  Archimedean  screws  have  been 
placed.  At  Liverpool  an  enormous  quan- 
tity of  these  Archimedean  screws  have 
been  placed  at  the  top  of  such  pipes,  and 
more  are  now  being  placed.  But  I  must 
tell  you  with  regard  to  these  that  Drs. 
Parkes  and  Burdon  Sanderson,  in  their 
Report  lately  on  the  Sanitary  Condition 
of  Liverpool,  made  experiments,  and 
found  that  these  Archimedean  screws 
altered  the  pressure  of  the  air  in  the 
sewers  to  a  very  trifling  extent,  so  that 
they  did  not  seem  to  be  of  any  great 
value. 

Another  plan  is  to  connect  the  rain- 
water pipes  with  the  sewers  directly,  or 
at  least  some  of  them,  and  to  leave  them 
untrapped.  If  you  do  this,  it  is  neces- 
sary that  rain  water  pipes  should  be 
thoroughly  well  constructed  and  well 
jointed,  or  else  air  will  escape  into  the 
neighborhood  of  the  houses.  But  the 
best  plan  of  all  is  to  have  plenty  of 
openings  into  the  main  sewer  directly 
over  it,  and  to  have  special  ventilating 
openings  connected  with  the  man  holes 
along  each  sewer  at  certain  intervals,  in 


the  middle  of  the  streets.  You  must 
have  man  holes,  and  where  a  sewer 
makes  a  bend  there  ought  to  be  a  man 
hole  ;  and  there  likewise  there  ought  to 
be  a  ventilating  shaft,  and  also  at  every 
one  of  the  steps  which  I  formerly  men- 
tioned to  you.  Where  you  have  a  steep 
incline  you  should  have  a  step  and  a  fall, 
and  there,  there  ought  to  be  a  flap  and 
a  ventilation  shaft  provided  with  char- 
coal trays. 

There  are  two  or  three  ways  of  doing 
this,  one  is  to  have  a  ventilating  shaft  at 
the  side  of  the  man  hole.  The  air  that 
comes  up  the  man  hole  passes  into  the 
ventilating  shaft  and  through  the  char- 
coal and  out  into  the  street,  and  the  air 
is  deodorized  by  passing  through  the 
charcoal.  That  is  one  way.  The  dust 
and  dirt  which  will  collect  at  the  bottom 
of  the  shaft  can  be  easily  removed 
through  the  man  hole.  Another  plan  is 
to  suspend  charcoal  trays  at  intervals  in 
the  man  hole  itself,  and  then  to  have  an 
opening  through  which  the  deodorized 
gas  goes.  If  you  have  plenty  of  these 
openings  along  the  sewers  into  the  streets 
there  will  not  be  much  nuisance.  Then 
besides  ventilation,  sewers  generally  re- 
quire flushing,  or  at  any  rate  cleaning 
out.  A  deposit  occurs  in  certain  parts. 
Now  the  old  plan  used  to  be  to  make  all 
main  sewers  so  that  a  man  could  go 
through  them.  That  plan  is  not  now 
employed,  because  flushing  has  been 
adopted  instead  of  cleansing  out  by  hand 
labor,  that  is  to  say  to  a  very  consider- 
able extent.  Flushing  is  performed 
either  by  stopping  the  sewage  at  certain 
places  and  so  giving  it  a  higher  head, 
which  is  the  plan  often  adopted,  or  by 
having  some  special  reservoirs  of  water 
(collected  for  the  purpose)  at  the  higher 
parts  of  the  sewers  which  can  be  allow- 
ed to  rush  down  them  ;  or  again,  by 
making  arrangements  with  the  water 
companies  for  the  supply  of  a  sufficient 
amount  of  water  to  flush  them  continu- 
ally. And  they  should  be  flushed  regu- 
larly, or  deposit  is  sure  to  occur.  The 
Paris  plan  of  flushing  the  sewers  is  in- 
teresting. You  know  they  have  in  Paris 
enormous  subways  under  the  streets,  and 
the  sewer  runs  along  at  the  bottom  of 
the  subway.  This  subway  has  a  rail  on 
each  side  of  it,  and  they  flush  the  sewer 
in  this  way  :  a  wagon  is  run  along  these 
rails,  and  there  is  a  flap  which  descends 


WATER   SUPPLY   AND    DRAINAGE. 


359 


from  the  wagon  into  the  sewage  below. 
The  force  of  the  sewage  pushes  this  flap 
on,  and  carries  the  wagon  on  too,  and 
the  flap  of  course  displaces  everything 
before  it.  A  certain  amount  of  space  is 
left  beside  the  flap,  so  that  the  sewage 
rushes  past  this,  and  it  in  fact  chases 
everything  before  it  that  stands  in  its 
way,  so  far  as  deposit  is  concerned.  Of 
course  the  expense  of  flushing  sewers 
with  water  is  very  much  less  than  that 
of  cleansing  them  by  hand  labor.  I 
could  give  you  some  instances  of  the 
amounts  of  the  cost  in  each  instance,  but 
I  do  not  know  that  it  is  necessary. 

We  have  now  followed  the  course  of 
water  from  the  place  where  it  is  collect- 
ed into  the  town,  and  we  have  also  des- 
cribed sewers.  I  began  by  describing 
to  you  the  outfalls,  because  that  is  the 
natural  way  of  proceeding,  not  because 
the  water  followed  that  course,  but  be- 
cause, before  you  have  small  drains  and 
sewers  in  a  town,  you  want  the  outfall 
and  the  main  sewers. 

I  have  now  before  I  go  any  further  a 
few  more  points  to  tell  you  with  regard 
to  the  house  sewers,  or  house  drains,  as 
they  are  generally  called.  In  the  first 
place,  I  have  already  told  you  that  the 
fall  of  the  house  drains  should  not  be 
less  than  1  in  60.  Then,  the  next  point 
is  that  house  drains  ought  not  to  run 
underneath  the  basements  of  houses. 
They  generally  do  so,  as  you  know  per- 
fectly well.  If  they  do  they  ought  to 
be  made  of  impervious  pipes  laid  in  con- 
crete. The  next  point  is  that  they  ought 
invariably  to  be  ventilated.  If  the  water 
closet  system  is  used  perhaps  the  best 
way  of  ventilating  them  is  to  allow  the 
pipe  which  comes  from  the  closets — the 
soil  pipe — provided  it  descends  outside 
the  house,  as  it  always  should,  to  be  un- 
trapped  at  the  bottom,  and  to  be  open 
at  the  top,  so  that  the  air  from  the  house 
sewer  finds  exit  into  the  open  air  con- 
tinually. If  the  water  closet  plan  is  not 
adopted  there  ought  to  be  one  or  more 
special  pipes  for  ventilating  the  drain 
carried  up  to  the  highest  point.  Or, 
again,  some  of  the  rain  water  pipes  can 
be  left  untrapped  ;  but  this  is  not  so 
good  a  plan.  If  the  soil  pipe  be  inside 
the  house  it  should  be  trapped  at  the 
bottom  and  ventilated  at  the  top,  and 
then  a  special  ventilating  pipe  must  be 
provided  for  the  sewer.     Another  plan, 


an  excellent  one,  in  addition  to  this,  if 
the  house  drain  be  long  enough,  is  to  cut 
it  off — to  make  a  break  in  it,  as  it  were — 
before  entering  the  main  sewer,  and  that 
is  done  by  making  it  discharge  into  a 
ventilating  shaft.  There  is  a  swing  flap 
on  the  end  of  the  house  drain  in  the 
shaft,  which  is  shut  except  when  the 
water  is  running.  The  air  which  comes 
up  from  the  street  sewer  into  the  shaft 
cannot  pass  up  the  house  drain,  but 
ascends  through  trays  of  charcoal,  and 
finds  its  way  out  into  the  open  air 
thi-ough  openings  which  are  left  between 
the  bricks  at  the  top  of  the  shaft.  The 
whole  thing  is  covered  with  a  stone  slab, 
just  above  the  level  of  the  ground.  If 
you  want  additional  security  you  can 
place  a  syphon  between  the  ventilating 
shaft  and  the  street  sewer. 

Now  if  a  trap  is  placed  in  the  cellars, 
or  basement  of  a  house  communicating 
with  the  drain,  a  precaution  has  to  be 
taken,  if  there  is  any  chance  of  the  sew- 
age backing  up.  In  that  case  a  trap  has 
to  be  placed  which  will  prevent  sewage 
from  flooding  the  basement.  This  is 
done  by  means  of  a  heavy  flap  trap. 

The  common  traps  used  for  yards,  and 
even  for  back  kitchens,  and  so  on,  are 
what  are  called  bell  traps.  They  are 
about  the  worst  kind  of  things  that 
could  be  devised,  and  that  is  why  I  men- 
tion them.  The  bell  trap  merely  consists 
of  a  sort  of  inverted  tumbler  placed  over 
the  head  of  the  pipe  that  leads  into  the 
drain.  The  rim  of  this  tumbler  dips 
into  a  groove,  which  is  supposed  to  be 
filled  with  water.  The  water  that  passes 
through  the  perforated  top  which  is  fixed 
on  to  the  tumbler  can  find  its  way  round 
the  edges  of  this  bell,  as  it  is  called,  and 
so  into  the  drain.  The  danger  is  this, 
that  the  instant  this  top  is  taken  off  it 
takes  the  bell  off  as  well,  and  then  sewer 
air  can  get  up  into  the  house  or  yard. 
Now  these  things  are  continually  being 
taken  off,  or  left  off,  and  therefore  that 
kind  of  trap  should  never  be  used.  The 
best  to  put  instead  of  it  is  an  earthen- 
ware syphon  trap.  The  advantage  of 
this  is,  that  if  the  top  is  taken  off,  as  it 
continually  is,  to  sweep  the  yard  or  base- 
ment, it  does  not  matter  at  all,  bacause 
the  top  has  nothing  to  do  with  the  trap 
itself.  With  this  syphon,  if  you  want 
to  ventilate  the  drain  at  that  particular 
.  point,  yon  can  have  a  hole  made  at  the 


360 


VAN   NOSTRAND'S   ENGINEERING   MAGAZINE. 


top  of  the  bend  (some  are  made  with  a 
hole),  and  then  you  can  carry  up  a  venti- 
lating pipe  from  it.  If  you  have  two 
ventilating  pipes  you  must  carry  them 
to  different  heights,  one  not  very  high, 
and  the  other  to  a  considerable  height ; 
but  practically  one  is  sufficient.  Another 
thing  that  you  can  do — especially  if  the 
trap  is  in  the  basement  of  the  house — 
you  can  make  any  waste  pipe  end  in  the 
side  of  it,  through  a  hole  in  the  side 
above  the  water,  and  yet  below  the 
cover,  so  that  you  do  not  get  the  place 
flooded  if  the  holes  in  the  cover  are 
stopped  up,  as  they  are  apt  sometimes  to 
be.     This  is  a  very  convenient  plan. 

Sinks  ought  always  to  be  against  ex- 
ternal walls.  They  almost  always  used 
to  be  built  (and  now  often  are)  against 
internal  walls.  Their  pipes  have  no 
more  business  to  go  straight  into  drains 
than  the  waste  pipes  of  cisterns  ;  they 
should  always  be  carried  out  into  the 
yard,  and  made  to  end  over  one  of  these 
traps,  or  else  they  should  be  carried  into 
the  side  of  it.  The  same  thing  is  true 
of  rain  water  pipes.  Unless  rain  water 
pipes  are  constructed  with  the  view  of 
ventilating  the  sewer,  and  are  made  with 
proper  joints,  they  ought  to  end  above 
the  traps. 

We  now  come  to  the  consideration  of 
the  disposal  of  a  particular  kind  of  re- 
fuse matter,  namely,  excretal  refuse 
matter.  I  want  first  to  prove  to  you 
that  it  is  necessary  to  get  rid  of  refuse 
matter  generally,  and  especially  so  of 
this  particular  kind  of  refuse  matter 
from  the  neighborhood  of  habitations. 
I  could  quote  to  you  from  any  number 
of  reports  showing  that  the  general 
death  rate,  and  also  the  death  rate  from 
certain  specific  diseases,  especially  ty- 
phoid fever  and  cholera,  depends  to  a 
very  great  extent  upon  the  amount  of 
filth,  and  especially  of  excretal  filth, 
that  is  in  and  about  the  habitations  of 
people. 

Take  the  following  opinion  from  the 
evidence  given  by  Mr.  Kelsey  before  the 
Health  of  Towns  Commission  (1844). 
When  asked,  "Does  the  state  of  filth  and 
the  effluvia  caused  by  defective  sewer- 
age, by  cesspools  or  privies,  and  decom- 
posing refuse  kept  in  dust  bins,  power- 
fully affect  the  health  of  the  popula- 
tion?" he  says,  "Yes,  it  does;  it  always 


occasions  a  state  of  depression  that  ren- 
ders persons  more  liable  to  be  acted 
upon  by  other  poisons,  even  if  it  be  not 
the  actual  cause  of  it.  The  line  of  habi- 
tations badly  cleansed,  and  in  this  con- 
dition, almost  formed  the  line  of  cholera 
cases." 

Then,  after  a  description  of  cellar 
dwellings,  which  are  even  now  preva- 
lent in  some  of  our  large  towns — in  this 
case  referring  to  Liverpool — Dr.  Duncan 
pointed  out  that  the  ward  "  where  the 
largest  proportion  (more  than  one  half) 
of  the  population  resides  in  courts  or 
cellars,  is  also  the  ward  in  which  fever 
is  most  prevalent,  1  in  27  of  the  inhabit- 
ants having  been  annually  attended  by 
dispensaries  alone ; "  and  he  remarks 
that  "  people  do  not  die  simply  because 
they  inhabit  places  called  courts  or  cel- 
lars, but  because  their  dwellings  are  so 
constructed  as  to  prevent  proper  venti- 
lation, and  because  they  are  surrounded 
with  filth,  and  because  they  are  crowded 
together  in  such  numbers  as  to  poison 
the  air  which  they  breathe." 

Well,  then,  illness  is  caused  if  these 
refuse  matters  are  not  removed  from  the 
neighborhood  of  habitations,  and.  illness 
with  all  its  attendant  misfortunes  and 
difficulties. 

Now  what  plans  have  been  adopted 
for  removing  these  matters  from  habita- 
tions ?  That  is  one  thing  to  be  consid- 
ered ;  and  another  thing  to  be  consider- 
ed is,  are  these  excretal  matters  of  any 
value;  can  anything  be  done  with  them^ 
and  if  so,  how  can  the  most  be  got  out 
of  them? 

Now,  if  I  tell  you  what  their  composi- 
tion is,  you  will  see  at  once  that  they 
must  be  of  considerable  value;  and  when 
you  reflect  that  these  refuse  matters  con- 
stitute a  great  proportion  of  the  refuse 
matters  of  our  bodies,  you  will  see  at 
once  that  they  must  contain  the  same 
elements  as  our  food,  and  that  therefore 
there  is  at  any  rate  a  possibility  of  their 
being  used  for  the  reproduction  of  food- 
Now,  what  is  their  composition?  The 
results  of  a  great  number  of  analyses, 
which  are,  however,  only  sufficiently  com- 
plete in  the  case  of  males  of  from  15  to 
50  years  of  age,  show  that  the  mean 
amounts  in  ounces  of  the  various  con- 
stituents during  24  hours  are  as  fol- 
lows : 


WATER  SUPPLY   AND    DRAINAGE. 


361 


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03 


Now,  what  does  that  mean  ?  Nitro- 
gen and  phosphates  are  the  very  things 
we  get  to  use  as  manures,  and  we  can 
from  this  chemical  composition  of  the 
excreta  calculate  their  relative  and  abso- 
lute value. 

In  the  first  place  I  want  to  point  out 
to  you  that  the  amount  of  valuable  mat- 
ter contained  in  the  urine  in  the  24 
hours  is  considerably  greater  than  that 
contained  in  the  faeces  in  24  hours. 
Now,  that  I  tell  you  at  once,  in 
order  that  you  may  not  run  away  with 
the  fallacy  that  is  sometimes  indulged  in 
that  you  may  throw  away  the  urine  of  a 
population  so  long  as  you  retain  the 
faeces,  and  that  you  will  get  the  greatest 
amount  of  manure  from  the  latter.  On 
all  heads  the  matters  contained  in  the 
urine  are  in  larger  proportion  than  in  the 
fasces,  and  especially  as  regards  the  im- 
portant matters,  e.  g.,  the  nitrogen  is 
about  nine  times  as  much. 

To  estimate  the  value,  it  is  convenient 
to  take  amounts  that  are  passed  in  a 
year,  and  it  has  been  calculated  that  the 
average  amount  of  ammonia — represent- 
ing the  nitrogen  in  the  form  of  ammonia 
— discharged  annually  by  one  individual, 
taking  the  average  of  both  sexes  and  of 
all  ages,  is  about  13  lbs.,  or  nearly  that; 
and  it  has  been  estimated  that  the  money 
value  of  the  total  constituents  of  the  ex- 
creta is,  in  urine,  7s.  3d.,  and  in  faeces 
about  Is.  3d.,  giving  a  total  of  about  8s. 
6d.  a  year,  so  that  you  see  at  once  that 


the  value  of  the  urine  is  about  six  times 
as  much  as  the  value  of  the  faeces.  When 
you  consider  that  about  ten  times  more 
urine  is  passed  (by  weight)  than  fseces> 
you  see  that  faeces  are  more  valuable 
than  urine,  weight  for  weight,  although 
the  total  faeces  are  much  less  sraluable 
than  the  total  urine.  There  is,  then,  no- 
doubt  about  the  value. 

The  next  thing  is,  what  are  the  plans 
that  have  been  attempted  for  utilizing 
it?  The  earliest  plan,  and  one  that  is 
defended  by  many  up  to  the  present 
day — and  by  many,  I  was  going  to  say, 
who  ought  to  know  better — the  earliest 
plan  consists  in  keeping  the  faeces,  and 
a  certain  small  amount  of  urine  for  a 
longer  or  shorter  period  in  or  about  the 
premises  in  some  form  or  another.  And 
there  are  two  ways  in  which  this  can  be 
done.  It  can  be  done,  as  it  is  in  many 
towns  even  now,  as  it  is  notably  in  many 
continental  towns,  as  Paris  and  Berlin 
and  Vienna.  It  can  be  done  either  by 
keeping  these  matters  in  a  semi-liquid 
state,  in  tanks  or  vessels  prepared  to  re- 
ceive them,  and  emptying  these  at  cer- 
tain times  and  taking  their  contents 
away  to  be  used  as  manure,  or  it  can  be 
done  by  mixing  these  matters  with  cer- 
tain refuse  which  will  to  some  extent  dry 
them  ;  and  some  such  refuse  is  found  in 
all  houses,  and  is,  to  wit,  ashes.  Nowr 
those  are  the  two  plans  that  have  been 
adopted — I  may  almost  say  from  time 
immemorial,  at  all  events  for  a  great 
many  years — in  order  to  collect  this 
valuable  manure;  that  is  to  say,  by  those 
who  have  made  any  attempt  to  collect  it 
at  all. 

Let  us  take  the  first  plan  and  consider 
it  for  a  few  minutes — the  plan  of  digging 
a  hole  in  the  ground  and  throwing  all 
this  refuse  matter  into  it.  When  this  is 
done,  unless  the  hole  in  the  ground  is  im- 
pervious, a  great  amount  of  this  refuse 
matter  will  percolate  into  the  soil  around, 
and  get  into  wells.  In  certain  towns 
this  has  been  actually  encouraged.  There 
are  certain  towns  where  holes  have  been 
made  to  receive  the  refuse  matters  of  the 
population  in  pervious  sandstone  strata, 
with  the  express,  distinct,  and  avowed 
object  of  letting  the  liquid  matters,  and 
as  much  as  possible  of  the  solid  matters, 
precolate  the  soil  and  get  away  as  best 
they  could.  These  dumb  wells,  as  they 
are  called,  have  been  made  and  shut  up 


362 


VAN  NOSTRAND'S   ENGINEERING  MAGAZINE. 


with  the  deliberate  intention  of  not  be- 
ing opened  for  many  years,  and  in  certain 
places  the  soil  has  been  so  absorbent  that 
when  opened  the  wells  have  been  almost 
invariably  found  empty.  Now  that  plan 
need  only  be  stated  to  be  condemned.  In 
all  these  towns  the  well  water,  which  is 
often  the  only  supply  for  the  people,  is 
largely  polluted,  and  is  in  fact  to  a  great 
extent  supplied  by  these  very  dumb 
wells,  which  are  often  close  by  ;  and  in 
almost  every  town  where  there  is  an 
epidemic  of  typhoid  fever  you  find  an 
inspector  going  down  from  the  Local 
Government  Board,  and  reporting  that 
this  is  the  case. 

Now,  the  improvement  on  this  bad 
plan,  or  want  of  plan,  in  places  where  it 
is  not  done  away  with,  is  to  line  the  pits 
with  cement,  and  to  provide  a  drain  from 
them  into  the  nearest  sewer.  Thus  the 
cistern  becomes  merely  a  pit  in  which  to 
collect  the  solid  matters,  while  you  allow 
the  liquid  matters,  which  are  the  most 
valuable,  and  which  are  just  as  likely  to 
become  offensive,  to  run  into  the  sewer. 
You  collect  the  solid  matter  which  is  less 
valuable,  and  which  is  rendered  still  less 
valuable  by  having  much  of  its  valuable 
material  dissolved  out,  by  the  liquid  which 
is  allowed  to  run  away. 

The  other  plan  is  to  do  as  is  done  in 
Paris,  to  make  these  large  cesspools  (so 
large  that  they  take  six  months,  or  even 
a  year,  to  fill),  under  the  houses  or  under 
the  courts,  to  make  them  impervious,  and 
not  drain  them  at  all.  Of  course  the 
pits  are  only  theoretically  impervious, 
but  practically  very  many  of  them  cer- 
tainly are  not  so.  But,  however,  sup- 
posing that  they  are,  they  in  any  case 
requiring  a  ventilating  shaft,  or  the  foul 
air  which  collects  in  them  will  find  its 
way  through,  somehow  or  other,  and  will 
poison  the  air  of  the  house.  Another 
danger  is,  that  if  they  are  not  ventilated, 
and  even  sometimes  if  they  are  ventilated, 
the  men  who  go  into  them  may  be  suffo- 
cated by  the  poisonous  gases  accumulated 
in  them. 

The  first  of  these  plans,  in  which  the 
liquid  matters  all  run  away,  is  confessed- 
ly a  failure.  You  deliberately  take  and 
throw  away  all  the  most  valuable  part, 
and  the  part  which  remains  is  not  only 
of  no  value,  but  is  a  distinct  expense, 
because  no  one  will  take  it  away  unless 
he  is  well  paid  for  it,  so  that  there  is  a 


very  considerable  loss  on  that  system. 
And  so  the  system  cannot  be  called  one 
of  utilization.  Then,  the  disadvantage  of 
the  Paris  plan,  apart  from  the  general 
disadvantage  of  having  such  a  thing  as 
an  immense  cesspool  underneath  each 
house,  is  found  in  the  emptying  of  them. 
This  operation  causes  a  fearful  nuisance, 
even  although  they  are  now  emptied  by 
means  of  carts  in  which  a  partial  vacuum 
is  first  created,  so  that  when  the  hose  is 
attached  to  the  cart  and  placed  into  the 
pit  the  semi-liquid  stuff  rises  up  and  fills 
the  tonneau,  as  they  call  it.  And  then  I 
may  tell  you,  as  a  matter  of  fact — I  could 
give  you  the  figures — that  the  system 
does  not  pay  ;  that  the  collection  costs 
so  much  that  the  manure  made  from  the 
stuff  does  not  pay  the  cost  of  collecting. 

Let  us  consider,  now,  some  improved 
systems  in  which  this  manure  is  collected, 
mixed  with  ashes  and  household  refuse, 
and  sold  in  a  semi-dry  state,  because  this 
is  a  plan  which  has  been  very  much  de- 
fended of  late.  These  plans  are  develop- 
ments of  the  old  midden — a  heap  in  the 
yard  at  the  back  of  the  house,  into  which 
all  kinds  of  refuse  were  thrown. 

The  first  improvement,  as  in  the  case 
of  the  cesspool,  was  to  make  a  kind  of 
pit  lined  with  cement.  There  are  differ- 
ent contrivances  employed.  There  is  one 
which  is  known  as  the  Manchester  plan, 
and  another  known  as  the  Hull  plan,  and 
so  on  ;  but  in  all  the  ashes  are  thrown 
into  the  pit,  so  as  to  make  a  semi-solid 
mass. 

The  conditions  necessary  for  them  are 
these  : — In  the  first  place  they  must  re- 
ceive no  moisture  from  the  soil  around. 
In  the  second  place,  they  ought  to  allow 
no  liquid  to  escape  from  them,  because, 
if  so,  they  are  confessedly  failures.  It 
is  plain  that  the  object  of  all  these  sys- 
tems where  the  excretal  matters  are  to 
be  kept  out  of  the  sewers  must  be  to 
separate  them  entirely  from  the  sewage, 
because,  if  you  do  not,  you  have  still 
sewage  to  treat.  We  have  already  seen 
that  the  water  supply  of  the  town  goes 
into  it  to  be '  soiled,  and  you  require 
sewers  to  take  it  away.  You  have  got, 
therefore,  water  which  is,  to  a  certain 
extent,  dirty.  The  theory  of  persons 
who  support  those  systems  which  I  am 
now  describing  is  that,  if  you  prevent  the 
most  foul  part  of  the  refuse  matters  from 
getting  to  the  sewers,  you  will  not  then 


WATER   SUPPLY   AND   DRAINAGE. 


363 


require  sewers  so  large  to  begin  with  ; 
and,  also,  that  you  will  not  require  to 
treat  the  sewage  afterwards,  but  will 
be  able  to  turn  it  into  a  river  without 
any  disadvantage.  Now,  if  these  cess- 
pools and  these  midden  closets  require  to 
drain  their  liquid  contents  into  the  sewers, 
the  sewage  will  certainly  have  to  be 
treated  just  as  much  as  if  you  were  to 
allow  the  whole  of  the  refuse  matter  of 
the  town  to  get  into  the  sewers  ;  and 
that  is  proved  by  the  fact  that  the  sew- 
age of  towns  where  you  have  cesspools 
and  midden  pits  drained  into  the  sewers 
is  considerably  more  foul,  and  is  within 
a  very  little  of  being  as  strong,  as  the 
sewage  of  water  closeted  towns,  so  that 
it  requires  treatment  at  least  as  much  as 
the  latter  does. 

The  next  condition  with  these  midden 
heaps  is  that  they  must  secure,  practi- 
cally, as  much  dryness  of  the  contents  as 
possible  ;  and  then  they  require  an  effi- 
cient covering  up  of  the  refuse  matters 
by  the  ashes  that  are  thrown  down,  and 
that  is  done  in  various  ways.  Lastly, 
they  require  ventilating. 

Now,  with  either  of  these  systems,  it 
is  desirable  to  have  the  receptacle  as 
small  as  possible  ;  it  is  desirable  for  sani- 
tary reasons,  though  not  for  economical 
ones,  to  have  the  receptacle  as  small  as 
possible,  so  that  as  little  of  these  matters 
shall  be  retained  about  the  premises  as 
possible.  The  midden  closet  used  at 
Hull  consists  of  an  impervious  receptacle, 
which  is  not  sunk  into  the  ground  at  all, 
but  is,  in  fact,  merely  the  space  directly 
under  the  seat  of  the  closet,  the  front 
board  being  movable,  so  that  the  sca- 
vengers can  get  the  stuff  when  full. 
That,  no  doubt,  is  by  far  the  best  of  these 
simple  ash  closets. 

After  this  we  pass  on  to  a  still  greater 
improvement,  to  what  you  might  call  a 
temporary  cesspool — that  is  to  say,  a 
simple  "tub  or  box  placed  underneath  the 
seat  to  collect  the  excretal  matters,  these 
tubs  or  boxes  being  collected  every  day 
by  contractors  and  their  contents  used 
for  manure. 

I  may  tell  you  at  once  that  this  is 
really  the  system  out  of  which  most  is 
got  in  the  way  of  profit.  There  is  no 
doubt  of  it  whatever.  This  is  the  system 
that  has  been  practiced  in  China  for 
thousands  of  years.  It  is  the  system 
which  is  practiced  now  in  the  neighbor- 


hood of  Nice,  where  they  grow  orange 
trees  and  scented  flowers,  and  where  they 
grow  a  large  quantity  of  things  which 
require  rich  manure  ;  and  it  is  perfectly 
certain  that  it  is  the  system  in  which 
there  is  least  waste. 

Now,  this  system  has  been  very  much 
revived  of  late  in  certain  towns.  In 
Edinburgh  and  Glasgow,  and  especially 
in  many  foreign  towns  —  in  Berlin, 
Leipsic,  and  in  Paris  —  this  is  a  plan 
which  is  adopted  on  a  large  scale. 
Of  course,  the  difficulties  of  the  system 
are  enormous,  and  the  nuisance  is  con- 
siderable. As  far  as  the  difficulties  ar  - 
concerned,  I  may  tell  you  what  Dr. 
Trench,  of  Liverpool,  has  calculated  in 
regard  to  that  town  ;  he  calculates  that 
the  space  that  would  be  required  for  the 
spare  receptacles  for  the  borough  of 
Liverpool  would  be  11  acres,  2  roods, 
32^  perches  ;  that  if  put  on  a  railway 
four-abreast  they  would  extend  a  dis- 
tance of  12  miles.  Now,  you  see  at  once 
that  a  system  which  requires  anything  of 
that  sort  is  not  a  system  likely  to  be 
adopted  for  any  large  town.  But,  mind, 
there  is  no  doubt  whatever  about  this, 
that  for  small  places  it  is  an  infinitely 
more  healthy  and  more  reasonable  system 
in  every  way  than  either  of  the  other 
two  plans  that  we  have  considered.  It 
is  carried  out  with  a  simple  bucket,  in 
which  the  refuse  matters  cannot  be 
allowed  to  remain  for  a  long  time,  be- 
cause it  is  not  large  enough,  and  because 
they  would  become  too  offensive.  This 
system  is  evidently  better  for  health  than 
keeping  the  matters  about  the  premises  for 
a  long  time  in  any  other  form  whatever. 
A  variety  of  this  plan  is  to  be  found  in 
what  are  called  the  trough  latrines  that 
are  used  in  many  large  manufactories. 
This  simply  consists  of  a  trough  which 
runs  below  a  row  of  seats,  which  trough 
can  be  emptied  into  barrels  by  lifting  a 
plug  at  the  lower  end  ;  the  stuff  is  taken 
away  to  farms. 

There  are  two  or  three  varieties  of  the 
tub  or  pail  plan.  One  is  known  as  the 
Goux  system,  and  another  as  the  Eureka 
system  ;  these  systems  have  been  much 
praised  of  late.  They  are  simply  pail 
systems,  in  which  some  deodorizer  or 
some  absorbent  is  used.  In  the  Goux 
system  there  is  a  sort  of  double  pail,  with 
an  absorbent  between  the  two  pails  ;  and 
the  idea  is  to  do  awav  with  some  of  the 


364 


van  nostrand's  engineering  magazine. 


offensiveness  of  the  tub  or  pail  sys- 
tem. 

Now,  I  must  say  a  few  words  to  you 
about  the  dry  earth  system,  which  has 
been  so  much  praised.  In  the  first  place 
I  may  tell  you  that  sifted  ashes  are  some- 
times used  instead  of  dry  earth,  because 
they  are  always  at  hand,  and  that  there 
are  several  plans  for  the  use  of  sifted 
ashes  which  are  attempts  to  obviate  the 
difficulties  which  are  met  with  in  the 
procuring  of  dry  earth.  It  is  found  that 
when  a  sufficient  quantity  of  dried  and 
sifted  earth,  especially  of  particular  kinds, 
is  thrown  upon  refuse  matters,  that  they 
are  deodorized,  and  that  they  may  be 
kept  for  a  very  long  time  without  be- 
coming offensive.  The  conditions  are 
these  :  in  the  first  place  the  earth  must 
be  dried,  and  in  the  second  place  it  must 
be  deposited  on  the  refuse  matters  in  de- 
tail, as  it  is.  called,  that  is  to  say,  you 
must  not  take  a  great  heap  of  excretal 
matters  and  throw  a  lot  of  earth  upon  it, 
but  you  must  throw  a  little  earth  upon 
it  each  time  the  heap  is  increased  by  any 
more  refuse  matters.  It  is  found,  then, 
that  about  one  pound  and  a  half  of  dry 
earth  is  sufficient  to  deodorize  the  excre- 
tal matters  that  are  passed  at  one  time 
by  an  individual.  With  regard  to  the 
kind  of  earth,  almost  any  earth  will  do 
except  sand  and  chalk. 

The  next  point  is,  that  such  earth  may 
be  used  several  times  over.  After  it  has 
been  used  once,  it  requires  merely  to  be 
dried  again  and  sifted,  and  you  cannot 
tell  it  at  sight  at  all  after  it  has  been 
used  two  or  three  times  from  that  which 
has  been  used  once  ;  you  do  not  see  any 
difference  whatever  ;  all  the  organic  mat- 
ters and  all  the  matters  that  would  be 
offensive  are  entirely  absorbed  and  ren- 
dered inoffensive  to  the  smell,  and  so 
long  as  it  is  kept  dry  this  earth  remains 
quite  inodorous. 

There  are  all  sorts  of  forms  of  closets, 
and  so  on,  that  have  been  contrived  for 
utilizing  dry  earth  in  this  way,  but  there 
is  not  the  slightest  necessity  that  I  should 
describe  these  plans  to  you.  I  will  there- 
fore go  on  now  to  tell  you  of  the  results 
that  have  attended  the  application  of  this 
system  at  various  places,  and  the  advan- 
tages and  disadvantages  of  the  system. 
In  the  first  place,  with  this  system  it  is  a 
sine  qua  non  that  no  liquids  are  to  be 
thrown  into  the  earth  closet,  so  that  it  is 


a  system  which  does  not  provide  for 
slops  ;  that  is  against  it  to  begin  with. 
Thenif  any  liquidsareaccidentallythrown 
in,  or  if,  as  is  the  case  in  certain  places, 
the  air  is  exceedingly  damp,  or  if  the 
contents  get  moist  in  any  way,  you  have, 
to  all  intents  and  purposes,  a  cesspool 
without  its  advantages,  or  without  the 
special  precautions  that  are  commonly 
taken  with  regard  to  cesspools.  That  is 
another  disadvantage  of  the  system,  we 
shall  find  more  directly. 

Now  for  the  advantages.  The  ad- 
vantages, perhaps,  are  best  shown  by 
giving  some  statements  as  to  the  work- 
ing of  the  system  at  different  places. 
At  Broadmoor  the  lunatic  asylum  is  sup- 
plied with  earth  closets.  The  water 
closets  with  which  the  place  was  origi- 
nally supplied  were  done  away  with,  and 
the  earth  closet  system  adopted.  A  mix- 
ture of  earth  and  ashes  is  used,  but  the 
slops  are  allowed  still  to  pass  through 
the  drains.  Here,  you  see,  you  have  got 
every  advantage  that  such  a  system 
could,  have.  You  have  sewers  originally 
made  by  Mr.  Menzies,  made  for  the  water 
closet  system;  and  so  they  can  send  just 
what  they  like  into  them,  and  treat  the 
earth  closet  in  a  sort  of  drawing-room 
fashion — if  I  may  so  call  it — I  mean  give 
it  its  best  chance. 

Then  at  various  schools  it  has  been 
found  to  answer  very  well.  The  simplest 
form  of  it  is  a  mere  trough  into  which 
the  refuse  matters  fall  and  into  which 
earth  is  thrown.  At  various  jails  the 
plan  has  also  been  used  with  consider- 
able advantage.  At  one  place,  where 
there  was  an  attempt  made  to  save  alt 
the  faeces  and  urine  of  the  boys  in  the 
school  in  this  way,  it  was  found  that  four 
pounds  of  dry  earth  a  day*  was  required 
for  each  boy.  I  mention  that  to  you  to 
show  you  the  absolute  impracticability 
of  doing  a  thing  of  that  sort  on  a  large 
scale.  The  expense,  of  course,  would  be 
enormous. 

Where  the  plan  has  been  used  as  a 
temporary  arrangement  it  has,  on  the 
whole,  succeeded  very  well,  and  espe- 
cially so,  for  instance,  at  Wimbledon 
Camp.  At  Wimbledon  Camp  there  is 
no  doubt  it  has  been  an  enormous  im- 
provement on  the  old  system.  Now  you 
see  at  once  that  that  was  a  temporary 

*  That  would  be  125  tons  a  week  for  a  population  of 
10,000. 


WATER   SUPPLY   AND   DRAINAGE. 


385 


arrangement,  that  they  could  get  plenty 
of  earth,  and  so  there  was  very  little  to 
be  wondered  at  that  a  system  which 
does,  if  it  is  properly  carried  out,  de- 
odorize offensive  matters  should  have 
been  there  so  far  a  success. 

Now,  I  must  tell  you  a  little  about 
the  Indian  experience.  The  Indian  ex- 
perience has  been  unfavorable  to  this 
system,  but  there  are  many  statements 
made  in  Indian  reports  to  the  effect  that 
it  is  a  considerable  improvement  on  some 
of  the  systems  that  were  in  vogue  before. 
That  you  would  easily  believe  if  I  read 
you  a  description  of  some  of  the  systems, 
or,  rather,  of  the  want  of  system,  that 
they  had  before  they  adopted  this  plan. 
The  Army  Sanitary  Commission  make 
the  following  statement  : — "  It  is  insuffi- 
cient to  remove  only  one  class  or  cause 
of  impurities,  and  to  leave  the  others  ; 
and  no  sanitary  proceeding  which  does 
not  deal  effectually  with  all  of  them  can 
be  considered  as  sufficient  for  health." 

"  The  following  sources  of  impurity 
require  to  be  continually  removed  from 
inhabited  buildings  in  India  as  else- 
where ;  (a)  solid  kitchen  refuse  includ- 
ing debris  of  food;  (b)  rain  water  which 
would  if  left  in  the  subsoil  tend  to  gen- 
erate malaria  ;  (c)  all  the  water  brought 
into  the  station  except  that  which  acci- 
dentally evaporates.  This  water  is  used 
for  drinking,  cooking,  washing,  baths 
and  lavatories.  The  amount  cannot  be 
taken  at  less  than  twelve  gallons  per  head 
for  every  healthy  man,  woman,  and 
child,  iucluding  servants;  from  thirty  to 
thirty-five  gallons  per  head  for  every 
sick  man  per  day,  exclusive  of  water  for 
horses.  .  .  .  Practically,  this  water 
in  all  climates,  but  especially  in  India, 
becomes,  if  not  safely  disposed  of,  an  in- 
evitable source  of  disease  and  ill-health. 
It  contains  a  large  amount  of  putrescible 
matter,  and  if  urine  were  mixed  with  it, 
it  would  become  so  noxious  that  it  would 
matter  very  little  whether  or  not  the 
contents  of  latrines  were  added  to  this 
other  sewage  ;  (d)  the  matter  from  lat- 
rines, including  solid  and  fluid  excreta 
at  about  one  pound  per  man  per  day,  or, 
in  round  numbers,  half  a  ton  per  day 
per  thousand  men." 

Those  are  the  matters  which  will  re- 
quire to  be  removed.  Now  the  Commis- 
sioners go  on  to  say  that  the  solid  debris 
being  removed  by  hand  or  cart  labor, 


the  refuse  water  must  "  either  be  passed 
into  cesspits,  or  it  must  be  carried  away, 
or  it  must  be  allowed  to  find  an  outlet 
where  it  can  by  surface  drains— probably 
into  the  sub-soil." 

Then,  farther  on,  they  say  that  the 
latrine  matter,  with  which  alone  the  dry 
earth  system  proposes  to  deal,  "  is  to  the 
fluid  refuse  of  barracks,  hospitals,  cook 
houses,  and  so  forth,  as  1  to  190  ;  that 
is,  for  every  pound  of  human  excreta  re- 
moved under  the  dry  earth  system  there 
are  in  every  well  regulated  establishment 
about  190  of  fluid  refuse  which  must  be 
otherwise  disposed  of."  You  see  at  once 
that  this  is  absolutely  condemnatory  of 
the  system  for  use  in  permanent  "bar- 
racks, and  I  think  you  will  come  to  the 
conclusion  that  I  have  come  to,  namely, 
that  it  is  a  system  that  is  only  fit  for 
temporary  places,  like  the  camp  at 
Wimbledon.  It  is  perfectly  plain  that 
it  is  absurd  to  have  two  systems,  a  sys- 
tem of  sewers  to  carry  away  the  foul 
water  of  a  station— for  that  you  must 
have — and  another  system  for  carrying 
away  a  certain  portion  of  the  excreta! 
matter,  which  might  all  perfectly  well 
be  allowed  to  go  away  with  the  foul 
water. 

As  for  the  utilizing  of  it  in  this  way,  I 
do  not  believe  in  it  at  all.  I  mean  to 
say  that  the  cost  of  bringing  in  dry  earth 
into  a  station,  and  especially  into  a  large 
town,  and  then  of  carrying  it  away 
again,  would  be  considerably  greater 
than  the  money  that  would  be  got  for 
the  manure.  You  will  see,  and  I  dare 
say  you  have  seen,  that  the  manure  col- 
lected under  the  dry  earth  system  has 
been  put  down  as  worth  all  sorts  of 
fabulous  sums.  Well,  it  is  not  worth 
anything  of  the  kind.  It  is  the  greatest 
mistake  to  suppose  so.  The  manure 
from  the  dry  earth  system  is  a  good  gar- 
den soil,  and  it  is  not  anything  more. 
It  is  not  a  manure.  And  this  earth  that 
has  been  passed  three  times  through  the 
closets  is  nothing  more  than  that,  as  you 
will  see  in  the  report  of  the  British  As- 
sociation Sewage  Committee.  In  that 
report  there  are  given  the  results  of 
analyses  of  the  earth  after  passing  once, 
and  after  passing  twice,  and  after  pass- 
ing three  times  through  the  closet,  and 
it  is  said  that  after  passing  three  times 
through  it  is  nothing  more  than  a  rich 
garden   soil,  and  it  will  not  pay  for  in- 


366 


VAN   NOSTRAND's   ENGINEERING   MAGAZINE. 


earring  the  expense  of  carriage  to  a  long 
distance  ;  so  that  the  utilization  question 
is  certainly  not  met  by  the  dry  earth 
system.  This  is  what  I  wanted  to  come 
to. 

I  may  as  well  tell  you  that  it  has  been 
attempted  to  apply  this  system  to  a 
town.  One  part  of  Lancaster  is  supplied 
with  dry  earth  closets,  and  there  are  sev- 
eral villages  in  which  it  has  been  tried. 
In  villages  it  seems  to  answer  very  well 
when  looked  after,  In  a  town,  for  some 
of  the  reasons  that  I  have  given  you,  it 
fails.     There  is  no  doubt  about  that. 

That  will  finish  our  consideration  of 
the  systems  which  propose  to  separate 
the  excretal  refuse  as  if  it  were  some- 
thing totally,  and  entirely,  and  essentially 
distinct  from  all  other  refuse  matter 
forming  the  sewage  of  a  town.  Those 
systems  all  go  upon  a  wrong  principle. 
This  refuse  matter  is  dangerous  to 
health,  and  those  systems,  one  and  all, 
go  upon  the  principle  that  these  matters 
may  be  retained  in  and  about  houses  as 
long  as  possible,  so  long  as  they  do  not 
create  a  nuisance,  or  so  long  as  they  are 
not  felt  to  be  a  nuisance.  Now  that 
position  is  obviously  wrong.  All  these 
systems  depend  upon  leaving  such  mat- 
ters as  long  as  possible  about  the  houses. 
The  object  of  them  all  is  to  produce  a 
certain  result  with  as  little  expense  as 
possible.  It  is  perfectly  plain  that  the 
longer  this  refuse  matter  is  left  about 
houses,  under  all  these  systems, — I  do 
not  care  which  one  you  take, — the  cheap- 
er the  plan  will  be  carried  out,  so  that 
there  is  a  tendency  in  all  these  systems 
to  leave  dangerous  refuse  matters  about 
premises  for  a  very  long  time.  Now, 
the  answer  is  that  they  are  perfectly  de- 
odorized or  disinfected,  as  the  case  may 
be.  The  answer  to  that  is—if  your  sys- 
tem is  perfect,  they  are  deodorized  in 
some  cases ;  for  instance,  in  the  dry 
earth  system  they  are  deodorized.  But 
if  they  are  not,  all  the  danger  arises  that 
could  arise  from  any  other  of  the  bad 
systems  I  have  described  to  you.  Then, 
again,  the  fallacy  is  entertained  that  de- 
odorization  and  disinfection  mean  the 
same  thing.  It  is  certain  they  do  not. 
We  know  quite  well  that  the  dry  earth 
system  deodorizes  refuse  matters.  They 
do  not  putrif y  and  cause  offensive  smell 
after  deodorization,  but  we  do  not  at  all 
know  that   that  system  disinfects  mat- 


ters ;  and  there  is  not  the  slightest  rea- 
son for  supposing  that  this  earth,  if  at 
any  time  rendered  moist, — and  we  do 
not  know  whether  or  not  disinfection 
takes  place  even  when  dry, — that  this 
earth  may  not  then  be  dangerous  and 
have  infecting  properties.  I  mean  to 
say  we  do  not  know  that  the  excreta  of 
cholera  patients,  or  typhoid  fever  pa- 
tients are  disinfected,  as  well  as  deodor- 
ized, by  this  mixture  with  dry  earth,  and 
so  I  think  you  will  all  agree  with  me 
that  the  plan  which  has  for  its  principle 
the  removal  of  these  excretal  matters 
immediately  from  the  vicinity  of  hibita- 
tions  (utilizing  them  afterwards,  if  pos- 
sible), that  the  plan  which  goes  upon 
the  principle  of  removing  them  in  the 
cheapest  way  possible,  viz.,  by  water 
carriage  and  by  gravitation,  removing 
them  at  the  same  time  with  all  the  other 
refuse  matters  of  the  population  (with 
the  single  exception  of  the  ashes),  I 
think  you  will  agree  with  me  that  that 
is,  after  all,  the  most  reasonable  plan. 
And  I  do  not  hesitate  to  say  that  nothing 
has  contributed  so  much  to  lower  the 
death  rate  of  towns  as  the  introduction 
of  the  water  carriage  system. 


The  tunnel  which  has  been  bored  un- 
der Durdham  Down,  and  which  as  form- 
ing one  section  of  the  works  of  the 
Clifton  Extension  Railway  will  put  the 
Great  Western,  Midland,  and  Bristol 
and  Exeter  systems  into  direct  commu- 
nication with  the  Channel  Docks  at 
Avonmouth,  being  now  completed,  was 
passed  through  by  the  Mayor  of  Bristol, 
Mr.  C.  J.  Thomas,  and  a  number  of  citi- 
zens interested  in  the  Docks  and  railway 
extension.  The  length  of  the  tunnel  is 
1737  yards,  and  the  gradient  throughout 
1  in  64.  It  has  been  bored  through  rock 
of  the  hardest  description,  every  foot  of 
which  had  to  be  blown  away  ;  about 
104,000  cubic  yards  or  250,000  tons  of 
rock  had  to  be  got  out.  Mr.  W.  J. 
Lawrence,  who  is  constructing  the 
Channel  Docks,  was  the  contractor  for 
the  work,  but  the  boring  of  the  tunnel 
was  sublet  to  the  Machine  Tunneling 
Company,  and  has  been  carried  out  un- 
der the  personal  superintendence  of  then1 
representative,  Mr.  Bell,  C.  E.  It  is  ex- 
pected that  Colonel  Yolland  will  make 
the  official  inspection  of  the  tunnel  and 
line. 


THE  INDIAN   TRIGONOMETRICAL   SURVEY. 


367 


THE  INDIAN  TRIGONOMETRICAL  SURVEY. 


From  "Nature." 


One  does  not  usually  expect  to  find 
much  of  general  interest  in  the  Report  of 
a  Trigonometrical  Survey.  Col.  Walk- 
er's admirably  drawn-up  Report,  how- 
ever, includes  some  matter  of  more  than 
special  value  ;  indeed,  many  of  the  de- 
tails connected  with  the  immediate  work 
of  the  Survey  are  calculated  to  interest 
the  general  reader,  they  are  concerned 
to  such  a  large  extent  with  the  peculiar 
difficulties  to  be  overcome  by  the  various 
parties,  difficulties  which  make  ordinary 
survey  work  look  like  mere  child's  play. 

The  Index  Chart  prefixed  to  the  Re- 
port enables  one  to  form  a  very  full  idea 
of  the  work  which  has  already  been  done, 
and  of  how  much  there  is  yet  to  do. 
From  Cape  Comorin  to  Peshawur  and 
all  along  the  Himalayan  frontier,  and 
from  Kurrachee  on  the  west  to  Burmah 
on  the  east,  the  country  is  covered  with 
an  intricate  net-work  of  triangulation,  in- 
cluding, however,  many  gaps  which  will 
take  many  years  to  fill  up.  Shooting  out 
from  the  northern  border  of  the  system 
of  triangulation  are  numerous  aurora-like 
lines  indicating  the  secondary  triangu- 
lation to  fix  the  peaks  of  the  Himalayan 
and  Sooliman  ranges.  We  cannot  go  into 
the  details  of  the  work  of  the  Survey, 
and  must  content  ourselves  with  a  brief 
summary  of  the  out-turn  of  work  during 
the  year  under  review,  and  with  a  refer- 
ence to  a  few  of  the  more  interesting 
side  topics. 

Of  Principal  Triangulation,  with  the 
great  theodolites  of  the  Survey,  seventy 
triangles,  embracing  an  area  of  7,190 
square  miles,  and  disposed  in  chains 
which,  if  united,  would  extend  over  a 
direct  distance  of  302  miles,  and  in  con- 
nection with  which  three  astronomical 
azimuths  of  verification  have  been  meas- 
ured. Of  Secondary  Triangulation,  with 
vernier  theodolites  of  various  sizes,  an 
area  of  5,212  square  miles  has  been 
closely  covered  with  points  for  the  topo- 
graphical operations,  an  area  of  3,650 
square  miles  has  been  operated  in  pari 
passu  with  the  principal  triangulation 
but  exterior  thereto,  and  in  an  area  of 
12,000  square  miles — in  the  ranges  of 
mountains  to   the   north    of  the  Assam 


Valley  which  are  inhabited  by  independ- 
ent tribes  —  a  large  number  of  peaks 
have  been  fixed,  many  of  which  have 
already  been  found  serviceable  in  the 
geographical  operations  now  being 
carried  on' with  the  military  expedition 
against  the  Dufflas.  Of  Topographical 
Surveying,  an  area  of  534  square  miles 
has  been  completed  in  British  portions 
of  the  Himalayas,  on  the  scale  of  one  inch 
to  the  mile,  an  area  of  2,366  square  miles 
in  Kattywar  on  the  two-inch  scale,  and 
areas  of  690  and  63  square  miles  respect- 
ively, in  Guzerat  and  in  the  Dehra  Dun, 
on  the  scale  of  four  inches  to  the  mile. 
Of  Geographical  Exploration  much  valu- 
able work  has  been  done  in  Kashgharia 
and  on  the  Pamir  Steppes,  in  connection 
with  Sir  Douglas  Forsyth's  mission  to 
the  Court  of  the  Atalik  Ghazi,  and 
several  additions  to  the  geography  of 
portions  of  the  Great  Thibet  and  of  Xe- 
paul  have  been  obtained  through  the 
agency  of  native  explorers. 

In  the  course  of  the  operations  of  the 
year  under  review  the  northern  section 
of  the  Brahmaputra  Meridional  Series 
has  been  completed  whereby  two  impor- 
tant circuits  of  triangulation  formed  by 
it  with  the  Assam  and  East  Calcutta 
Longitudinal  Series  to  the  north  and 
south,  the  Calcutta  Meridional  and  the 
Eastern  Frontier  Series  to  the  west  and 
east,  have  been  closed.  The  Straits  of 
the  Gulf  of  Manaar  have  been  recon- 
noitered,  with  a  view  to  connecting  the 
triangulation  of  India  with  that  of  Cey- 
lon, which  has  been  found  to  be  feasible. 

Probably  the  most  important  features 
in  the  operations  of  the  principal  triangu- 
lation of  the  year  are  the  resumption  of 
the  chain  of  triangles  in  Burmah,  and 
the  completion  of  the  Bangalore  Meri- 
dional Series  for  the  revision  of  the 
southern  section  of  the  Great  Are. 

Referring  to  the  revision  of  certain 
important  triangulations  which  were  or- 
iginally executed  at  the  commencement 
of  the  present  century  with  very  inferior 
instruments,  Colonel  Walker  expresses 
his  conviction  that  no  portion  of  the 
principal  triangulation  remains  which 
will  ever  require  to  be  revised,  and  that 


368 


VAN   NOSTRAND'S   ENGINEERING   MAGAZINE. 


the  last  of  the  old  links  in  all  the  great 
chains  of  triangles  which  might  with 
any  reason  have  been  objected  to  as 
weak  and  faulty,  have  now  been  made 
strong  and  put  on  a  par  with  the  best 
modern  triangulation. 

The  pendulum  observations  have  been 
completed,  and  the  final  results  are  now 
being  computed  and  prepared  for  publi- 
cation. 

Considerable  assistance  was,  moreover, 
rendered  to  Col.  Tennant  in  the  opera- 
tions connected  with  the  observation  of 
the  Transit  of  Venus ;  the  Appendix 
contains  Mr.  Hennessey's  account  of  his 
observations  at  Mussooree,  the  details  of 
which  have  already  appeared. 

The  reports  of  the  various  district 
superintendents  are  very  full,  and  con- 
tain a  good  deal  that  is  of  general  inter- 
est ;  the  accompanying  district  sketch- 
maps  are  of  great  use  in  enabling  one  to 
read  these  reports  with  understanding. 
We  shall  briefly  refer  to  some  of  the 
points  of  more  general  interest. 

In  Major  Branfill's  report  on  the  Bang- 
alore Meridional  Series,  a  very  interest- 
ing phenomenon  is  noticed  in  connection 
with  the  Cape  Comorin  base-line.  The 
operations  of  1873-74  were  intended  to 
close  in  a  side  of  the  polygon  around  the 
base-line  which  had  been  completed  in 
1868-69  ;  but  it  was  found  that  one  of 
the  two  stations  on  the  side  of  junction 
had  disappeax-ed.  This  station  was  situ- 
ated on  a  remarkable  group  of  Red  Sand 
Hills,  where,  in  1808,  Col.  Lambton  had 
constructed  a  station  by  driving  long 
pickets  into  the  drift  sand;  in  1869, 
Major  Branfill,  finding  no  trace  of  these 
pickets,  had  caused  a  masonry  well  to  be 
sunk  to  a  depth  of  ten  feet,  where  it 
reached  what  was  believed  to  be  firm 
soil  below  ;  but  during  the  interval  of 
four  years  this  well  had  been  undermin- 
ed, and  nothing  remained  thereof  but 
some  scattered  debris.  It  would  appear 
that  the  sand  hills  travel  progressively 
in  the  direction  from  west-north-west  to 
east-south-east,  which  is  that  of  the  pre- 
vailing winds  in  this  locality  ;  if  Col. 
Lambton's  station  was  situated  on  the 
highest  point  of  the  hills  and  in  a  simi- 
lar position  relatively  to  the  general 
mass  as  Major  Branfill's,  then  the  hills 
must  have  traveled  a  distance  of  about 
1,060  yards  to  the  E.S.E.,  for  the  results 
of  the  triangulation  show  that  this  is  the 


distance  between  the  positions  of  the 
two  stations  ;  thus  the  rate  of  progres- 
sion would  be  about  seventeen  yards  per 
annum.  From  Major  Branfill's  Notes  on 
the  Tinnevelly  district,  which  are  ap- 
pended to  the  General  Report  for  1868- 
69,  it  appears  that  certain  measurements 
of  the  eastward  drift  had  made  it  as 
much  as  440  yards  in  the  four  years 
1845-48  ;  but  the  distance  between  the 
trigonometrical  stations  of  1808  and 
1869  probably  affords  the  most  accurate 
measure  which  has  hitherto  been  obtain- 
ed of  the  rate  of  progress  of  this  re- 
markable sand-wave,  which  gradually 
overwhelms  the  villages  and  fields  it 
meets  with  in  its  course,  and  has  never 
yet  been  effectually  arrested  ;  numerous 
attempts  have  been  made,  by  growing 
grass  and  creepers  and  planting  trees  on 
the  sands,  to  prevent  the  onward  drift, 
but  they  have  hitherto  been  unsuccessful. 
Mr.  Bond,  one  of  Major  Branfill's  staff, 
managed  to  procure  an  interview  with  a 
couple  of  the  wild  folk  who  live  in  the 
hill  jungles  of  the  western  Ghats,  to  the 
southwest  of  the  Palanei  hills.  A  strange 
dwarfish  people  had  often  been  heard  of 
as  frequenting  the  jungles  near  the  sta- 
tion of  Pemalei,  in  the  north-west  corner 
of  the  Tinnevelly  district,  but  until  Mr. 
Bond  caught  these  two  specimens  no 
trace  of  them  had  been  seen  by  the  mem- 
bers of  the  Survey.  These  two  people, 
a  man  and  a  woman,  believed  themselves 
to  be  100  years  old,  but  Mr.  Bond  sup- 
poses the  man  to  be  about  twenty-five, 
and  the  woman  18  years  of  age.  "The 
man,"  Mr  Bond  states,  "  is  4  feet  6|- 
inches  in  height,  26^  inches  round  the 
chest,  and  18£  inches  horizontally  round 
the  head  over  the  eyebrows.  He  has  a 
round  head,  coarse  black,  woolly  hair, 
and  a  dark  brown  skin.  The  forehead  is 
low  and  slightly  retreating  ;  the  lower 
part  of  the  face  projects  like  the  muzzle 
of  a  monkey,  and  the  mouth,  which  is 
small  and  oval,  with  thick  lips,  protrudes 
about  an  inch  beyond  his  nose  ;  he  has 
short  bandy  legs,  a  comj)aratively  long 
body,  and  arms  that  extend  almost 
to  his  knees  ;  the  back  just  above  the 
buttock  is  concave,  making  the  stern  ap- 
pear to  be  much  protruded.  The  hands 
and  fingers  are  dumpy  and  always  con- 
tracted, so  that  they  cannot  be  made  to 
stretch  out  quite  straight  and  flat  ;  the 
palms  and  fingers  are  covered  with  thick 


THE   INDIAN   TRIGONOMETRICAL   SURVEY. 


369 


ekin  (more  particularly  so  the  tips  of  the 
fingers),  and  the  nails  are  small  and  im- 
perfect ;  the  feet  are  broad  and  thick 
skinned  all  over  ;  the  hairs  of  his  mous- 
tasche  are  of  a  greyish  white,  scanty  and 
coarse  like  bristles,  and  he  has  no  beard. 

"  The  woman  is  4  feet  6-£  inches  in 
height,  27  inches  round  the  chest  (above 
the  breasts),  and  19^  horizontally  round 
the  head  above  the  brows  ;  the  color  of 
the  skin  is  sallow,  or  of  a  nearly  yellow 
tint  ;  the  hair  is  black,  long  and  straight, 
and  the  features  well  formed.  There  is 
no  difference  between  her  appearance  and 
that  of  the  common  women  of  that  part 
of  the  country.  She  is  pleasant  to  look 
at,  well  developed,  and  modest."  Their 
only  dress  is  a  loose  cloth,  and  they  eat 
flesh,  but  feed  chiefly  on  roots  and 
honey. 

"  They  have  no  fixed  dwelling  places, 
but  sleep  on  any  convenient  spot,  gener- 
ally between  two  rocks  or  in  caves  near 
which  they  happen  to  be  benighted. 
They  make  a  fire  and  cook  what  they 
have  collected  during  the  day,  and  keep 
the  fire  burning  all  night  for  warmth  and 
to  keep  away  wild  animals.  They  wor- 
ship certain  local  divinities  of  the  forest, 
Rakas  or  Rakari,  and  Pe  (after  whom 
the  hill  is  named,  Pe-malei)." 

The  woman  cooks  for  and  waits  on  the 
man,  eating  only  after  he  is  satisfied. 

The  means  taken  for  tidal  observations 
in  the  Gulf  of  Kutch  promise  to  lead  to 
valuable  results.  The  object  of  these 
observations  is  to  ascertain  whether  secu- 
lar changes  are  taking  place  in  the  rela- 
tive level  of  the  land  and  sea  at  the  head 
of  the  gulf.  Very  great  difficulties  were 
found  in  selecting  suitable  stations  for 
fixing  the  tide-gauges,  as  the  foreshores 
of  the  gulf  consist  mainly  of  long  mud- 
banks,  which  often  stretch  miles  into  the 
sea,  and  are  left  bare  at  low  water,  when 
they  are  intersected  by  innumerable  tor- 
tuous and  shallow  creeks,  whose  shifting 
channels  would  be  very  unfavorable 
positions  for  tide-gauges.  Only  three 
points  suitable  for  tidal  stations  were 
met  with  on  the  coasts  of  the  gulf :  at 
Hanstal  Point,  near  the  head  of  the  gulf; 
at  Nowanar  Point,  half  way  up,  on  the 
Northern  or  Kutch  coast  ;  and  at  Okha 
Point,  on  the  southern  coast,  opposite  the 
island  of  Beyt.  .  None  of  these  points, 
however,  are  situated  in  ports  or  harbors, 
where  piers,  jetties,  landing-stages,  or 
Vol.  X1IL— No.  4—24 


docks  might  have  been  utilized  ;  on  the 
contrary,  they  are  all  situated  at  some 
distance  from  the  nearest  inhabited  lo- 
calities, and  present  no  facilities  what- 
ever. The  operations  had  thus  to  be  of 
the  very  simplest  nature.  The  only 
practicable  plan  was  to  have  the  tide- 
gauges  set  up  on  shore,  over  wells  sunk 
near  the  high-water  line,  and  connected 
with  the  sea  by  piping.  The  wells  are 
iron  cylinlers,  with  an  internal  diameter 
of  twenty-two  inches,  which  slightly 
exceeds  the  diameter  of  the  float  ;  the 
cylinders  were  made  up  in  sections  of 
fifty  inches  in  length,  the  lowest  of  which 
is  closed  below  with  an  iron  plate,  and 
the  whole,  when  bolted  together,  forms 
a  water-tight  well,  into  which  water  can 
only  enter  through  the  piping  for  effect- 
ing connection  with  the  sea.  The  piping 
is  of  an  internal  diameter  of  two  inches, 
which  has  been  computed  to  be  sufficient 
to  permit  of  the  transmission  of  the  tidal 
wave  to  the  well  without  sensible  retard- 
ation. Iron  piping  is  laid  from  the 
well  to  the  line  of-  low  water  ;  it  is 
brought  vertically  up  from  the  bot- 
tom of  the  well  nearly  to  the  surface 
of  the  ground,  and  is  then  carried  down 
to  the  sea,  where  flexible  gutta-percha 
piping  is  attached,  and  carried  into  the 
deej)  water.  The  outer  piping  terminates 
in  a  "  rose,"  which  is  suspended  a  few 
feet  above  the  bed  of  the  sea  by  a  buoy, 
in  order  to  prevent  the  entrance  of  silt 
as  much  as  possible,  and  it  can  be  read- 
ily detached  from  the  iron  piping  when- 
ever it  has  to  be  cleaned. 

After  many  difficulties,  and  even  dan- 
gers to  life,  Capt.  Baird's  party  managed 
to  get  the  gauges  erected  and  set  to 
work,  and  what  with  the  tidal  observa- 
tions, observations  of  the  barometric 
pressure,  the  velocity  and  direction  of 
the  wind,  and  the  amount  of  rainfall— 
for  each  station  has  been  provided  with 
means  for  making  such  observations — 
very  valuable  results  may  be  expected. 

Lieut.  Gibbs'  notes  on  the  portion  of 
the  Dang  Forests,  in  the  Guzerat  district, 
visited  by  him  in  1874,  are  of  great  in- 
terest, and  we  regret  that  space  forbids 
us  referring  to  them  in  detail.  His  ob- 
servations on  the  inhabitants  of  this  re- 
gion are  of  special  value  ;  he  also  seems 
to  have  paid  considerable  attention  to 
the  fauna,  flora,  and  geology  of  the  dis- 
trict. 


370 


VAN   NOSTRAND'S   ENGINEERING    MAGAZINE. 


Capt.   Heaviside's  lively  narrative  of  j 
the    pendulum   -work    in   India,    of   his ' 
journey  home,  and   of  the  operations  at 
Kew,  will  also  be  read  with  interest. 

Two  narratives  of  somewhat  unusual 
interest  are  given  in  the  Appendix.  One 
of  these,  by  Lieut.-Col.  Montgomerie, ' 
gives  an  account  of  a  journey  to  the 
Namcho  or  Tengri  Nur  Lake,  in  Great 
Thibet,  about  ninety  miles  north  of  the  i 
Brahmaputra,  by  a  native  explorer,  dur- 
187.1—72.  The  explorer  was  a  semi- 
Thibetan,  a  young  man  who  had  been 
thoroughly  trained  for  the  work,  and 
who  was  accompanied  by  four  assistants. 
The  party  set  out  from  Kumaon  in  No-  j 
vember,  and  crossed  the  Brahmaputra  at 
Shigatze,  and  amid  considerable  hard- 
ships made  their  way  northwards,  reach- 
ing the  lake  about  the  end  of  January, 
when  they  found  it  completely  frozen 
over,  although  the  water  is  so  salt  as  to  j 
be  unfit  for  drinking.  The  party  in- 
tended  to  travel  all  round  the  lake,  which 
is  15,200  feet  above  the  sea,  fifty  miles 
long  and  from  sixteen  to  twenty-five 
miles  broad,  and  intended  to  proceed 
further  to  the  northward  and  take  com- ! 
plete  surveys,  but  were  robbed  of  nearly 
all  they  had,  and  were  thus  compelled  to 
beat  a  rapid  retreat,  which  they  did  by 
way  of  Lhasa. 

During  the  greater  part  of  his  journey  j 
to  the  Namcho  Lake  the  explorer  found 
the  streams  all  hard  frozen,  and  he  was 
consequently  much  struck  by  the  number 
of  hot   springs  which  he  met  with,  and 
more  especially  by  the  great  heat  of  the  j 
water  coming  from  them,  his  thermome-  j 
ter  showing  it  to  vary  from  130°  to  183°  j 
Fahrenheit,  being  generally  over   150°,  I 
and  often  within  a  few  degrees   of  the 
boiling  point,  being   in   one    case    183° 
when  the  boiling  point  was  183f°.     The  ! 
water  generally  had  a  sulphurous  smell, 
and   in   many    cases   was    ejected    with 
great  noise  and  violence;  in  one  place  the  J 
force  was  sufficient  to  throw  the  water 
up    from    forty   to    sixty   feet.      These 
springs  in  some  respects  seem  to  resem- 
ble the  geysers  of  Iceland. 

To  the  south  the  lake  is  bounded  by  a 
splendid  range  of  snowy  peaks,  flanked 
with  large  glaciers,  culminating  in  the 
magnificent  peak  "  Jang  Ninjinthangla," 
which  is  probably  more  than  25,000  feet 
above  the  sea.  The  range  was  traced  for 
nearly  150  miles,  running  in  a  north-east- 


erly direction.  To  the  north  of  the  lake 
the  mountains  were  not,  comparatively 
speaking,  high,  nor  were  there  any  high 
peaks  visible  further  north  as  far  as  the 
explorer  could  see  from  a  commanding 
point  which  he  climbed  up  to.  He  only 
saw  a  succession  of  rounded  hills  with 
moderately  flat  ground  in  betwen  them. 
Immediately  north  he  saw  a  lake  of 
about  six  miles  in  length,  which  he  was 
told  was  called  Bui  Cho,  from  the  borax 
(bul)  which  is  produced  there  in  large 
quantities,  supplying  both  Lhasa  and 
Shigatze  with  most  of  the  borax  that 
they  require. 

■The  Tengri  Nur  or  "  Namcho"  Lake 
is  considered  to  be  a  sacred  place,  and 
although  at  such  a  very  great  distance 
from  habitations  and  so  high  above  the 
sea,  it  boasts  of  several  permanent  mon- 
asteries and  is  visited  by  large  numbers 
of  pilgrims.  There  are  several  islands  in 
the  lake,  two  of  them  large  enough  for 
monasteries  :  at  the  time  the  explorer 
was  there  the  Lamas  on  the  islands 
kept  up  their  communication  with  the 
shore  by  means  of  the  ice,  but  he  did  not 
hear  as  to  what  was  done  in  summer. 
Fish  are  said  to  be  abundant,  and  mod- 
ern lake  shells  were  found  on  the  shore 
as  well  as  fossil  shells,  which  were  very 
numerous  and  of  all  sizes. 

The  narrative  contains  many  other 
valuable  observations  made  on  the  people 
and  the  country  through  which  he 
traveled ;  there  is  a  good  map  of  the 
route. 

The  other  narrative  is  quite  equal  in 
interest  to  that  just  referred  to.  It  con- 
sists of  extracts  from  a  native  explorer's 
narrative  of  his  journey  from  Pitoragarh 
in  Kumaon  via  Jumla  to  Taelum,  and 
then  down  through  Nepaul,  along  the 
Gandak  River,  to  British  territory. 
The  explorer,  who  had  to  exercise  much 
determination  and  ingenuity,  took  minute 
notes  by  the  way  of  all  he  saw,  and  has 
added  much  to  our  knowledge  of  the 
geography,  the  people,  and  the  products 
of  a  region  comparatively  unknown. 
He  had  to  cross  many  rivers  by  the  way, 
which  was  generally  done  by  means  of 
ropes  suspended  between  the  banks. 
The  explorer  wished  to  proceed  much 
further  than  Tadum,  which  is  a  little 
beyond  the  Brahmaputra,  in  Great 
Thibet,  but  was  prevented  by  the  head 
man  of  the. village.     He  started  on  July 


IRON   AS   A    CONSTRUCTIVE   MATERIAL. 


371 


1,  1873,  and  reached  British  territory 
again  about  the  end  of  November,  after 
having  traveled  nearly  500  milei-}.  We 
have  space  to  notice  only  one  interesting 
phenomenon  which  he  observed.  At 
Muktinath,  near  Kagbeni,  about  11,280 
feet  above  the  sea,  in  N.  lat.  29°  and  E. 
long.  83°  45',  about  600  feet  south  of 
the  temple,  is  a  small  mound  with  a  little 
still  water  at  its  base,  having  a  sulphur- 
ous smell.  From  a  crevice  in  this  mound, 
at  the  water's  edge,  rises  a  flame  about 
a  span  above  the  surface.  The  people 
of  the  place  told  the  explorer  that  the 


water  sometimes  increases  in  quantity 
sufficiently  to  flow  into  the  crevice  ;  the 
flames  then  disappear  for  a  while,  and 
there  is  a  gurgling  noise,  a  report,  and 
the  flames  burst  up  and  show  again. 
This  spot  is  called  Chume  Giarsa  by  the 
Bhots. 

Our  readers  will  see,  from  the  cursory 
glance  we  have  been  able  to  take  at 
this  Report,  that  it  contains  much  valu- 
able matter  apart  from  the  immediate- 
work  of  the  Survey,  the  members  of 
which  are  doing  good  service  to  India 
and  to  science. 


IRON  AS  A  CONSTRUCTIVE  MATERIAL/- 


From  "The  Architect. 


It  is  only  of  late  years  that  iron,  as 
compared  with  other  metals,  has  been 
used  as  a  constructive  material,  but  it 
was  known  and  employed  for  various 
other  purposes  from  the  very  earliest 
times  ;  and  though  it  is  now  the  metal 
of  all  others  the  most  frequently  used 
by,  and  is  the  best  adapted  of  any  to  the 
requirements  of,  the  architect  or  engi- 
neer, it  is,  as  I  say,  comparatively  re- 
cently that  its  great  value  for  building 
and  constructive  purposes  has  been  fully 
appreciated,  and,  to  a  certain  extent, 
utilized  ;  and  it  is  with  the  hope  of 
showing  that  it  may  be  employed  in  a 
still  better  manner  than  at  present,  I 
venture  to  take  up  your  time  this  even- 
ing. 

Though  the  use  of  iron  by  architects 
in  building  structures  has  enormously 
advanced,  the  credit  of  discovering  and 
applying  the  great  advantages  that  iron 
unquestionably  possesses  over  almost 
every  other  material  to  constructive  pur- 
poses, is  due,  I  think,  to  the  engineers 
and  not  the  architects.  Architects  as  a 
body  have  neglected  and  slighted  this 
universally  useful  metal,  either  rejecting 
it  altogether,  or  employing  it  as  it  were 
under  protest,  and  as  if  they  were 
ashamed  of  it ;  they  use  it  in  fact  as  a 
drudge,  and  not  as  I  venture  to  think 
they  should,  as  a  valuable  friend,  equal 
indeed  to  most  other  building  materials 


*  A  paper  read  before  the  Royal  Institute  of  British 
Architects  by  Mr.  C.  H.  Driver. 


and  superior  to  some  ;  valuable  both  for 
constructive    and    decorative    purposes, 
and   I    apply   these   terms   in  the  same 
sense  as  we  employ  them  when  speaking 
of  wood,  stone,  or  any  other  material  we 
use  in  building  ;  and  while  it  is  remark- 
able that  we  should  have  thus  neglected 
it,  the  way  in  which  engineers  seized  it  is 
no  less  remarkable,  for  they  with  wonder- 
ful acuteness  brought  their  science  and 
practical   knowledge   to   bear   upon    it, 
producing  results  that  ought  to  be  an 
example  to  us  ;  for,  as  a  rule,  engineers, 
with  regard  to  brick  or   stone,  pay  us 
the  compliment  of  copying  as  well  as 
they   can   our   architectural   forms   and 
practice  ;  but  with    respect   to  iron  the 
reverse  is  the  case,  as  they,  finding  that 
architects  had  done,  I  Avill  not  say  could 
do,  little  or  nothing  with  it,  struck  out 
a  path  for  themselves,  and  it  cannot  be 
denied,  have  achieved  in  it  a  great  suc- 
cess.    I  think,  however,  it  is  unfortunate 
to  some  extent  that  they  did  so,  for  it  is 
in  a  great  measure  the  cause  of  the  want 
of  appreciation  iron  obtains  from  archi- 
tects, not  because  architects  are  jealous 
of  the  success  of  the  engineers,  but  rather 
because  of  the  disgust  they  feel  at  the 
inartistic    result   of   their   labors.      Can 
this  be  remedied,  and  can  iron  be  placed 
in  its  proper   position    with    regard    to 
architecture  ?     I  venture  to  hope  it  mav, 
by   taking   advantage  of  the   practical 
skill    and    knowledge   which    engineers 
have   already   obtained,    and   upon   the 
foundation  laid  by  them,  advancing  step 


372 


VAN  nostrand's  engineering  magazine. 


by  step,  till  we  succeed  in  finding  uses 
for  iron  both  in  construction  and  deco- 
ration, which,  while  perfectly  adapted 
to  the  material,  will  yet  combine  and 
harmouize  with  those  we  have  hereto- 
fore had  in  use. 

Let  us  consider  for  a  moment  some  of 
the  principal  attributes  of  iron,  and  then 
see  how  architects  generally  take  advan- 
tage of  them.  As  regards  wrought  iron 
— first,  it  is  very  strong,  bearing  a  work- 
ing tensile  strength  of  from  five  to  six 
tons,  and  a  compressive  strain  of  from 
four  to  five  tons  per  inch  of  section,  and 
as  regards  strength  it  is  as  twenty-seven 
to  five  as  compared  with  oak,  and  as 
twenty-seven  to  four  as  compared  with 
fir,  and  yet  if  it  is  employed  as  a  beam 
or  girder,  it  is  generally  so  swaddled  up 
with  cradling  and  lath  and  plaster,  that 
as  much  room  is  taken  up  by  it  as  if  it 
had  been  a  beam  of  oak  or  fir.  Then 
again  it  is  very  light  as  compared  with 
its  strength,  but  by  the  same  process  at 
last  mentioned,  its  weight  is  brought  up 
to  that  of  a  wood  beam.  It  is  very 
ductile,  easily  hammered  to  any  variety 
of  shape,  and  yet  almost  the  only  form 
ever  given  to  a  wrought  iron  girder 
when  used  in  building,  is  that  of  the 
ordinary  rolled  or  plate  girder. 

Again,  iron,  though  very  durable,  is 
not  an  imperishable  material,  and  this 
'  appears  to  be  practically  forgotten,  for 
though,  unlike  wood  and  perhaps  stone, 
it  is  free  from  internal  deterioration,  yet 
it  is  liable  to  serious  destruction  by  rust 
and  oxydation  of  its  outer  surfaces,  a 
most  important  point  considering  the  fact 
that  but  little  excess  of  material  is  usually 
provided  than  is  absolutely  necessary 
for  the  required  work,  and  therefore  it 
would  be  but  reasonable  to  suppose  that 
when  used  arrangements  should  be  made 
by  which  all  parts  of  a  girder  or  col- 
umn could  be  readily  inspected  ;  but  in 
the  system  in  vogue  the  reverse  is  the 
case,  for  the  girder  is  so  covered  and 
hidden  up  that  no  inspection  is  possible, 
nor  can  any  means  be  taken  to  paint,or 
otherwise  preserve  it  from  the  inevitable 
destruction  that  must  result  from  rust. 
It  is  almost  the  same  as  regards  cast 
iron  ;  it  is  a  material  admirably  adapted 
for  columns,  from  its  fitness  to  bear 
great  compressive  strains,  and  by  its 
very  nature  capable  of  assuming  almost 
any  form  that   architects   may  design, 


from  a  plain  column  to  the  most  elabo- 
rate effort  of  ornamental  art  the  mind 
can  conceive,  yet  as  ordinarily  employed 
the  cast-iron  column  is  either  a  plain 
round  shaft  with  a  square  cap  and  base- 
plate with  gusset-pieces  to  strengthen 
their  connection  with  the  shaft,  or  as  a 
story-post  like  a  girder  standing  up  on 
end  ;  this  column  or  story-post  is  often 
covered  with  lath  and  plaster,  and  ap- 
pears in  the  glorified  shape  of  a  Doric, 
Ionic,  or  Corinthian  column,  with  cap, 
&c,  to  match,  or  as  is  the  case  in  most 
shops,  it  is  left  in  its  native  bareness  be- 
hind a  plate-glass  front. 

I  repeat  that  we  are  glad  enough  to 
make  use  of  the  strength,  lightness,  and 
adaptability  of  iron,  but  we  are  ashamed 
to  acknowledge  that  we  have  employed 
it,  and  therefore  cover  and  hide  it  up  ; 
and  I  think  this  arises'.in  a  great  measure 
from  the  idea  (a  mistaken  one,  however) 
that  iron  does  not  accord  with  other 
materials,  and  is  unsuited  for  architect- 
ural forms,  and,  therefore,  if  we  use  it 
(as  at  the  present  time  we  are  almost 
compelled  to  do)  we  should  do  our  best 
to  hide  it  up  as  much  as  possible  ;  and  it 
is  argued  that  it  is  necessary  to  lath, 
plaster,  and  case  it  up  to  satisfy  the  eye, 
as  from  its  strength  so  little  is  required 
that  no  effect  can  be  obtained  in  using 
it,  and,  therefore,  it  is  better  to  cover  it 
up  with  other  materials  to  avoid  the 
thinness  and  poverty  of  appearance  that 
is  produced  when  employed,  alone,  in  the 
same  way  that  the  flesh  covering  the 
bones  produces  a  beautiful  form,  and  at 
the  same  time  hides  a  ghastly  skeleton. 
But  does  the  hiding  up  of  iron  by  other 
material  meet  the  object  intended,  viz., 
better  effect?  (and  setting  aside  for  a 
moment  the  principle  of  honesty  of  con- 
struction) is  not  the  result  obtained  most 
unsatisfactory  ?  For  owing  to  the  intro- 
duction of  iron  much  larger  spaces  are 
bridged  over  without  requiring  columns 
and  arches  than  heretofore,  and  hence 
there  is  produced  a  bareness  and  an  ap- 
parent weakness  anything  but  satisfac- 
tory to  the  eyes.  As  an  example,  I  will 
take  that  most  familiar  one  to  all,  the 
shop  front ;  there,  as  a  rule,  we  have  a 
structure  of  three,  four,  or  more  stories 
high,  with  elaborate  and  massive  archi- 
tectural features,  columns,  cornices,  pedi- 
ment, &c,  piled  up  with  lavish  richness, 
all  carried  apparently  by  a  stone  lintel 


IKON   AS   A   CONSTRUCTIVE   MATERIAL. 


373 


of  twenty,  thirty  or  forty  feet  span,  and 
of  an  absurdly  little  depth  in  proportion 
to  what  in  appearance  it  has  to  carry 
over  a  huge  field  of  plate  glass  ;  while, 
as  we  all  know,  the  real  work  of  support- 
ing the  fine  front  is  done  by  the  wrought 
or  cast-iron  girder,  which  is  hidden  be- 
hind the  stone  fascia  aided  by  cast-iron 
columns  or  story-posts,  as  the  case  may 
be.  The  effect  is  not  pleasing  or  satis- 
factory for  it  is  untruthful,  and  I  contend 
that  if  the  money  spent  upon  the  sham 
lintel  that  forms  the  casing  to  the  girder 
were  spent  upon  the  girder  and  column 
by  making  them  pleasing  in  design  and 
form,  the  effect  would  not  only  be  much 
better  but  positively  good,  for  though 
we  should  still  have  the  wide  span  and 
the  plate  glass  under  as  before,  yet  we 
should  see  how  the  building  above  was 
really  carried,  and  as  we  know  that  iron 
i«  strong  and  capable  of  doing  its  work, 
the  eye  as  well  as  the  mind  would  be 
satisfied. 

With  regard  to  this  point,  viz.,  the 
satisfaction  of  the  eye,  it  is  possible  that 
the  eye  may  require  some  amount  of 
education  before  it  becomes  accustomed 
to  the  use  of  iron  and  its  employment  in 
•onnection  with  other  material.  For  we 
are  so  accustomed  to  see  beams,  columns 
and  brackets  of  certain  proportions  that 
we  are  at  first  sight  shocked  at  the  idea 
of  detached  columns  of  twenty-five  or 
thirty  diameters  carrying  great  loads,  or 
slender  beams  carrying  a  heavy 'build- 
ing ;  and  it  is  difficult  to  adjust  their 
proportions  with  the  styles  of  architec- 
ture we  have  in  use.  But  I  have  hopes 
that  architects  will,  if  they  give  the  mat- 
ter their  earnest  attention,  with  the  sin- 
cere desire  to  succeed,  produce  designs 
for  iron  which,  though  not  perhaps  ex- 
actly in  accordance  with  any  existing 
particular  style,  shall  yet  harmonize,  even 
perhaps  by  contrast,  with  them.  Iron 
sometimes  meets  with  other  but  very 
different  treatment  from  the  hands  of 
architects,  and  I  hardly  know  which  is 
the  worst,  for  instead  of  being  hidden, 
it  is  brought  prominently  forward,  but 
then  not  as  iron,  but  something  else,  such 
as  stone  or  wood,  especially  so  in  the 
case  of  cast-iron,  for  not  only  is  it  made 
to  represent  the  last-named,  but  it  also 
appears  in  the  guise,  or  rather  disguise, 
of  wrought  iron.  I  may  instance  balus- 
trades, vases,  parapets,  tracery,  &c.     A 


prominent  example  of  its  misuse  in  this 
way  is  seen  in  the  parapet  and  spandrels 
of  Westminster  Bridge,  though  happily, 
however,  these  were  not  the  work  of  an 
architect. 

There  is,  I  think,  another  reason  why 
architects  as  a  rule  ignore  iron  as  a  con- 
structive material,  and  that  is  perhaps 
the  most  general  one,  viz.,  few  of  them 
comparatively  know  anything  about  it, 
never  studying  or  looking  upon  it  other 
than  as  the  aforesaid  useful  drudge,  and 
this  more  especially  so  with  respect  to 
wrought  iron,  and  as  to  cast,  they  may 
perhaps  use  it  for  columns,  railings, 
finials,  or  rain-water  gutters  and  spout- 
ings,  but  these  they  take  ready  designed 
from  an  ironfounder's  catalogue,  and 
they  may,  or  which  is  more  often  the 
case,  may  not  harmonize  with  the  rest  of 
their  design,  they  thinking  it  is  not 
worth  their  while  to  take  the  trouble  to 
design  such  things  for  themselves.  Or 
if  they  want  a  wrought-iron  girder,  they 
are,  perhaps,  able  to  work  one  out  from 
the  simple  formulas  given  in  the  various 
handbooks  ;  or,  as  is  more  likely,  they 
leave  it  to  the  builder's  foreman.  But 
if  the  quantity  reqvrired  is  large,  and 
the  work  important,  they  then  employ 
an  engineer  to  work  out  the  calculations, 
and  as  the  engineer  (with  every  respect 
to  him)  cares  nothing  about  art,  but  a 
great  deal  as  to  whether  his  girders  are 
strong  and  economical,  it  is  very  prob- 
able that  the  resultant  work  is  ugly,  and 
as  without  doubt  the  ordinary  plate 
girders  and  columns,  used  in  buildings 
generally,  are  ugly,* the  architect  natur- 
ally enough  covers  them  up  with  a  ma- 
terial he  does  know  something  about, 
and  therefore  can  design  in  ;  but  if  the 
architect  did  know  and  understand  as 
much  about  iron  he  would  calculate  for 
himself,  and  study  to  so  design  his  gird- 
ers or  columns,  or  whatever  else  he  may 
require,  that  the  result  should  be  artistic 
and  suitable  to  the  structure  for  which  it 
was  intended. 

Surely  architects,  if  they  will,  can  so 
design  their  girders  in  wrought  or  cast 
iron  that  they  shall  be  pleasing  and  ef- 
fective. Let  them  but  take  the  trouble 
to  draw  them  out  and  calculate  them  for 
themselves,  they  will  soon  find  it  easy 
enough  to  arrange  flanges,  webs,  cover 
plates,  angle  and  tee  irons  so  symmetri- 
cally as  to  be  pleasing,  and  still  preserve 


374 


VAN  nostrand's  engineering  magazine. 


the  necessary  scientific  proportions  and 
the  relation  of  the  several  parts  to  each 
other  in  a  practical  manner — plates  and 
angle  and  tee  irons  are  now  rolled  in 
such  length  that  very  large  spaces  may 
be  spanned  by  girders  without  any  cover 
or  junction  plates  being  required.  As 
for  instance,  plates  can  be  obtained  from 
20  to  25  feet  long  by  2  to  3  feet  wide  ; 
angle  and  tee  irons  up  to  30  or  35  feet 
or  even  40  feet.  Many  varied  forms  and 
even  mouldings  could  and  would  be 
rolled,  if  manufacturers  found  there 
was  a  demand  for  them,  and  that  it 
would  pay  to  make  the  necessary  rolls. 

JReveiting  for  a  moment  to  the  point 
that  the  constructive  employment  of 
iron  is  of  comparatively  lai.e  date,  it  is 
worthy  of  remark  the  significant  fact 
that  the  artists  of  the  Middle  Ages  had 
brick  and  stone  and  other  materials,  but 
no  iron — at  least  not  in  quantities  they 
could  make  structural  use  of,  and  they 
.  made  such  good  use  of  the  materials 
they  had  that  we  are  feign  to  copy  them. 
Is  it  not  therefore  fair  to  suppose  that 
if  they  had  had  iron  at  their  command 
as  we  have,  they  would  have  produced 
works  in  that  material  as  admirable  as 
are  their  works  in  others  ?  and  I  am 
justified  in  assuming  this  from  the  won- 
derfully beautiful  works  they  achieved 
in  the  ornamental  wrought-iron  work 
they  did  make.  I  cannot  help,  therefore, 
feeling  that,  to  a  certain  extent,  the  poor 
results  we  have  accomplished  with  all 
the  facilities  we  have  at  our  command  is 
not  a  cheering  instance  of  the  progress 
of  true  ai*t  in  these  modern  times. 

There  is  yet  another  matter  closely 
connected  with  iron  as  a  constructive 
material  which  requires  attention,  and 
that  is  the  relative  positions  in  which 
wrought  and  cast  iron  should  be  placed, 
viz.,  whether  in  internal  or  external 
work,  and  this  more  especially  applies  to 
ornament.  Xow  it  is  a  certain  and  well- 
known  fact  that  wrought  iron  is  much- 
more  susceptible  to  the  influence  of 
weather  as  regards  oxydation  than  cast, 
and  though,  therefore,  there  can  be  no 
question  as  to  the  superior  art  and  beauty 
of  wrought  iron,  yet  it  is  a  matter  worthy 
of  some  consideration,  if  it  be  not  more 
advisable,  for  the  sake  of  durability,  to 
employ  cast  iron  for  ornamental  work 
externally,  and  confine  our  use  of  wrought 
iron  to  purposes  of  internal  decoration. 


I  am  perfectly  aware  that  in  advocating 
the  use  of  cast  iron  ornament  at  all  I  am 
touching  upon    dangerous  ground,  as  I 
know  that  among  many  of  the  highest 
authorities   there    is    a    strong    feeling 
against  it,  but  be  this  as  it  may,  the  fact 
remains  the  same  that  cast  iron  is  better 
adapted  for  external  work  than  wrought, 
!  and  I  am  inclined  to  think  that  the  feel- 
ing which  undoubtedly  does  exist  against 
|  it  is  due  to  the  way  in  which  it  is  mis- 
j  used,  and  that  if  the  design  is  properly 
I  adapted  to  the  material  one  of  the  prin- 
>  cipal  objections  to  its  application  is  re- 
I  moved.     I  know  it  is  said  that  cast  iron 
ornament  is  inartistic,  showing  no  feeling, 
utterly   wanting    in    individuality,    and 
vulgar  in  the  extreme,  so  that  cast  iron 
ornament  has  almost  become  a  by-word; 
but    surely   it    is    unfairly   treated,   for 
might  not  the  same  be  said  of  work  in 
bronze  ?     A  work  in  cast  iron  requires  to 
have   a   model   prepared   and   a   mould 
made,  so  also   does    a  work   in  bronze. 
The  iron  has  to  be  melted  and  run  into 
the  mould,  and  it  is  the  same  with  bronze ; 
if  the  model  is  badly  designed  and  badly 
executed  in  either  case,  the  resultant  cast 
will  be  bad  also. 

With  respect  to  iron  as  a  constructive 
material,  the  different  qualities  of  the 
metal  used  is  a  very  important  and  seri- 
ous point,  much  more  so  than  at  first 
sight  appears  ;  for,  as  in  the  case  of  cast 
iron,  there  is  not  only  a  great  difference 
of  strength  in  the  different  brands,  but 
also  in  the  same  iron,  from  the  manner 
in  which  it  is  manufactured,  and  it  is  al- 
most impossible  to  judge  by  the  outward 
appearance  of  a  casting  whether  the  iron, 
used  is  good  or  bad,  for  even  when  frac- 
tured it  requires  great  skill  and  exper- 
ience to  do  so.  I  do  not,  however,  pur- 
pose to  go  into  this  matter  this  even- 
ing. 

Hitherto  I  have  only  spoken  of  mat- 
ters which  concern  iron  as  a  building- 
material,  but  I  propose,  with  your  per- 
mission, before  closing  my  Paper,  to  add 
a  few  remarks  upon  constructive  orna- 
mentation of  ironwork,  or,  as  it  would 
perhaps  be  better  to  put  it,  the  orna- 
mental construction  of  ironwork  ;  for, 
though  in  my  previous  remarks,  I  have 
several  times  referred  to  ornamental 
work  in  iron,  it  has  been  irrespective  of 
its  being  constructive  or  otherwise.  I 
can,  however,  only  give  a  passing  glance 


KEPORTS    OF   ENGINEERING    SOCIETIES. 


375 


.at  it,  for  the  subject  is  one  which  in  itself 
would  extend  to  almost  any  length. 

We  most  of  us  know  what  ornamen- 
tal construction  consists  of  in  wood  or 
stone  as  opposed  to  constructing  for  or- 
nament, but  it  is,  I  confess,  difficult  to 
apply  the  principles  which  guide  us  in 
the  last-named  materials  to  iron  ;  for 
though  it  is  true  we  can,  as  I  have  said, 
so  arrange  our  tee  and  angle  irons,  webs 
and  plates,  &c,  that  they  shall  be  sym- 
metrical, that  is  not  all  that  is  required, 
for  true  ornament  does  not  consist  in 
symmetry  alone,  though  symmetry  is  a 
very  important  element  in  it.  We  are 
placed  in  this  difficulty,  that  almost  any 
ornament  we  employ  on  constructive 
ironwork  has  to  be  itself  constructed, 
thus  flying  in  the  face  of  that  golden 
rule  of  ornament  which  tells  us  to  "  or- 
nament our  construction  and  not  to  con- 
struct for  ornament."  When  working 
with  wood  and  stone  and  some  other 
building  materials  we  can  build  in  blocks 
or  masses  of  material,  and  cut  and  carve 
them  as  it  seemeth  to  us  best,  and  it  can 
hardly  be  said  that  we  are  able  to  do 
this  in  the  same  sense  in  iron  ;  but 
though  we  cannot  carve  it,  we  can 
stamp,  emboss,  engrave,  and  even  mould 
it  if  we  will,  for  machinery  is  now  so 
powerful  that  mouldings,  splays,  cham- 
fers, &c,  can  be  executed  in  this  mate- 
rial with  nearly  the  same  facility  as  in 
wood;  and  there  is  some  ground  for  con- 
solation in  the  fact  that  whatever  diffi- 
culties we  may  have  to  encounter  with 
respect  to  having  to  construct  for  orna- 
ment in  iron,  the  same  difficulty  has  to  be 
met  with  in  respect  to  all  other  metals, 
and  I  am  inclined  to  take  advantage  of 
"  there  being  no  rule  without  an  excep- 
tion," and  make  that  exception  in  favor 
■of  iron  and  all  other  metals;  but  though 
we  may  have  in  some  measure  to  con- 
struct our  ornament,  I  think  we  should 
be  careful  to  so  manage  it  that  the  orna- 
ment we  do  employ  shall  not  be  wholly 
useless,  and  that  if  it  does  not  add  much 
to  the  strength  of  the  structure  it  shall 
not  at  least  be  detrimental,  and,  therefore, 
all  added  ornament  in  ironwork  should 
I  think  be  of  the  very  lightest  descrip- 
tion, and  if  not  actually  constructive,  it 
should  at  least  grow  naturally  from,  and 
appear  to  be  part  of,  the  real  construct- 
ive portion  of  the  work. 

Time,  however,  will  not  permit  to  go 


further  into  this  point,  which  is  in  itself 
a  sufficient  subject  for  a  paper,  which  at 
some  future  time  I  may  ask  to  be  allow- 
ed to  read. 

Allow  me,  in  conclusion,  to  thank  you 
for  your  attention,  and  at  the  same  time- 
to  request  your  kind  indulgence  for 
much  that  I  have  said.  Many  of  you, 
as  I  know,  have  already  by  your  works 
anticipated  my  ideas  with  respect  to  con- 
structive and  architectural  ironwork  ; 
and  to  you,  therefore,  my  remarks,  I 
fear,  have  been  tedious.  But  still,  I 
hope,  you  will  endorse  my  views,  as  I 
have  been  encouraged  to  maintain  them 
by  the  knowledge  that,  among  those  who 
stand  the  highest  in  our  profession, 
there  are  some  who  have  not  thought  it 
beneath  them  to  design  in  iron,  and  with 
successful  results — pardon  me,  if  I  men- 
tion the  name  of  one,  our  honored  Presi- 
dent, Sir  George  Gilbert  Scott. 


REPORTS  OF  ENGINEERING  SOCIETIES, 

The  New  York  Society  op  Practicax 
Engineering  held  its  third  quarterly  ses- 
sion for  the  year  1875,  in  Cooper  Union,  on  the 
evenings  of  September  7th,  8th,  9th  and  10th. 
The  President,  James  A.  Whitney,  delivered 
the  annual  address  on  the  evening  first  named. 
Subject — "The  relation  of  Patent  Laws  to 
American  Agriculture,  Arts,  and  Industries." 
At  the  subsequent  meetings  other  elaborate 
papers  were  read  ;  on  the  "Minor  Economies 
of  Manufacturers,"  by  James  C.  Bayles,  editor 
of  the  Iron  Age  ;  on  the  "Industrial  Uses  of 
Blast  Furnace  Slag,"  noticed  elsewhere  in  our 
columns,  by  Frederick  A.  Luckenbach,  M.  E. ; 
on  "  Steam  Propulsion  on  Canals,"  by  George 
Ed.  Harding.  Briefer  essays  were  also  read  ; 
on  "  Stationary  Fire  Extinguisher  Pipes,"  by 
Henry  Palmieri,  M.  E.  ;  and  on  the  "  Testing 
of  Water  Pipes  and  Mains,"  by  Ernst  Bilkuber, 
M.  E.  The  President's  address  has  been  pub- 
lished in  pamphlet  form  by  the  Society.  The 
next  session  will  be  held  the  latter  part  of 
November  next. 

INSTITUTION  OP  ClVIL  ENGINEERS.  —  The 
council  of  the  Institution  of  Civil  Engin- 
eers have  awarded  the  following  premiums  : — 
Telford  medals  aud  Telford  premiums  to  the 
following  gentlemen  : — to  Mr.  W.  Hackney, 
for  his  paper  on  "  The  Manufacture  of  Steel:  " 
Mr.  H.  E.  Jones,  for  his  paper  on  "  The  Con- 
struction of  Gasworks  ; "  Mr.  A.  R.  Binnie. 
for  his  paper  on  "  The  Nagpur  Waterworks;  " 
■Mr.  G.  F.  Deacon,  for  his  paper  "  On  the  Sys- 
tem of  Constant  and  Intermittent  Water  Sup- 
ply, and  the  Prevention  of  Waste  ;  "  Telford 
premiums  to  M.  J.  Gaudard,  of  Lausanne,  for 
his  ' '  Notes  on  the  Consolidation  of  Earth- 
works ;•"  to  Professor  Prestwich,  for  his  paper 
"  On  the  Origin  of  the  Chesil  Bank  ; "  to  Mr. 


376 


VAN  NOSTRAND's   ENGINEERING   MAGAZINE. 


J.  T.  Smith,  for  his  paper  "  On  Bessemer  Steel 
Rails  ; "  to  Mr.  C.  Colson,  for  his  "Details  of 
the  Working  Tests  and  Observations  on  Port- 
land Cement ; "  to  Mr.  T.  C.  Watson,  for  his 
"Description  of  the  Use  of  Facines  in  the 
Public  Works  of  Holland;"  a  Watt  medal 
and  the  Manby  Premium,  to  Mr.  J.  C.  Hawk- 
shaw,  for  his  paper  on  "The  Construction  of 
the  Albert  Dock  at  Kingston-upon-Hull."  The 
Council  have  likewise  awarded  the  following 
prizes  to  students  of  the  Institution  : — Miller 
prizes  to  the  following  gentlemen  : — Mr.  A.  E. 
Baldwin,  for  his  paper  on  "The  Design  and 
Construction  of  Lock  Gates;"  Mr.  J.  C.  Inglis, 
for  his  paper  ' '  Experiments  on  Current  Me- 
ters and  their  Bearing  on  the  Hydraulics  of 
Rivers  ;  "  to  Mr.  W.  B.  Myers,  for  his  "  Com- 
parison of  the  various  forms  of  Girder  Bridges, 
showing  the  Advantages  of  the  Schwedler 
Bridge  ;  together  with  an  elucidation  of  the 
Theoretical  Principles  of  the  same  ; "  Mr.  A. 
S.  Moss,  for  his  paper  on  "The  River  Hum- 
ber;"  Mr.  W.P.  Orchard,  for  his  paper  on  "Hy- 
draulic Calculations  relating  to  Water  Pressure 
and  Walls  to  resist  it,  Gauging  of  Water,  the 
Flow  of  Water  in  open  Channels  and  in  Pipes ;" 
Mr.  J.  Tysoe,  for  his  paper  on  "The  Manu- 
facture of  Illuminating  Gas  from  Coal  ;  "  Mr. 
J.  C.  Mackay,  for  his  paper  on  "Concrete." 
The  following  note  has  also  been  issued  by  the 
Council : — "It  has  frequently  occurred  that  in 
papers  which  have  been  considered  deserving 
of  being  read  and  published,  and  have  even 
had  premiums  awarded  to  them, 'the  authors 
may  have  advanced  somewhat  doubtful  theo- 
ries, or  may  have  arrived  at  conclusions  at  va- 
riance with  received  opinions.  The  Council 
would,  therefore,  emphatically  repeat,  that  the 
institution  must  not,  as  a  body,  be  considered 
responsible  for  the  facts  and  opinions  advanc- 
ed In  the  papers  or  in  the  consequent  discus- 
sions ;  and  it  must  be  understood  that  such 
papers  may  have  medals  and  premiums  award- 
ed to  them,  on  account  of  the  science,  talent, 
or  industry  displayed  in  the  consideration  of 
the  subject,  and  for  the  good  which  may  be 
expected  to  result  from  the  discussion  and  the 
inquiry  ;  but  that  such  notice,  or  award,  must 
not  be  considered  as  any  expression  of  opinion, 
on  the  part  of  the  institution,  of  the  correct- 
ness of  any  of  the  views  entertained  by  the 
authors  of  the  papers." — Engineer. 


IRON  AND  STEEL  NOTES. 

A  German  paper  states  that  the  steel  works 
of  Frederick  Krupp,  of  Essen,  are 
about  to  receive  a  very  important  addition  to 
their  machinery.  The  largest  steam-hammer 
at  use  at  these  works  at  the  present  time  is 
one  capable  of  working  a  mass  of  steel  50  tons 
in  weight,  and  erected  at  a  cost  of  2,800,000 
francs.  It  is  now  in  contemplation  to  build  a 
new  steam-hammer  capable  of  beating  up  a 
mass  of  steel  of  double  the  weight,  viz.,  100 
tons.  The  new  machine,  it  is  estimated,  will 
cost  5,000,000  francs,  and  will  be  the  most 
powerful  in  the  world,  and  it  may  be  expected 
that  the  size  and  weight  of  the  German  artil- 
lery will  be  enormously  increased. — Engineer. 


Purifying  Iron. — Mr.Wm.  Baker,  of  Willen- 
hall,  employs  a  vessel  or  trough  placed 
between  the  furnace  and  the  moulds  or  other 
receiver  for  the  molten  metal,  and  forms  the 
vessel  or  trough  preferably  oblong  and  a  few 
inches  deep  on  one  side  and  shelving  up  to  the 
top  on  the  other  side.  He  closes  the  end  of  the 
vessel  or  trough  to  retain  the  metal  to  be  acted 
upon,  and  forms  an  opening  in  the  top  of  each 
end,  one  for  the  admission  and  the  other  for 
the  discharge  of  the  molten  metals.  He  forces 
air  through  tuyeres  placed  along  that  side  of 
the  vessel  or  trough  to  which  the  bottom 
shelves  up,  and  inclines  the  tuyeres  towards 
the  surface  of  the  metal  with  their  nozzles 
nearly  touching  the  metal,  so  that  the  air  will 
be  forced  into  and  through  the  metal.  He  car- 
ries up  the  sides  of  the  vessel  or  trough  and 
covers  the  top  with  a  perforated  plate.  The 
metal  flows  through  the  vessel  or  trough  and 
is  purified  by  the  action  of  the  injected  air. — 
Mining  Journal. 

Cast  Iron  Chilled  Wheels  for  Carriages, 
— A  number  of  gentlemen  interested  in 
I  railways,  engineers  and  others,  met  at  the  ma- 
i  chine  works  of  Mr.  Horn,  Millbank  Row, 
Westminster,  lately,  for  the  purpose  of  wit- 
nessing the  results  of  tests  applied  to  the  "cast 
iron  chilled  wheels"  manufactured  by  Barnum, 
Richardson  &  Co.,  of  the  Salisbury  Ironworks, 
Connecticut.  It  was  stated  that  these  wheels 
have  been  in  use  for  a  long  time  both  in  the 
United  States  and  Canada  on  almost  all  the 
railways  of  these  countries,  with  the  result 
that  on  some  lines  they  are  now  used  to  ths 
exclusion  of  all  others.  The  experience  of 
America,  where  the  frost  is  so  severe,  would,, 
therefore,  seem  to  be  in  favor  of  these  wheels, 
but  as  an  opinion  existed  in  England  that  they 
were  easily  fractured,  the  manufacturers  re- 
solved to  try  the  question  by  experiment,  and 
hence  the  appeal  to  the  tests  applied.  These 
were  certainly  of  a  severe  kind,  and  it  was  not 
until  the  wheels  had  been  struck  267  times 
with  two  hammers  weighing  28  lbs.  and  32 
lbs.  respectively,  that  the  iron  partially  gave 
way.  It  is  claimed  for  the  wheels  that  they 
are  not  only  the  most  safe,  but  the  most  dur- 
able and  economical — London  Mining  Journal. 

Dephosphorization  of  Iron  Ores. — The 
following  process  for  effecting  the  de- 
phosphorization of  iron  ores  has  been  patented 
by  its  inventor,  M.  G.  Velge,  of  Liege  : — 
When  a  substance  containing  phosphate  ol 
iron  is  fused  with  two  or  three  times  its  weight 
of  a  mixture  of  carbonate  of  soda  and  potash, 
the  phosphorus  can  be  removed  in  the  form  of 
alkaline  phosphate  by  washing.  Although  this 
process  is  applicable  to  the  treatment  of  small 
quantities  only,  its  principle  is  that  upon  which 
M.  Velge  bases  his  own.  He  found  (1)  that 
chloride  of  sodium  can  be  substituted  for  these 
carbonates  ;  (2)  that  it  is  sufficient  to  add  to 
the  ore  a  weight  of  this  reagent  only  a  trifle 
in  excess  of  the  phosphate  contained  in  the 
substance — say  6  parts  of  salt  to  5  of  phosphate, 
or  1  lb.  of  salt  to  about  l-5th  lb.  of  phosphor us; 
(3)  when  the  mixture  has  been  well  made  the 
ore  should  not  be  fused,  but  kept  for  some 
time  at  a  mere  red  heat.     When  the  gases 


IRON   AND   STEEL   NOTES. 


377 


have  all  been  given  off,  water  slightly  acidulat- 
ed with  hydrochloric  acid  is  added,  and  the 
phosphate  dissolves  after  a  little  time.  At  first 
he  used  to  crush  the  ore  and  the  salt  together, 
but,  beside  the  expense  of  the  operation  com- 
pared with  the  low  cost  of  the  matter  operated 
on,  the  final  result  was  unsatisfactory.  The 
ore  came  out  in  powder,  with  which  there  was 
every  chance  of  choking  the  blast.  He  then 
proceeded  to  dry  strongly,  or  slightly  calcine, 
poros  ores,  adding  to  them  a  concentrated  so- 
lution of  sea-salt.  This  solution  was  taken 
up  very  greedily  by  the  roasted  ores,  some 
varieties  absorb. ug  as  much  as  40  per  cent,  of 
their  weight.  In  this  way  all  the  molecules  of 
phosphorus  are  brought  into  the  presence  of 
the  salt.  After  calcination  and  successive 
washings  the  quantity  of  phosphorus  held  by 
the  ore  was  reduced  from  1.25  per  cent,  to 
less  than  one  two-thousandth.  Practically, 
perhaps,  so  high  a  degree  of  perfection  would 
hardly  be  arrived  at,  but  it  it  is  contended  by 
the  inventor  that  the  process  itself  is  quite 
satisfactory.  Four  operations  are  involved  in 
the  dephosphorization  : 

(1.)  The  desiccation  of  the  ore  by  waste  heat 
or  other  suitable  method.  If  there  be  much 
phosphorus  to  remove,  it  will  be  best  only  to 
use  such  ores  as  lose  much  water  on  drying. 
On  the  other  hand,  if  the  ores  contain  but 
little  phosphorus,  it  will  be  useless  to  dry 
them. 

(2.)  The  absorption  of  a  solution  of  salt, 
stronger  or  weaker,  according  to  the  propor- 
tion of  phosphorus. 

(3.)  Calcining. — In  the  ordinary  way  the 
gases  of  the  blast-furnace  are  available  for  cal- 
cining, and  when  this  is  the  case,  the  calcining 
can  be  effected  in  a  vertical  oven,  the  gases 
being  kindled  from  below.  In  the  absence  of 
such  gases,  a  reverberatory  furnace  must  be 
employed,  for  the  calcining  in  a  vertical  fur- 
nace by  admixture  of  coal  has  the  effect  of 
partly  reducing  and  melting  the  ore,  and  thus 
rendering  the  washing  almost  impossible. 
Not  only  are  the  pores  of  the  ore  choked  in 
part,  but,  in  the  case  of  silicious  ores,  the 
phosphate  of  soda  is  converted  into  silicate  of 
soda.  In  making  use  of  the  blast  furnace 
gases  all  the  carbonic  oxyde  is  consumed  be- 
fore reaching  the  ore,  and  there  is  no  sign  of 
reduction,  even  at  the  brightest  red  heat. 

(4.)  Washing. — The  ore  should  be  left  for 
several  days  in  vessels  filled  with  water,  taking 
care  to  renew  the  water  frequently,  and  to  add 
at  each  renewal  a  small  quantity  of  hydroch- 
loric acid.  The  water  by  itself  would  have 
but  a  small  effect  upon  the  phosphate.  It  is 
of  the  greatest  importance  to  conduct  the 
washing  with  care,  for  the  success  of  the  oper- 
ation depends  upon  it. — Iron. 

UTILIZATION    OF    SLAG — ADDRESS    BY    F.    A. 
LiUCKENBACH    BEFORE    THE     SOCIETY     OF 

Engineering. — Frederick  A.  Luckenbach  ad- 
dressed the  New  York  Society  of  Practical 
Engineering  at  their  last  session.  The  speak- 
er's topic  was  ' '  The  Industrial  Uses  of  Blast 
Furnace  Slag,"  and  was  illustrated  by  the  ex- 
hibition cf  specimens.  The  subject  was  fur- 
ther discussed  by  Prof.  Whitney,  the  Presi- 


dent of  the  Society,  and  by  Messrs.  Moore, 
Sutton,  Roosevelt,  and  others.  The  main 
points  of  Mr.  Luckenbach's  paper  are  as  fol- 
lows : 

Slag  is  a  chemical  compound,  the  combina- 
tion of  an  acid  with  various  bases,  and  is  as 
much  a  salt  as  the  sulphate  of  alumina  or 
potassa.  Its  formation  is  strictly  governed  by 
the  laws  of  chemistry.  The  silica  is  the  acid, 
and  the  lime,  alumina,  magnesia  and  the  alka- 
lies are  the  basis.  Iron  ores  are  generally  sili- 
cious. If  when  an  ore  is  placed  in  a  blast  fur- 
nace and  smelted  no  ba?e  is  added,  in  seeking 
a  base  the  ore  will  seize  on  the  oxyde  of  iron, 
combine  with  it  and  carry  it  off  as  slag.  To 
prevent  this,  limestone,  which  is  a  base,  is 
added.  A  certain  quantity  of  silica  requires  a 
certain  amount  of  lime  to  saturate,  another 
quantity  of  magnesia,  and  another  of  alumina  ; 
all  of  which  quantities  will  vary  with  their 
chemical  equivalents.  Having  then  analyses 
of  all  the  material  of  the  charge,  the  propor- 
tions of  each  may  be  so  calculated  as  to  pro- 
duce a  certain  slag.  But  with  slag,  as  with 
other  chemical  compounds,  there  may  be  two 
atoms  of  base  to  one  of  acid,  two  of  acid  to 
one  of  base,  or  one  of  base  to  one  of  acid  ; 
and,  according  as  this  is  the  case,  they  are 
called  basic,  acid,  or  neutral  slags.  The  acid 
slags  are  the  most  fusible,  the  aeutral  next, 
and  the  basic  the  least  so.  Slag  is  sometimes, 
according  to  the  proportions  of  its  component 
parts,  a  material  easily  fusible,  and  possessed 
of  other  definite  qualities,  and  at  other  times  a 
comparatively  infusible  material.  Such  being 
the  character  of  the  product,  it  has  been  a 
problem  of  great  difficulty  to  determine  what 
general  system  can  be  hit  upon  which  for  any- 
given  purpose  will  utilize  all  the  different  vari- 
eties of  slag. 

The  first  recorded  plan  for  the  utilization  of 
slag  was  that  of  John  Payne  in  England,  in 
1728.  He  proposed  molding  the  dross  by  fus- 
ing or  melting  with  such  mixtures  as  will  pre- 
vent its  being  brittle,  and  also  give  it  different 
colors,  so  as  to  make  it  more  ornamental  and 
useful.  After  this  came  Moshet's  plan  of  1815, 
for  reworking  slag  to  obtain  the  iron  left  in  it. 
Then  Crawshay  and  Moshet  invented  a  process 
for  recovering  the  iron  believed  to  exist  in  the 
refuse  of  copper  smelting,  which  process  ap- 
pears to  be  the  first  use  of  water  for  pulveriz- 
ing molten  slag.  In  1852,  Alexander  Cunning- 
ham claimed  that  sulphate  of  alumina  and 
alum  could  be  obtained  from  slag.  In  1853, 
William  and  John  Longmand  thought  blast- 
furnace slag  could  be  formed  into  shapes  suit- 
able for  pavements  of  streets.  In  the  same 
year  George  Robinson  proposed  a  new  plan. 
The  slag  was  to  be  run  in  a  molten  state  upon 
a  heated  iron  table  and  formed  into  sheets  by 
rolling.  The  plates  were  then  to  be  annealed 
and  applied  for  roofing  and  other  purposes. 
In  the  following  year  Smith,  Bessemer  & 
Longsdon  secured  a  patent  on  a  process  in 
which  slag  was  to  be  turned  into  table  tops, 
chimney  pieces,  statues,  etc.  Joseph  Woodard 
of  Yorkshire,  patented  a  process  for  making 
bricks  of  slag  for  building  purposes.  A  com- 
pany of  capitalists  have  lately  began  to  make 
bricks  by  this  process. 


378 


VAN  nostrand's  engineering  magazine. 


Their  prospectus  asserts  that  the  brick  will 
withstand  a  crushing  force  of  over  four  tons 
per  cubic  inch,  being  five  times  more  than  or- 
dinary brick  will  bear.  All  these  projects 
have  proved  failures.  The  secret  of  securing 
homogeneity  in  structure,  irrespective  of 
chemical  composition,  was  not  discovered,  al- 
though the  practice  of  annealing  gave  a  faint 
and  shadowy  hint  of  the  direction  in  which  it 
might  be  found.  Mr.  Luckenbach  read  the 
details  of  an  invention  of  his  own,  which  he 
claimed  to  be  an  improvement  in  the  means 
of  annealing  castings  made  of  blast  furnace 
slag,  and  which  is  designed  to  provide  for  the 
manufacture  of  paving  and  building-blocks, 
fire-brick,  and  other  articles  from  the  slag. 


RAILWAY  NOTES. 

Improvements  rjsr  Tramways. — The  inven- 
tion of  Messrs.  Niemann  and  Geigee,  of 
Vienna,  consists  in  lajung  the  rails  of  tram- 
ways on  a  number  of  supports  or  chairs  made 
"by  preference  of  cast  metal,  and  if  of  metal 
they  are  made  hollow  in  the  shape  of  an  open 
"box,  and  bridged  over  on  the  top  with  a  recess 
to  receive  the  rail,  so  that  the  upper  surface  of 
box  and  rail  is  practically  level.  .  The  box  may 
be  filled  in  with  any  suitable  material.  For  | 
fixing  the  rails  to  the  chairs  small  keys  or  ■ 
wedges  are  driven  into  grooves  formed  on  one 
side  of  the  recess,  pressing  the  rail  against  the 
other  side  of  recess.  To  keep  the  gauge,  tie 
rods  may  be  used. 

Fast  Kailway  Travel. — With  the  improve- 
ments made  by  all  the  principal  American 
railroads  in  the  last  few  years,  by  which  a  per- 
fection of  track  has  been  secured,  equal,  per- 
haps, to  any  in  the  world,  the  speed  of  our 
^express  trains  is  not  only  rivaling  the  best  time 
of  England,  but  in  some  respects  surpasses 
the  grandest  achievements  of  travel  attained 
in  the  mother  country.  It  is  no  unusual  thing 
for  trains  in  the  United  States  to  run  at  a  speed 
exceeding  thirty  miles  an  hour  for  long  con- 
tinuous distances,  and  even  this  rate  is  consid- 
ered slow  on  some  of  the  main  lines.  As  an 
instance  of  what  can  be  done  by  our  roads,  it 
is  well  to  state  a  recent  occurrence.  Some 
two  weeks  ago,  a  special  train  passed  west- 
ward over  the  Pennsylvania  Railroad,  carrying 
an  excursion  of  eastern  editors  and  literati  on 
their  way  to  California.  The  train  ran  from 
Harrisburg  to  Altoona,  a  distance  of  132  miles, 
in  exactly  three  hours,  without  stopping.  So 
regular  was  the  speed,  and  so  smooth  the 
tracks  that  scarcely  any  of  the  party  could 
realize  the  fact  that  they  had  been  traveling 
through  the  mountains  of  Pennsylvania  at  the 
rate  of  forty-four  miles  an  hour,  when  the 
time  and  distance  were  made  known  over  the 
dinner  table  at  the  foot  of  the  Alleghenies. — 
The  Railway  World. 

A  Railroad  Three  Hundred  Feet  Above 
a  City. — It  is  difficult  to  imagine  any- 
thing better  adapted  to  produce  a  vivid  and 
startling  impression  on  the  memory  than  the 
first  sight  of  Morlaix,  Brittainy,  as  approached 
by  rail.     The  city  lies  on  both  sides  a  deep, 


narrow  valley  and  the  railroad  springs  across 
the  chasm  on  a  magnificent  viaduct  300  feet 
high.  Entirely  unprepared  for  anything  of 
the  sort,  the  traveler  finds  himself  taking  a 
bird's  eye  view  of  a  city  of  the  middle  ages. 
There  it  lies,  300  feet  below,  almost  as  if  it 
were  in  the  days  when  Mary,  Queen  of  Scots, 
passed  through  on  her  way  to  Holyrood 
and  the  scaffold.  The  precipitous,  winding, 
narrow,  darksome  streets,  the  peaked  roofs, 
misshapen  by  time  and  studded  with  curious 
dormer  windows,  are  still  there  as  when  she 
looked  upon  them  centuries  ago,  when  with 
brilliant  pageant  she  and  her  cortege  of  knights 
and  ladies  swept  through  Morlaix  with  laughter 
and  song.  Should  it  be  a  festal  day  or  a  fair, 
the  sight  is  still  more  unique,  for  the  square  is 
then  crowded  with  booths  and  peasants  in 
various  costumes,  and  it  is  positively  white 
with  the  starched  caps  of  the  women.  The 
city  is  divided  by  the  river  of  Morlaix,  an  es- 
tuary up  which  ships  come  into  the  heart  of 
the  town.  The  banks  of  the  river  are  faced 
with  granite,  and  affords  a  fine  promenade  on 
each  side.  A  smaller  stream  dashes  roaring- 
down  the  streets,  bringing  to  the  dirty  lanes  of 
the  crowded  town  the  music  of  the  pure  foun- 
tains whence  it  came. — Railway  Review. 

The  Narrow  Gauge  en  Switzerland. — The 
first  Swiss  narrow  gauge  line,  opened  in 
June,  1874,    runs    irom  Lausanne  (on    Lake 
Geneva),  to  Echallens,  and  is  of  a  length  of 
about  9+  miles.      The  gauge  is    one  metre. 
This  line,  which  is  now  being  extended  to  La 
i  Sarraz,     7i  miles  beyond  Echallens,  is  laid 
partly  into  the  turnpike  road  ;  the  maximum 
gradients  are  1  in  25,  and  the  smallest  curves 
have   a  radius  of  three  chains.     The  rolling 
stock,  which  has  been  acquired,  together  with 
the  rails,  from  the  original  Mont  Cenis  mid-rail 
line,  consists  of  two  locomotives,  twelve  pass- 
enger carriages,  five  luggage  vans,  and  twenty- 
one  goods  wagons  •,  the  two  locomotives  how- 
■  ever,  have  since  been  replaced  by  tank  engines 
.  bought  at  the  Creusot  works,  and  there  has 
!  also  been  added   a  small  tank  engine  from 
Krauss  and  Co.,  of  Munich.     Including  rolling 
!  stock,  the  lines  has  cost  but  £5,000.  per  mile. 
The  working  speed  averages  12  miles  an  hour, 
and  although  the  goods  traffic  is  small,  the  un- 
dertaking has  proved  a  very  profitable  one  ; 
this  being  due,  besides  the  modest  amount  of 
'  capital  engaged,  to   a  very  simple   mode  of 
management. 

The  Rigi  metre-gauge  road,  a  portion  of 
which  was  already  open  last  season,  has  been 
finally  opened  in  June  last.  The  maximun  gra- 
dients (worked  by  the  adhesion  of  tank  engines 
of  20  tons  weight)  are  1  in  20.  The  rolling 
stock  consists,  besides  the  three  tank  engines, 
but  of  three  passenger  carriages  and  of  three 
open  goods  wagons.  The  carriages  on  two 
four-wheeled  bogies  have  each  of  them  accom- 
modation for  55  passengers,  there  being  eleven 
parallel  transverse  benches,  each  of  which  is 
adjacent  to  a  side  door.  No  tourist  climbing 
up  the  Rigi  by  either  of  the  two  rack  railways, 
should  omit  a  ride  on  this  most  interesting 
"  little  wonder"  of  a  narrow  gauge  line,  only 
about  four  miles  in  length,  but  showing  along 


ENGINEERING   STRUCTURES. 


379 


its  serpertine  course  from  Kaltbad  to  the 
Scheideck  an  ever-varying  panorama  of  the 
■most  picturesque  Alpine  world.  At  the  latter 
station  the  line  reaches  an  altitude  of  1648 
metres,  or  a  little  over  one  mile  above  sea 
level  ;  this  is  therefore  actually  the  highest 
railway  in  Europe.  Like  the  other  Rigi  rail- 
ways, the  narrow  gauge  road  is  of  course  only 
open  from  May  to  October,  that  is  to  say  for 
about  six  months  in  the  year. 

We  next  come  to  the  Undertaking  of  the 
Swiss  Society  for  Narrow  Gauge  Railways  un- 
der the  direction  of  President  Dr.  Dubs.  This 
society,  which  was  founded  in  September, 
1872,  by  some,  of  the  leading  Swiss  bankers 
and  engineers,  obtained  in  the  course  of  1873 
concessions  for  the  building  and  working  of 
about  80  miles  of  metre-gauge  railways,  situ- 
ated in  different  Swiss  cantons.  But  owing  to 
the  great  and  protracted  financial  crisis  of 
1874,  the  society  was  unfortunately  obliged  to 
postpone  the  execution  of  the  greater  portion 
of  these  projects,  and,  in  fact,  only  the  metre- 
gauge  railway  in  the  Canton  of  Appenzel  was 
proceeded  with,  has  a  length  of  sixteen  miles, 
and  the  class  of  rolling  stock  adopted  has  been 
fully  illustrated  and  descrrbrd  by  us  {vide  page 
489  of  our  last  volume  and  page  29  of  the 
present  volume).  Including  everything,  this 
line — established  on  a  very  difficult  ground — 
has  cost  £9,600  per  mile;  but  a  line  of  the  nor- 
mal gauge  of  4  ft.  8|  in.  would  have  cost,  ac- 
cording to  careful  estimate,  at  the  least  £25, 600 
per  mile. 

Among  the  narrow  gauge  lines  now  being 
executed  in  Switzerland,  the  longest  will  be 
that  from  Geneva  to  Lausanne  along  the  Jura 
Mountains.  Including  the  lake  branches  to 
Nyon  and  Morges,  the  length  of  this  line  will 
be  55  miles ;  the  gauge  being  likewise  one 
metre.  This  line  is  being  constructed  by  a 
local  board,  who  will  receive  from  the  Canton 
of  Vaud  a  subvention  of  £70,000.  There  are 
other  narrow  gauge  projects  in  the  south  of 
Switzerland,  regarding  which,  however,  we 
have  at  the  present  moment  no  precise  data  ; 
but  counting  now  the  lines  enumerated  above 
as  either  opened,  building,  or  concessioned, 
there  will  be — at  the  end  of  another  year — a 
Swiss  narrow  gauge  reseau  to  a  total  extent  of 
about  156  miles  in  operation. 

Finally,  we  have  .to  notice  here  the  narrow 
gauge  tramways  projected  by  the  well-known 
Swiss  locomotive  engineer,  Mr.  A.  Brunner. 
These  are  to  be  worked  by  two-storied  motive 
power  cars,  and  a  concession  has  been  granted 
for  such  a  line  running  from  Zurich  to  some 
suburbs  of  that  town.  In  connection  with 
this  interesting  subject,  we  must  not  omit  to 
point  out  that  this  progress  of  narrow  gauge 
railways  in  Switzerland, as  well  indeed  of  their 
extension  throughout  the  world,  is  in  the  larg- 
est measure  due  to  the  untiring  energy  of 
Mr.  R.  F.  Fairlie.  It  was  chiefly  by  means  of 
his  writings,  which  have  been  translated  into 
most  modern  languages,  that  the  advantages 
of  the  system  he  may  be  said  to  have  inaugu- 
rated were  thoroughly  understood. — Engineer- 
ing. 


ENGINEERING  STRUCTURES. 

The  Tunis  Expedition. — News  from  the 
Tunis  Expedition  has  been  received  to  the 
15th  ult.  The  Marquis  Antinori  and  Captain 
Barattieri  have  visited  Gerba  Island.  The  ex- 
plorers on  the  southern  coast  of  the  Gulf  of 
Gabes  sought  for  the  ancient  canal  connecting 
Syrtes  Minor  with  Palus  Tritonia,  but  found 
none.  The  engineers  have  returned  from  the 
Palustral  Basin.  They  examined  the  eastern 
shores.  The  result  of  their  observations  will 
be  published  shortly.  The  heat  has  caused 
the  wild  animals  and  birds  to  disappear,  but 
specimens  of  fossils,  stpne  utensils,  and  weap- 
ons were  abundant.  The  health  and  spirits  of 
the  party  were  excellent.  Colonel  Galvagni 
has'  collected  interesting  ethnographica1  ;  nd 
statistical  details. 

The  Suez  Canal. — The  opening  of  this 
isthmus  was  supposed  at  one  time  to  re- 
store to  the  Mediterranean  ports  of  France, 
and  especially  Marseilles,  their  old  splendor, 
instead  of  wThich  most  of  the  steamers  prefer 
to  proceed  direct  through  the  Straits  of  Gib- 
raltar, thus  leaving  the  French  railways  to 
their  own  greediness.  Nor  has  the  French 
merchant  navy  been  in  due  proportion  benefit- 
ed by  the  opening  of  the  new  sea-road  to  the 
far  East.  The  French  Shipping  passing 
through  the  canal  decreases,  relatively  speak- 
ing, from  year  to  year.  In  1870,  436,000  tons 
burtheu  passed  through  the  canal,  of  which 
269,000  were  English,  and  one-fifth,  or  84,000 
only,  French.  In  1874,  the  proportion  of 
French  bottoms  is  found  to  be  reduced  to  220,- 
000  tons,  or  less  than  one-tenth,  2,423,000  tons 
having  passed  the  canal,  out  of  which  1,797,- 
000  were  under  the  English  flag.  The  other 
navies,  although  below  the  absolute  figure  for 
France,  are  progressing  more  rapidly.  Thus, 
since  1872,  four  times  more  Dutch  ships  used 
the  canal,  while  the  increase  of  the  French 
navigation  was  only  40  per  cent. 

The  Mississippi  Improvements. — The  Board 
of  Engineers,  which  assembled  for  the 
purpose  of  considering  the  plans  of  Captain 
Eads  for  the  improvement  of  the  Mississippi, 
have  concluded  their  labors  for  the  present. 

The  following  gentlemen  constituted  the 
Board  at  its  recent  session  :  Gen.  Barnard, 
President  ;  Sir  Chas.  A.  Hartley,  Gen.  Alex- 
ander, Messrs.  Roberts,  Whiteomb,  and  Sick- 
les. After  considerable  discussion,  the  Board 
agreed  unanimously  upon  the  following  re- 
port : 

I.  With  regard  to  the  priority  of  construe" 
I  tion  of  different  parts  of  the  work,  the  Board 
!  recommended  that   the  seats   of    both   jetties 
I  and  of  the   spar  joining   the  west  jetty  with 
j  the  right  bank  be  protected  with  mattresses 
j  throughout  this  entire  length — that  is,  that  first 
j  of  all  the  foundation  of  the  east  jetty  be  se- 
cured  out  to  a  depth  of  30  feet,  and  of  the 
west  jetty  to  20  feet.     They  further  recom- 
mend that  the  east   jetty  be  carried  up  the 
water  line  before  raising  the  mattress  wall  of 
the  west  jetty  to  the  same  level,  and  that  the 
construction  details  of  the  pier-heads  be  left 


380 


VAN   NOSTRAND'S   ENGINEERING   MAGAZINE. 


till  the  Commission  can  meet  at  the  jetties  this 
Fall.  J 

II.  After  attentive  examination  of  the  plan 
of  construction,  consisting  of  a  combination 
of  willow  mattresses  and  stone,  now  in  execu- 
tion by  Mr.  Eads,  the  Board  find  it  to  be  a 
modification  of  methods  long  in  use  in  Hol- 
land and  elsewhere.  It  is  essentially  the  same 
as  that  applied  to  the  jetties  of  the  mouth  of 
the  Oder,  and  also  to  the  jetties  at  the  new 
mouth  of  the  Maas,  so  satisfactorily  as  to  draw 
from  the  legislative  body  of  Holland  the  ex- 
pression that  "their  complete  success  has  re- 
moved all  doubts  as  to  the  possibility  of  mak- 
ing piers  at  sea  on  our  coast."  It  is  moreover 
essentially  the  same  as  that  adopted  by  the  re- 
cent Commission  (1874)  for  these  works. 

III.  The  Board  advise  that  Bayou  Grande 
be  left  open  for  the  present. 

The  same  Commission  will  reassemble  at 
the  mouth  of  the  Mississippi  during  the  latter 
part  of  October  or  the  first  days  of  November. 

The  St.  Gothard  Tunnel.— The  interna- 
tional Commissioners,  whose  duty  it  is  to 
inspect  and  report  upon  the  progress  made 
with  the  St.  Gothard  Tunnel  and  railway, 
have  this  year  required  a  more  detailed  state- 
ment of  the  work  executed  than  has  been 
hitherto  furnished.  This  statement  appears  in 
a  tabular  form  accompanied  with  explanations 
and  remarks  in  the  Politecnico,  a  scientific 
journal  published  at  Milan.  From  it  we  learn 
that  during  the  last  three  months  before  the 
publication  of  the  report  there  had  been  ex- 
cavated at  the  Goenechen  or  Swiss  side  of  the 
mountain  341.3  metres,  being  at  the  rate  of 
3.71  metres  per  day,  and  on  the  Italian  side  at 
Acrolo,  184  metres,  or  at  the  rate  of  only  2 
metres  per  day,  which  together  would  give  a 
progress  at  the  rate  of  2,100  metres  per  annum, 
the  comparatively  slow  progress  made  on  the 
Italian  side  being  due  to  the  hard  nature  of 
the  rock  met  with,  through  which  fortunately, 
however,  little  water  percolated,  so  that  the 
work  was  not  impeded  by  that  hitherto  pre- 
vailing obstacle.  With  reference  to  the  ma- 
sonry and  the  excavation  of  the  tunnel  to  its 
full  dimensions — these  are  (says  the  report) 
evidently  proceeding  so  slowly  that  series  em- 
barrassment is  likely  to  result  from  having  too 
great  a  length  of  the  small  tunnel  or  drift  way 
excavated  in  advance  of  the  completed  work. 
The  number  of  perforators  in  operation, 
worked  by  compressed  air,  are  stated  to  be 
sixteen  m  number,  the  compression  of  the  air 
being  effected  by  water  power.  We  are  left 
uninformed  as  to  the  length  of  the  tunnel 
actually  completed,  as  opposite  the  heading  in 
the  tabular  statement  "Length  of  Tunnel 
Completed,"  no  figures  appear.  As  regards 
that  portion  of  the  St.  Gothard  railway  which 
follows  the  valley  of  the  river  Ticino,  the 
works  appear  to  have  been  prosecuted  with 
considerable  energy,  as  trains  have  been  run- 
ning on  the  sections  Lugano- Chiasso  and 
Biasco  and  Biasco-Bellinzona  ever  since  De- 
cember 6  last,  or  exactly  three  years  since  the 
formation  of  the  St.  Gothard  Railway  Com- 
pany. As  regards  the  section  Bellinzona-Lo- 
carno,  it  has  not  been  opened  in  consequence 


of  the  damage  done  by  floods,  which  had  ren- 
dered it  impossible  to  construct  the  iron  bridge 
at  Verzasca.  There  are  still  incomplete  in  two> 
other  sections  of  the  line  many  complementary 
works,  and  in  some  instances  the  trains  have 
to  pass  through  tunnels  in  which  the  centres 
and  supports  still  remain.  These  lines  have 
been  opened  rather  in  compliance  with  a  strin- 
gent clause  in  the  concession  than  that  they 
can  be  considered  in  a  fit  state  for  traffic. 


ORDNANCE  AND  NAVAL. 

Field  Artillery  Experiments  at  Dart- 
moor.— The  series  of  trials  of  the  effect 
of  the  fire  of  our  service  horse  artillery  and 
field  artillery  on  broken  ground  representing 
the  conditions  of  actual  warfare,  is  now  in 
progress.  The  principal  objects  are  the  trial 
of  the  relative  effects  of  shrapnel  shell  with 
time  and  percussion  fuzes,  of  common  shell 
burst  with  powder,  and  also  with  gun  cotton 
with  the  surrounding  space  filled  with  water, 
and  the  cotton  fired  by  a  detonator ;  the 
efficiency  of  Capt.  Nolan's  range  finder,  as 
compared  with  the  employment  of  individual 
judgment  and  trial  shots  to  ascertain  the  dis- 
tance of  an  enemy.  It  is  proposed  to  review 
the  result  of  these  experiments  when  the  series 
is  completed. — Engineer 

The  Deutschland. — This  iron-armored  fri- 
gate, the  sister  ship  to  the  Kaiser,  built 
for  the  Imperial  German  Government  by 
Messrs.  Samuda  Brothers,  from  the  design  of 
Mr.  E.  J.  Reed,  is  now  almost  ready  to  be 
handed  over.  She  is  at  present  in  the  Millwall 
Docks.  It  is  said  that  there  is  no  dry  dock  on 
the  Thames  large  enough  to  hold  her.  Though 
her  length  is  only  280ft.,  her  beam  is  03ft.; 
still  we  should  have  thought  that  she  could 
have  been  accommodated  either  in  Messrs. 
Lewis  and  Stockerill's  dry  dock,  or  at  the 
Thames  Ironworks.  Perhaps,  however  the 
German  Government  like  to  save  a  few  pounds 
as  much  as  any  one  else.  The  magnificent 
work  put  into  her  both  by  Messrs.  Samuda 
and  by  Messrs.  Penn,  who  have  supplied  the 
engines,  deserves  the  highest  commendation. 
Indeed,  the  engines  are  a  picture  to  feast  the 
eye  upon — their  compactness  and  finish  being 
so  admirable.  We  notice  that  in  these  two 
frigates  Messrs.  Penn  have  introduced  some 
improvements  which  are  not  to  be  found  in 
any  of  their  previous  engines.  Formerly  the 
screw-shaft  worked  upon  only  three  bearings, 
with  the  turning- wheel  at  the  after  end  of  the 
engine  room,  situated  about  the  middle  of  a 
length  of  shaft  between  two  bearings  some 
lift,  apart,  by  which  great  vibration  was 
caused.  Now  a  fourth  bearing  has  been  intro- 
duced, and  the  turning-wheel  placed  in  the 
centre  of  the  engine-room,  by  which  means 
great  steadiness  ensues.  This  arrangement 
also  admits  of  the  shaft  being  made  in  two 
pieces,  and  coupled  in  the  centre.  The  Kaiser 
and  Deutschland  are  also  provided  with  steam 
starting-gear,  which  we  do  not  remember 
having  seen  before  fitted  by  Messrs.  Penn  to 
trunk-engines.  The  Deutschland  is  complete 
with  the  exception  of  her  guns,  of  which  she 


BOOK   NOTICES. 


381 


is  to  carry  eight  26in.  jguns  of  22  tons  each, 
and  one  22in.  gun  of  18  tons.  These  are  to 
be  supplied  in  Germany,  by  Messrs.  Krupp, 
of  Essen,  who  will  also  fit  the  racers  for  them. 
— Engineer. 

BOOK  NOTICES. 

ow  to  Teach  Chemistky.  By  Edward 
Frankland,  F.  R.  S.  London  :  J.  &  A. 
Churchill.  For  sale  by  D.  Van  Nostrand. 
Price  $1.25. 

This  is  simply  a  condensed  report  of  six  lec- 
tures delivered  by  Dr.  Frankland,  and  care- 
fully summarized  by  one  of  the  science  teach- 
ers at  South  Kensington. 

The  suggestions  afforded  to  teachers  are  of 
the  highest  value,  not  only  as  to  the  order  of 
subjects,  but  in  reference  to  the  manipulation 
of  apparatus  in  illustrating  the  science. 

The  diagrams  are  numerous  and  excellent. 

Notes  on  Certain  Explosive  Agents.  By 
Walter  N.  Hill,  S.  B.  Boston :  John 
Allyn.  For  sale  by  D.  Van  Nostrand.  Price 
$1.00. 

This  work  is  in  the  form  of  a  pamphlet  of 
seventy  pages ;  but  within  this  space  is  includ- 
ed an  epitome  of  the  present  knowledge  of  all 
the  explosive  agents  at  present  in  use. 

The  topics  treated  in  separate  chapters  are  : 
I.  Explosions  and  Explosive  Bodies;  II.  Nitro- 
Glycerine  ;  III.  Gun  Cotton  ;  IV.  Picrates  and 
Fulminates;  V.  Classes  of  Explosive  Mixtures; 
VI.  Use  of  Nitro-Glycerine  and  Gun  Cotton. 

Some  folding  plates  illustrated  the  manufac- 
ture of  Nitro-Glycerine. 

A  Dictionary  op  Chemistry.  By  Henry 
Watts,  B.  A. ,  F.  R.  S.  London :  Long- 
mans, Green  &  Co.  Second  Supplement.  For 
sale  by  D.  Van  Nostrand.     Price  $15.00. 

The  Second  Supplement  to  this  well  known 
work  completes  the  record  of  chemical  dis- 
covery down  to  1873,  and  contains  the  more 
important  advances  in  science  made  in  1874. 

The  volume  is  quite  as  large  as  either  of  the 
others. 

The  leading  contributors,  with  the  list  of 
their  contributions,  are  given  herewith  : 

H.  E.  Armstrong,  F.  C.  S.—  Phenols— Sul- 
phur Chlorides. 

G.  C.  Foster,  B.  A.,  F.  R.  S—  Magnetism. 

H.  E.  Roscoe,  F.  R.  S. — Chemical  Action  of 
Light,  Spectral  Analyses. 

Robert  Warrington,  Esq.,  F.  C.  S.— Fodder, 
Maize,  Malt,  Oats,  Root  Crops. 

IIhe  Mechanic's  Friend  ;  A  Collection  op 
Receipts  and  Practical  Suggestions. 
With  numerous  Diagrams  and  Woodcuts. 
Edited  by  Wm.  E.  A.  Axon,  F.  S.  S.  New 
York  :  D.  Van  Nostrand.     Price  $1.50. 

This  convenient  little  volume  is  made  up  of 
those  applications  of  Physics  and  Chemistry, 
with  which  amateurs  chiefly  delight  to  deal. 

Most  of  the  matter  has  appeared  in  the  col- 
umns of  the  English  Mechanic  during  the  past 
two  or  three  years,  such  selections  having 
been  made  from  those  columns  as  seemed 
most  valued  by  the  readers. 

Upon  such  subjects  as  the  following  there 


are  several  articles  by  as  many  differe  n 
inal  writers  :  Bronzing,  Cements,  Dyes,  Elec 
tricity,  Gilding,  Glass  Working,  Glues,  Horol- 
ogy, Lacquers,  Locomotives,  Magnetism, - 
Metal  Working,  Photography,  Pyrotechny, 
Solders,  Steam  Engines,  Telegraphy,  Taxider- 
my, Varnishes  and  Water  Proofing. 

Perhaps  the  more  interesting  portions  of  the 
book  to  the  mechanic  will  be  those  relating  to 
Tools,  Locks,  and  Special  Processes  in  Me- 
chanical Engineering  and  Chemistry. 

The  illustrations  are  all  good. 

Rudiments  of  Geology.  By  Samuel  Sharp, 
F.  S.  A  ,  F.  G.  S.     London  :  E.  Stanford, 
1875.     Price  $1.75. 

The  introductory  portion  of  this  little  bock 
was  originally  prepared  for  use  in  the  writer's 
class,  and  is  now  published,  with  large  addi- 
tions, for  the  benefit  of  persons  similarly  cir- 
cumstanced, and  of  private  students.  Neither 
could  desire  a  more  useful  help,  for  we  know 
of  no  book  in  which  the  principles  and  facts 
of  geology  are  so  well  epitomized,  or  in  which 
either  are  stated  in  such  a  clear  and  popular 
manner.  The  introductory  part  deals  with  the 
generalities  of  the  subject,  its  divisions,  the 
materials  of  the  earth's  crust,  and  the  manner 
in  which  these  have  been  formed  and  modified, 
all  of  which  is  presented  in  such  order  as  to 
be  both  easily  comprehended  and  remembered 
by  the  learner.  The  second  part  is  strati- 
graphical  and  paleontological,  and  in  it  the 
different  formations  are  described  in  ascending 
order,  and  their  construction  and  characteristic 
fossils  indicated.  Much  that  is  important  in 
the  philosophy  of  the  science  is  also  communi- 
cated in  this  division,  and  the  work  as  a  whole 
may  be  honestly  recommended  to  educators 
and  self-educators  alike  as  a  cheap  and  reliable 
handbook. 

hydrology  of  south  africa  ;  or  details 
of  the  Former  Hydrographic  Condi- 
tion of  the  Cafe  of  Good  Hope,  and  of 
Causes  of  its  Present  Aridity.  Compiled 
by  John  Croumbie  Brown,  LL.  D.  Kirk- 
caldy :  J.  Crawford. 

The  above  title  explains  fully  the  scope  of 
the  work.  It  is  a  valuable  contribution  to  the 
science  of  Physical  Geography.  The  practi- 
cal bearings  of  the  subject  are  not  at  first  ap- 
parent, but  are  none  the  less  real.  The  de- 
crease or  increase  of  rainfall  in  different  sec- 
tions of  our  country  is  a  subject  upon  which 
we  have  no  definite  knowledge.  Such  changes 
are  so  slow  that  much  time  is  required  to 
gather  data  enough  to  establish  the  fact  of  any 
permanent  change.  In  the  case  of  South. 
Africa,  the  writer  finds  that  a  close  study  of  its 
topography  yields  much  information  of  value. 

The  contents,  as  given  by  chapters,  are  as 
follows  :  Testimony  supplied  by  the  Physical 
Geography  of  South  Africa  ;  Testimony  in  re- 
gard to  former  condition  of  South  Africa  sup- 
plied by  Geology ;  Indications  of  former 
Hydrographic  Conditions  ;  Hydrographic  Con- 
dition within  the  Historic  Period  ;  Primary 
Cause  of  Desiccation  of  South  Africa  ;  Secon- 
dary Causes ;  Aridity  and  Water  Supply  be- 
yond the  Colonized  portions  of  the  Country  ; 
Water  Supply  within  the  Colony. 


382 


VAN  nostrand's  engineering  magazine. 


The  writer  has  availed  himself  of  the  testi- 
mony of  standard  authorities,  and  extracts 
from  former  writings  are  quite  abundant. 
There  are  no  maps  nor  illustrations  of  any- 
kind. 

Practical    Geometry    and    Engineering 
Drawing.     By  G.   Sydenham  Clarke, 
E.  E.     London,  1875. 

Lieut.  Clarke  is  instructor  in  geometrical 
drawing  at  Cooper's  Hill  College,  and  a  few 
words  from  his  preface  will  best  explain  the 
origin  as  well  as  the  plan  of  his  book.  In 
dealing  with  large  numbers  of  students,  the 
writer  felt  the  want  of  "  a  text-book  which  ex- 
plained first  principles  fully  and  S3rstematically, 
which  preserved  a  clear  and  logical  sequence 
throughout  its  pages,  and  which  furnished 
examples  bearing  directly  on  the  subject-mat- 
ter of  each  chapter.  Existing  works  did  not 
satisfactorily  meet  the  case.  Some  supposed 
the  student  to  know  too  much,  others  gave 

him  credit  for  knowing  nothing The 

objects  of  the  Avriter  have  been  to  bring  gen- 
eral principles  into  prominence,  to  illustrate 
those  principles  by  a  variety  of  problems  fully 
explained,  pointing  out  at  the  same  time  any 
peculiarities  worthy  of  remark  ;  and  finally,  to 
append  to  each  chapter  a  number  of  problems 
with  occasional  hints  as  to  their  solution." 
The  plan  thus  sketched  out  is .  systematically 
adhered  to,  each  chapter  in  the  section  on 
solid  geometry  starting  from  principles  and 
definitions,  going  through  explanations  in  de- 
tail, and  concluding  with  examples.  Two 
chapters  on  the  methods  of  execution  of  en- 
gineering drawings,  and  the  selection  and  use 
of  drawing  instruments,  furnish  the  student 
with  common  sense  practical  hints  on  subjects 
which,  though  secondary,  are  not  unimportant 
in  regard  to  rendering  drawings  clear,  neat  and 
intelligible.  — Builder. 

The  Mechanic's  Guide  :  a  Practical  Hand 
Book  for  the  Use  of  Engineers,  Me- 
chanics, Artisans,  &c.  By  W.  V.  Shelton. 
Charles  Griffin  &  Co.     Price  $3.75. 

The  compiler  of  this  treatise,  who  is  fore- 
man of  the  Imperial  Ottoman  gun  factories  at 
Constantinople,  states  as  his  object  "  the  gath- 
ering into  one  connected  whole  the  principal 
subjects  relating  to  various  branches  of  the 
mechanical  art,  and  placing  be  fore  readers  who 
may  not  have  much  leisure  for  study  a  concise 
and  simple  explanation  of  general  principles, 
together  with  illustrations  of  their  adaptation 

to  practical  purposes The  book  is  the 

work  of  a  praotical  mechanic,  who  may  not 
have  the  language  of  a  professor  at  command, 
but  who  has  tried,  to  the  best  of  his  ability,  to 
supply,  honestly  and  thoroughly,  information 
such  as  he  knows  to  be  greatly  needed  by  in- 
telligent mechanics  of  the  present  day."  The 
book  is,  in  fact,  intended  to  be  to  the  working 
mechanic  what  Molesworth's  and  other  pocket 
books  are  to  the  engineer  and  architect.  It  is 
a  book  of  reference  giving  arithmetical  formu- 
lae and  practical  instructions  for  the  carrying 
out  of  a  great  many  problems  in  mechanical 
work,  especially  in  regard  to  the  setting  out 
and  proportioning  of  parts  of  machinery. 
Numerous  tables,  of  the  weights  and  specific 


gravities  of  materials,  the  circumference  and 
areas  of  circles,  &c,  are  added  in  an  appendix; 
and  the  volume  appears  to  be  the  result  of  con- 
siderable thought  and  care,  as  well  as  practical 
experience.  Short  treatises  on  arithmetic, 
practical  geometry,  and  mensuration,  precede 
the  experimental  chapters. 


MISCELLANEOUS. 

Plummet  Lamp  for  Surveying  in  Mines.— 
An  ingenious  lamp  for  the  use  of  mine  sur- 
veyors has  been  designed  by  Mr.  Heller  (of 
Heller  and  Brightly),  of  Philadelphia,  and  was 
described  in  a  paper  read  before  the  American 
Institute  of  Mining  Engineers  at  the  St.  Louis 
meeting.  The  improved  lamp  can  be  used 
either  with  or  without  the  safety  apparatus, 
according  as  fire-damp  may  or  may  not  be  pres- 
ent. The  safety  apparatus  resembles  to  a  cer- 
tain extent  that  of  the  Musseler  lamp.  It  con- 
sists of  a  ring  and  plate  united  by  four  rods. 
The  plate  has  a  cylindrical  hole  in  the  mid- 
dle, and  four  apertures  distributed  radially 
around  it.  In  the  centre  cylindrical  hole  is  fit- 
ted a  conical  brass  chimney,  which  projects  be- 
low the  plate  and  is  fastened  thereto,  being 
kept  vertical  by  four  wire  braces,  or  stays, 
which  are  soldered  to  the  top  of  the  chimney, 
and  to  the  outer  edge  of  the  plate.  The  top  of 
the  chimney  terminates  in  an  in  inverted  frus- 
tum of  a  cone  which  is  made  hollow,  and  is 
drilled  full  of  small  holes.  The  inside  is  lined 
with  one  thickness  of  wire  gauze.  On  the  up- 
per part  of  the  cone  is  screwed  a  brass  cap,  com- 
posed mainly  of  a  brass  ring  and  wire  gauze  ; 
the  smoke,  &c,  pass  out  through  the  latter. 
This  cap  must  be  cleaned  from  time  to  time, 
depending  upon  how  much  the  lamp  is  used, 
and  how  much  it  smokes.  It  is  as  well  to  car- 
ry an  extra  cap  in  the  pocket,  which  can  be 
put  on  when  the  dirty  one  is  taken  off.  An 
easy  way  to  clean  the  cap  is  to  allow  a  jet  of 
steam  to  blow  through  it.  The  four  radial 
apertures  in  the  plate  are  also  covered  by  two 
thicknesses  of  wire-gauze.  Between  the  top  of 
the  plumb  bob  and  the  bottom  of  the  plate,  and 
inside  of  the  four  vertical  wires,  is  inserted  a 
cylinder  of  glass.  When  the  safety  apparatus 
is  to  be  used  the  compensating  ring  is  removed 
from  the  ring  and  placed  upon  the  plate,  which 
has  two  conical  holes  corresponding  to  those 
in  the  ring  ;  the  ring  is  unscrewed  from  the 
top  of  the  plumb-bob,  and  another  ring  is 
screwed  on  in  its  place  with  the  glass  cylinder 
on  top  of  the  plum-bob.  As  the  second  ring 
is  screwed  up  the  glass  cylinder  is  clamped 
between  the  plumb-bob  and  the  plate,  making 
nearly  an  air-tight  joint ;  the  lamp  having  been 
lighted  before  the  safety  apparatus  was  screwed 
on,  is  now  ready  for  use.  The  air  passes  down 
through  the  four  radical  orifices  in  the  plate, 
which  are  covered  with  two  thicknesses  of 
wire  gauze,  is  heated  by  the  flame  and  rises 
through  the  chimney  passing  out  through  the 
wire  gauze  top.  The  glass  is  quite  thick  and 
well  annealed.  He  has  allowed  the  lamp  to 
burn  nearly  an  hour,  until  the  glass  was  quite 
hot,  and  then  thrown  cold  water  upon  it  with- 
out producing  any  effect  whatever  on  the  glass. 
The  wick  should  not  be  high,  as  a  very  short 


MISCELLANEOUS. 


383 


one  gives  light  enough  and  not  much  smoke. 
The  best  kerosene  (of  as  high  a  test  as  possible)  [ 
should  be  used  in  the  lamp,  as  the  latter  gets 
warm.     The  top  of  the  wire  gauze  covering  of  I 
the  chimney  becomes  more  or  less  clogged  with 
lamp-black,  which  can  be  removed  from  time  ] 
to  time  with  a  fine  brush. 

Diamond  Rock  Boring.  —A  party  of  gentle- ! 
men  connected  with  mining,  amongst  j 
whom  were  Messrs.  H.  Cain,  0.  E.  Bainbridge,  j 
J.  Walton,  T.  D.  Bolton,  T.  Rummey,  V. 
Hodgson,  F.  H.  Edwards,  T.  Kell,  and  others, 
met  at  the  Hope  Level,  Stanhope,  on  Saturday  ! 
last,  to  witness  the  work  which  is  now  being  i 
carried  on  by  the  Diamond  Rock-Boring  Com-  j 
pany,  under  the  superintendence  of  their  agent, 
Mr.  C.  Adkin.  Major  Beaumont,  M.  P.,  the' 
managing  director  of  the  company,  and  in- 
ventor of  the  system,  was  present,  and  fully 
explained  the  working  of  the  machinery,  which 
consists  of  a  motor,  similar  in  construction  to 
a  horizontal  steam  engine,  worked  by  com- 
pressed air,  the  exhaustserving  to  ventilate  the 
tunnel.  The  machine  itself  consists  of  a  bed- 
plate, on  which  are  fitted  two  standards  ;  on 
these  are  fitted  movable  saddles  for  carrying 
the  drills,  which  can  be  worked  at  any  angle 
and  in  any  position,  power  to  drive  these  being- 
given  from  the  motor  by  means  of  a  diagonal 
shaft,  driving  bevel  gearing.  The  drills  con- 
sist of  a  brass  quill  and  nut,  mounted  in  a  cast- 
iron  frame,  through  which  passes  a  hollow 
screwed  drill  bar,  on  the  one  end  of  which  is 
fixed  the  crown,  or  boring  tool,  which  is  simply 
a  small  steel  tube,  set  at  the  end  with  pieces  of 
carbonate  (diamonds  in  an  uncrystallized  state.) 
On  the  other  end  is  /screwed  a  water  union, 
fixed  to  a  flexible  pipe,  through  which  is  forced 
a  supply  of  water  when  drilling  which  not  only 
tends  to  keep  the  crown  cool,  but  also  removes 
the  debris  resulting  from  the  borings  from  the 
holes.  On  the  nut  is  placed  a  firiction  clutch, 
so  arranged  by  means  of  a  screw  that  should 
the  drill  come  on  strata  of  such  a  nature  that 
it  cannot  be  bored  at  the  maximum  speed,  the 
friction  nut  slips,  and  only  allows  the  nut  to 
feed  forward  the  drill  bar  at  the  actual  speed 
at  which  the  rock  is  bored,  which  was,  as  we 
saw  on  Saturday,  in  hard  limestone  at  the  rate 
of  4  in.  per  minute. 

The  method  of  working  is  as  follows  : — The 
machine,  which  is  on  wheels  running  on  rails 
laid  on  the  floor  of  the  tunnel,  is  run  to  the 
face ;  the  standards  are  then  tilted  forward 
into  position  by  means  of  power  supplied  from 
the  motor,  and  firmly  fixed  to  the  roof  by 
means  of  screw-jacks  at  the  top  of  the  stand- 
ards. A  set  of  holes  are  then  put  in  at  various 
angles  and  in  different  positions  in  the  face  of 
the  rock  from  4  to  5  ft.  deep,  when  the  stand- 
ards are  tilted  back,  and  the  machine  run  back 
to  a  safe  distance,  when  the  holes  are  blasted, 
and  the  debris  removed. 

The  work  at  Hope  Level  was,  previous  to 
being  taken  up  by  the  Diamond  Rock-Boring 
Company,  being  driven  by  hand  labor  at  a 
speed  of  from  1  to  Hyard  per  week,  while  now 
the  rate  of  progress  is  from  10  to  12  yards,  thus 
clearly  showing  that  a  speed  of  eight  times 
that  of  hand-labor  can  be  obtained  by  the  use 


of  this  machinery,  which  where  the  mineral 
resources  of  a  place  is  required  to  be  fully  and 
speedily  developed  would  be  a  decided  advan- 
tage, and  we  doubt  if  similar  results  than  those 
above  given  can  be  obtained  by  any  other 
machinery  ;  and  in  a  district  like  Weardale, 
where  so  much  mineral  is  yet  undeveloped, 
we  are  surprised  that  the  Diamond  rock-boring 
machinery  has  not  been  more  generally 
adopted. — Mining  Journal. 

Bricks  and  Brick-Drying. — We  have  re- 
ceived some  particulars  of  a  brick-making 
process  at  works  set  up  by  Mr.  Stephens  at 
Kidwelly.  Upon  entering  the  works  the  first 
thing  to  be  seen  is  a  stone-crushing  machine, 
into  which  the  stones  are  cast  and  crushed  to 
pebble  size  ;  from  thence  they  are  shoveled 
into  a  pan,  over  which  two  large  rollers  are 
worked,  which  grind  the  stone  to  powder. 
Both  the  pan  and  rollers  are  lined  with  chilled 
iron,  and  so  are  proof  to  damage  by  the  hard 
silica  stones  from  Mynydd-y-garreg.  While 
the  grinding  process  goes  on  a  small  white 
stream  of  a  liquid  compound  falls  into  the  pan 
which  brings  the  powdered  stone  into  the  sub- 
stance of  mortar  ;  then  it  is  delivered  to  the 
moulder,  who  deposits  the  composition  into  a 
double-mould,  places  it  into  a  press,  which 
answers  the  purpose  of  pressing  closely  the 
bricks  and  of  forcing  them  out  of  the  mould . 
Then  a  lad  carries  them  on  a  sheet  of  iron  and 
places  them  in  the  oven  for  drying  under  the 
new  process.  This  oven  is  constructed  very 
much  on  the  same  principle  as  a  baker's  ovenr 
only  considerably  larger,  but  in  lieu  of  one 
floor  their  are  several  tiers  constructed  of  up- 
right and  horizontal  irons  about  5in.  apart, 
upon  which  to  lay  the  bricks,  so  that  the  oven 
can  be  filled  from  bottom  to  top,  capable  of 
storing  about  10,000.  When  the  oven  is  full, 
the  iron  doors  are  closed  up  air  tight.  Certain 
flues  admit  the  hot  air,  and  the  bricks  are  said 
to  be  thoroughly  dried  in  from  three  to  four 
hours.  Under  the  old  process  it  would  take 
twelve  hours,  with  the  consumption  of  two 
tons  of  coal  and  the  labor  of  several  persons 
over  a  large  area  of  ground  to  dry  5,000  bricks; 
under  the  new  system  10,000  bricks  can  be 
dried  in  three  or  four  hours  with  2  cwt.  of 
coal,  with  less  than  half  the  manual  labor,  and 
without  the  extreme  exhaustion  caused  to  the 
workmen  from  being  hours  in  the  old  dry- 
houses.  The  originator  of  the  idea  is  Mr.  P. 
Conniff,  an  experienced  man  in  the  trade. 

Refractory  Clays. — The  study  of  the  re- 
fractory properties  of  a  clay  of  given 
composition  is  one  most  important  to  metal- 
lurgical operations.  Dr.  Carl  Bischof  has  for 
some  time  been  devoting  his  attention  to  the 
investigation  of  this  subject,  with  the  double 
object  of  estimating  the  refractory  properties 
of  a  clay  of  any  given  composition,  and  also 
their  respective  behavior  in  the  presence  of 
liquefied  metal.  He  has  found  a  wonderful 
relation  almost  constant  between  the  chemical 
composition  and  the  properties  of  any  clay 
provided  that  the  physical  conditions  "are  in 
all  cases  the  same.  The  refractory  power  of 
clays  is  determined  by  the  quantity  of  pure 
pulverized  quartz  with  which  it  is  "necessary 


384 


VAN   NOSTRAND'S   ENGINEERING   MAGAZINE. 


to  mix  them  in  order  that  they  should  present 
any  considerable  resistance  at  high  tempera- 
ture. Instead  of  the  quartz,  a  mixture  of 
equal  parts  of  silica  and  alumina  may  be  used 
with  advantage,  in  order  to  obtain  even  greater 
precision  still  in  the  results.  The  proportion 
of  this  mixture  added  should  be  rather  greater 
than  that  of  the  quartz.  The  refractory  prop- 
erties of  the  clays  are  represented  by  reference 
to  a  standard  clay  whose  refractory  power  is 
taken  at  100.  This  typical  fireclay,  when  a 
portion  of  the  mixed  silica  and  alumina  has 
been  added,  and  been  exposed  to  a  heat  suffi- 
cient to  melt  iron,  breaks  with  an  earthy  frac- 
ture, and  seizes  the  tongue  when  applied,  and 
absorbs  an  ink-mark  traced  by  a  pen  on  its 
fracture.  This  should  be  the  characteristics 
of  all  the  good  refractory  clajrs.  To  find  the 
respective  co-efficients  in  each  case,  multiply 
the  reduction  or  increase  in  the  quantity  of 
mixed  silica  and  alumina  added  (taking  the 
amount  of  the  typical  clay  as  1)  by  10  and  sub- 
tract the  product  from  100,  the  remainder 
will  give  the  respective  refractory  co-efficients 
of  the  different  clays,  that  of  the  type  being 
100. 

The  action  of  liquid  cast-iron  on  the  clays 
has  been  estimated  by  mixing  four  parts  of 
iron  with  100  parts  of  the  clay  investigated. 
At  the  melting  heat  of  Wrought  iron,  the  influ- 
ence of  the  oxyde  of  iron  has  been  found  nil ; 
the  lime,  however,  and  the  potassium  have 
produced  a  vitreous  surface.  The  manganese 
produces  a  similar  effect,  taking  place  inter- 
mediately with  the  lime  and  potassium.  The 
chemical  analysis  and  the  experiments  have 
clearly  shown  that  the  proportions  between 
the  alumina  and  silica,  or  between  the  alumina 
and  the  cast-iron,  vary  in  the  same  proportion 
as  the  co-efficients  of  resistance.  This  rule 
was  subject  to  a  few  exceptions,  but  it  was 
proved  that  these  exceptions  were  owing  to 
the  physical  condition  of  the  clay.  It  is  then 
but  necessary  to  pay  attention  to  dryness  or 
dampness  of  the  clay  to  obtain  accurate  pre- 
knowledge  of  results  from  the  chemical  com- 
position of  the  clays. 

The  above  general  principles  will  also  apply 
equally  as  well  to  the  case  of  clays  subject  to 
the  action  of  glass,  of  slags,  of  metals,  of 
metallic  oxydes,  of  bases,  and  of  salts,  of  cin- 
ders, &c.  There  is  a  perfectly  definite  com- 
position to  be  produced  in  the  typical  clay  to 
give  the  best  possible  refractory  and  resisting 
powers.  Here,  again,  the  aetion  of  the  metal, 
&c. ,  on  the  clay  is  found  to  be  less  strong  as 
the  co-efficient  of  the  refractory  power  rises. 

Rotjx  and  Sarratj  have  previously  shown 
that  two  different  kinds  of  explosions  can 
be  produced  by  dynamite,  according  as  the 
substance  is  made  simply  to  deflagrate  (ex- 
plosion of  the  second  order),  or  to  detonate  by 
the  percussion  of  fulminate  of  mercury  (ex- 
plosion of  the  first  order),  and  that  the  force  of 
the  explosion  produced  by  the  same  quantity 
is  very  different  in  the  two  cases.  They  now 
find  that  the  majority  of  explosive  substances, 
gunpowder  included,  possess  the  same  remark- 
able property.  The  reciprocal  of  the  weight 
(due   corrections   made)   of   each  substance, 


which  when  exploded  in  one  and  the  other 
manner  sufficed  to  rend  similar  cast-iron  shells, 
gave  the  relative  explosive  forces.  Some  re- 
sults of  the  experiments  are  given  in  the  fol- 
lowing table,  the  explosive  force  of  gunpowder 
igniting  in  the  ordinary  manner  being  taken 
for  unity  : 

Name  of  substance.  Explosive  force. 

2d  Order.  1st  Order. 

Mercury  fulminate —  9.28 

Gunpowder 1.00  4.34 

Nitroglycerine 4.80  10.13 

Poroxyl  (gun  cotton) 3.00  6.46 

Picric  acid 2.04  5.50 

Potassium  picrate 1.82  5.31 

Barium  picrate 1.71  5.50 

Strontium  picrate 1.35  4.51 

Lead  picrate 1.55         5.94 

Of  the  hignest  practical  importance  is  the 
discovery  of  the  detonative  explosion  of  gun- 
powder induced  by  the  detonation  of  nitrogly- 
cerine— itself  set  off  by  the  fulminate  of  mer- 
cury— for  the  force  of  the  explosion  is  more 
than  four-fold  greater  than  that  obtained  by 
igniting  gunpowder  in  the  ordinary  manner. 
The  increased  force  of  gunpowder  and  gun 
cotton,  when  exploded  by  the  agency  of  de- 
tonation, was  fully  demonstrated  by  Abel  six 
years  ago .  The  authors  observe  that  the  mass 
of  the  substance  employed  for  exciting  deton- 
ation must  usually  bear  a  certain  proportion  to 
that  of  the  substance  to  be  exploded,  but  in 
some  cases  the  action  is  propagated  through- 
out the  latter  when  once  up  at  any  given 
point.  — Engineering. 

Electric  Resistance  of  Various  Metals. 
— M.  Benoit  has  measured  with  great  pre- 
cision the  electrical  resistance  of  various  met- 
als at  temperatures  from  0°  to  860°.  He  em- 
ployed both  the  method  of  the  differential 
galvanometer  and  of  the  Wheatstone's  bridge, 
and  for  each  method  has  measured  several 
specimens.  The  mean  of  these  is  given  in  the 
following  table,  the  second  column  giving  the 
resistance  of  a  wire,  39.37  inches  long  and 
having  a  cross  section  of  0 .03  inches  in  ohms, 
and  column  three  the  same  quantity  in  Sie- 
mens' units.  Column  four  gives  the  resistance 
compared  with  silver  : 

Metal.  Ohms.       Siemens. 

Silver,  A 0154  .0161  100 

Copper,  A 0171  .0179  90 

Silver,  A  (1) 0193  .0201  80 

Gold,  A 0217  .0227  71 

Aluminum,  A 0309 

Magnesium,  H 0423 

Zinc,  A.,  at  350° 0565 

Zinc,  H 0594 

Cadmium,  H 06S5 

Brass,  A  (2) -0691 

Steel,  A 1099 

Tin 1161 

Aluminum  bronze,  A  (3) 1189 

lron,A 1216 

PaUadium,A 1384 

Platinum,  A.... 1575 

Thallium 1831 

Lead 1985 

German  Silver,  A  (4) 2654 

Mercury 9564 

A,  annealed ;  H,  hardened ;  (1)  silver  .75 ;  (2)  copper 
64.2,  zinc  S3.1,  lead  0.4,  tin,  0.4 ;  (3)  copper  90,  ailuminum 
10 ;  (4)  copper  SO,  nickel  25,  zinc  25. 


.0324 

49.7 

.0443 

36.4 

.0591 

27.5 

.0621 

25.9 

.0716 

22.5 

.0723 

22.3 

.1149 

14 

.1214 

13.3 

.1243 

13 

.1272 

12.7 

.1447 

11.1 

.1647 

9.77 

.1914 

8.41 

.2075 

77.60 

.2775 

5.30 

1.0000 

1.61 

VAN     NO  ST  RAND'S 

ECLECTIC 

ENGINEERING    magazine. 


NO.  LXXXIII.-NOVEMBER,  1875 -VOL.  XIII. 


BRIDGE  AND  TUNNEL  CENTRES. 

By  JOHN  B.  McMASTER,  C.  B. 
Written  for  Van  Nostkand's  Engineering  Magazine. 


In  the  construction  of  stone  and  brick 
arches,  of  whatever  shape  and  span,  and 
to  whatever  use  applied,  whether  as  sup- 
ports for  roadways  or  roofs  of  tunnels, 
there  is  nothing  which  requires  more 
careful  attention  on  the  part  of  the  con- 
structing engineer,  than  the  centres. 
Independent  of  the  choice  of  material, 
of  the  exactness  with  which  each  stone 
is  cut,  and  the  care  with  which  it  is  laid 
in  place,  the  success  of  arches  of  great 
span,  their  settlement  and  ultimate  sta- 
bility depends  .essentially  on  the  care 
given  to  the  framing,  setting  up  and 
striking  of  the  centres.  The  slightest 
change  in  the  shape  of  the  frame  caused 
by  the  shrinking  of  an  ill-seasoned  tim- 
ber, or  the  yielding  to  compression  of  a 
badly  proportioned  brace,  will  assuredly 
be  followed  by  a  change  in  the  curve  of 
the  intrados,  which  may  possibly  result 
in  the  ruin  of  the  arch  itself. 

Well  constructed  centring,  therefore, 
is  indispensably  necessaiw  to  a  well  con- 
structed arch,  and  in  the  following  papers 
it  is  our  intention  to  offer  a  practical  in- 
vestigation of  the  principles  which  must 
be  followed  out  in  the  planning  and  me- 
chanical execution  of  all  such  centre 
frames  ;  to  determine  what  strains  must 
be  withstood,  at  what  point  they  act 
with  most  vigor,  and  by  what  eombina- 
Vol.  XIII.— No.  5—25 


tion  of  beams  and  by  what  system  of 
bracing,  the  greatest  strength  and  stiff- 
ness may  be  combined  with  the  utmost 
lightness  and  the  strictest  economy  of 
material. 

BRIDGE    CENTRES. 

Of  all  classes  of  centres,  the  most  com- 
plicated in  structure  is,  beyond  doubt, 
that  of  a  large  span  stone  bridge.  Like 
a  roof  frame,  it  consists  of  a  number  of 
vertical  pieces,  placed  in  the  direction  of 
the  span,  from  5  to  7  ft.  from  centre  to 
centre,  and  known  as  the  ribs,  upon  which 
are  placed  horizontal  pieces  or  laggings, 
and  on  these  latter  rest  the  voussoirs  till 
the  key  stone  course  is  driven  and  the 
arch  becomes  self-supporting. 

The  frame  in  its  turn  is  composed  of 
back  pieces,  or  short  beams  cut  on  the 
outer  edge  to  the  same  curve  as  the  in- 
trados of  the  arch,  a  horizontal  tie  beam. 
and  a  number  of  struts,  ties  and  braces,  the 
arrangement,  number  and  dimensions  of 
which,  will  depend  on  the  shape  and  span 
of  the  arch,  and  the  number  and  position 
of  the  points  of  support.  Whatever  may 
be  the  span  and  curve  of  the  arch,  and  the 
points  of  support  afforded,  experience 
has  amply  proved  that  the  ribs  should  be 
polygonal  in  shape,  with  short  sides  ; 
this  shape  being   given  by  forming  t... 


386 


VAN   NOSTRAND'S   ENGINEERING   MAGAZINE. 


back-pieces,  on  which  rest  the  laggings, 
of  two  or  more  courses  of  planks,  placed 
in  the  form  of  a  polygon  and  firmly  nail- 
ed together  ;  the  planks  in  each  course 
abutting  end  to  end  by  a  joint  in  the  di- 
rection of  the  radius  of  curvature  of  the 
arch,  and  breaking  joints  with  those  of 
the  other  course. 

For  light  arches  of  moderate  span,  or 
indeed  for  heavy  arches  of  wide  span 
when  firm  intermediate  points  of  sup- 
port can  be  had  between  the  abutments, 
the  back  pieces  may  be  strengthened  by 
struts  or  ties  placed  under  them,  well 
braced,  and  abutting  against  a  horizon- 
tal tie  beam.  This  beam  spans  the  arch 
a  little  above  the  springing  line,  is  bolt- 
ed to  the  back-pieces  at  either  side,  thus 
preventing  them  from  spreading  later- 
ally, and  if  well  sustained  by  props  f  rom 
beneath,  affords  a  firm  support  to  the 
struts  and  braces  of  the  rib.  In  by  far 
the  greater  number  of  cases,  however, 
where  headway  is  required  under  the 
centring  during  the  construction  of  the 
arch,  as  is  the  case  with  stone  bridges 
spanning  a  river  whose  navigation  can- 
not be  impeded,  or  whose  current  is  too 
swift  and  depth  too  great  to  give  firm 
points  of  support  to  the  props  of  the 
tie  beam,  it  becomes  necessary  to  do 
away  with  the  latter,  and  supply  its  place 
by  such  an  arrangement  of  beams  as  will 
transmit  the  strains  received  to  points 
of  support  at  the  abutments.  This  lat- 
ter class  of  centring  is  known  as  "re- 
troussee"  or  " cocket"  and  requires  a 
much  more  careful  and  elaborate  arrange- 
ment of  its  parts  than  the  former. 

We  have  therefore  two  classes  of 
bridge  centres  to  deal  with  ;  one  in 
which  the  frame  is  constructed  without 
regard  to  headway  beneath  it,  and  is 
supported  from  firm  points  of  support 
between  the  abutments,  and  one  arrang- 
ed to  leave  headway  under  the  frame, 
and  upheld  by  framed  supports  at  the 
abutments. 

Before  attempting  to  determine  the 
most  advantageous  arrangement  of  the 
pieces  which  must  compose  the  frame, 
their  number  and  the  dimensions  it  is 
necessary  to  give  them  in  order  that  they 
may  offer  a  solid  support  to  the  arch 
stones,  it  is  fitting  to  consider  the  effect 
of  the  load  the  ribs  are  expected  to  up- 
h  j]<J,  the  strains  it  produces,  the  points 


where  and   the  directions  in  which 
strains  act  and  their  intensity. 


the 


THE   STRAINS, 


The  strains  to  which  centre  frames  are 
subjected  arise  solely  from  the  pressure 
upon  the  back-pieces  and  laggings,  due 
to  the  weight  of  the  voussoirs  laid  upon 
them,  and  are  therefore  extremely  vari- 
able, depending  on  the  span  and  curve 
of  the  arch,  and  the  thickness  and  weight 
per  cubic  foot  of  the  voussoirs  which 
press  upon  the  centring.  It  is  not, 
however,  to  be  supposed  that  all  the 
voussoirs  from  springing  line  to  spring- 
ing line  do  press  upon  the  frames,  this 
depending  to  a  very  great  degree  on  the 
curve  of  the  arch.  If,  for  example,  we 
take  the  case  of  a  full  centre  arch  and 
starting  at  the  springing  line  on  either 
side  pass  towards  the  crown,  we  shall 
find  that  for  a  considerable  distance 
above  the  springing  line  the  stones  do 
not  exert  any  pressure  upon  the  ribs, 
but  that,  as  soon  as  this  point  is  passed, 
the  pressure  begins  and  increases  rapidly, 
reaching  its  maximum  intensity  just  be- 
fore the  keystone  course  is  driven  into 
place.  When  this  is  done  the  pressure 
is  almost  entirely  removed,  and  were  it 
not  for  the  slowness  of  the  mortar  in 
drying,  the  frame  work  of  the  arch 
might  be  done  away  with. 

And,  here,  I  would  mention  that,  al- 
though it  is  generally  held  that  when 
the  keying  course  is  placed,  the  vous- 
soirs, with  the  exception  of  a  few  courses 
at  the  crown,  cease  to  press,  I  have  found 
by  the  most  careful  experiments  with 
large,  well-framed  models,  that  the  thin- 
nest Chinese  paper  when  coated  with 
black  lead  and  placed  under  the  blocks 
of  arch  stone,  could  not  be  drawn  outt 
even  when  the  arch  was  keyed,  without 
considerable  resistance. 

Upon  further  examination  it  will  be 
found  that  these  voussoirs  which  lie  near 
the  springing  line  and  exert  no  pressure 
upon  the  laggings  and  back-pieces,  are 
all  of  them  contained  within  the  angle 
of  repose  ;  that  is  to  say,  the  voussoirs 
do  not  begin  to  press  upon  the  centring 
until  we  reach  one  whose  lower  joint 
makes  so  great  an  angle  with  the  hori- 
zon, that  the  stone  is  caused  to  slide 
along  its  bed  under  the  action  of  gravi- 
tation. This  angle  for  full  centre  arches 
has  been  fixed  at  from  28°  to  30°,  but 


BRIDGE  AND   TUNNEL   CENTRES. 


387 


the  quality  of  the  stone  and  mortar  used, 
will  cause  it  to  vary  greatly.  For  ordi- 
nary cut  stone,  we  may  with  safety  as- 
sume the  angle  of  friction  at  30°  with  the 
horizon  :  when  laid  in  thin  tempered 
mortar  it  is  increased  to  34°  or  36°,  and 
with  very  porous  stone,  such  as  free- 
stone, laid  in  full  mortar  it  will  reach 
almost  45°. 

It  is  to  be  observed,  however,  that  this 
is  not  strictly  true  unless  the  arch  is  of 
sufficient  thickness  at  bottom  to  prevent 
all  tendency  to  upset  inwards.  A  thick- 
ness of  iV  the  radius  of  curvature  is  usu- 
ally adopted  as  sufficient  for  this  pur- 
pose. 

Adopting  30°  as  the  angle  of  repose 
for  cut  stone,  the  number  of  voussoirs 
which  load  the  centre  will  depend  on 
the  curve  given  to  the  intrados.  If  we 
take,  for  instance,  a  full  centre,  an  oval 
and  a  flat  segmental  arch,  and  give  to 
each  the  same  number  of  voussoirs,  it  is 
evident  that  the  number  of  stones  which 
do  not  press  on  the  laggings  will  be 
greatest  in  the  full  centre,  less  in  the 
oval,  and  least  of  all  in  the  flat  segmen- 
tal arch,  because  in  this  latter  case  the 
stone  whose  lower  joint  makes  an  angle 
of  30°  with  the  horizon  will  be  found 
nearer  the  springing  line.  We  should 
expect,  therefore,  the  number  and  weight 
of  the  stones  being  the  same,  that  the 
segmental  arch  could  give  the  greatest 
load  to  the  centres,  and  the  full  centre 
arch  the  least ;  and  this  is  strictly  the 
case. 

In  estimating  the  load  upon  the  centres 
in  any  case,  it  is  to  be  remembered  that 
none  of  the  stones  bear  upon  the  ribs 
with  their  entire  weight,  a  part  of  this 
latter  being  consumed  in  overcoming 
friction.  The  determination  of  the 
amount  of  weight  thus  expended  is  a 
matter  of  some  mathematical  intricacy, 
and  we  are  indebted  for  its  solution  to 
M.  Couplet.*  By  his  calculation  he 
found  that  the  total  weight  of  the  vous- 
soirs which  do  press  on  the  laggings,  is 
to  the  weight  with  which  they  actually 
load  the  frame,  as  an  arc  of  60°  is  to 
twice  its  sine  less  the  same  angle  ;  or,  to 
express  it  algebraically,  denote  by  P  the 
total  weight  of  the  voussoirs  which  rest 
on  the  centring,  and  by  p,  the   weight 

*  iloaijire  dj  l'Acadeaiie  Aauie,  1792. 


with  which  they  load  the  centres,  and 
we  shall  have  the  expression 

P  :  p:  |arc  60°  :  2  sin  60°-arc  60°       (1) 

or 

P  (2  sin  60°  — arc  60°)  ^, 

P=~  Arc  60.  '       (2) 

If,  therefore,  we  suppose  the  radius  of 
a  circle  to  be  divided  into  10,000  equal 
parts,  the  circumference  will  contain 
62,832,  and  the  arc  of  60°  10,472,  and 
its  sine  is  equal  to  -^^/j^Seeo.  Substi- 
tuting these  values  in  the  above  equa- 
tion (1),  we  shall  have 

P  :  p\  ;i0472;  12X8660  — 10472      or 
P  \p\  '.10472  :  6848 

which  gives  us  a  ratio  of  3  to  2  very 
nearly.  Whence  we  see  that  the  vous- 
soirs in  a  full  centre  arch  which  press 
upon  the  laggings  will  do  so  with  but  f 
of  their  weight,  and,  taking  the  angle 
of  repose  on  each  side  at  30°,  only  on  § 
of  the  surface  of  the  centring.  We 
may,  therefore,  without  any  sensible 
error  take  9  of  the  gross  weight  of  the 
voussoirs  of  the  arch  to  express  the  load 
on  the  centres. 

With  an  arch  which  is  not  full  centre 
the  case  is  quite  similar.  We  will  take 
an  oval  of  three  centres  fulfilling  the 
conditions  that  each  of  the  three  arcs 
composing  it  shall  be  60°.  This  oval 
being  drawn,  it  is  at  once  apparent  that 
the  arcs  of  60°  at  each  end  of  the  oval 
do  not  differ  materially  from  that  of  30° 
in  the  full  centre  arch.  We  may,  there- 
fore, to  facilitate  calculation,  safely  as- 
sume that  the  stones  forming  these  two 
arcs  of  60°  do  not  press  on  the  centres, 
when  the  arch  is  all  up  except  the  key- 
stone, and  are  held  in  place  by  the  weight 
of  the  voussoirs  above  them.  There  re- 
mains then  but  the  central  arc  of  60°  to 
load  the  framing.  But  from  equation 
(1)  P  :  p  as  the  arc  of  60°  is  to  twice  its 
chord  less  the  arc  of  60°  ;  and  since  60° 
is  to  its  chord  very  nearly  as  22  to  21, 
we  may  without  sensible  error  express 
the  relation  of  P  to  p  by  the  ratio  of  11 
to  10.  When  we  have  found  the  gross 
weight  of  the  voussoirs  in  this  arc  of  60° 
it  follows  that  we  must  take  i?  of  their 
weight  to  express  the  load  on  the  fram- 
ing. 

The  chord  of  an  arc  of  60°  is  equal  to 


388 


VAN   NOSTRAND'S   ENGINEERING   MAGAZINE. 


the  radius,  and  the  radius  in  this  case 
being  10000,  the  chord  will  equal  10000, 
and  the  arc  of  60°,  10472.  Hence  we 
have  the  relation  10000  :  10472;  |21  :  22 
nearly. 

These  values  may  also  be  obtained 
from  the  integral  calculus,  in  which  case 
no  regard  is  taken  of  friction,  and  the 
formulae  are  therefore  a  little  uncertain. 


This  uncertainty,  however,  is  on  the  side 
of  safety,  for  when  we  leave  out  of  con- 
sideration the  pressure  expended  in  over- 
coming friction  we  are  forced  to  give  the 
ribs  and  laggings  unnecessary  strength. 

Referring  to  Figure  1,  we  wish  to  find 
the  load  which  the  voussoirs  between 
ABCD  give  to  the  centre's  rib. 


Fig.  1. 


Let  w  equal  the  weight  per  lineal  foot 
of  intrados  of  the  arch  resting  on 
the  rib. 

By  x  and  y  the  horizontal  and  vertical 
co-ordinates  respectively  of  the 
point  A. 

By  x'  and  y'  the  co-ordinates'of  D. 

By  r  the  radius  of  the  curve jrf  intra- 
dos at  A,  and 

By  x  the  angle  it  makes  with  the  hori- 
zon. 

By  P  the  gross  vertical  pressure  on 
the  rib  ofABCD. 

By  p  the  pressure  per  lineal  foot  of  in- 
trados at  A. 

Then  we  shall  have 


•J  o 


pdx 


(4) 


P'  being  the  greatest  vertical  load  on 
the  half  rib,  and  x"  the  horizontal  dis- 
tance from  the  middle  of  the  span  to  a 
point  where  p  is  zero. 

The  value  of  p  is  found  from  the  equa- 
tion 


p=W.  Cos  oc 


V  y 


W.  dy     .     (5) 


=  /    ,  pdx 


(3) 


From  this  we  may  compute  the  load  on 
any  vertical  post  at  this  point,  or  the 
vertical  component  of  the  load  on  the 
back  pieces. 

If  the  arch  had  been  completed  up  to 
the  keystone  course,  equation  (3)  would 
have  been 


which  will  evidently  be  greatest  when 

jt>=W.  Cos  a:  .     .     .     .     (6) 

When  the  arc  is  a  segment  of  a  circle 
not  greater  than  120°,  we  shall  have 
from  the  relation  between  the  sides  and 
angles  of  a  triangle,  the  following  values 
of  the  co-ordinates  : 

x=r  sin  oc  x'=r  since'  /  =  r(sin  a") 
y=r  (1  —  cos  oc  )         y'=r  (1  —  cos  cc') 

Substituting  these  values  in  equation  (5) 
we  shall  have 

p=w  (2  cos  oc  —cos  cc').     .     .     (7) 


BRIDGE   AND   TUNNEL   CENTRES. 


389 


And  from  the  expx-essiony=r(l— cos  x  ) 
we  have 

Cos  x  =- — -  : 
r 

and  from       y' ' =r  (1— cos  cc') 

Cos  cc'  = - 

r 

Substituting  this  in  equation  (7)  we  shall 
have 

_     /2r—2y_r—y'\ 


(2r—2 y    r—y  \ 


=w 


r-2y  +  y' 


(8) 


Equation  (6)  then  becomes  p=w  cos  cc 

v —  y 

=w -  the  greatest  value  for  a  given 

point  of  the  arch. 

Substituting  in  equation  (3)  the  value 
of  p  found  in  eq.  (8),  and,  reducing,  we 
obtain 

(9) 
P=wr[cc  —  cc'  — sin  oc  (cos  x  '  —  cos  x)] 

©r 

T>=to(l-r-Xr[;y-y>]) 

in  which  I  and  I'  represent  the  length  in 
feet  of  the  arcs  from  the  crown  E  (Fig. 
1)  to  the  points  A  and  D  respectively. 
Equation  (4)  then  becomes 

¥'=ior  (ccff— sin  oc"  [1  —  coscc"])    (10) 

To  find  the  gross  weight  of  that  por- 
tion of  the  arch  which  presses  on  the 
back  pieces  and  laggings,  it  is  necessary 
to  know  the  number  of  the  voussoirs, 
their  volume  and  weight  per  cubic  foot. 

The  weight  of  stone  generally  used 
in  arches  varies  from  120  to  180  pounds 
per  cubic  foot.  The  following  results 
were  obtained  from  the  examination  of 
a  number  of  specimens  of  American 
granite,  sandstone  and  limestone,  taken 
from  the  best  known  quarries  in  the 
country.  Of  seventy-two  specimens  of 
granite  examined,  the  greatest  weight 
per  cubic  foot  was  182.5  lbs.,  the  least 
161.2,  and  the  average  167.09  lbs.  Of 
fifty-three  specimens  of  sandstone  exam- 
ined, the  greatest  weight  per  cubic  foot 
was  164.4  lbs,  the  least  127.5,  and  the 
average  140.9  lbs.  Of  thirty -eight 
specimens  of  limestone,  the  greatest 
weight  per  cubic  foot  was  173.8,  the  least 
143.2,  the  average  162.9. 


We  may  therefore  without  sensible 
error  assume  the  average  weight  of  these 
three  classes  of  stone  as  follows  : 

Average  weight 
per  cubic  foot. 

Granite 167.09  lbs. 

Sandstone 140. 9    lbs. 

Limestone 162.9    lbs. 

Brick  (well  burnt) 92. 0    lbs . 

From  the  moment  the  angle  of  repose 
is  passed  and  the  first  voussoir  begins  to 
press  on  the  frames,  the  centring  be- 
comes subjected  to  a  seiies  of  strains 
which  increase  rapidly  up  to  the  time 
the  keystone  is  laid,  and  are  produced 
by  the  yielding  of  the  ribs  under  the 
weight  of  the  stones.  No  matter  how 
well  seasoned  and  admirably  proportion- 
ed the  timbers  may  be,  or  how  evenly 
the  load  may  be  distributed,  the  centre, 
pressed  more  and  more  severely  on  each 
side  by  the  successive  courses  of  vous- 
soirs laid  upon  it,  will  bend  in  on  the 
sides,  and  as  a  consequence  bulge  out  at 
the  crown,  to  be  in  turn  followed  by  a 
bending  in  of  the  crown  when  the  arch 
is  all  but  completed.  This  movement  of 
the  ribs  can  be  greatly  checked  and  the 
severity  of  the  resulting  strains  much 
lessened  by  loading  the  centres  at  the 
crown  with  the  spare  voussoirs  and  in- 
creasing the  load  as  the  arch  progresses. 
In  the  case  of  a  full  centre  arch  of  90 
feet,  and  composed  of  four  hundred  and 
eighty  courses  of  voussoirs,  the  cen- 
tring, when  the  fifteenth  course  of  vous- 
soirs on  each  side  were  laid  in  place,  had 
risen  three  inches  at  the  crown.  When 
loaded  with  325,000  lbs.,  it  settled  under 
it  two  inches  ;  but  when  the  twentieth 
course  was  completed  the  pressure  was 
so  great  that  it  again  rose  one  inch. 
When  the  arch  was  three-quarters  com- 
pleted it  had  again  sunk  one  inch  and 
three-quarters  in  consequence  of  the  ad- 
ditional load  and  the  compression  of  the 
wood,  still  leaving  a  rise  of  one  quarter 
of  an  inch.  This  yield  caused  the 
joints  at  the  twenty-second  course  to 
open  a  fraction  of  an  inch,  but  closed 
when  the  keystones  were  driven.  This 
distortion  of  the  centring  is  always 
greatest  for  full  centre  arches,  and  pro- 
portionally less  as  the  arch  becomes 
nearer  and  nearer  to  the  segmental. 

DIRECTION    OF    THE    STRAINS. 

To  find  the  direction  and  intensity  of 


390 


VAN  nostrand's  engineering  magazine. 


the  strain  at  any  point  of  the  rib,  we  re- 
sort to  the  usual  method  of  the  "  paral- 
lelogram of  forces."  Returning  to  Fig. 
1,  let  it  be  required  to  find  the  direction 
of  the  strain  caused  by  the  voussoirs 
ABCD.  Denote  by  F  the  centre  of 
gravity  of  this  part  of  the  arch,  and 
through  it  draw  a  vertical  line  G I  of  in- 
definite length,  and  cut  it  at  I  by  a  per- 
pendicular from  the  point  E  at  which 
the  curve  drawn  through  the  centres  of 
gravity  of  the  voussoirs — supposed  in- 
definitely small — cuts  the  line  AB. 
Complete  the  parallelogram  by  drawing 
the  line  IM  to  the  centre  of  arch,  and 
NL  parallel  to  it.  The  diagonal  IN 
will  then  express  the  weight  of  the  vous- 
soirs ABCD,  the  side  I L  the  pressure 
they  exert  upon  the  lower  part  of  the 
arch,  and  the  side  I  M  the  pressure  upon 
the  backpieces  of  the  rib. 

The  strains,  then,  upon  the  centring- 
take  the  direction  of  the  radius  of  cur- 
vature of  the  intrados,  and  it  now  re- 
mains to  consider  the  position  which 
should  be  given  to  the  beams  which  are 
to  withstand  the  strains,  their  numb  el- 
and dimensions. 

THE    PRINCIPAL    BEAMS    AND    THEIR 
POSITION. 

As  the  sole  object  of  the  framing  is  to 
uphold  the  voussoirs  and   transmit  the 
strains  it  receives  as  directly  as  possible 
to  firm  points  of  support,  the  beams  must 
be  so  arranged  as  to  do  this  with  the 
least  tendency  to  change  the  shape  of 
the  rib,  by  their  bending  or  breaking. 
The  condition  will   be   best  fulfilled   by 
giving  each  beam  a  position  such  that  it 
shall  offer  the   greatest   possible  resist- 
ance, and  this  will  be  accomplished  when  ; 
the  direction  of  the  fibres  of  the  beam  \ 
and  the   direction  of  the  strain  are  one ! 
and  the  same. 

If,  for  instance,  we  support  a  horizon-  j 
tal  beam  at  its  two  ends  and  load  it  in  i 
the  middle  it  will  offer  its  least  resist- 1 
ance  to  the  load.     If  now  we  raise  one  | 
end  so  that  the  direction  of  the  strain  is  \ 
oblique  to  the  fibres  of  the  beam,  the  re- 
sistance of  the  beam  to  bending  will  be 
found  to  have  increased  largely,  and  the  j 
resistance  in  this  latter  case,  will  be  to  j 
that  in  the  former  case,  as  the  cosine  of  j 
the  angle  made  by  the  direction  of  the 
strain   and  the  fibres  of  the  wood  is  to 
the  sine  of  90°  or  1. 


It  should  follow  from  this  that,  when 
the  angle  between  the  beam  and  the 
strain  is  zero,  the  resistance  becomes  in- 
finite, and  such  would  indeed  be  the  case 
were  it  not  for  the  compressibility  of  the 
wood  and  other  physical  causes  which 
weakens  its  strength.  It  is  sufficient, 
however,  for  us  to  know  that  when  the 
strain  is  carried  through  the  axis  of  the 
beam,  it  is  then  strongest,  and  that  a& 
the  force  becomes  more  and  more  oblique 
to  the  fibres  its  strength  decreases. 

Applying  this  fact  to  the  framing  of 
the  ribs,  it  follows  that  the  greatest  stiff- 
ness and  strength  will  be  gained  when 
the  principal  pieces  are  placed  in  the 
direction  of  the  strains,  or  in  the  direc- 
tion of  the  radii  of  curvature  of  the- 
arch  to  be  upheld.  This  deduction,  un- 
fortunately, is  under  certain  restrictions 
placed  upon  it  by  the  imperfections  of 
the  timber,  and  demands  of  economy 
and  the  circumstances  of  construction, 
which  make  its  practical  application  quite 
limited. 

To  illustrate,  we  will  once  more  return 
to  Fig.  1.  The  direction  and  intensity 
of  the  strain  on  the  backpieces  resulting 
from  the  weight  of  the  voussoirs  ABCD, 
will  then  be  represented,  as  we  have 
just  seen  by  the  line  VM,  and  that  of 
the  voussoirs  P  Q  by  the  line  V  S.  The 
beams,  therefore,  which  are  to  support 
these  stones,  in  order  that  they  may  of- 
fer the  utmost  resistance,  must  take  the 
direction  of  the  lines  VS  and  VM,  or 
radiate  from  the  centre  V  like  the  spokes 
of  a  wheel.  For  small  span  arches,  such 
an  arrangement  of  beams  undoubtedly 
answers  all  purposes  of  stiffness  and 
economy,  but  for  arches  of  larger  span 
where  timbers  of  thirty,  fifty,  or  even  a 
hundred  feet  in  length  would  be  requir- 
ed, it  fails  most  signally  ;  for  while  a 
beam  of  ten  feet  will  offer  great  resist- 
ance to  compression  when  loaded  in  the 
direction  of  the  fibres,  a  beam  of  fifty 
feet  will  be  almost  sure  to  bend  under 
the  action  of  the  strain,  and  hence  re- 
quire bracing.  This  system,  therefore, 
cannot  be  successfully  carried  into  prac- 
tice in  large  span  centres. 

To  overcome  this  difficulty  we  are- 
forced  to  resolve  the  force  represented 
by  the  line  S  V  into  two  components,  one 
vertical  and  represented  by  the  line  ST, 
and  one  horizontal  represented  in  direc- 
tion and  intensity  by  S  R.     By  a  similar 


BRIDGE   AND   TUNNEL   CENTRES. 


301 


treatment  of  the  force  represented  by 
VM,  we  shall  obtain  two  other  similar 
lines,  all  four  of  which  will  represent  the 
direction  of  three  beams,  which  can  be 
made  to  take  the  direction  of  the  two 
V"  S  and  V  M,  namely,  a  long  horizontal 
beam  spanning  the  arch  and  supported 
at  each  end  by  a  vertical  beam.  This 
horizontal  beam  is  the  tie  beam  to  which 
we  have  already  alluded,  and  is  gener- 
ally placed  at  points  about  45°  up  the 
•  arch.  The  voussoirs  above  this  beam 
are  then  supported  by  another  horizon- 
tal tie  upheld  by  small  vertical  beams 
abutting  on  the  lower  tie.  An  excellent 
illustration  of  this  system  of  framing  is 
found  in  centres  of  London  Bridge  over 
the  Thames,  built  in  1831  by  Rennie. 

There  will  frequently  arise  cases  in 
which  ribs  framed  in  this  manner  either 
on  account  of  the  quantity  of  material 
they  consume,  or  the  difficulty  of  finding 
firm  points  of  support  between  the  abut- 
ments, cannot  be  used  to  advantage.  It 
then  becomes  necessary  to  change  the 
point  of  support  T  of  the  beam  ST 
(Fig.  1)  to  a  point  t  nearer  the  abutment, 
and  for  the  sake  of  economy  we  may  do 
away  with  the  horizontal  and  vertical 
beams  tg,sS,  TS,  c  a  and  a  b,  supply- 
ing their  place  by  two  beams  t  S  and  S  e. 
These  two  beams,  therefore,  will  sustain 
the  strain  represented  by  the  line  S  V, 
and  the  efforts  they  resist  will  be  repre- 
sented in  direction  and  intensity  by  the 
sides  S  X  and  S  Y  of  the  parallelogram 
XY  constructed  on  S  V  as  a  diagonal. 

In  "  cocket "  centres,  therefore,  what- 
ever the  span  of  the  arch,  whether  large 
or  small,  whatever  the  shape,  whether 
full  centre,  oval  or  segmental,  a  great 
saving  of  material  may  be  made,  and 
abundance  of  strength  may  be  secured, 
by  placing  the  principal  beams  in  the 
direction  of  the  chords  of  the  curve  of 
the  intrados. 

The  length  that  should  be  given  to 
beams  thus  placed,  the  angle  they  should 
make  with  each  other  at  their  point  of 
junction,  the  manner  of  supporting,  and 
when  necessary  bracing  them,  are  points 
we  shall  reserve  for  future  consideration. 

There  are,  therefore,  thi*ee  methods  of 
arranging  the  principal  pieces  or  struts 
of  a  centre  frame. 

1°.  They  may  be  placed  in  the  direc- 
tion of  the  radii  of  curvature  of  the 
arch,  thus  giving  a  figure  of  invariable 


form  as  the  strain  at  anyone  point  is  re- 
ceived by  the  beam  in  the  most  favor- 
able position,  and  transmitted  through 
its  axis  directly  to  the  fixed  point  of  sup- 
port. 

2°.  They  may  be  placed  in  a  vertical, 
or  insvertical  and  horizontal  directions. 

3°.  The  curve  of  the  arch  may  be  di- 
vided into  a  number  of  arcs,  and  the 
beams  placed  in  the  direction  of  the 
chords  of  these  arcs. 

4°.  To  these  three  we  may  add  a  fourth, 
which  embraces  by  far  the  largest  num- 
ber of  centre  frames,  and  is  based  on 
two  or  all  of  the  preceding  methods.  In 
this  class  the  beams  are  not  arranged  in 
accordance  with  any  one  system,  but 
several  ;  as,  for  instance,  the  second  and 
third,  in  which  case,  as  we  shall  see  here- 
after, several  straining  beams  span  the 
arch  at  different  points,  and  are  sustain- 
ed by  inclined  struts  ;  or  if  all  three  sys- 
tems are  used,  we  may  use  the  straining 
beam  and  inclined  struts,  and  strengthen 
them  by  bridle  pieces  in  the  direction  of 
the  radii. 

It  would,  indeed,  be  quite  a  hopeless 
task  to  attempt  to  lay  down,  in  more 
than  a  general  way,  the  principles  which 
ought  to  rule  in  making  a  selection  of 
one  of  these  methods  to  the  exclusion  of 
the  remaining  three.  In  every  case  the 
choice  must  be  determined  largely  by  the 
circumstances  of  the  case,  the  points  of 
support,  the  shape  and  span  of  the 
frame,  and  the  strength  required.  If  the 
centre  is  to  be  "  cocket,"  the  arch  heavy, 
the  span  large,  and  considerable  head- 
way required  beneath  the  frame,  the 
third  or  fourth  arrangement  will  undoubt- 
edly afford  the  best  results  whatever 
may  be  the  shape  of  the  arch.  If  the 
arch  is  light,  the  span  moderate,  and  little 
or  no  headway  is  wanted,  then  the  sec- 
ond or  first  will  generally  be  most  con- 
venient. 

Theoretically,  the  first  method  will  in 
all  cases  afford  the  greatest  amount  of 
strength  and  stability  with  the  least 
amount  of  material,  since  the  beams  are 
then  capable  of  resisting  the  most  se- 
vere strains.  Nor  can  there  be  any 
doubt  that,  within  moderate  limits,  this 
result  actually  is  attained  in  practice, 
and  that  of  two  ribs  constructed  with 
the  same  number  of  beams,  of  the  same 
quality  of  wood  and  similar  dimensions. 
in  one  of  which  the  pieces  are  plae<  A 


W£ 


VAN   NOSTRAND'S   ENGINEERING    MAGAZINE. 


radially,  and  in  the  other  vertically  or 
inclined,  the  rib  arranged  on  the  former 
plan  will  be  decidedly  the  stronger  of 
the  two.  But,  unfortunately,  the  im- 
possibility of  always  obtaining  firm 
points  of  support  at  the  centre  of  curva- 
ture, the  difficulty  of  finding  sound,  well 
seasoned  timber  of  such  length  as  would 
be  required  in  arches  of  large  span,  and 
the  relation  which  exists  between  the 
length  and  strength  of  beams  under 
longitudinal  compression — the  strength 
varying  inversely  as  the  square  of  the 
length — restricts  its  application  to  cen- 
tre frames  of  very  small  span  and  rise. 
In  semi-circular  arches  of  twelve,  fifteen 
or  even  twenty  feet  span,  when  a  hori- 
zontal beam  can  be  used  at  the  springing 
line  this  arrangement  can  be  used  with 
great  success.  The  frame  then  consists  of 
the  tie  beam  and  two,  or  if  great  strength 
is  required,  three  radial  struts  which  sup- 
port the  backpieces  and  abut  against  the 
hoi*izontal  beam  at  the  centre  of  curva- 
ture.    These  struts,  when  two  are  used, 


should  be  inclined  on  the  right  and  left 
at  a  little  less  than  45°  to  the  horizon,  so 
as  to  meet  the  backpieces  at  the  point 
where  the  voussoirs  first  begin  to  press 
on  the  rib.  A  vertical  strut  is  in  such 
an  arrangement  of  little  or  no  use,  as  no 
strain  of  any  consequence  can  possibly 
reach  it  ;  the  voussoirs  almost  ceasing  to 
press  on  the  frame  when  the  keystone 
is  driven  down.  As  these  supports  are 
struts  and  not  bridle  pieces  clamping  the 
backpieces  and  tie  beam  between  them, 
the  joints,  especially  in  the  larger  and 
heavier  arches,  must  be  secured  by  pieces 
of  iron  placed  across  them  and  bolted  to 
the  backpieces  and  struts,  to  prevent  the 
joints  opening  in  consequence  of  the 
bulging  at  the  crown  as  course  after 
course  of  stone  is  laid  on  the  frame. 

In  frames  for  flat  segmental  arches  of 
a  span  as  great  as  sixty  or  seventy  feet 
and  rise  of  about  one-fifth  the  span,  as 
also  for  ovals  of  several  centres,  this 
radial  arrangement  may  be  slightly  modi- 
fied and  a  frame  produced  (Figure  2), 


7f»  S 


Fig.  2. 


which  shall  meet  all  the  requirements  of 
strength,  lightness  and  economy.  The 
rib  in  this  case  again  consists  of  a  hori- 
zontal tie  beam  spanning  the  arch  a  little 
above  the  springing  line,  generally  at 
the  first  voussoir  that  presses  on  the 
backpieces,  and  struts  placed  in  the  di- 
rection of  the  radii  of  curvature  and 
from  eight  to  ten  feet  apart  depending 
on- the  weight  of  the  arch.  These  struts, 
as  it  would  be  impossible  to  have  them 
actually  meet  at  the  centre  of  curvature, 


which,  for  an  arch  of  seventy  feet  span 
and  fifteen  feet  rise,  would  be  about 
forty-five  feet  from  the  circumference, 
go  no  further  than  the  tie  beam  and  are 
fastened  to  it  and  the  backpieces  by  the 
iron  bands  shown  in  the  figure. 

When  great  stiffness  is  required  in  the 
rib,  additional  braces  may  be  added,  as 
shown  in  Fig.  2,  dividing  the  rib  into  a 
number  of  triangles.  The  strains  re- 
ceived will  then  be  transmitted  through 
the  axes  of  the  beams,  and  as  all  unneo- 


BRIDGE   AND   TUNNEL   CENTRES. 


393 


essary  transversal  strains  will  be  avoid- 
ed, the  resistance  offered  by  the  braces 
will  be  the  greatest  possible.  In  all 
centre  ribs,  the  normal  pressure  being 
in  the  direction  of  the  radii  of  curvature, 
the  laggings,  backpieces  and  tie  beam, 
when  used,  will  of  necessity  be  subject- 
ed to  transversal  strain. 

Before,  however,  we  proceed  to  con- 
sider the  strains  to  which  the  beams  in 
centre  frames  are  subjected,  and  the  di- 
mensions we  must  give  them  in  order 
that  they  may  withstand  the  pressure 
put  upon  them,  we  would  offer  the  fol- 
lowing practical  rule  for  estimating  the 
pressure  of  any  arch  stone  in  any  part 
of  the  arch,  upon  the  centre  rib,  or  the 
pressure  upon  the  rib  at  any  stage  of  the 
construction  of  the  arch,  as  also  the 
pressure  when  the  arch  is  completed  up 
to  the  key  stone. 

It  has  been  well  established  by  the  ex- 
periments of  Rondelet,  that  a  stone 
placed  upon  any  inclined  plane  does  not 
begin  to  slide  on  that  plane  until  it  has 
reached  an  angle  of  inclination  to  the 
horizon  equal  to  30°.  It  is  obvious, 
therefore,  that  if  the  arch  stones  were 
placed  upon  one  another  they  would  not 
begin  to  press  on  the  centre  rib  till  the 
plane  of  the  lower  joint  of  one  of  them 
reached  an  angle  of  30°  with  the  horizon. 
It  has  been  found,  moreover,  that  the 
mortar  increases  this  angle,  for  hard 
etone  to  34°  or  36°,  and  for  soft,  porous 
stone  (in  semi-circular  arches)  to  42°. 
We  may,  then,  consider  the  pressure  to 
commence  in  general  at  the  joint  which 
makes  an  angle  of  32°  with  the  horizon. 
If  we  suppose  the  radius  to  represent 
the  pressure  the  tangent  will  then  repre- 
sent the  friction,  and  making  the  radius 
unity  the  friction  will  be  0.625.  The 
next  stone  will  press  a  little  more,  the 
third  still  more,  and  the  pressure  will 
thus  continue  to  grow  larger  and  larger 
with  each  succeeding  course.  The  rela- 
tion between  the  weight  of  an  arch  stone 
and  its  pressure  upon  the  rib  in  the  di- 
rection perpendicular  to  the  curve  is 
given  by  equation  : 


Q— W  (cos  a—f  sin  a) 


(11) 


in  which  Q  is  the  pressure,  W  the  weight 
of  the  arch  stone,  f  the  friction  =  0.625, 
and  a  the  angle  the  lower  joint  makes 
with  the  vertical.  The  following  table 
calculated  from  eq.  11,  gives  the  value 


of  Q  for  every  2°   of   curve   from   the 
angle  of  repose  ==  32''  up  to  60''  : 

When  the  angle  which  the  joint  makes 

with  the  horizon  is 

34" then  Q  =  .04  W 

When  36° "  Q  =  .08  W 

"  38° "  Q  =  .12  W 

"  40° "  Q  =  .17W 

"  42° "  Q  =  .21  W 

"  44° "  Q  =  .2o  W 

"  46° "  Q=.29W 

"  48c "  Q  =  .33  W 

"  50° "  Q  =  .37  W 

"  52° "  Q  =  .40  W 

"  54° "  Q  =  .44W 

"  56" "  Q  =  .48W 

"  58° "  Q  =  .52  W 

"  60° "  Q  =  .54W 

To  take  an  example  :  What  is  the 
pressure  on  a  backpiece  of  20°  in  length 
from  the  angle  of  repose,  the  ribs  of  the 
frame  being  placed  5  ft.  from  centre  to 
centre,  and  the  arch  stones  3  ft.  in  depth 
and  weighing  160  lbs.  per  cubic  foot. 
We  take  from  the  above  table  the  sum 
of  the  decimals  from  32°  —  52°  =  2. 26,  and 
multiply  this  by  the  weight  upon  2°  and 
the  product  will  equal  the  pressure. 
The  volume  of  the  stones  which  cover 
2°  =  5X3X2°. 

The  number  of  feet  contained  in  2°  is 
found  from  the  expression  2  X. 01745329 
X/,  in  which  r'  is  equal  to  the  radius 
of  the  arch  plus  one  half  the  depth  of  the 
arch  stone.  If  we  take  the  radius  '=■  25 
ft.,  then  the  depth  of  the  stones  being  3 
ft,  r'  =  26.5  and  number  of  feet  in  2° 
equals  .88  ft.,  whence  the  volume  of  the 
stones  which  press  on  the  2°  equals 
5x3x.88  =  13.4  cubic  feet,  and  the 
quantity  W=2144  lbs.  and  Q,  or  the 
pressure  on  the  backpiece  equals  4845 
lbs. 

If  we  denote  by^  a  the  angle  included 
between  the  upper  and  lower  joints  of 
an  arch  stone,  and  suppose  every  stone 
in  the  arch  to  have  the  same  weight  and 
equal  angle  <?,  then  the  pressure  of  any 
number  n  of  such  stone  upon  the  rib  will 
be  given  from  the  expression 

.    n+1  (12) 

Q=  YY+Sin     2    aX(cos  £  »o-/sin  hia) 
sin  ^  a 


394 


van  nostrand's  engineering  magazine. 


which  gives  the  total  pressure  on  one 
half  of  the  rib. 

This  equation  is  found  as  follows  :  j 
The  pressure  perpendicular  to  the  soffit 
is  W  (sin  a— f  cos  a),  or  W  (cos  a—f 
sin  a),  according  as  the  angle  a  is  mea- 
sured from  the  horizon  or  from  the  ver- 
tical drawn  through  the  crown.  If  now 
we  denote  by  a  the  angle  included  be- 
tween the  joints  of  one  stone,  and  sup- 
pose each  stone  alike  in  size  and  weight, 
the  pressure  of  any  number  n  of  such 
stones  will  evidently  be  found  by  getting 
the  sum  of  the  sines  and  cosines  of  na, 
or  expressed  in  formula, 

P=W  (sum  of  cosines  of  na— /Xsuni 
of  sines  of  na)     .     .     .     .     Eq.  A. 

By  trigonometry  we  obtain  two  expres- 
sions for  the  sum  of  the  sines  and  cosines 
of  a  number  of  angles  in  arithmetical 
progression,  viz.  : 

Sin  A  +  sin  (A  +  B)  +  sin  (A  +  n  B) 
_Cos  (A— £B)  —  cos  {A  +  n  +  ^B) 
2  sin  i  B 
_Sin.(A  +  £ttB)XBin  \  (n  +  l)'B 


sin  \  B. 
Also 

Cos  A  +  cos  (A  +  B)+cos  (A  +  wB) 

_— cos  (A  +  £  w  B)  X  sin  \  (n  +  1)  B 


sin  \  B. 

Applying  these  two  equations  to  the 
above  case,  we  shall  have  from  eq.  A, 

P=W  Eq.  B. 

n        .?i+l        „. ..    n         .    n  + 1  . 
eos  -aXsm  — — -a— /(sin-  aXsm  a) 

sin  ^  a. 

Or  taking  out  the  common  factors  W  and 

n  +  1 
sin     2        we  shall  have  equation   B  in 

sin-^  a 
the  form. 


P= 


WXsin 


n+1 


Eq.  (12) 


sin  ■£  a 


«x( 


n  .    n  \ 

cos  -  a— few.  -at 

2       J         2    / 


The  value  of  Q  may  also  be  obtained 
from  eq.  11  by  considering  that  when 
the  depth  of  the  arch  stone  is  nearly 
double  its  thickness  ;  its  weight  rests  on 
the  rib  at  the  angle  of  60°.  Equation  12 
is,  however,  the  best,  and  may  be  readily 
solved  by  logarithms. 


For  example  :  let  the  arch  be  semi- 
circular and  a  =  2°,  then  wa= 29°  and 
/=.625.     Put  equation  12  in  the  form 

.    n  +  1 

P=W-!  cos$naXmn  ~!Ta 
sin  -£  a  X  R 

„  .     ,  .     n+\     \ 

f  sin  *  n  «X  sin  — —  a  f 

—J-  2        f 

sin  {axR 

log  cos   na  =log  cos  29°=9. 941819 

n  + 1 
log  sin  — —  a=log  sin  30°  =  9.698970 


19.639789 


log  sin  £  a  =  log  sin  1°=   8.241855 
R  =10.000000 


18.241855 

Difference  =   1.397934 

=  log  24.68 

log/    =    log  .625=  —    1.795880 

log  sin  |  na=tog  sin  29°  =  9.6855 71 

n+1 
log  sin  ---a  =  logsin30°  =  9.69897O 


19.180421 


log  sin  &  a  =  log  sin  1°=   8.241855 
R  =10 


18.241855 
Difference=  0.938669  = 
log  8.55 

Hence    the  weight   on  the  half    rib    is 
24.68  —  8.55  =  16.13  W. 

In  a  frame  constructed,  as  that  shown 
in  Fig.  2,  the  determination  of  the 
strains  is  a  matter  of  great  simplicity,, 
and  may  be  had  either  from  arithmetical- 
calculation  or  by  constructing  the  paral- 
lelogram of  forces.  The  strain  on  any 
radial  strut  as  B  G  would  be  found  by 
calculating  from  eq.  11  the  pressure  on 
D  E,  taking  half  of  it  and  supposing  it  to 
act  at  B  in  the  direction  B  G.  The  strain 
on  any  inclined  strut,  as  E  G  or  E  H,  may 
be  found  by  estimating  from  eq.  11,  the 
strain  on  B  H  taking  one  half  of  it,  and 
supposing  it  to  act  at  E  in  the  direction 
of  the  radius  at  that  point,  and  denote 
by  8  and  8'  the  angles  these  pieces  make 
with  the  direction  of  the  force.  Then, 
if  these  angles  are  unequal 


BRIDGE   AND   TUNNEL   CENTRES. 


39$ 


s=- 


P  sin  S' 


and  S'= 


P  sin  & 


(13) 


"sin  (b  +  &')  sin  (&  +  &') 

And  if  the  two  beams  make  equal  angles 
with  the  direction  of  the  force,  then  the 
strain  in  the  direction  of  each  is  the  same 
and  expressed  by 


S=, 


2  cos  & 


(14) 


Of  all  methods  of  calculating  the  strain 
on  the  different  beams,  by  far  the  sim- 
plest, is  to  actually  construct  the  dia- 
gram of  forces  to  a  given  scale  and  find 
the  pressure  by  measurement.  In  above 
case,  for  example,  draw  E  e  parallel  to 
the  direction  of  the  force  to  any  con- 
venient scale,  say  -h  inch  equal  1,000 
lbs.,  which,  supposing  the  pressure  at 
E=  10,000  lbs.  will  make  Ee=one  inch. 
From  E  draw  E  g  parallel  to  E  G ;  also 
EA  parallel  toEB,^and  e^to  EA  and 
eh  to  ~Eg.  Then  E  g  being  measured 
will  give  the  pressure  on  the  beam  E  G 
to  which  it  is  drawn  parallel. 

When  we  have  once  ascertained  the 
strain  which  any  beam  in  a  frame  will 
have  to  undergo  and  resist,  the  next  step 
is  to  determine  the  dimensions,  or  rather 
the  area  of  cross  section,  the  beam  must 
have  to  withstand  this  pressure  without 
injury.  Whatever  may  be  the  length  of 
the  beam,  this  section  may  be  obtained 
from  the  following  formulae  :  If  the 
strain  is  one  of  compression  in  the  direc- 
tion of  the  length,  then 

A=?L 
K 

in  which  A  is  the  section  required  in 
square  inches,  F  the  crushing  force  to 
which  the  beam  is  subjected,  and  K  the 
resistance  to  crushing.  When  the  strain 
is  a  transverse  or  breaking  strain,  then 

A-K, 

in  which  K'  is  the  modulus  of  rupture  of 
the  beam. 

In  place  of  K  and  K',  however,  which 
are  the  ultimate  resistance  to  crushing 

K  K' 

or  rupture,  we  must  use  —   and  — ,  in 

.   n  n 

which  n  is  the  factor  of  safety,  usually 
taken  as  10  for  wood.  The  values  of  K 
and  K'  are  variously  stated  by  different 
writers   on   the  strength   of    materials. 


Those  given  below  for  the  woods  mostly 
used  in  centre  frames  are  from  Rankinei 


Wood. 

1 
Value  of  1    Value  of  K' 
K  in  lbs  j         in  lbs. 

Ash  

9,000 
5,400 
6,200 
10,000 
6,000 

12,000 

9,900 

7,100 
10,000-13,000 
10,600 

Oak,  English 

If  it  is  not  always  possible  to  obtain 

these  values  of  K  and  K\  a  very  safe 

method,  and  one  easily  remembered,  is 

to  find  from  the  diagram  of  forces  the 

strain  on  a  beam  in  lbs.,  and  divide  this  by 

1,000;  the  result  will  be  the  cross  section 

of  the  beam  in  inches.     Thus,  if  a  tim- 

.-,-,-,•!  ■,-,       36,000 

ber  is  loaded  with  36,000  lbs.,      '        —36 

'    1,000 

in.,  and  the  beam  should  be  6  in.  X6  in, 

Example. 

Required  the  proper  dimension  of 
the  scantling  of  a  centre  rib  of  a  seg- 
mental arch  of  60  feet  span  and  9  feet 
rise  ;  the  arch  stones  to  consist  of  old 
quarry  granite,  weighing  165  pounds  per 
cubic  foot,  and  three  feet  in  depth  ;  the 
rib  to  be  of  the  pattern  shown  in  Fig.  2. 
The  frames  to  be  placed  5  ft.  from  centre 
to  centre. 

The  first  step  is  to  find  the 
weight  of  the  arch  stone  for  1°  of  the 
curve.  The  span  is  60  ft.,  the  radius  is 
50  ft.,  and  the  arch  stones  being  3  ft. 
thick  the  radius  of  the  arch  passing 
through  their  centre  is  51.5  ft.  The 
length  of  1°  is,  therefore,  .01745329X 
51.5  =.89  ft.  Then  5X3X-89  =  13-* 
cubic  ft.,  the  solid  contents  of  lc  of  the 
arch  ring,  and  this  multiplied  by  165 
gives  the  weight  of  1°  =  13.3X1 65  = 
2195  pounds.  Now  the  arch  being  a 
very  flat  segmental,  it  is  evident  that  all 
the  arch  stones  will  press  upon  the  rib. 
If  then  we  calculate  the  weight  of  the 
stones  between  E  E',  and  suppose  them 
to  act  with  one  half  their  entire  weight 
at  C  in  the  direction  CH,  it  is  evident 
that  this  will  be  the  greatest  pressure 
that  C  H  will  be  required  to  support. 
The  arc  EE'==20°,  and  the  weight  for 
1°  being  2195  lbs.,  the  pressure  at  C  is 
21950  lbs.,  and  the  beam  CH  should  be 


396 


VAN  nostrand's  engineering  magazine. 


21950 


=  21.9  inches  or4|X5  in-     To  find 


1000 

the  dimensions  of  E  G  and  E  H  take  eq. 
12.  Then  a—1",  w=20°,  /=.625,  W 
=  2195. 


Q= 


2195  +  182236 

.008727 


X  (984808  —.625  X 

173648)  =  18301  lbs. 

Take  this  and  lay  it  off  to  any  conven- 
ient scale  on  the  line  E  e,  and  from  E 
draw  E^r  parallel  to  EG,  and  EA  to 
EH  and  as  before  eg  and  eh.  Then 
measuring  E  h  by  the  same  scale  it  will 
be  found  to  equal  10250  lbs.  ;  the  beam 
EH  then  must  be  3£  in.  by  3  in.  In  the 
same  manner  the  pressure  on  B  G  is  found 
to  be  18301  lbs.,  and  the  beam  must  be 
4{  in.X4  hi.  To  find  the  strain  on  the 
inclined  strut,  estimate  from  eq.  12  the 
weight  of  the  arch  stones  between  A 
and  C,  add  to  this  half  the  weight  of 
the  rib  and  let  the  gross  weight  act  ver- 
tically at  the  point  K,  and  lay  it  off  to 
any  scale  on  the  vertical  line  K  K',  and 
draw  K'  L'  parallel  to  the  horizontal  tie 
beam.  The  line  K  L'  being  measured 
will  give  the  strain  on  the^beam  K_L'. 

Frames  arranged  on  the  second  meth- 
od, with  the  principal  pieces  all  vertical, 
afford  centres  of  great  simplicity  of 
structure  and  of  almost  as  much  strength 
as  one  with  radial  struts — supposing,  of 
course,  that  the  number  and  dimensions 
of  the  struts  are  the  same  in  each  case — 


and  of  much  greater  strength  than  one 
constructed  with  inclined  beams,  since 
the  nearer  the  angle  the  direction  of  the 
strain  makes  with  the  fibres  of  the  wood 
approaches  a  right  angle  the  less  be- 
comes the  resistance  of  the  beam.  In 
segmental  and  oval  arches  of  large  span, 
the  difference  in  the  strength  of  ribs  ar- 
ranged on  the  vertical  and  radial  plan 
is  comparatively  insignificant,  as  the 
radius  being  very  large,  the  vertical 
beams,  especially  near  the  crown  where 
the  strain  is  severe  and  most  strength 
is  required,  do  not  depart  much  from  the 
direction  of  the  radius. 

The  objection  to  this  vertical  bracing 
of  the  frame  is  that  it  requires  the  use 
of  a  horizontal  tie  beam,  unless  the  rib 
is  constructed  as  a  girder  resting  upon 
framed  abutments  of  its  own.  If  the 
former  arrangement  is  used,  the  struts 
should  be  placed  from  five  to  eight  feet 
apart,  depending  on  the  strength  requir- 
ed, and  mortised  to  the  tie  beam  and 
backpiece.  When  the  beams  are  of  such 
length  that  there  is  danger  of  their  bulg- 
iug  or  curving  under  the  load  laid  on 
them,  they  may  be  strengthened  by  di- 
agonal braces  or  horizontal  wales.  Of 
the  two,  the  diagonal  braces  are  to  be 
preferred  as  they  not  only  give  stiffness 
to  the  posts,  but  sustain  a  portion  of  the 
load  on  the  backpieces  in  case  any  of  the 
piles  under  the  horizontal  tie  beam  should 
give  way.  Figure  3  represents  the  rib 
of  a  full  centre  arch  of  75  ft.  spaa  ar- 


Fig.  3. 


BRIDGE   AND   TUNNEL   CENTRES. 


897 


ranged  with  the  principal  pieces  placed 
vertically  and  strengthened  with  a  hori- 
zontal waling  piece  made  double,  and 
braces  abutting  under  the  backpieces. 
The  strains  on  the  different  beams  com- 
posing such  a  frame,  and  their  necessary 
dimensions  may  be  computed  with  ease 
by  the  method  just  explained.  It  should, 
however,  be  remembered  that  beams 
which  are  to  be  notched  must  have  their 
dimensions  increased  beyond  those  given 
by  calculation,  in  as  much  as  notching 
will,  even  when  not  very  deep,  cut  down 
the  strength  of  a  beam  from  one  third 
to  one  half.  In  computing  the  strains 
on  the  braces  a,  a,  we  may  consider  the 
pressure  at  their  abutting  point  to  be 
the  sum  of  the  pressures  on  the  vertical 
and  two  inclined  braces  which  meet 
there,  and  make  no  allowance  for  the 
resistance  of  the  horizontal  beam. 

The  third  and  fourth  systems  of  ar- 
ranging the  principal  pieces,  afford  an 
almost  unlimited  number  of  designs  for 
centre  ribs,  which  are  especially  worthy 


of  notice,  in  that  they  are  applicable  to 
every  possible  shape  and  span  that  can 
be  given  to  stone  arches,  and  may  be 
constructed  with  or  without  intermediate 
points  of  support,  according  as  circum- 
stances will  admit.  The  principles  which 
control  such  arrangements  are  few  and 
simple.  The  beams  should  as  far  as  pos- 
sible abut  end  to  end:  they  should  inter- 
sect each  other  as  little  as  may  be  since 
every  joint  causes  some  degree  of  set- 
tlement, and  halving  destroys  fully  half 
the  strength  of  the  beams  halved. 
When  the  framing  is  composed  of  a 
number  of  beams  crossing  each  other, 
pieces  tending  towards  the  centre  should 
be  notched  upon  and  bolted  to  the  fram- 
ing in  pairs  :  ties  should  also  be  continu- 
ed across  the  frame  at  points  where 
many  timbers  meet.  Particular  atten- 
tion must,  furthermore,  be  given  to  the 
manner  of  connecting  the  beams  so  that 
there  shall  be  no  tendency  to  rise  at  the 
crown  under  the  action  of  the  varying 
load,     Figure   4   affords   an  illustration 


Fig.  4. 


of  a  very  simple  method  of  arranging 
the  timbers  for  arches  of  small  span. 
The  inclined  struts  abut  against  horizon- 
tal straining  beams  placed  at  different 
points  on  the  soffit,  and  to  add  greater 
strength  to  the  framing,  and  to  prevent 
the  horizontal  beam  from  sagging,  bridle 
pieces  are  placed  in  the  direction  of  the 
radii  of  curvature.  The  chief  difficulty 
with  such  arrangement  as  this  is,  that 
as  they  require  beams  of  great  length 
-hey  can  be  used  to  advantage  only  in 
mall  span  arches. 


The  centre  frames  for  the  Waterloo 
Bridge  over  the  Thames  were  construct- 
ed on  this  principle,  but  in  this  case  no 
horizontal  beams  were  used.  Under  the 
backpieces  were  placed  blocks  each  sup- 
ported by  two  inclined  struts  which 
made  equal  angles  with  the  radius  drawn 
through  the  centre  of  the  block.  In  a 
small  span  arch,  these  struts  would  have 
rested  on  framed  supports  placed  at  the 
opposite  abutments  of  the  arch  ;  but  in 
the  Waterloo  Bridge,  to  avoid  the  incon- 
veniences  resulting   from   crossing    the 


398 


VAN   NOSTRAND  S    ENGINEERING   MAGAZINE. 


struts,  and  of  building  beams  where  struts 
of  sufficient  length  could  not  be  obtain- 
ed from  single  beams,  the  ends  of  sev- 
eral struts  were  received  into  cast-iron 


sockets  placed  at  their  point  of  crossing 
and  suspended  by  bridle  pieces. 

Figure  5  is  a  good  design  for  a  cockefc 
centre  of    large    span.     Here  the  C  F', 


Fig 


H  F  and  D  d,  are  placed  in  the  direction 
■of  the  radii  of  curvature  and  made 
double  ;  the  remaining  braces  are  single. 
In  determining  the  proper  dimensions 
for  the  scantling  of  such  a  frame,  we 
may  take  §  of  the  total  pressure  on  the 
.arc  H  H',  and  suppose  it  to  act  at  C  in 
the  direction  C  F',  which  will  evidently 
be  the  greatest  load  this  timber  will  have 
to  sustain.  The  strain  upon  the  E  DF 
will  then  be  equal  to  £  the  load  on  BH, 
and  that  on  H  F  as  \  D  C.  That  on  the 
beams  E  F  and  F  F'  is  to  be  found  from 
the  diagram  of  forces,  Fig.  5.  Here  hf 
which  is  in  the  direction  of  H  F  produc- 
ed, represents  the  pressure  on  this  beam; 
EA  is  drawn  parallel  to  E  F,  and  ef 
parallel  to  F  F',  which  being  measured 
give  the  strain  on  E  F  and  F  F'  respec- 
tively. If  it  is  desirable  to  obtain  the 
•dimensions  of  the  beams  with  great  ac- 
curacy we  may  use  the  following  formu- 
lae :  If  we  assume  the  relation  between 
the  breadth  and  depth  to  be  .6  to  1 
(which  is  an  excellent  proportion),  then 
for  an  inclined  beam  whose  angle  of  in- 
-clination  to  the  horizon  is  (5. 

■^=i/Li/wrxcoS£x<*  .  .  (io) 

r  0.6 


And  for  a  horizontal  beam 


r      0.6 


(16) 


In  which  a  is  to  be  found  from  the  ex- 

.       40XWX*> 
pression 


-a,  in  which  b  is 


L3  W 

the  deflection  of  a  beam  whose  breadth 
is  b,  depth  is  d,  length  L,  and  load  W. 
For  pine  this  quantity  a  is  from  .0112  to 
.0105,  and  for  the  best  oak  .00934.  Eq. 
15  or  16  will  give  the  depth  in  inches. 
If  it  so  happens  that  the  value  of  a,  in 
the  above  equation,  cannot  be  obtained 
either  by  actual  experiment  or  from 
tables,  we  may  make  the  square  of  one 
side  equal  to  twice  the  square  of  the 
other,  which  will  give  a  ratio  of  7  to  5 
very  nearly,  and  use  the  equation 


d=  0.0046 


108Xy 


■io. 


cos  b 


Where  w  is  the  load,  I  the  length,  and  b 
the  angle  the  beam  makes  with  the  ver- 
tical, and  d  the  dimension  of  the  smaller 
side,  equal  $  of  the  larger.  In  centre 
frames,  however,  such  a  degree  of  exact- 
ness is  rather  unnecessary,  since,  by  al- 
lowing 1,000  lbs.  to  the  square  inch  we 


TESTING   RAILWAY   STEEL   AXLES. 


399 


can  obtain  the  cross  section  from  the 
load  with  all  the  accuracy  desirable  in 
practice. 

The  transversal  strain  on  any  one  back- 
piece  or  segment  of  the  rib  under  the 
laggings  may  be  obtained  from  the  ex- 
pression 

S=Psec0      .     .     .     (17) 

4>  being  the  angle  the  backpiece  makes 
with  the  horizon,  and  P  the  vertical  com- 
ponent of  the  pressure  on  the  same  piece 
found  by  any  of  the  methods  already 
explained,  or  from 

•     •     (18) 


(H*) 


P=W|L--A 
r 


W  being  the  pressure  on  each  lineal  foot 
of  the  segment,  L  its  length  ;  r  the 
radius  of  curvature  at  the  point  in  ques- 
tion, x  the  distance  of  the  lower  end 
of  the  backpiece  from  the  vertical 
through  the  crown  of  the  arch  and  the 
centre  of  curvature,  and  h  the  distance 
between  the  two  ends  of  the  segment 
measured  vertically. 

The  strain  upon  any  one  of  the  lag- 
gings will  depend,  independent  of  the 
^weight  of  the  arch  stones,  on  the  dis- 
tance of  the  ribs  from  centre  to  centre, 
the  place  the  lagging  occupies  in  the 
arch  and  the  manner  in  which  the  lag- 
gings are  attached  to  the  backpieces  of 
the  frame.  As  regards  the  latter  point, 
there  are  two  ways  of  making  them  fast 
to  the  rib.  They  may  be  placed  directly 
•on  the  backpiece  and  nailed  to  it,  or  they 


may  be  mounted  on  folding  wedges 
placed  between  each  bolster  or  lagging 
and  the  rib,  which  latter  arrangement 
will  be  considered  in  detail  when  we 
come  to  speak  of  the  striking  plate. 
The  bolsters,  moreover,  may  be  placed  on 
the  rib  in  such  wise  that  they  touch  each 
other,  or  may  be  separated  by  a  space 
equal  to  their  own  breadth.  The  former 
method  is  most  usually  resorted  to  in 
the  construction  of  brick  arches,  and  is 
illustrated  in  Fig.  4  ;  the  latter  is  used 
in  building  stone  arches,  and  is  illustrated 
in  Fig.  2.  By  separating  the  laggings 
in  this  wise  a  considerable  saving  of  tim- 
ber is  effected,  while  the  air  is  also  given 
freer  access  to  the  joints  of  the  arch  and 
the  mortar  much  sooner  dried.  When 
these  pieces  are  separated,  it  is  evident 
that  the  cross  section  of  each  must  be 
slightly  greater  than  when  they  are 
placed  touching  each  other,  and  that  the 
section  of  the  laggings  placed  near  the 
crown  should  be  larger  than  those  near 
the  angle  of  repose.  This  latter  point 
is  not  worth  considering  in  practice  un- 
less the  arch  stones  are  very  heavy,  for 
in  arches  of  the  ordinary  span  and  weight 
the  saving  thus  effected  in  the  timber  is 
hardly  worth  the  labor  of  calculation. 
In  determining  the  proper  dimensions  of 
the  laggings,  it  is  sometimes  customary 
to  insure  against  any  deflection,  by  sup- 
posing the  entire  load  on  each  lagging  to 
act  at  its  middle  point  and  calculate  for 
a  beam  strained  in  this  manner. 


TESTING  RAILWAY  STEEL  AXLES. 

From  "  The  Engineer." 


A  pamphlet  now  before  us,  written  in 
German,  contains  matter  of  much  inter- 
est to  British  steel  makers  executing  for- 
eign orders  for  axles.  It  is  too  well 
known  to  some  of  our  readers  that  their 
work  is  subjected  by  the  inspectors  of 
their  foreign  customers  to  very  unusual 
and  severe  tests,  resulting  in  so  much 
loss  and  interruption  that  first-class  mak- 
ers in  Sheffield  have  often  refused  such 
orders.  Now  the  results  before  us  cut 
at  the  very  root  of  the  whole  system, 
and  point  to  the  conclusion  that  the  tests 
adopted  by  foreign  railways  especially 
defeat  their  own  purpose.  The  paper, 
the  results  of  many  careful  experiments, 
.represents  a  considerable  amount  of  work 


and  time  on  the  part  of  a  countryman  of 
ours  in  Vienna,  a  son  of  the  Mr.  John 
Haswell  so  well  known  in  the  profession. 
Experiments  were  made  on  twenty-nine 
steel  carriage  axles,  of  which  two  were 
of  crucible  steel  and  the  remaining 
twenty-seven  of  Bessemer  metal.  Four 
new  iron  axles  were  also  tried,  and,  in 
addition,  two  locomotive  iron  axles. 

As  is  generally  known,  the  mode  of 
procedure  usually  adopted  by  continen- 
tal railway  engineers  is  to  take  one  out 
of  each  hundred  axles,  and  test  it  to  de- 
struction. It  is  usually  stipulated  in  the 
caJiir  des  charge*  that  the  whole  lot  may 
be  rejected  if  this  one,  or  at  most  a  sec- 
ond, do  not  stand  the  trial,  as  several 


4C0 


VAN    NOSTRAND'S   ENGINEERING   MAGAZINE. 


English  makers  have  found  to  their  cost. 
Some  of  these  tests  are  very  severe  : 
such  is  that  required  by  the  Austrian 
Northern  Railway,  according  to  which 
all  five-inch  steel  axles,  when  set  on  sup- 
ports nearly  five  feet  apart,  must  under- 
go blows  from  a  weight  of  about  7  cwt., 
falling  from  a  height  of  nearly  19  ft.,  in- 
creased by  two  feet  for  each  successive 
blow.  In  this  way  it  must  withstand  a 
bend  of  9  in.,  and  a  further  bending  back 
of  9  in. — the  operations  being  continued 
until  the  axle  has  withstood  more  than  six 
thousand  foot-pounds.  A  lighter  test  is 
that  of  the  Southern  Railway  Company, 
who  require  for  their  4|  in.  steel  axles 
that,  with  a  distance  between  the  sup- 
ports of  nearly  5  ft.,  they  shall  withstand 
a  bend  of  more  than  9f  in.,  under  a  7 
cwt.  monkey,  falling  from  a  height  of 
nearly  15  ft.  They  must  then  allow 
themselves  to  be  bent  back  straight  in 
the  same  manner  without  breaking.  In 
fact,  almost  every  other  company's  en- 
gineer has  a  different  test,  differing  as  to 
the  distance  between  the  supports,  the 
Aveight  of  the  monkey,  the  height  of  its 
fall.  The  requirements  as  to  extension, 
compression,  and  ultimate  resistance  vary 
just  as  much,  so  that  we  cannot  wonder 
if  the  very  axles  rejected  by  one  com- 
pany are  bought  and  set  to  work  by  an- 
other. In  truth,  the  process  is  merely 
that  generally  adopted  for  rails,  of  which 
a  certain  percentage  is  taken  at  haphaz- 
ard out  of  the  lot,  and  bent  or  fractured. 
This  case,  however,  is  scarcely  the  same 
as  that  of  an  axle — a  much  more  import- 
ant and  responsible  component  part  of  a 
working  line. 

The  increase  of  traffic  has  led  the  Ger- 
man lines  of  late  years  to  increase  the 
load  on  the  goods  trucks  by  nearly  25 
per  cent.,  and  they  hoped  to  find  their  ac- 
count in  replacing  iron  axles  with  others 
of  steel.  The  results  in  actual  practice 
scarcely  responded  to  these  apparently 
well-founded  expectations.  In  fact,  some 
of  their  railway  engineers  are  now 
strongly  recommending  a  return  to 
wrought  iron.  The  truth  seems  to  be 
that  the  steel  works,  in  the  face  of  such 
a  system  of  testing,  found  it  safest 
simply  to  deliver  the  softest  and  most 
ductile  steel,  able  to  withstand  the  maxi- 
mum number  of  blows  f rom  the  monkey. 
Hence  the  steel  axles  used  are  actually 
of  much   softer  material  than  those  of 


ron,  too  soft  for  their  work,  liable  to 
permanent  sets,  and  deficient  in  elastic- 
ity. An  axle  made  of  lead  would  as  re- 
gards ductility  certainly  beat  iron,  and 
withstand  more  blows  without  actual 
fracture.  The  results  in  practice  are 
little  less  than  disastrous.  It  is  stated 
that  one  of  the  greatest  lines  in  Austria,, 
possessing  extensive  steel  works  of  its 
own,  has  had,  under  this  system  of  test- 
ing, so  many  fractures  of  steel  axles  that 
they  are  being  replaced  by  axles  of 
wrought  iron.  The  practice  is  certainly 
not  that  recommended  or  adopted  by  our 
best  railway  engineers.  As  a  rule  few, 
if  any,  English  lines  test  their  axles,  and 
a  warranty  from  the  maker  is  usually 
deemed  sufficient.  A  chance  return  to 
this  procedure  afforded  its  own  lesson. 
A  year  or  two  ago,  one  of  the  largest 
German  lines  ordered,  somewhat  in  a 
hurry,  a  number  of  axles  from  an  Eng- 
lish firm.  These  axles  did  not  by  any 
means  stand  the  tests;  but,  on  the  in- 
specting engineer  telegraphing  home  for 
instructions,  he  was  told  to  receive  them,. 
They  are  now  in  use,  behaving  exceed- 
ingly well  under  heavy  traffic. 

The  conclusions  to  which  Mr.  Haswell 
arrives  are  that  the  very  severe  tests 
have  simply  resulted  in  producing  steel 
axles  much  softer  than  those  of  iron  ; 
that  the  proof  of  one  or  two  axles  out 
of  a  hundred  is  no  criterion  of  the  qual- 
ity of  steel  axles,  as  axles  from  the  very 
same  works,  forged  with  the  greatest 
care,  gave  quite  different  results. 

The  examination  of  the  question  and 
the  experiments  carried  out  by  Mr.  R. 
Haswell  were  undertaken  under  the  aus- 
pices of  a  committee  of  members  ap- 
pointed by  the  Vienna  "  Institution  of 
Civil  Engineers  and  Architects."  The 
results  were  also  very  completely  laid 
before  them  at  a  meeting  held  for  the 
purpose.  Any  action  to  be  taken  on  the 
conclusions  of  their  own  committee  was, 
however  adjourned  sine  die  by  these 
gentlemen.  Whether  they  were  afraid 
to  accept  the  responsibility,  or,  for  any 
other  reason,  they  declined  to  express 
any  decisive  opinion,  we  hope  that  this 
sufficiently  important  and  interesting 
question  will  be  takan  up  again,  and  be 
brought  sooner  or  later  to  a  definite  set- 
tlement. It  would  be  regretable  if  the 
expenditure  of  so  much  work,  time, 
and  money  should  lead  to  no  result. 


WATEK  SUPPLY   AND    DRAINAGE. 


401 


WATER  SUPPLY  AND  DRAINAGE.* 

By  W.  A.  CORFIELD,  Esq.,  M.A.,  M.D. 

IV. 

UTILIZATION    OF   SEWAGE. 


Before  describing  to  you  the  composi- 
tion of  sewage  and  the  ways  in  which 
it  has  been  proposed  to  treat  it,  I  have  a 
few  words  to  say  to  you  about  the  con- 
•  struction  of  the  apparatus  in  houses,  es- 
pecially as  to  the  construction  of  the  ap- 
paratus used  for  the  removal  of  such 
effete  matters  from  houses.  I  am  going 
to  say  a  word  or  two  on  this  subject  be- 
cause of  the  importance  of  the  points 
connected  with  it — points  that  every  one 
of  you  ought  to  know. 

In  the  first  place,  the  simplest  form  of 
closet  that  can  be  used  is  one  with  an 
earthenware  pan  and  syphon,  all  in  one 
piece,  which  of  course,  so  long  as  it  is 
not  broken,  always  retains  a  certain 
quantity  of  water  in  it.  The  advan- 
tage of  this  closet  is  that  it  can  always 
be  readily  cleansed.  In  towns  where  a 
more  complicated  form  of  apparatus  has 
been  tried  for  the  poorer  classes  and  for 
persons  who  are  not  careful,  water 
closets  have  always  failed.  One  of  the 
great  arguments  for  the  supporters  of  all 
the  dry  systems,  and  especially  of  the 
dry  earth  system,  has  been  that  the  water 
system  has  failed  because  persons  will 
not  take  reasonable  care  ;  but  that  has 
been  where  the  apparatus  has  been  too 
complicated,  as  has  often  been  the  case 
in  London.  Now  in  towns  supplied  with 
apparatus  of  that  sort  there  is  much  less 
risk  of  anything  getting  out  of  order  ; 
anything  that  finds  its  way  into  the 
syphon  can  be  easily  got  out  again,  and 
in  fact  nothing  short  of  pushing  an  iron 
rod  in,  and  making  a  hole  in  it,  is  likely 
to  do  any  harm,  and  when  a  hole  is  made 
in  it  it  is  easily  detected,  because  the 
Avater  will  not  then  remain  in  the 
syphon  ;  in  fact  nothing  is  easier  than  to 
discover  such  a  damage. 

In  the  next  place  they  are  cheap.  One 
very  important  point  about  this  system, 
especially  if  these  closets  have  to  be  in- 
side houses  or  dwellings,  is  that  there 
should  be  a  hole  in  the  syphon,  at  the 


*  Abstract  of  lectures  delivered  before  the  School  of 
Military  Engineering  at  Chatham. 

Vol.  XIII.— No.  5—26 


highest  point  of  the  pipe  above  the  water, 
and  leading  into  the  drain,  and  that  at 
this  point  there  should  be  attached  a 
ventilating  pipe.  Any  sewer  ga.-o< 
arising  will  then  be  taken  off  by  that 
pipe,  which  should  be  carried  to  a  suffi- 
cient height  and  turned  over  at  the  end. 

As  to  the  water  supply  any  simple 
apparatus  will  do  for  that  ;  the  usual 
plan  is  to  have  a  wire,  which,  when 
pulled,  lifts  a  plug  in  the  cistern,  and 
water  runs  down  a  pipe  which  generally 
ends  in  the  side  of  the  pan,  the  aperture 
being  so  directed  that  it  whirls  the  water 
round  the  pan  ;  and  the  waste  pipe  of 
the  cistern  supplying  these  may,  if  that 
cistern  is  outside  the  house,  and  is  only 
used  to  supply  the  closet,  be  made  to 
end  in  the  same  supply  pipe.  There  is 
very  little  harm  in  that,  but  it  should 
not  be  done  if  the  same  cistern  is  used 
for  supplying  drinking  water,  which 
ought  not  to  be  the  case,  although  it  so 
often  is.  A  more  complicated  form  of 
water  closet,  which  is  commonly  used, 
requires  a  word  of  notice.  In  this  sort 
you  have  what  is  called  a  D  trap,  and 
above  that  there  is  what  is  known  as  a 
container,  which  is  a  large  iron  vessel 
opening  below  into  the  water  in  the  trap. 
Water  always  remains  in  this  D  trap  up 
to  the  level  of  the  outlet.  It  is  called  a 
D  trap  from  its  shape  ;  it  is  like  a  D 
placed  thus  C3  The  pipe  which  lead? 
from  the  container  (which  is  the  iron 
vessel  immediately  under  the  pan,  and  in 
which  the  basin  moves)  dips  under  the 
surface  of  the  water  in  the  D  trap. 

Now  a  few  points  of  caution  about 
this  method  are  necessary.  This  is  the 
apparatus  which  is  accused  of  having 
brought  us  a  large  amount  of  typhoid 
fever,  diarrhcea,  and  even  cholera  in  large 
towns,  which  we  should  not  have  had 
otherwise,  and  no  doubt  to  a  certain  ex- 
tent the  system  is  to  blame  for  it.  And 
I  am  going  to  show  you  where  it  is  to 
blame  for  it,  and  what  precautions  we 
have  to  take  to  prevent  this. 

One  way  in  which  it  is  to  blame  is 


402 


VAN  NOSTRAND  S   ENGINEERING   MAGAZINE. 


that  the  descent  pipe,  called  the  soil 
pipe,  is  a  very  convenient  place  to  make 
the  waste  pipe  of  the  drinking  water 
cistern  end  in,  and  so,  very  frequently  in 
houses  this  waste  pipe  comes  down  and 
ends  there.  The  soil  pipe  goes  out  of 
the  D  trap,  and  then  joins  the  main  soil 
pipe  of  the  house,  or  becomes  itself  the 
main  or  perhaps  the  only  soil  pipe.  This 
main  soil  pipe  is  very  seldom  open  at  the 
top,  unless  it  has  been  purposely  so  con- 
structed, and  so  any  foul  air  in  the  drain 
below,  or  in  the  soil  pipe  itself  cannot 
get  away,  and  so  it  simply  goes  up  the  j 
waste  pipe  of  the  drinking  water  cistern, 
and  in  fact  the  waste  pipe  of  that  cistern 
forms  the  ventilator  of  the  soil  pipe,  and 
any  poisonous  matters  in  the  ah'  in  it 
are  absorbed  by  the  water,  and  drunk, 
and  this  is  unquestionably  one  of  the 
causes  of  the  spread  of  typhoid  fever. 
The  waste  pipe,  however,  should  not  end 
there,  but  should  end,  as  I  have  before 
told  you,  outside  in  the  open  air. 

Now  supposing  there  is  no  waste  pipe 
ending  there,  the  foul  air  which  accumu- 
lates in  the  soil  pipe  will  have  a  good 
many  of  its  ingredients  absorbed  by 
this  water  in  the  D  trap,  and  they  will 
be  given  out  at  the  surface  of  the  water 
into  the  "container."  As  soon  as  the 
apparatus  is  worked,  and  the  pan  let 
clown  so  that  the  water  runs  out  of  it, 
then  the  foul  gases,  which  have  been 
collecting  under  pressure  in  the  container, 
immediately  issue  into  the  house. 

Now  how  can  that  be  prevented  ? 
There  are  two  ways  of  preventing  it. 
In  the  first  place,  this  soil  pipe  should  be 
open  at  the  top,  and  then  you  will  never 
have  sewer  air  with  pressure  on  the  T> 
trap  That  is  quite  clear.  Or,  if  you 
do  not  carry  the  soil  pipe  itself  up  to  the 
top,  there  should  be,  say,  a  1-inch  leaden 
pipe  going  from  it  up  to  the  top  of  the 
house,  and  turned  over,  ending  at  some 
convenient  place,  not  near  the  outlet  of 
the  chimney.  So  thus  you  prevent  any 
foul  air  from  collecting  in  the  soil  pipe 
and  rendering  the  water  in  the  D  trap 
fouler  than  it  need  be  ;  but  the  D  trap 
is  always  full  of  water,  the  apparatus  is 
seldom  worked  so  long  as  to  replace  all 
that  water,  and  so  it  remains  always 
more  or  less  foul.  The  foul  matters  in 
the  D  trap  putrefy,  and  so  foul  air  col- 
lects in  the  container,  and  as  soon  as  the 
apparatus  is  worked,  this  foul  air  in  the 


container  immediately  rushes  out,  be- 
cause it  has  been  collecting  in  considerable 
quantities,  a  thing  which  you  must  all 
have  observed  over  and  over  again. 
That  can  be  prevented  perfectly  well,  so 
well  indeed,  as  to  render  closets  manage- 
able even  in  the  most  inconvenient  situa- 
tions in  which  they  can  be  placed,  and 
in  such  situations  they  frequently  are 
placed  in  many  of  the  large  houses  in 
London  ;  underneath  staircases,  and 
close  to  drawing  rooms,  or  even  opening 
directly  out  of  bed-rooms,  and  in  such 
places.  Although  they  should,  if  possi- 
ble, be  removed  from  such  situations, 
they  can  be  made  perfectly  sweet  in  a 
very  simple  way,  and  that  is  done  by 
making  a  hole  in  the  container,  attaching 
a  small  ventilating  pipe  to  it,  which  pipe 
is  taken  through  the  wall  of  the  house 
and  made  to  end  in  some  convenient  sit- 
uation, and  then  you  never  get  any  foul 
air  accumulating  under  pressure,  to  rush 
out  when  the  pan  is  moved  and  the 
water  in  it  let  fall  into  the  container. 

The  valve  closet  is  a  great  improve- 
ment upon  this,  inasmuch  as  the  con- 
tainer is  merely  a  small  box  in  which  the 
valve  works,  whereas  the  volume  of 
water  used  is  much  greater. 

Those  are  the  chief  points  about  this 
rather  complicated  apparatus,  which  is 
evidently  not  fit  for  the  use  of  careless 
persons.  Now  for  the  kind  of  apparatus 
fit  to  be  employed  when  large  numbers 
of  persons  use  the  same  place.  There 
has  been  an  apparatus  contrived  called 
"The  Trough  Water  Closet."  I  spoke 
to  you  before  about  "  Trough  Latrines." 
They  are  not  water  closets  ;  they  are 
constructed  in  very  much  the  same  way, 
but  in  the  "  Trough  Latrines,"  the  ex- 
creta are  collected  for  the  day,  and  then 
are  emptied  into  a  cart  and  taken  away. 
That  is  a  modification  of  the  "Pail  Sys- 
tem." 

The  "  trough  water  closet"  may  be 
briefly  described  thus.  Underneath  the 
row  of  seats  there  is  a  trough  made  of 
iron  or  slate,  or  any  convenient  material 
of  the  sort.  This  trough  at  its  lower 
end  has  a  connection  with  a  sewer,  the 
mouth  of  which  is  fitted  with  a  plug  ; 
which  plug  can  be  moved  up  and  down 
by  a  lifting  apparatus  in  a  separate  com- 
partment, which  can  only  be  got  at  by 
the  person  who  has  charge  of  the  place  ; 
because,  of  course,  among  large  bodies 


WATER   SUPPLY   AND   DRAINAGE. 


403 


of  men,  there  must  always  be  a  man  ap- 
pointed to  have  charge  of  this,  just  as 
in  the  case  of  the  earth  closets.  This 
compartment  can  only  be  got  at  by  this 
particular  man,  and  he  has  access  in  or- 
der that  he  may  lift  up  or  let  down  the 
plug. 

At  the  other  end  you  have  a  water  tap 
supplied  from  a  cistern  ;  the  man  who 
has  charge  of  the  place  comes  at  night, 
lifts  up  the  plug,  lets  the  contents  all 
run  away  into  the  drain,  then  washes 
out  the  trough,  lets  down  the  plug, 
charges  the  trough  with  a  little  water, 
and  leaves  it  till  the  next  day.  That  is 
the  "  Trough  Water  Closet,"  and  that  is 
the  most  convenient  form  of  closet  for 
use  by  large  bodies  of  persons,  especially 
of  careless  persons. 

As  an  instance  of  the  success  of  these 
closets,  I  may  mention  the  town  of 
Liverpool.  Dr.  Buchanan  and  Mr.  Rad- 
cliffe,  say — "  Nothing  could  be  more  ad- 
mirable than  the  working  of  the  Liver- 
pool arrangement,  and  nothing  could  be 
more  marked  than  the  difference  between 
them  and  what  are  called  water  closets, 
in  the  poor  neighborhoods  of  London 
and  other  large  towns."  Dr.  Hewlett 
also  gives  a  favorable  opinion  with  re- 
gard to  these  closets.  He  says — "  The 
trough  water  closets  in  use  at  Liverpool, 
and  the  self -flushing  tumbler  water  clos- 
ets at  Leeds,  where  they  answer  remark- 
ably well,  appear  to  me  to  be  the  best 
kind  for  use  in  poorer  districts,  especially 
for  closets  which  are  frequented  by  more 
than  one  family."  These  opinons  are 
sufficient. 

The  tumbler  water  closet  is  very 
nearly  on  the  same  principle.  There  is 
a  very  nearly  level  trough  with  a  con- 
nection with  the  drain  at  the  lower  end  ; 
at  the  other  end  there  is  a  sort  of  swing 
bucket  which  is  placed  below  a  tap. 
The  water  is  running  from  this  tap  con- 
tinually, but  slowly,  and  the  rate  at 
which  it  shall  run  is  subject  to  arrange- 
ment. As  soon  as  the  bucket  contains  a 
certain  amount  of  water,  it  tips  over, 
empties  its  contents  into  the  trough, 
washing  away  whatever  is  in  the  trough 
down  into  the  drain.  This  plan  is  also 
reported  to  be  an  excellent  one.  Of 
course  the  water  supply  and  the  buckets 
are  placed  in  a  separate  compartment, 
and  can  only  be  got  at  by  one  person.  ■ 

We  pass  on,  now,  to  consider  the  com- 


position of  sewage.  This  has  been  well 
stated  in  the  first  report  of  the  Rivers' 
Pollution  Commissioners,  in  the  follow- 
ing words  "  Sewage  is  a  very  complex 
liquid  ;  a  large  proportion  of  its  most 
offensive  matters,  is,  of  course,  human 
excrement,  discharged  from  water  closete 
and  privies,  and  also  urine  thrown  down 
gulley  holes.  Mixed  with  this,  there  Lfi 
the  water  from  kitchens,  containing  veg- 
etable, animal,  and  other  refuse,  and  that 
from  wash-houses,  containing  soap,  and 
the  animal  matters  from  soiled  linen. 
There  is  also  the  drainage  from  stables 
and  cowhouses,  and  that  from  slaughter 
houses,  containing  animal  and  vegetable 
offal.  In  cases  where  privies  and  cess- 
pools are  used  instead  of  water  closets, 
or  these  are  not  connected  with  the 
sewers,  there  is  still  a  large  proportion 
of  human  refuse,  in  the  form  of  chamber 
slops  and  urine.  In  fact  sewage  cannot 
be  looked  upon  as  composed  solely  of 
human  excrement  diluted  with  water, 
but  as  water  polluted  with  a  vast  variety 
of  matters,  some  held  •  in  suspension, 
some  in  solution." 

Now  there  are  great  variations  in  the 
composition  of  sewage  at  different  times 
of  the  year,  and  also  at  different  times  of 
the  day  and  night.  But  there  is  not  a 
great  amount  of  difference  between  the 
composition  of  the  sewage  of  towns 
where  there  are  water-closets,  and  the 
composition  of  the  sewage  where  there 
are  not.  In  the  first  report  of  the  Riv- 
ers' Pollution  Commissioners,  it  is  shown 
that  there  is  "  a  remarkable  similarity  of 
composition  between  the  sewage  of  mid- 
den towns  and  that  of  water  closet 
towns.  The  proportion  of  putrescible 
organic  matter  in  solution  in  the  former, 
is  but  slightly  less  than  in  the  latter, 
whilst  the  organic  matter  in  suspension 
is  somewhat  greater  in  midden  than  in 
water  closet  sewage." 

I  must  now  give  you  an  account  of 
what  the  average  sewage  may  be  taken 
to  be.  You  may  take  it  that  an  average 
sewage  has  this  composition  ;  in  100,000 
parts  of  it  there  are  about  72  of  total 
solid  matters  in  solution,  which  total 
solid  matters  include  between  four  and 
five  of  organic  carbon,  something  over 
two  of  organic  nitrogen,  from  six  to 
seven  of  ammonia,  and  from  ten  to 
eleven  of  chlorine.  Besides  these  72 
parts  of  dissolved   matters,  it    contains 


404 


TAN   NOSTRAND'S   ENGINEERING  MAGAZINE. 


44  or  45  parts  of  suspended  matters,  of 
which  about  24  are  mineral,  and  20  or  21 
organic.  Now  that  is  the  average. 
There  are  extremes.  The  variation  of 
the  London  sewage  in  total  combined 
nitrogen,  is  from  three  parts  to  eleven  in 
100,000,  so  that  you  see  there  are  very- 
considerable  differences.  And  this  is 
partly  due  to  the  fact,  which  is  plain 
enough,  that  there  is  a  greater  amount 
of  refuse  thrown  into  the  sewers  at  one 
time  than  at  another,  but  still  more  to 
the  great  variations  in  the  amount  of 
water.  As  an  instance  of  variation 
with  the  time  of  the  year,  I  may  tell 
you  that  during  the  winter  before  last, 
the  average  amount  of  ammonia  in  100,- 
000  parts  of  the  sewage  of  Romford, 
was  from  five  to  six  parts,  whereas  in 
the  previous  summer,  the  average  was 
only  two  and  a  half  to  four.  So  that 
the  value  varies  considerably  at  different 
times  of  the  year.  It  varies  because  a  con- 
siderable amount  of  rainfall  is  allowed  to 
get  into  the  sewers.  It  would  vary  little 
in  towns  where  very  little  rainfall  is  allow- 
ed to  get  into  the  sewers,  and  where  the 
water  supply  is  pretty  constant  through- 
out the  year.  The  variation  in  composi- 
tion during  the  day  and  night  is  very 
important,  and  during  the  night,  in  many 
towns,  the  sewage  is  very  little  more 
than  water. 

Now  as  to  the  value — you  may  calcu- 
late the  value  of  sewage  in  two  ways. 
Thus  you  may  calculate  it  approximate- 
ly, from  the  number  of  persons  who  con- 
tribute to  make  it,  and  from  the  value 
that  we  have  assigned  to  the  refuse  mat- 
ters coming  from  each  person  during 
the  year.  We  have  assigned  8s.  4d.  a 
year  for  these  matters,  but  we  will  take 
the  lowest  value  ever  assigned  to  them, 
which  is,  that  the  annual  excreta  of  a 
human  being,  taking  an  average  of  all 
ages,  are  worth  6s.  8d.  a  head.  That 
value  was  assigned  by  Messrs.  Lawes 
and  Gilbert,  and  they  have  never  been 
valued  at  less.  So  that,  taking  no  other 
refuse  at  all,  if  you  can  get  at  the  ex- 
cretal  refuse  matters  of  a  population  of 
three  millions,  it  ought  to  be  worth 
£1,000,000  per  annum,  as  far  as  that  cal- 
culation goes. 

But  you  may  calculate  the  value, 
again,  from  the  composition  of  sewage 
itself.  And  if  you  do  that,  you  will  find 
that  the  money  value  of  the  substances 


dissolved,  say  in  100  tons  of  average 
sewage,  is  about  15s.,  while  the  money 
value  of  the  suspended  matters  is  only 
about  2s.  The  value,  then,  of  these 
constituents,  is  aboxit  15s.  for  the  dis- 
solved matters,  and  2s.  for  the  suspend- 
ed matters  ;  that  is  to  say,  that  100  tons 
of  average  sewage  are  worth  17s.,  or 
about  two  pence  a  ton. 

If  you  consider  that  you  do  not  always 
get  average  sewage,  or  sewage  of  an 
average  composition,  and  that  very  often 
the  sewage  is  extremely  diluted  so  that, 
instead  of  there  being  something  like 
the  dry  weather  average  of  sixty  tons 
per  head  per  annum,  you  often  get  100, 
or  even  more,  it  is  plain  that  we  must 
not  take  so  high  a  value  as  that  I  have 
just  stated  for  it,  and  so  it  is  usual  to 
take  a  value  of  one  penny  per  ton,  in- 
stead of  two  pence.  If  then  you  take 
this  sewage  at  a  penny  per  ton,  as  con- 
taining on  an  average  about  four  grains 
of  ammonia  in  a  gallon,  as  it  does,  or 
between  five  and  six  in  100,000  parts,  as 
I  said  before,  then  you  may  consider 
that  sewage  is  worth  one  farthing  per 
ton  for  every  grain  of  ammonia  per  gal- 
lon it  contains. 

And  again,  if  you  take  the  total 
amount  of  sewage  of  three  millions  of 
persons  at  an  average  dilution  of  about 
80  tons  per  head  per  annum,  and  put  it 
at  the  value  of  Id.  per  ton,  you  will  find 
it  comes  to  almost  exactly  the  same  as 
the  calculation  made  the  other  way,  viz., 
something  over  £1,000,000. 

Now  what  are  we  to  do  with  this  sew- 
age which  has  the  value  which  I  have 
just  assigned  to  it,  that  is  to  say,  which 
has  that  value  if  you  can  get  the  nianu- 
rial  properties  out  of  it  ?  The  general 
plan  at  present  is  to  turn  it  into  the  riv- 
ers. This  plan  has  arisen  because  the 
sewers  we  use  were  originally  built  for 
drains,  and  meant  for  drains,  and  there- 
fore naturally  discharged  into  the  rivers, 
and  it  is  no  doubt  from  this  circumstance 
that  we  have  so  many  attempts  to  keep  a 
certain  proportion  of  the  manurial  refuse 
out  of  the  sewers  by  means  of  midden 
closets,  and  pail  closets,  and  earth  clos- 
ets and  so  on,  and  also  with  a  view  to 
the  prevention  of  the  fouling  of  the 
rivers.  Well  there  are  two  kinds  of  evils 
that  arise  from  the  fouling  of  rivers,  two^ 
especially,  but  there  are  plenty  of  others 
in  addition.     The  first  is  that  these  riv- 


WATER   SUPPLY   AND   DRAINAGE. 


405 


ers,  even  when  they  are  large  ones,  get 
to  a  certain  extent  blocked  up  by  the 
sediment  that  is  deposited  from  the  sew- 
ers ;  this  is  the  case  even  with  the 
Thames.  In  the  year  1867  it  was  point- 
ed out  that  there  was  going  on  a  forma- 
tion of  extensive  shoals  in  the  River 
Thames  outside  the  main  drainage  out- 
falls near  to  Barking  Creek  and  Cross- 
ness. These  deposits  were  very  exten- 
sive. 

Near  the  southern  outfalls  for  in- 
stance a  depth  of  fully  seven  feet  of 
deposit  was  found,  and  in  fact  it  was 
going  on  to  such  an  extent  that  it 
threatened  to  interfere  seriously  with 
the  navigation.  Plans  can  be  seen 
which  show  that  a  narrowing  of  the 
bed  of  the  stream  had  been  going  on 
even  since  this  was  pointed  out  in  1867. 
Besides  that,  it  was  also  shown  that  the 
tide  did  not  carry  away  the  matters  sus- 
pended in  sewage.  Experiments  were 
made  by  Mr.  Frank  Foster  first,  and 
afterwards  repeated  by  Mr.  Bazalgette 
and  Captain  Burstal — which  show  that 
suspended  matters,  floating  bodies,  were 
carried  down  by  the  tide  to  a  certain 
point,  and  then  carried  up  again  farther 
than  the  point  at  which  they  were  orig- 
inally thrown  into  the  stream,  and  it  is  a 
fact  that  a  certain  amount  of  sewage  de- 
posit takes  place  above  the  outfalls  into 
the  River  Thames.  Now  in  small 
streams  as  well  as  in  navigable  rivers 
this  is  of  course  a  very  serious  matter. 
That  is  the  first  thing.  Then  perhaps  a 
less  important  matter,  but  still  one  of 
some  importance,  is  that  fish  are  killed 
in  rivers  into  which  sewage  is  turned. 
They  are  not  killed  by  fresh  sewage,  but 
they  are  killed  by  the  gases  which  are 
given  off  by  the  decomposing  deposit  at 
the  bottom  of  the  river,  by  sulphuretted 
hydrogen  especially. 

Then  the  next  danger  is  the  pollution 
oi  the  drinking  water  of  towns  lower 
down  on  the  rivers,  and  this  has  gone  on 
to  a  very  considerable  extent,  to  such  an 
extent  that  at  last  Londoners  have  found 
out  what  they  are  drinking,  and  all  the 
towns  on  the  River  Thames  have  got  in- 
junctions to  prevent  them  turning  their 
sewage  into  the  river.  This  comes  to  a 
climax  when  you  have  a  case  where  a 
town  actually  turns  its  own  sewage  into 
-a,  river  at  a  particular  place,  and  a  mile 
further  down  takes  out  its  water  supply. 


That  occurs  in  a  town  in  England  at  the 
present  moment. 

If  the  towns  are  not  to  turn  their  sew- 
age into  a  river,  what  can  they  do  ?  You 
see  the  sewage  contains  suspended  mat- 
ters and  dissolved  matters,  and  both 
among  the  suspended  matters  and  dis- 
solved matters  are  substances  that  are 
injurious  to  health  if  drunk  with  water. 
You  see  also  that  the  dissolved  matters 
are  considerably  more  valuable  than  the 
suspended  matters,  in  the  proportion  of 
15  to  2.  But  this  was  not  always  known, 
and  so  the  first  attempts  at  purifying 
the  sewage  consisted  of  simply  straining 
it.  The  sewage  was  strained  and  the 
suspended  matters  were  thus  separated 
and  were  then  sold  as  manure,  or  mixed 
with  town  ashes  and  sold  for  manure, 
and  the  somewhat  clarified  sewage  was 
then  allowed  to  escape  into  the  stream. 
That  is  the  practice  carried  on  in  a  great 
many  towns  at  the  present  time.  The 
suspended  mattei's  are  worth  compara- 
tively little,  and  you  lose  the  best  por- 
tion of  the  manurial  matters.  In  the 
second  place  the  purification  of  the 
stream  is  only  partially  effected,  because 
the  clarified  sewage  that  runs  into  the 
stream  putrifies  after  it  gets  there,  and 
you  get  the  stream  fouled  to  a  very  con- 
siderable extent,  "  so  that  that  plan  is 
evidently  not  sufficient. 

Then  come  different  chemical  processes. 
The  purification  was  attempted  by  vari- 
ous chemical  processes,  and  it  is  still  at- 
tempted to  precipitate  the  valuable  in- 
gredients dissolved  in  the  sewage  as  well 
as  the  suspended  matters.  Now  there 
are  plenty  of  ways  in  which  you  can 
clarify  foul  water,  but  you  see  at  once 
that  it  is  not  so  easy  to  precipitate  those 
particular  matters  that  are  in  solution  in 
sewage,  because  you  see  in  the  first  place 
that  the  most  important  constituent,  or 
at  any  rate  one  of  the  most  important 
constituents,  the  most  important  from 
its  quantity  at  any  rate,  is  the  ammonia. 
You  know  perfectly  well  that  you  can- 
not precipitate  salts  of  ammonia  on  a 
large  scale  at  all  from  a  dilute  solution, 
and  you  will  see,  therefore,  at  once,  that 
all  attempts  to  precipitate  the  valuable 
matter  of  sewage  are  likely  to  fail,  even 
from  that  cause  alone.  Then  in  the  next 
place  you  have  organic  matter  in  solu- 
tion. Now  we  do  not  know  of  any  sub- 
stance at  present  which  can  be  iised  on 


406 


VAN   NOSTRAND'S   ENGINEER  TNG   MAGAZINE. 


a  large  scale  at  any  rate,  that  can  be  re- 
lied upon  to  precipitate  organic  matters 
in  solution,  especially  organic  matters  in 
the  state  in  which  they  are  in  sewage, 
viz.  :  in  a  state  of  very  rapid  decom- 
position, and  these  are  the  substances 
matter  which  are  most  dangerous,  and 
which  have  to  be  separated,  so  that  you 
will  be  prepared  to  find  that  most  of  the 
precipitation  processes  have  failed.  You 
will  find  a  long  description,  and  an  ex- 
cellent one,  of  most  of  these  processes  in 
the  Second  Report  of  the  Sewage  Com- 
missioners, published  in  1861,  giving  the 
results  of  many  analyses.  Several  of 
these  processes  are  capable  of  precipi- 
tating at  any  rate  one  important  in- 
gredient in  sewage,  and  that  is  the  phos- 
phoric acid,  an  important  ingredient 
which  can  be  precipitated  in  several 
ways,  and  they  also — some  of  them — 
precipitate  some  of  the  organic  matters. 

Now  these  are  some  of  the  more  im- 
portant precipitation  processes  brought 
before  the  public.  In  the  first  place 
there  is  the  lime  process  which  was  prac- 
tised at  Tottenham  and  Leicester,  and 
some  other  places,  and  which  merely 
consisted  in  adding  a  certain  proportion 
of  milk  of  lime  to  the  sewage.  The  re- 
sult of  this  process  was  that  no  element 
of  agricultural  value  that  was  in  solu- 
tion was  precipitated  by  it  except  the 
phosphoric  acid.  The  suspended  matters 
were  very  fairly  well  removed  from  the 
sewage  (that  you  can  do  perfectly  well 
by  straining),  and  sometimes  the  amount 
of  organic  matter  in  solution  was  in- 
creased, because  some  of  the  organic 
matter  originally  in  suspension  passed 
into  a  state  of  solution,  which  it  always 
will  do  by  mere  agitation,  and  also  the 
amount  of  ammonia  contained  in  the 
sewage  was  increased,  so  that  by  that 
process,  as  well  as  by  some  others,  the 
water  discharged  into  the  river  some- 
times contained  actually  more  impure"  in- 
gredients than  the  sewage  contained  in 
solution,  some  of  the  organic  matters  in 
suspension  having  passed  into  a  state  of 
solution.  A  fault  of  the  lime  process  is 
that  the  precipitated  matter  remaining 
is  alkaline,  so  that  much  of  the  ammonia 
it  contains  is  given  off,  and  the  next 
thing  is  that  it  is  nearly  worthless. 

The  Rivers'  Commissioners  pronounce 
it  "  a  conspicuous  failure,  whether  as  re- 
gards the  manufacture  of  valuable  man- 


ure or  the  purification  of  the  offensive 
liquid."  The  next  that  I  have  to  men- 
tion is  a  variety  of  the  lime  process,  in 
which  lime  and  per-salts  of  iron  were 
mixed  and  used.  This  is  a  much  better 
plan,  because  the  per-salts  of  iron  will 
fix  the  sulphuretted  hydrogen  and  all 
the  phosphoric  acid.  The  fault  of  this 
jdan  is,  that  it  does  not  precipitate  any- 
thing else  that  the  lime  process  did  not,, 
and  its  virtue  is  this,  that  it  deodorizes 
the  liquid  and  the  precipitate.  Salts  of 
iron  have  been  used  alone,  and  they  da 
without  doubt  deodorize  the  water,  and 
precipitate  the  phosphates  and  the  sus- 
pended matters,  but  they  only  delay  the 
decomposition  of  it,  and  again  they  are 
too  expensive. 

Then  several  processes  in  which  clay 
was  a  precipitating  ingredient  may  be 
mentioned.  In  the  first  place,  Holden's, 
in  which  sulphate  of  iron,  lime,  and  coal 
dust,  with  some  clay  are  used,  and  An- 
derson's, which  is  very  much  the  same  as 
Bird's,  which  consists  in  the  addition  to 
the  sewage  of  crude  sulphate  of  alumina. 
Stothert's  consists  of  the  addition  of  sul- 
phate of  alumina  with  sulphate  of  zinc 
and  charcoal. 

And,  lastly,  the  celebrated  A.  B.  C.  pro- 
cess. The  A.  B.  C.  process  was  so  called 
from  the  chief  ingredients  that  were 
used,  with  the  object  of  precipitating 
the  sewage,  namely,  alum,  blood  and 
charcoal.  You  have  all  probably  heard 
sufficiently  about  the  A.  B.  C.  process 
lately.  You  know  the  Company  has  at- 
tempted to  purify  some  of  the  sewage 
of  London,  at  Crossness,  and  no  doubt 
you  have  heard  that  a  combined  report 
has  been  issued  by  the  Engineer  and  the 
Chemist  of  the  Metropolitan  Board  of 
Works,  which  report  shows  perfectly 
well  that  although  the  sewage  was  at  any 
rate  clarified,  and  although  there  was  a 
certain  amount  of  purification  effected 
(we  can't  say  exactly  what  amount,  as  in 
this  report  we  have  not  the  analysis  of 
the  original  sewage) ;  although  that  was 
the  case,  the  manure  produced  was  not 
worth  more  than  twenty  shillings  a  ton, 
while  the  cost  of  producing  it  was  £6  6s. 
4d.  !  Then  there  is  a  process  known  as 
Hide's  process,  which  is  chiefly  a  de- 
odorizing process.  A  mixture  of  lime 
and  tar,  and  chloride  of  magnesium  is 
used  ;  the  precipitate  is  of  very  little 
value.     Carbolates  and  sulphites  of  liine, 


WATER   SUPPLY   AND   DPvAIN"AGE. 


407 


and  magnesia,  have  also  been  proposed 
as  precipitants  which  would  also  deodor- 
ize the  sewage.  At  Carlisle,  carbolic 
acid  is  used  to  deodorize  the  sewage. 

There  are  two  or  three  processes  in 
which  phosphates  have  been  used.  The 
idea  of  using  phosphates  to  precipitate 
sewage  was  this, — that  the  precipitate 
produced  by  other  substances,  like  lime 
and  clay,  which  are  useless  as  manures, 
will  not  sell,  because  it  will  not  bear  the 
cost  of  carriage  ;  but  if  you  add  a  sub- 
stance which  is  itself  a  manure,  and  pre- 
cipitate the  suspended  matters  with  it, 
then  they  would  sell,  and  then  you  would 
get  a  manure  that  is  worth  carrying. 

Now,  the  first  phosphate  process  has 
been  proposed  over  and  over  again.  In 
England  it  goes  by  the  name  of  Blyth's 
process,  and  the  principle  of  it  was  this; 
— there  is  a  salt  of  phosphoric  acid  (to 
wit,  the  phosphate  of  magnesium,  am- 
monium and  hydrogen,  a  triple  phos- 
phate), which  salt  is  insoluble  in  water 
containing  salts  of  ammonia,  and  it  was 
thought  that  by  adding  a  salt  of  mag- 
nesia and  super-phosphate  of  lime,  or 
super-phosphate  of  magnesia  and  lime 
water,  to  sewage,  that  a  precipitate  of 
this  triple  phosphate  would  take  place. 
The  result  was  that  it  was  found  to  be 
the  most  expensive  process  ever  adopted, 
and  that  a  great  proportion  of  the  phos- 
phate added  went  away  in  the  effluent 
water.  The  salt  in  question  is  not  at  all 
insoluble  in  pure  water.  It  is  only  in- 
soluble in  water  containing  an  excess  of 
ammonia  ;  so  that  the  condition  for  the 
success  of  this  experiment  was  that  the 
water  turned  into  the  river  was  rich  in 
ammonia  —  an  obvious  condition  for 
failure  of  the  experiment— and  the  re- 
sult was  the  loss  of  a  great  amount  of 
the  substances  added.  That  process  has 
failed  over  and  over  again. 

Then  we  have  a  phosphate  process 
patented  by  Messrs.  Forbes  and  Price. 
In  this  process  an  insoluble  phosphate  of 
alumina  in  large  quantities  is  used,  and 
it  is  rendered  soluble  by  being  mixed 
with  strong  hydro-chloric  acid.  This  is 
mixed  with  sewage,  lime  water  then  is 
added,  and  the  result  is  that  the  sus- 
pended matters  are  carried  down  very 
completely,  and  the  sewage  is  left  very 
clear.  All  offensiveness  is  entirely  taken 
away  ;  the  effluent  water  passes  off  con- 
taining all  the  ammonia  that  the  sewage 


contained  before,  and  at  any  rate  the 
greater  portion  of  the  organic  matter  in 
solution.  This  process,  therefore,  could 
only  be  used  as  a  preliminary  process  to 
some  other  treatment.  I  will  not  say 
any  more  about  that. 

Then  recently  another  phosphate  pro- 
cess has  come  forward,  called  Whit- 
thread's.  That  process  has  been  report- 
ed on  by  the  Committee  of  the  British 
Association  appointed  for  the  considera- 
tion of  the  treatment  and  utilization  of 
sewage,  and  that  process  is  the  only  pre- 
cipitating process  with  respect  to  which 
it  has  ever  been  said  that  it  does  precipi- 
tate most  of  the  organic  matter  that  is 
in  solution.  It  precipitates  all  the  sus- 
pended matters,  and  so  far  as  the  pre- 
liminary experiments,  which  were  carried 
on  under  the  supervision  of  the  Commit- 
tee of  the  British  Association, — as  far 
as  those  preliminary  experiments  go,  this 
process  depends  upon  the  use  of  a  sub- 
stance known  as  di-calcic  phosphate,  a 
particular  form  of  phosphate  of  lime, 
which  seems  to  have  the  property  of 
carrying  down  organic  matters  in  solu- 
tion. The  deodorization  is  also  com- 
plete. It  does  not  in  any  way  remove 
the  ammonia  in  solution,  and  it  remains 
to  be  seen  whether  that  process,  or  in- 
deed any  other  process,  is  capable  on 
the  large  scale  of  so  removing  the  organ- 
ic matters  in  solution  that  the  liquid  may 
at  any  rate  be  harmless  after  it  is  thrown 
away. 

Lastly,  I  have  to  mention  to  you  Gen- 
eral Scott's  process.  General  Scott's 
process  consists  in  mixing  the  sewage 
with  a  certain  amount  of  lime  and  of 
clay.  It  has  been  reported  on  by  the 
Rivers'  Pollution  Commissioners  and  by 
the  British  Association  Sewage  Commit- 
tee. About  10  cwt.  of  lime  and  8  ewt. 
of  clay  are  added  to  400,000  gallons  of 
sewage.  This  mixture  of  lime  and  clay 
is  added  in  considerably  greater  propor- 
tions than  the  precipitants  are  added 
under  the  other  processes.  "With  the 
others  you  add  as  little  as  possible. 
With  General  Scott's  process  you  add  a 
great  deal.  Well,  this  mixture  is  added 
to  the  sewage  in  the  sewers  before  it 
gets  to  the  tanks,  and  the  result  is  that 
the  sewage  is  entirely  deodorized,  and  as 
soon  as  it  arrives  at  the  precipitating 
tanks  and  is  allowed  to  settle,  the  whole 
of  the  suspended  matters,  including  the 


408 


VAN"   NOSTRAND'S   ENGINEERING   MAGAZINE. 


lime  and  clay  "which  have  been  added, 
are  deposited  at  the  bottom  of  the  tanks. 
This  deposit  is  run  out  in  a  semi-liquid 
condition  as  soon  as  there  is  enough  of 
it.  It  is  then  dried,  or  it  may  be  com- 
pressed by  "what  is  known  as  Needham 
and  Kite's  Press.  Needham  and  Kite's 
Press  is  a  press  which  has  a  number  of 
canvas  bags  in  it,  into  "which  bags  this 
mud  is  run.  They  are  then  pressed  to- 
gether by  a  hydraulic  press.  A  certain 
portion  of  water  is  thus  squeezed  out  of 
the  mud,  leaving  it  in  a  comparatively 
dry  state.  It  is  then  taken  up  in  lumps, 
dried  by  heat  if  necessary,  and  placed  in 
a  kiln.  A  fire  is  lighted  below  it  with  a 
small  quantity  of  coal,  and  it  burns. 

"  The  area  is  laid  out  in  square  beds 
intersected  with  roads  and  paths,  along 
which  are  constructed  the  main  carriers 
which  receive  the  sewage  from  the  out  • 
fall  sewer  and  distribute  it  over  the 
beds."  As  soon  as  it  is  once  set  alight 
there  is  no  necessity  to  put  any  more 
coals  in  the  kiln.  The  sewage  deposit 
with  the  clay  and  lime  is  supplied  from 
the  top  of  the  kiln,  and  it  is  gradually 
taken  out  as  it  is  burnt,  through  an  open- 
ing in  the  bottom,  and  no  more  coal  is 
required.  There  is  sufficient  organic 
matter  in  the  deposit  for  it  to  go  on 
burning,  when  once  well  lighted,  for  any 
length  of  time.  The  result  is  the  pro- 
duction of  a  cement,  and  an  excellent 
cement.  This  cement  can  be  made  of 
different  qualities,  and  it  certainly  an- 
swers perfectly  well  as  a  cement,  and 
the  process  causes  no  offence. 

The  result  on  the  sewage  is  that  it  is 
clarified,  and  the  phosphoric  acid  con- 
tained in  solution  is  precipitated,  so  that 
this  cement  contains  phosphoric  acid. 
The  ammoniacal  salts  are  left  in  solu- 
tion, and  the  organic  matters  in  solution 
are  not  touched  by  the  process,  or  rather 
they  may  occasionally  be  increased  from 
some  of  those  matters  in  suspension 
passing  into  a  state  of  solution.  The 
cement  prepared  can  be  used  as  ordinary 
cement  ;  or  it  has  been  suggested  by 
General  Scott  that  in  places  where  lime 
is  already  used  as  a  manure,  it  would  be 
considerably  better  to  use  this  sewage 
lime,  after  it  has  been  calcined,  on  ac- 
count of  the  proportion  of  phosphoric 
acid  in  it.  It  is  a  process,  then,  that 
does  not  at  all  pretend  to  purify  the  sew- 
age ;    it   merely   pretends   to   afford    a 


means  of  dealing  with  the  suspended 
matters  of  the  sewage,  and  to  leave  it  in 
a  condition  in  which  it  is  better  fitted 
for  treatment  afterwards. 

We  pass  on  now  to  the  remaining 
methods  for  the  treatment  of  sewage, 
which  depend  upon  the  filtration  of  it 
through  soil.  I  have  described  to  you 
the  effects  of  the  filtration  of  foul 
water  through  gravel  and  sand  and  char- 
coal. You  may  say  this  can  be  done  for 
water  containing  a  small  amount  of  im- 
purity, but  can  it  be  done  for  water  con- 
taining a  large  amount  of  organic  mat- 
ters both  in  suspension  and  solution,  as 
is  the  case  with  sewage  ?  Now,  filtra- 
tion may  be  of  two  kinds  ;  at  any  rate 
there  are  two  principal  kinds,  downward 
and  upward.  You  may  either  pour  the 
water  on  to  the  surface  of  the  filter  and 
allow  it  to  pass  through,  or  you  may 
conduct  the  water  underneath  the  filter, 
and  let  it  rise  up  through  the  filtering 
material.  By  the  first  process,  which  is 
known  as  downward  filtration,  sewage 
can  be  satisfactorily  purified  on  one  con- 
dition, namely,  that  the  filtration  shall 
be  intermittent.  I  told  you  how  a  filter 
purifies,  and  you  will  see  at  once  that 
this  is  a  necessary  condition  for  the  puri- 
fication of  sewage.  If  you  have  sewage 
falling  on  a  filter  bed  and  passing 
through  it  to  drains  below,  the  organic 
matters  in  that  sewage  are  only  oxydiz- 
ed,  if  there  is  air  in  the  filter;  and  there 
cannot  be  air  in  the  filter  unless  your  pro- 
cess is  intermittent.  But  if  your  process 
is  intermittent,  when  you  stop  pouring 
sewage  on  to  the  filter  bed,  the  remain- 
ing water  trickles  down  into  the  drain 
below,  and  so  fills  your  filter  with  air. 
You  must  have  an  intermittent  process. 

That  shows  you  again  why  .  upward 
filtration  is  not  capable  of  purifying 
sewage.  Supposing  you  have  water  ad- 
mitted underneath  the  filter,  and  that  it 
is  so  constructed  that  it  can  rise  up  to 
the  surface  of  the  bed  and  flow  off  it, 
your  filter  bed  is  always  charged  with 
water.  Upward  filtration  then  does  not 
afford  the  means  of  aerating  the  water. 
By  intermittent  downward  filtration  we 
have  a  means — as  pointed  out  by  the 
Rivers'  Pollution  Commissioners  (1868) 
— a  means  of  satisfactorily  purifying- 
sewage. 

Experiments  conducted  by  filtering- 
London  sewage  through  15  feet  of  sand 


WATER   SUPPLY   AND   DRAINAGE. 


409 


showed  in  the  first  place  that  "  the  pro- 
cess of  upward  filtration  through  sand 
is  insufficient  in  the  purification  of  sew- 
age from  soluble  offensive  matters  ;  .  .  . 
.....  on  no  occasion  was  the  effluent 
water  in  a  condition  fit  to  be  admitted 
into  running  streams,"  but  that  the 
"  process  of  intermittent  dovmward$\tv&- 
tion  through  either  sand  or  a  mixture  of 
chalk  and  sand  effects  a  very  satisfactory 
purification  of  sewage  when  the  sewage 
treated  amounts  to  5.6  gallons  per  cubic 
yard  of  filtering  material  in  24  hours  ; 
but  that  the  purification  becomes  uncer- 
tain and  unsatisfactory  when  the  rate  of 
filtration  is  doubled,  that  is  when  the 
sewage  treated  amounts  to  11.2  gallons 
per  cubic  yard  in  24  hours."  And  so  on. 
And  then  the  amount  of  purification  is 
given,  and  the  value  of  different  soils  as 
purifying  agents.  Now,  filtration  through 
charcoal  has  been  used  in  one  process, 
the  process  known  as  Messrs.  Weare's 
process  ;  the  process  has  been  used  in 
the  filtration  of  the  sewage  of  the  work- 
house at  Stoke-upon-Trent.  One  would 
have  expected,  if  the  experiment  had 
been  conducted  properly,  that  it  would 
have  been  a  success.  However,  all  the 
sewage  of  that  particular  place  was  ex- 
ceedingly strong,  and  although  it  was 
purified  to  a  considerable  extent  by 
Weare's  process,  it  is  not  reported  fav- 
orably on  in  the  report  of  the  British 
Association  Committee,  and  it  has  not 
been  employed  on  a  larger  scale.  Then 
intermittent  downward  filtration  through 
soil  has  been  employed  as  a  means  of 
purifying  sewage  on  a  very  large  scale 
at  Merthyr  Tydfil  by  Mr.  Bailey  Denton, 
and  this  has  been  reported  on  by  the 
Rivers'  Pollution  Commissioners  and 
also  by  the  British  Association  Commit- 
tee. 

"  Merthyr-Tydfil  contains  a  population 
of  50,000 — I  am  now  coating  from  the 
proof  sheets  of  last  year's  report  of  the 
British  Association  Committee — but  ac- 
cording to  information  supplied  to  the 
Committee,  the  excretal  refuse  of  not 
more  than  two-fifths  of  this  number  is 
discharged  into  the  sewers,  although  the 
slops  and  other  liquid  refuse  from  a  fur- 
ther like  number  (20,000)  is  stated  to  be 
admitted.  It  is  not  surprising,  therefore, 
that  the  sewage  is,  as  afterwards  appears, 
weak."  "An  area  of  about  20  acres 
lias,  under  the  supervision  of  a  member 


of  the  Committee,  been  converted  into  a 
filter  bed  for  the  practice  of  the  system 
of  downward  filtration  originated  by 
the  Rivers'  Pollution  Commissioners,  as 
above  described."  "The  soil  of  this 
area  consists  of  a  deep  bed  of  gravel 
(probably  the  former  bed  of  the  River 
Taff,  which  is  embanked  up  on  the  east' 
side  and  is  raised  above  the  valley)  com- 
posed of  rounded  pebbles  of  the  Old 
Red  Sandstone  and  Coal-measure  forma- 
tions, interspersed  with  some  loam  and 
beds  of  sand,  forming  an  extremely  por- 
ous deposit,  and  having  a  vegetable 
mould  on  the  surface." 

"  The  land  has  been  pipe-drained  at  a 
depth  of  less  than  7  feet,  and  the  pipes 
are  concentrated  at  the  lowest  corner, 
where  the  effluent  water  is  discharged 
into  the  open  drain  which  leads  to  the 
river  Taff  at  some  distance  down  the 
valley." 

"  The  sewage  before  entering  the  farm 
is  screened  through  a  bed  of  '  slag '  which 
arrests  the  coarser  matters.  It  is  applied 
to  the  land  intermittently,  for  the  area 
being  divided  into  4  plots  or  beds,  it  is 
turned  on  each  one  for  6  hours  at  a  time, 
leaving  an  interval  of  18  hours  for  rest 
and  aeration  of  the  soil."  So  that  you 
see  the  right  principal  is  carried  out 
there.  When  the  Rivers'  Pollution 
Commissioners  reported  on  intermittent 
downward  filtration  through  soil,  they 
said  that  it  could  be  used  to  purify  sew- 
age. They  also  said,  and  it  was  so 
thought,  that  the  sewage  would  be  en- 
tirely wasted  ;  that  the  greater  amount 
of  it  is  wasted,  as  you  will  directly  see  ; 
but  that  it  need  not  be  entirely  wasted 
we  can  see  from  these  experiments  at 
Merthyr-Tydfil,  where  large  crops  are 
grown  upon  the  limited  area. 
"  The  surface  of  the  land  was  cultivated 
to  a  depth  from  16  to  18  inches,  and  laid 
up  in  ridges,  in  order  that  the  sewage 
might  run-down  the  furrows,  while  the 
ridges  were  planted  with  cabbages  and 
other  vegetables." 

Well  now,  this  process  has  been 
carried  out  on  a  large  scale,  and  it  has 
been  examined  with  the  following  re- 
sults by  the  "Rivers'  Pollution  Com- 
missioners," and  also  by  the  "British 
Association  Committee,"  and  both  sets 
of  examiners  have  come  to  the  conclusion 
that  the  purification  is  satisfactory.  I 
am  not  going  to  give  you  the  numbers, 


410 


VAN  nostrand's  engineering  magazine. 


but  I  am  just  going  to  give  you  one  or 
two  facts  about  it.  In  the  first  place, 
when  you  look  at  the  analysis  of  the 
sewage  of  a  filter  bed  like  this,  you  always 
have  to  take  into  consideration  the  pos- 
sibility of  dilution  of  the  sewage  with 
subsoil  water,  and  in  this  place  the  dilu- 
tion of  the  sewage  with  water  from  the 
river  Taff  is  considerable.  In  the  sum- 
mer it  was  diluted  with  certainly  more 
than  an  equal  volume  of  subsoil  water, 
and  the  gaugings  in  the  winter  showed 
that  each  gallon  of  sewage  had  become 
mixed  with  about  2  gallons  of  subsoil 
water.  When  this  is  allowed  for,  if  you 
compare  the  results  of  the  analysis  of 
the  effluent  water  with  that  of  the  analy- 
sis of  the  sewage,  you  find  first  that  the 
suspended  matters  are  all  removed.  Then 
with  regard  to  the  dissolved  matters,  the 
nitrogen,  instead  of  appearing  as  it  does 
in  sewage  as  ammonia  and  organic  nitro- 
gen, appears  as  nitric  acid  ;  it  has  very 
nearly  all  been  oxydized, — ra  result  that 
we  get  from  purification  of  drinking 
waters  by  filtration  ;  but  the  importance 
and  interest  of  the  matter  is,  that  after 
making  allowances  for  dilution  with 
subsoil  water,  the  total  amount  of  nitro- 
gen in  the  effluent  water  is  almost  ex- 
actly the  same  as  the  total  amount  of 
nitrogen  in  the  dissolved  matters  in  the 
sewage,  although  in  a  different  con- 
dition ;  that  is  to  say,  that  the  nitogen 
retained  by  the  land  is  almost  exactly 
equivalent  to  the  amount  of  nitrogen  in 
the  suspended  matters.  The  effluent 
water,  I  may  tell  you,  was  so  pure,  both 
in  the  winter  and  in  the  summer,  that  in 
the  winter  nearly  all  the  nitrogen  in  it 
was  in  the  form  of  nitrates  and  nitrites, 
and  in  the  summer  Iths  of  it  was  in  the 
same  oxydized  and  harmless  condition. 
We  have  now  to  consider  the  subject 
of  sewage  irrigation.  I  have  shown  you 
that  by  filtration  through  the  soil  in  a 
particular  manner,  sewage  could  be  sat- 
isfactorily purified  ;  could* be  purified, 
in  fact,  so  that  the  water  which  had 
passed  through  a  filter  of  sand,  gravel, 
or  soil,  was,  practically  speaking,  drink- 
ing water.  It  is  perfectly  plain,  there- 
fore, that  if  you  enlarge  the  area  of  your 
filter,  and  pass  the  sewage  through  a 
certain  depth  of  soil,  you  can  in  that 
way,  even  without  the  action  of  plants, 
satisfactorily  purify  sewage.  But  as  ir- 
rigation farms  existed  before  intermittent 


downward  filtration  was  thought  of,  it 
is  neccessary  for  us  to  consider  v  hether 
it  is  sufficient  merely  to  turn  the  sewage 
on  to  unprepared  land — whether  it  is 
sufficient  that  this  should  be  done  with- 
out making  it  a  necessity  that  the  sew- 
age should  pass  through  the  soil. 

There  are  now,  at  any  rate,  two  classes 
of  irrigationists.  One  set  tells  you  that 
an  irrigation  farm  is  nothing  in  the 
world  but  a  very  large  filter  ;  that  it  is 
absolutely  necessary  for  the  purification 
of  the  sewage  at  all  times  of  the  year 
that  the  sewage  should  pass  through  the 
land.  I  mean  to  say  they  will  tell  you 
that  at  certain  times  of  the  year,  at  any 
rate,  if  the  sewage  does  not  pass  through 
the  land,  it  will  not  be  satisfactorily 
purified,  and  that  there  is  danger  of  its 
not  being  satisfactorily  purified  at  any 
time. 

Others  again  say  that  it  is  not  neces- 
sary that  the  sewage  should  pass  through 
the  soil  into  drains,  and  that  it  is  not 
even  necessary  that  the  land  should  be 
drained  in  many  cases  at  any  rate.  In 
the  first  place,  there  can  be  no  doubt 
that  upon  almost  all  impervious  soils, 
sewage  can  be  purified  by  surface  action 
to  a  very  large  extent  indeed.  At  some 
of  our  sewage  farms  they  work  upon 
this  principal.  The  sewage  does  not 
pass  through  the  soil  at  all.  On  the 
soil  plants  are  growing,  and  they  take 
up  the  organic  matters,  ammonia,  &c, 
from  the  sewage  ;  and  the  water  which 
passes  off,  the  overflow,  is  remarkably 
pure.  But  it  will  remain  for  us  to  con- 
sider bye  and  bye,  whether,  when  plant 
action  is  least,  this  would  be  the  case, 
whether  in  such  cases  the  effluent  water 
should  not  be  left  in  an  impure  condition. 
Well,  now  you  have  sewage  brought  on 
to  a  farm,  if  you  are  able  to  do  it,  by 
gravitation,  if  not,  by  pumping.  On  the 
farm  tanks  are  constructed  ;  as  a  rule, 
two  tanks,  the  one  being  merely  to  be 
used  while  the  other  is  cleaned  out. 
Tanks  are  considered  by  many  persons 
as  not  specially  necessary,  but  they  are 
so,  both  for  the  separation  and  collection 
of  the  grosser  suspended  matters  and 
also  for  storing  the  night  sewage.  The 
sewage  is  run  out  from  one  of  the  tanks 
neither  from  the  top  nor  from  the  bot- 
tom. At  the  bottom  the  sediment  is 
allowed  to  deposit.  At  the  top  the  scum 
accumulates,  covers  over  the  surface  of 


WATER   SUPPLY   AND   DRAINAGE. 


411 


the  liquid,  and  to  a  great  extent  dimin- 
ishes the  offensive  ordor.  The  sewage 
is  allowed  to  run  out  between  the  scum 
at  the  top  and  the  sediment  at  the  bot- 
tom. One  of  the  simplest  ways  of  effect- 
ing this  is  by  means  of  a  kind  of  flood- 
gate (such  as  one  you  may  see  at  Bren- 
ton's  farm,  near  Romford),  made  of 
pieces  of  board  slid  down  one  over  an 
other  ;  rings  are  fixed  to  the  sides  of 
these  boards,  so  that  one  or  more  of 
them  may  at  any  time  be  lifted  a  little 
by  means  of  a  rod  with  hooks  at  the  end, 
and  then  the  sewage  will  run  out  through 
the  gap  made  ;  the  lower  part  of  the 
flood  gate  keeping  back  the  sludge,  and 
the  upper  boards  keeping  back  the  scum. 
The  sewage  flows  either  directly  into  the 
carriers,  or  when  it  has  to  be  pumped, 
into  the  pumping  well. 

To  take  the  sewage  on  to  the  land 
from  the  tanks,  you  may  use  concrete 
carriers,  as  they  are  the  easiest  made, 
and  the  cheapest.  If  you  want  the  work 
to  look  particularly  well,  you  can  use 
brick- work,  or  earthenware,  at  the  Tun- 
bridge  Wells. 

If  the  carriers  have  to  be  lifted  above 
the  ground,  as  where  there  is  a  pumping 
station  on  the  farm  itself,  they  are  best 
made  of  sheet  iron,  supported  on  wooden 
tressels.  They  must  have  simple  taps 
which  can  be  opened  by  merely  taking 
out  a  plug. 

These  carriers  run  in  directions  which 
depend  upon  the  slope  of  the  land. 

In  the  first  place,  I  may  tell  you  that 
the  best  sort  of  land  to  irrigate  is  flat 
land — quite  flat— and  then  that  which 
gently  slopes.  The  main  carriers  are  to 
run  at  right  angles  to  the  slopes  of  the 
land.  They  are  carried  under  the  roads 
by  means  of  inverted  syphons,  and  then 
the  land  is  divided  at  right  angles  to 
these  carriers  into  parallel  beds. 

I  am  now  describing  to  you  the  plan 
which  I  believe  to  be  the  best. 

The  land  is  arranged  in  ridges  and 
furrows,  the  crests  of  the  ridges  running 
at  right  angles  of  the  main  carriers  and 
down  the  middle  of  each  bed,  so  that 
each  bed  slopes  slightly  from  the  middle 
towards  each  side.  At  Brenton's  Farm, 
where  you  can  see  the  plan  at  work, 
the  beds  are  30  feet  across.  Along  the 
top  of  the  ridge  there  is  run  a  minor 
carrier.  This  is  merely  a  groove  made 
along  the  crest  of  the  ridge  by  a  plough. 


The  taps  on  the  main  carriers  are  just 
opposite  to  the  beginning  of  these  minor 
carriers,  and  the  sewage  can  be  let  out 
of  the  taps  and  allowed  to  run  along  the 
minor  carriers.  When  the  minor  car- 
rier is  full  the  sewage  overflows  and 
runs  over  the  bed  down  each  side  into 
the  furrows  between  it  and  the  adjacent 
bed.  It  may  be  allowed  to  run  into  the 
minor  carrier  as  long  as  no  pounding 
occurs  in  the  furrow.  That  is  the  "  ridge 
and  furrow  plan." 

There  is  another  system  called  the 
"  catch- water  system."  In  that  plan  the 
sewage  is  taken  in  carriers  along  con- 
tour lines.  The  carrier  along  the  high 
contour  line  is  filled,  and  the  sewage 
stopped  at  a  particular  place  ;  it  over- 
flows and  runs  down  the  slope  of  the 
land  into  the  carrier  below.  You  can 
see  that  at  work  at  many  irrigation 
farms. 

There  is  a  variety  of  that  called  the 
"  pane  and  gutter"  system.  I  do  not 
know  that  I  need  explain  it  in  detail. 
The  land  is  divided  into  pieces  or 
"  panes,"  running  down  the  slope,  and 
at  right  angles  to  the  main  carriers,  and 
the  sewage  is  run  over  the  surface  of 
these  "panes"  from  the  higher  carriers 
into  the  lower  ones. 

There  has  been  for  a  long  time  at 
Milan  a  plan  of  simply  flooding  the 
whole  of  the  land,  but  in  this  way 
marshes  are  produced.  The  first  obvious 
disadvantage  of  the  catch-water  and 
pane  and  gutter  plans  is  that  some  land 
gets  much  more  than  the  rest ;  because 
all  the  sewage  that  flows  over  the  lowest 
level  of  a  bed  must  pass  over  the  whole 
bed  from  the  top.  If  the  land  below 
gets  enough,  the  land  above  gets  too 
much,  besides  the  fact  that  the  lower 
beds  get  all  the  water  that  flows  off  the 
upper  ones.  On  the  other  hand,  with 
the  "  ridge-and-f urrow "  system  I  de- 
scribed before,  you  can  just  allow  each 
particular  bit  exactly  the  amount  it 
wants. 

A  boy  goes  along  the  carrier,  turning 
on  and  off  the  taps  as  they  are  wanted, 
and  a  man  walks  up  and  down  the  ridges 
and  stops  the  sewage  at  intervals,  so 
that  it  overflows  the  minor  carrier  on 
each  side  and  runs  over  the  bed. 

Any  channels  that  convey  sewage  may 
be  open.  There  is  no  reason  whatever 
for  covering  them  over.      The    loss  of 


412 


VAN  NOSTRAND' S   ENGINEERING   MAGAZINE. 


ammonia,  &c,  from  the  sewage  is  per- 
fectly inappreciable  even  after  a  passage 
for  a  very  long  time  through  the  open 
air,  as  proved  hy  the  experiments  of  the 
Rivers'  Pollution  Commissioners.  You 
know  already  that  hy  passing  it  through 
soil  sewage  can  be  purified.  Now,  a  few 
words  about  passing  it  over  the  surface 
•of  the  soil.  The  Committee  of  the 
British  Association  have  made  experi- 
ments upon  this  very  point  ;  and  I  have 
compaxisons  of  the  results  of  the  purifi- 
cation of  sewage  during  very  severe 
winter  weather  at  some  different  farms. 
Now  the  first  of  these  is  Beddington 
Farm,  Croydon.  Here  the  analysis 
showed  "that  the  nitrogen  that  is  lost 
on  this  farm  is  lost  for  the  most  part  in 
the  form  in  which  it  came  into  the  land, 
and  that  mere  surface  action  (which  is 
relied  on  here),  is  not  sufficient  to  cause 
the  oxydization  of  the  ammonia  and  or- 
ganic matters  contained  in  the  sewage. 
At  the  same  time  the  purification  effected 
was  certainly  very  considerable." 

Then  again,  the  effluent  water  at  the 
Norwood  farm  during  the  severe  frost, 
was,  practically  speaking,  sewage  con- 
taining nearly  half  the  amount  of  the 
ammonia  that  the  sewage  put  on  the 
farm  did.  It  contained  very  little  nitro- 
gen in  the  form  of  nitrates.  You  know 
I  told  you  that  the  main  action  of  a  fil- 
ter was  the  conversion  of  ammonia  and 
the  nitrogen  contained  in  organic  matters 
into  nitric  acid.  So  that  the  amount  of 
nitric  acid  in  effluent  water  is  a  test  of 
the  oxydizing  action  of  the  filter..  At 
the  same  time  the  analysis  of  the  effluent 
water  at  Brenton's  Farm,  Romford, 
showed  that  the  purification  was  very 
satisfactory  indeed,  for  the  effluent 
water  only  contained  a  very  small  quan- 
tity of  actual  ammonia,  that  is  to  say, 
about  0.14  parts  in  100,000,  as  against 
-5.6  contained  in  the  sewage,  and  of 
albuminoid  ammonia  only  0.059  parts 
Temained  out  of  0.524  in  the  sewage, 
wdiile  the  effluent  water  contained  no 
less  than  1.2  parts  of  nitrogen  in  the 
form  of  nitrates  and  nitrites. 

In  winter,  when  little  action  of  vege- 
tation is  going  on,  mere  passage  over  the 
soil  will  not  purifiy  sewage  satisfactorily. 
The  effluent  water  which  goes  off  the 
land,  is,  to  all  intents  and  purposes  sew- 
age. On  the  other  hand,  there  is  a  per- 
fectly clear  proof,  that  during  winter  if 


you  pass  the  sewage  through  the  soil,  as 
at  Brenton's  Farm,  purification  goes  on 
just  the  same  as  at  any  other  time  of  the 
year  when  vegetation  is  growing. 

Even  during  the  summer  there  is  a 
risk  that  the  sewage  may  not  be  satis- 
factorily purified  where  the  catch-water 
principal  is  adopted.  This  happened  at 
Reigate,  where  the  sewage  was  passed 
over  one  field  and  then  over  another,  and 
the  effluent  water  that  came  off  the  lower 
part  of  the  second  field  was  actualy  more 
impure  in  several  ways  than  that  which 
came  on  to  it  from  the  first  field  ;  that 
is  to  say,  that  this  second  field  was  to  a 
certain  depth  so  absolutely  saturated 
with  sewage,  that  the  water,  or  sewage, 
or  whatever  you  like  to  call  it  that  came 
from  the  first  field"  actually  became 
more  impure  the  further  it  went.  It  was 
in  fact  made  stronger  by  the  amount  of 
evaporation  which  went  on,  and  is 
another  conclusive  proof  that  surface 
action  is  not  sufficient. 

These  results  seem  to  me  decisive  in 
favor  of  the  construction  of  irrigation 
farms  as  large  filters.  Then  we  come  to 
the  practical  point — that  it  is  therefore 
necessary  that  they  should  be  drained. 

On  this  head  the  British  Association 
Committee  express  the  following  opin- 
ion : — 

"  It  may  seem  almost  superfluous  for 
the  Committee  after  so  many  years  of 
general  experience  throughout  the  coun- 
try, to  argue  in  favor  of  the  subsoil 
drainage  of  naturally  heavy  or  naturally 
wet  land,  with  impervious  subsoil,  for 
the  purposes  of  ordinary  agriculture ; 
but  some  persons  have  strongly  and  re- 
peatedly called  in  question  the  necessity 
of  draining  land  when  irrigated  with 
sewage  ;  and  the  two  farms  at  Tunbridge 
Wells,  to  a  great  extent,  and  more  es- 
pecially the  Reigate  farm  at  Earlswood, 
have  been  actually  laid  out  for  sewage 
irrigation  on  what  may  be  called  the 
'  saturation'  principal ;  so  that  it  appears 
to  the  Committee  desirable  to  cail  atten- 
tion to  the  fact,  that  if  drainage  is 
necessary  where  no  water  is  artificially 
applied  to  the  soil,  it  cannot  be  less 
necessary  after  an  addition  to  the  rain- 
fall of  100  or  200  per  cent.  But  a  com- 
parison of  the  analysis  of  different  sam- 
ples of  effluent  waters  which  have  been 
taken  by  the  Committee  from  open 
ditches  into   which   effluent   water   was 


WATER   SUPPLY   AND   DEAINAGE. 


415 


overflowing  off  saturated  land,  and  from 
subsoil  drains  into  which  effluent  water 
was  intermittently  percolating  through 
several  feet  of  soil,  suggests  grave 
doubts  whether  effluent  water  ought 
ever  to  be  permitted  to  escape  before  it 
has  percolated  through  the  soil." 

There  are  some  other  plans  that  have 
been  suggested  for  the  distribution  of 
sewage,— one  is  by  means  of  the  ordi- 
nary agricultural  drainage.  That  is  ob- 
viously perfectly  absurd.  It  is  impos- 
sible to  imagine  that  sewage  could  be 
purified  by  turning  it  into  agricultural 
drains  below  the  roots  of  the  plants. 
Another  plan,  very  much  advocated,  is 
to  conduct  it  in  pipes  just  out  of  reach 
of  the  plow,  and  then  to  distribute  it 
over  the  land  and  plants  by  means  of 
hose  and  jet.  The  thing  that  is  im- 
mensely against  this,  is  the  expense  from 
the  enormous  amount  of  labor ;  also, 
that  if  sewage  farms  are  not  to  be  (and 
they  certainly  need  not  be)  nuisances,  it 
is  not  by  squirting  the  sewage  about 
that  we  shall  attain  that  object.  As  to 
the  flood  plan  which  is  pursued  at  Milan, 
I  do  not  think  I  heed  say  more  than  two 
words  about  it.  It  is  perfectly  plain 
that  we  don't  want  to  make  sewage 
marshes,  at  any  rate  here.  There,  at 
Milan,  the  water  meadows  cause  ordi- 
nary marsh  fevers.  They  do  not  cause 
any  of  the  diseases  that  it  was  expected 
sewage  farms  would  cause  ;  they  do  not 
favor  in  any  way  such  diseases  as  chol- 
era or  typhoid  fever,  which  diseases  are 
spread  to  a  very  great  extent  by  means 
of  the  intestinal  evacuations  of  those 
suffering  from  them.  I  think  perhaps 
as  I  have  gone  into  the  question  of  pub- 
lic health,  I  may  just  say  the  word  or 
two  that  I  have  to  say  upon  that  point. 
I  do  not  think  you  would  find  a  single 
case  definitely  proved  against  sewage 
farms  —  badly  conducted  as  many  of 
them  are — where  they  have  been  injuri- 
ous to  health,  except  in  this  way.  If 
water  that  contains  poison  from  sewage 
that  has  flown  over  the  land  and  that 
has  not  percolated  through  it,  if  that 
water  is  drunk,  it  is  very  likely  poison- 
ous. That  has  been  the  case  once  or 
twice.  The  farms  have  not  caused  by 
noxious  emanations  any  injury  to  the 
health  of  neighborhoods  where  they 
have  been  placed.  I  do  not  think  there 
is  the  slightest  evidence  to  show  that. 


Then  about  the  water  that  passes  from 
them.  It  is  said  that  in  certain  cases  it 
has  poisoned  the  wells  in  the  neighbor- 
hood. There  is  no  evidence  of  anything 
of  the  sort.  Where  these  cases  have 
been  inquired  into,  it  has  been  found 
that  the  wells  have  not  been  poisoned 
from  the  sewage  farms,  but  by  foul  mat- 
ters from  j>erfectly  different  sources.  It 
is  true  that  in  one  or  two  cases  in  which. 
the  water  which  had  passed  over  the 
sewage-meadows  was  drunk,  a  certain 
number  of  people  got  typhoid  fever. 
In  sewage-meadows  where  surface  action 
is  relied  upon  there  is  considerable  dan- 
ger that  the  overflow  of  the  channels 
should  be  mistaken  for  fresh  water.. 
You  understand  that  when  a  sewage 
farm  is  a  large  filter,  and  the  effluent 
water  is  collected  in  subsoil  drams,  this 
water  is  perfectly  fit  to  drink.  I  can 
tell  you  of  a  sewage  farm  where  it  is 
usually  drunk  by  the  workmen.  There 
is  a  well  on  that  particular  farm,  the 
water  of  which  is  excellent,  and  there  is 
no  reason  why  it  should  not  be  so.  Our 
own  drinking  water  in  London,  and  in 
most  large  towns,  has  got  purified  from 
all  kinds  of  impurities  by  passage 
through  gravel  and  sand.  Dr.  Angus 
Smith  tells  us  that  we  could  not  drink 
rain-water  if  collected  from  the  clouds 
anywhere  near  t©  large  towns  ;  it  would 
be  too  foul,  and  would  haAre  to  be  passed 
through  soil  in  order  to  be  purified. 

Well  now,  the  last  point  that  I  have 
to  notice  in  connexion  with  the  public 
health  is  the  alleged  danger  from  the 
spread  of  entozoic  diseases  by  means  of 
sewage  irrigation.  Dr.  Cobbold,  the 
great  authority  upon  entozoa,  thinks 
that  if  sewage  farms  are  spread  much 
over  the  land,  we  shall  have  more  of  en- 
tozoic diseases,  and  that  deaths  from, 
them  will  become  much  more  frequent,, 
and  he  even  suggested  that  an  entozon 
which  is  very  fatal  in  some  parts  of 
Northern  Africa  (the  Bilharzia  hsema- 
tobia)  might  become  prevalent  in  this 
country.  But  that  entozoon  is,  in  the 
first  place,  prevalent  in  those  countries 
especially  during  the  hot  seasons.  In 
the  second  place,  we  know  next  to  no- 
thing about  the  different  stages  it  goes 
through,  during  which  it  no  doubt  in- 
habits different  animals  (snails,  &c.)  ; 
and  lastly,  Dr.  Cobbold  himself  has 
shown  that   the   larva?  of   this  parasite 


414 


VAN  nostrand's  engineering  magazine. 


cannot  live  in  impure  water.  So  we  may 
dismiss  that  at  once.  Then  with  regard 
to  ordinary  entozoa.  In  the  first  place, 
there  is  no  sort  of  evidence  whatever  to 
show  that  they  have  been  spread  in 
cattle  at  farms  where  irrigation  has  been 
going  on  for  200  years.  Professor  Chris- 
tion  has  distinctly  stated  that  he  has 
never  been  able  to  trace  entozoic  disease 
to  the  Craigentinny  meadows  near  Edin- 
burgh, neither  is  there  evidence  that  this 
has  been  done  anywhere  else.  It  is  very 
easy  to  say  that  the  eggs  of  the  entozoa 
are  in  the  sewage  when  it  is  carried  on 
to  the  land,  and  that  the  larvae  will  be 
developed  as  soon  as  the  plants  are  eaten 
by  animals.  In  the  first  place,  you  must 
know  that  it  is  necessary  that  these  eggs 
should  be  living  and  fertilized  too,  and 
they  have  the  smallest  chance  of  living 
that  anything  can  possibly  have  by  the 
time  they  get  with  the  sewage  to  the 
land,  for  they  have  a  considerable  dis- 
tance to  go  before  they  get  to  the  farm; 
they  are  tossed  about  in  an  alkaline 
liquid,  their  natural  habitat  being  acid 
excretions  ;  they  are  turned  on  to  the 
ground  and  taken  down  into  the  soil 
with  the  water.  However,  to  prevent 
any  apprehension  on  this  score  the  sim- 
plest thing  is  to  have  the  grass  cut  and 
carried  to  the  stalls,  and  not  to  graze 
animals  upon  it.  Many  Of  the  best  irri- 
gationists  insist  upon  this. 

Some  investigations  of  this  matter 
were  made  by  the  British  Association 
Committee. 

"  An  ox  which  had  been  fed  for  the 
previous  22  months  entirely  on  sewage 
grown  produce"  was  slaughtered  and 
carcass  examined  by  Dr.  Cobbold,  Pro- 
fessor Marshall  and  myself  ;  no  trace  of 
any  entozoic  disease  was  found  in  it,  al- 
though most  carefully  looked  for.  Dr. 
Cobbold  suggests  several  reasons  for 
this  result,  and  one  of  these  is  the  free- 
dom of  the  sewage  farm  from  snails  and 
insects,  in  the  bodies  of  which  many  of 
these  entozoa  go  through  different  stages 
of  their  existence  ;  it  seems,  therefore, 
that  the  sewage  kills  those  creatures 
which  are  necessary  for  the  existence  of 
these  entozoa  in  their  different  stages. 
Dr.  Cobbold  also  examined  under  the 
microscope  portions  of  "  flaky  vegetable 
tufts,"  collected  from  the  sides  of  the 
minor  sewage  carriers,  and  found  that, 
although  they  contained  animal  as  well 


as  vegetable  life,  they  contained  "  no 
ova  of  any  true  entozoon."  So  that  you 
see  that  as  far  as  we  have  got  positive 
evidence  it  is  entirely  against  the  theory 
that  entozoic  diseases  are  spread  in  cat- 
tle, and  from  them  down,  by  means  of 
sewage  irrigation. 

Now  a  few  words  about  the  crops. 
The  most  suitable  crop  for  sewage  is 
Italian  rye  grass.  This  plant  will  take 
up  a  very  large  amount  of  sewage.  If 
you  read  the  reports  of  the  sewage  of 
Towns  Commissioners  you  will  find  the 
results  of  experiments  upon  the  amounts 
of  meadow  grass  grown  with  different 
quantities  of  sewage. 

There  was  an  average  increase  of  about 
4  tons  of  grass  for  each  thousand  tons 
of  sewage  applied,  per  acre  :  the  maxi- 
mum amount  of  the  latter  being  about 
9,000  tons  per  acx^e  per  annum.  The 
largest  amount  was  about  33  tons  of 
green  grass  per  acre  in  one  year,  and  3*7 
tons  in  another.  Some  of  the  land  was 
not  supplied  with  sewage  at  all ;  other 
parts  with  3,000,  6,000,  and  9,000  tons 
per  acre  per  annum.  The  increase  of 
produce  was  much  greater  with  the  first 
3,000  tons  of  sewage  than  it  was  when 
the  amount  was  increased  from  3,000  to 
6,000  tons,  and  more  from  3,000  to  6,000 
than  from  6,000  to  9,000.  So  that  the 
increased  amount  of  sewage  did  not  jDro- 
duce  a  proportionately  increased  amount 
of  j)roduce.  The  increase  of  produce 
per  1,000  tons  of  sewage  was  when  3,000 
tons  were  applied  about  5  tons  of  green 
grass,  when  6,000  tons  were  applied  4 
tons  2|  cwt.,  and  when  9,000  tons  were 
applied  3  tons  3^  cwt.  And  the  results 
given  by  Italian  rye  grass  showed  about 
the  same  increase  of  produce.  It  was 
also  found  that  an  earlier  cut  of  green 
grass  could  be  obtained  by  means  of 
sewage  irrigation. 

Experiments  were  made  about  the 
quality  as  well  as  about  the  quantity, 
and  it  was  found  that  the  grass  contain- 
ed a  smaller  actual  amount  of  dry  solid 
matters  when  grown  with  sewage,  but 
was  richer  in  nitrogen,  and  was,  in  fact, 
more  readily  assimilable  —  more  milk 
could  be  got  from  it. 

The  main  result  of  irrigation  farms 
must  be  the  feeding  of  cattle  and  the 
production  of  milk.  The  sewage  is 
turned  into  Italian  rye  grass,  and  is  re- 
turned to  the  town  from  which  the  sew- 


WATER  SUPPLY   AND   DRAINAGE. 


415 


age  has  come  as  milk,  butter,  cheese  and 
beef. 

Then,  if  Italian  rye  grass  can  be 
grown,  every  grass  and  almost  anything 
else  can  as  well.  You  will  see  that  denied 
even  to  this  day,  in  spite  of  the  fact  that 
almost  everything  else  has  been  grown 
with  it.  These  different  plants  can  be 
grown  upon  land  which  is  absolutely  and 
perfectly  valueless  in  an  agricultural 
point  of  view  without  sewage,  even  upon 
blowing  sea  sand,  and  you  can  see  in 
many  parts  of  England  excellent  crops 
now  growing  by  means  of  the  use  of 
this  rich  manure.  Cereals  can  be  grown 
perfectly  well  with  considerable  returns. 
In  1868  and  1869  (at  Lodge  Farm,  Bark- 
ing), wheat,  winter  oats,  rye  and  cab- 
bages were  grown.  In  1868  wheat  was 
grown  on  a  slope  of  shingle.  It  had 
two  dressings  of  sewage  equal  to  450  or 
500  tons  in  all.  The  results  were  5  qr. 
-3  bush.,  as  against  3  qr.  5  bush,  without 
sewage,  with  4£  loads  of  straw,  as  against 
3  to  the  acre.  The  winter  oats  yielded 
8  qr.  of  corn,  with  three  loads  of  straw 
to  the  acre.  Among  other  vegetables 
must  be  especially  mentioned  beet-root. 
From  experiments  which  have  been 
made  there  seems  very  little  doubt  that 
beet-root  can  be  grown  for  the  produc- 
tion of  sugar  in  almost  any  quantity. 
Professor  Voelcker  has  analyzed  some 
of  the  beet-roots  grown  on  sewage,  and 
they  gave  13.19  per  cent,  of  sugar,  while 
the  beet-roots  from  Holland,  Suffolk  and 
Scotland,  only  gave  from  nine  to  ten  per 
cent,  of  it  at  the  outside. 

Well,  now  a  word  or  two  about  the 
times  when  you  don't  want  sewage  on 
the  land.  There  may  be  times  when 
you  don't  want  it  at  all — times  when  the 
sewage  is  too  dilute,  and  the  land  is  very 
wet,  as  during  heavy  floods  ;  and  this  is 
a  very  strong  argument  for  keeping  the 
drainage  water,  properly  so  called,  out 
of  the  sewage,  the  utilization  of  sewage 
is  thereby  rendered  very  much  easier. 
The  best  dilution  for  sewage  is  when  it 
represents  25  to  30  gallons  per  head  of 
the  population.  If  you  keep  the  drain- 
age water  as  much  as  possible  separate, 
you  can  always  turn  it  into  it  as  a  dilu- 
ent when  more  water  is  wanted. 

The  amount  of  sewage  required  per 
acre  varies  much  with  different  crops  and 
with  different  soils,  but  it  is  usually  con- 
sidered that  the  sewage  of  from  35  to  40 


persons  is  sufficient  per  acre  on  the  aver- 
age, although  in  many  instances  much 
more  than  that  is  applied. 

On  every  sewage  farm  there  should  be 
a  piece  of  fallow  land  to  be  used  as  a 
filter,  not  with  the  view  of  any  great  re- 
turn, but  simply  with  a  view  to  purify- 
ing the  sewage  whether  the  crop  on  that 
particular  land  happens  to  want  it  or  not, 
when  it  is  not  wanted  on  any  other  part 
of  the  farm. 

You  see,  then,  that  intermittent  down- 
ward filtration  through  soil  and  irriga- 
tion farming,  with  passage  of  the  liquid 
through  the  soil,  are  the  only  means  at 
present  known  for  purifying  sewage,  and 
these  may  be  well  continued,  with  some 
deodorizing  process,  which  will  prevent 
the  sludge  in  the  tanks  from  being  offen- 
sive, except  where  the  tanks  are  in  the 
open  country,  when  this  is  hardly  neces- 
sary ;  and  you  see  also  that  these  pro- 
cesses in  themselves  are  in  no  way  in- 
jurious to  the  health  of  the  neighbor- 
hood where  they  are  carried  on  ;  one  of 
them,  irrigation  farming,  with  the  con- 
dition mentioned  above,  also  affords  the 
only  method  known  by  which  the  valua- 
ble manurial  ingredients  dissolved  in 
sewage  can  be  utilized — can  be  turned 
into  wholesome  food  for  man  and  beast; 
and  it  is  therefore  for  you  in  those 
parts  of  the  world  in  which  you  may  be 
stationed,  and  where  you  will  have  to 
advise  on  such  matters,  to  use  your  in- 
fluence in  obtaining  the  adoption  of  the 
water-carriage  system,  as  before  de- 
scribed, in  connection  with  a  properly 
carried  out  plan  of  irrigation  farming. 

The  removal  of  waste  matters  is  the 
first  thing  to  consider,  their  utilization 
the  second  ;  where  you  have  both,  there 
you  are  best  able  to  compete  with  dis- 
ease and  death. 


Extension  or  Telegraphy  in  France. 
—The  engineers  of  the  river  service  of 
France  have  been  instructed  to  draw  up 
for  the  principal  navigable  watercourses 
of  Fiance  plans  for  the  establishment  of 
a  telegraphic  service  similar  to  that 
which  has  just  been  inaugurated  on  the 
Seine.  At  all  the  sluices  and  flood-gates 
on  the  river  telegraph  poles  have  been 
set  up,  and  the  service  of  the  river  is 
much  facilitated  by  the  quick  transmis- 
sion of  the  state  of  level. 


416 


VAN  nostrand's  engineering  magazine. 


TOUGHENED  GLASS. 

From  "The  Engineer." 


Several  months  have  elapsed  since 
wonder  was  first  excited  by  the  announce- 
ment that  something  approaching  in 
properties  to  the  mythical  malleable 
glass  of  antiquity  had  been  discovered. 
It  was  no  new  material  that  was  brought 
forward,  and  scarcely  even  a  new  pro- 
cess, but  something  very  like  the  old  and 
well-known  process,  as  applied  to  steel, 
of  tempering  it  in  oil.  It  was  alleged 
that  common  glass,  or  to  endeavor  to 
extract  from  the  accounts  something  a 
little  more  exact,  that  flint  glass  contain- 
ing lead,  from  which  the  thin  plates  on 
which  ice  is  served  are  blown,  or  plate- 
glass  containing  no  lead,  could  be  made 
greatly  more  resistant  by  heating  either 
of  these  to  some  known  high  tempera- 
ture and  plunging  the  glass  into  some 
mixture  of  oil  with  tarry  matter,  this 
mixture  being  also  heated  to  some  known 
temperature  ;  and  it  was  added  that  the 
air  of  the  apartment  in  which  the  opera- 
tion was  conducted  must  be  at  some  fixed 
temperature  also.  But  these  tempera- 
tures, though  alleged  to  be  essential  to 
the  success  of  the  process,  were  most  un- 
satisfactorily kept  secret,  and  we  were 
called  upon  to  admire  the  result  of  an 
imperfectly  divulged  process  as  enabling 
the  glass  treated  by  to  become  far  more 
resistant  to  impact  by  the  recital  of  such 
very  crude  experiments  as  those  recorded 
by  us  in  April  last,  in  which  a  6in. 
square  plate  of  glass  set  loosely  in  a 
wooden  frame  like  a  schoolboy's  slate 
was  broken  by  the  fall  on  to  its  face  of 
a  2  oz.  brass  weight  from  a  height  of 
2ft.,  whilst  it  required  an  iron  weight  of 
8  oz.  falling  from  a  height  of  6ft.  to 
break  a  similar,  but  rather  thinner,  piece 
of  the  same  glass  which  had  been  sub- 
jected to  M.  La  Bastie's  process.  The 
difference  between  the  work  done  in 
both  cases  is  about  as  one  to  twelve,  and 
this  really  does  not  represent  fully  the 
difference  of  resisting  power  in  the  two 
cases,  because,  as  has  been  demonstrated 
by  Dr.  Young  and  others,  the  power  of 
impulse  to  produce  fracture  in  brittle 
bodies  increases  with  the  velocities  of 
impact  independently  of  the  work  lodged 
in  the  impelled  body,  and  also  with  the 


rigidity  of  the  striking  body,  the  iron 
weight  being  here  more  rigid  than  a  brass 
one.  For  all  this  the  experiment  is  an 
extremely  unsatisfactory  one.  "Why 
should  the  plates  of  glass  be  set  in  a 
wooden  frame  at  all  in  place  of  being 
simply  laid  upon  a  flat  rigid  surface  with 
a  square  aperture  through  it  nearly  the 
size  of  the  plate  ?  The  slightest  inequal- 
ity of  bearing  or  of  greater  or  less  loose- 
ness wherewith  the  glass  was  held  in  the 
wooden  frame  might  so  materially  affect 
the  result  as  to  deprive  the  experiment 
of  all  scientific  value,  though  we  may 
admit  it  as  demonstrative  of  a  great  dif- 
ference in  resistance  to  impact.  We  are 
told  also  that  this  process  greatly  in- 
creases the  resistance  of  a  strip  of  glass 
to  a  steady  tensile  force  ;  it  is  added 
also  that  if  a  piece  of  glass  which  has 
been  subjected  to  La  Bastie's  process  be 
broken  by  impulse  it  is  not  fractured  in 
certain  irregular  lines  radiating  from  the 
point  of  impact,  but  that  the  whole  piece 
breaks  up  into  small  fragments  like  those 
into  which  a  Rupert's  drop  breaks  ex- 
plosively when  its  tail  is  pinched  off. 
Furthermore,  it  appears  by  the  account 
of  experiments  made  officially  by  agents 
of  M.  de  La  Bastie,  before  glass  manu- 
facturers at  Pittsburgh,  U.  S.,  which  we 
copied  from  the  Pittsburgh  Herald  in  a 
recent  impression,  that  when  once  the 
slightest  abrasion  is  made  "  upon  the 
surface  of  this  glass  the  entire  piece  was 
reduced  to  powder."  If  we  are  to  rely 
upon  the  facts  as  stated,  the  La  Bastie 
glass  is  as  completely  in  the  condition 
of  a  Rupert's  drop  as  it  might  be,  if  in 
place  of  being  tempered  in  oil  and  tar,  it 
had  been  dropped  liquid  into  water- 
Now,  if  this  be  so,  if  in  accordance  with 
the  somewhat  crude  speculations  which, 
without  anything  of  experimental  sup- 
port, have  been  hazarded  to  account  for 
the  changed  condition  of  the  glass,  we 
admit  for  the  moment  that  its  exterior 
and  interior  layers  are  held  in  a  state  of 
mutual  constraint  by  unequal  contrac- 
tion, how  is  it  possible  that  glass  in  such 
a  state  should  offer  a  greater  resistance 
to  a  steady  tensile  strain  than  the  same 
glass,  all  of  whose  particles  were  in  a 


TOUGHENED   GLASS. 


4T7 


state  of  repose,  and  free  from  mutual 
constraints.  Is  the  fact  certain  that 
there  is  any  such  increase  of  ultimate 
tensile  resistance  conferred  by  this  pro- 
cess ?  If  it  really  be  so,  it  would  only 
add  to  the  inexplicable  character  alleged 
as  to  other  of  the  results  of  this  process; 
but  for  anything  that  has  as  yet  come  to 
our  knowledge,  this  alleged  increase  of 
ultimate  tensile  resistance  may  rest 
merely  upon  delusive  experiment. 

Every  physicist  is  aware  of  the  almost 
insuperable  difficulties  which  attend  all 
attempts  to  determine,  experimentally, 
the  tensile  resistance  of  very  rigid  bod- 
ies. The  discrepancy  between  recorded 
experiments  made  by  competent  physic- 
ists upon  bodies  far  less  rigid  than  glass, 
such  as  bell  metal,  speculum  metal,  &c, 
amply  prove  this  ;  and  still  more  so  do 
the  results  obtained  by  Messrs.  Fairbairn 
and  Tate,  upon  several  species  of  glass 
itself.  These  last  indicated  a  resistance 
to  compression  as  compared  with  that  to 
tension  so  enormously  exceeding  those 
of  any  other  known  bodies,  as  to  war- 
rant the  conclusion  that  while  the  ex- 
periments on  compression  made  upon 
short  cylinders  or  prisms  may  be  nearly 
correct,  those  recorded  for  the  resistance 
to  tension  are  greatly  below  the  truth, 
arising  from  the  almost  certain  depai't- 
ure,  of  the  line  of  pull  from  the  axis  of 
the  piece.  It  seems  possible,  therefore, 
that  the  alleged  greater  tenacity  of  the 
La  Bastie  glass  may  be  a  result  of  its 
possessing  within  certain  very  narrow 
limits  greater  flexibility  than  ordinary 
glass,  so  that  when  subjected  to  a  tensile 
strain,  it  is  enabled  to  slightly  alter  its 
form,  so  as  more  nearly  to  admit  of  the 
pull  passing  through  the  axis  of  the 
piece.  We  would  not  be  understood, 
however,  as  offering  any  opinion  on  this 
point,  but  merely  suggesting  it  as  one 
of  those  to  be  borne  in  view  in  the 
further  experiments  that  must  be  con- 
ducted before  even  the  most  primary 
facts  of  this  curious  subject  can  be  said 
to  be  established.  In  the  account  to 
which  we  have  above  referred,  we  find 
some  further  statements  which  appear  to 
us  inexplicable,  if  not  contradictory  ;  it 
is  alleged  that  La  Bastie's  process  was 
anticipated  as  far  back  as  the  year  1822, 
at  the  works  of  Bakewell,  Pears,  and 
Co.,  and  that  for  the  purpose  of  render- 
ing ordinary  glass — flint  glass  we  must 
Vol.  X1IL— No.  5—27 


presume — less  liable  to  fracture  when 
undergoing  the  process  of  ornamental 
cutting  by  the  glass  grinder's  wheel,  it 
was  previously  boiled  in  fish  oil,  which 
it  is  alleged  prevented  further  annoy- 
ance by  fracture  during  the  grinding. 

Now,  as  the  process  of  glass  grinding 
or  cutting  is,  until  the  stage  for  polish- 
ing be  reached,  neither  more  nor  less 
than  one  of  abrasion  upon  a  grit  stone 
or  a  lead  lap  coated  with  emery,  and  as 
it  is  stated  that  the  slightest  abrasion 
of  the  surface  causes  the  La  Bastie  glass 
to  fly  to  pieces  by  a  scratch,  so  it  is  ex- 
tremely difficult  to  see  why  an  exactly 
opposite  result  to  that  recorded  should 
not  have  taken  place  by  this  boiling  in 
oil.  Besides  the  great  need  of  corrobo- 
ration thus  suggested,  this  alleged 
American  process  is  no  anticipation  at 
all  of  La  Bastie's  ;  the  two  processes 
are  entirely  distinct,  and  we  certainly 
should  not  be  prepared  by  any  known 
analogy  to  believe  that  cold  glass,  we 
presume  already  annealed  in  the  ordin- 
ary way  in  the  "  leer,"  should  have  its 
physicial  properties  altered  as  described 
by  being  kept  immersed  for  any  length 
of  time,  however  great,  in  fish  oil,  which 
boils  at  a  temperature  between  the  melt- 
ing point  of  tin  and  that  of  lead. 

In  a  lecture  delivered  at  a  meeting  of 
the  Society  for  the  Encouragement  of 
Arts  and  Manufacturers  on  the  2nd  of 
June  last,  we  find  some  other  statements 
which  seem  more  or  less  irreconcileable 
with  each  other.  It  is  there  admitted 
that  if  only  a  corner  be  broken  off  by  a 
blow  from  a  plate  of  this  glass  the  whole 
plate  flies  into  fragments.  It  is  also  ad- 
mitted that  plates  of  this  glass  cannot 
be  cut  by  the  glazier's  diamond.  Not 
indeed,  we  must  infer,  because  the  sur- 
face of  the  glass  be  increased  in  hard- 
ness to  such  an  extent  as  to  equal  that 
of  the  diamond,  but  that  the  stroke  made 
by  the  diamond  does  not  produce  a 
straight  and  even  fracture  as  in  ordinary 
glass,  but  one  jagged  and  irregular,  and 
which  may  diverge  more  or  less  from 
the  path  that  the  diamond  has  described : 
yet  we  are  informed  that  this  same  glass 
may  be  engraved  upon  by  fluoric  acid, 
which  we  should  not  be  prepared  to 
doubt,  and  also  may  be  engraved  by 
Tilghman's  sand  blast  process,  a  fact  as 
to  which  we  must  entertain  much  doubt 
in  view  of  the  difficulty  of  producing  a 


418 


VAN   ^STRAND'S   ENGINEERING   MAGAZINE. 


straight  diamond  cut,  and  of  the  state- 
ment that  the  breaking  off  of  a  corner, 
or   a   surface   abrasion,   breaks    up    the 
whole   piece.     Brewster,    indeed,  found 
that  a  considerable  portion  of  the  bulb- 
ous  end    of   a  Rupert's  drop  might  be 
slowly  and   carefully  ground    off   upon 
the  lapidary's  wheel  without  that  always 
producing   its   explosion,    provided    the 
surface   being   ground    off   was    always 
normal  to  the  axis  of  the  drop,  but  this 
is  a  very  different  thing  from  the  rough 
vibratory  grinding  produced  by  the  or- 
dinary work  of  the  glass  cutter.   Amongst 
the  points  left  in  obscurity  as  to  the  La 
Bastie  process  is  one  which  may  be  far 
from   immaterial.     Is   it  necessary  that 
the  glass  taken  from  the  glass-house  pot, 
formed    by   blowing  or   otherwise    and 
annealed,   must  be  let  to  cool  and  then 
heated  again    up    to   redness,   or  there- 
abouts, before    being   quenched   in   the 
hydrocarbon  oil  bath  ;  or,  is  the  result 
equally  attained   by   taking   the    glass 
directly  it  has  become  stiffened  from  the 
glass  blower's  pipe  or  mould,  and  while 
still  at  the  requisite   high  temperature, 
and  at  once  quenching    it  in  the   bath 
without    any    intermediate    process    of 
annealing  and  cooling  ?     No  experiment 
nor  sufficient  information   has  been  re- 
corded as  to  this,   but  from  some  facts 
stated   in   the  discussion  following  the 
lecture  to  which  we  have  above  alluded, 
it  may  be  inferred  that  the  same  effects 
would  be  produced  if  the  temperature  at 
the  moment  of  immersion  be  the  same 
whether  the  glass,  without  being  allow- 
ed  to  cool   on   blowing,    were    at    once 
dropped  into  the  hydrocarbon  bath,  or 
whether,   having  been  let  cool,  it  were 
again  slowly   heated  up  to  a  sufficient 
temperature  and   then  passed   into  the 
bath.     The  real  point  of  practical  diffi- 
culty in  either  case  seems  to  be  that  the 
glass  when  dropped  into  the  bath  must 
be  at  a  temperature  so  nearly  approach- 
ing that  of  its  fusion  as  to  be  soft  and 
viscous,  and  that  if  it  be  let  to  cool  but 
a  little  below  this  point  the  effect  of  the 
bath  is  partial  and  incomplete.     What- 
ever happens  as  a  result  of  the  La  Bastie 
process  is  something  obviously  different 
from  that  of  annealing  as  heretofore  un- 
derstood, and  when  closely  examined  al- 
most all  analogy  between   this  process 
and  the  tempering  of  hardened  steel  in 
oil  disappears. 


The  steel  has  been  already  heated  to  a 
temperature  at  which,  if  quenched  in 
water,  it  would  become  intensely  hard, 
and  in  that  condition,  if  fractured,  breaks 
with  a  fracture  approaching  the  vitreous 
in  its  character.  The  heat  of  the  piece 
is  carried  off  in  the  water  with  immense 
rapidity  by  the  generation  of  steam, 
which  is  condensed  as  rapidly  as  it  is 
formed  in  the  remoter  parts  of  the  fluid, 
aided  also  by  the  rapid  currents  induced 
in  the  latter  by  difference  of  temperature, 
and  also  by  rapid  influx  of  cold  water. 
Heated  to  the  same  temperature  and 
quenched  in  oil,  however,  the  steel  is 
cooled  by  convection  and  conduction, 
and  in  a  liquid  of  probably  low  conduc- 
tivity and  of  so  much  viscidity  as  to  re- 
tard circulatory  currents  ;  it  is,  therefore, 
cooled  rapidly  indeed  as  compared  with 
the  time  of  a  like  amount  of  cooling  in 
still  aii",  but  by  no  means  suddenly. 
The  result  is,  that  whereas  the  steel  sud- 
denly cooled  in  water  may  be  broken  by 
a  sharp  blow,  in  other  words,  has  its 
range  of  resilience  greatly  diminished,  in 
the  latter  case  the  metal  has  its  rigidity 
greatly  reduced,  and  its  elastic  resilience 
exalted,  so  far  that  from  breaking  up  by 
a  blow  or  a  scratch,  it  is  at  once  both 
toughened  and  strengthened,  both  as 
against  steady  strains  and  impacts.  Nor 
are  the  conditions  of  the  process,  as  here 
described,  indispensable  to  the  result, 
except  in  the  case  of  very  large  masses, 
to  which  the  process  of  tempering, 
known  for  ages,  cannot  be  applied.  The 
sword  blade  heated  to  a  redness  and 
quenched  in  cold,  water  cannot  be  bent 
much  more  than  a  piece  of  glass  of  like 
size  and  form  without  fracture  ;  but  let 
the  hardened  steel  be  heated  slowly  over 
a  fire  until  it  is  hot  enough  to  cause  tal- 
low or  oil  to  blaze  off  from  its  surface, 
and  the  blade  be  now  quenched  again  in 
water,  the  result  is  the  well-known 
strength  and  elasticity  of  the  sword 
blade.  The  only  point  of  real  commu- 
nity between  the  two  processes  is  that 
the  change  in  physical  constitution  of 
the  metal  appears  to  take  place  at  about 
the  temperature  at  which  fixed  oils  begin 
to  volatilize  and  ignite.  But  the  steel 
is  a  compound,  and  a  most  peculiar  one. 
No  simple  metal,  so  far  as  experimental 
knowledge  yet  goes,  presents  the  faintest 
trace  of  those  phenomena  which  charac- 
terize more  or  less  the   chemical   com- 


TOUGHENED    GLAfiS. 


419 


pounds  of  iron  and  carbon  wherever  the 
percentage  of  the  latter  is  so  small  that 
it  is  all  in  combination  with  the  metal. 
Copper,  for  example,  when  heated  to  a 
full  red  or  to  any  high  temperature  be- 
low that,  and  suddenly  quenched  in 
water,  is  not  hardened  nor  yet  tempered, 
but  has  its  ductility  and  softness  in- 
creased to  the  utmost  and  its  elasticity 
reduced  to  the  lowest  point,  and  yet  the 
copper  may  contain  metalloids  in  some 
state  of  combination  and  in  almost  as 
large  proportions  as  in  the  carbon  in  the 
finest  steels.  There  therefore  seems  to 
be  but  a  faint  analogy,  and  that  probably 
merely  a  superficial  one,  between  the 
tempering  of  steel  and  this  so-called  tem- 
pering of  glass.  As  to  what  takes  place 
which  produces  the  physical  changes  in 
either  case  we  are  almost  in  equal  igno- 
rance. The  facts,  however,  as  regards 
steel  have  been  observed  and  recorded 
with  considerable  care  ;  not  so  those 
which  respect  this  process  of  La  Bastie, 
which  was  excited  so  much  wonderment 
and  some  expectations  as  to  useful  re- 
sults in  the  arts,  which  if  the  facts  so 
far  be  correctly  observed  are  likely  to 
prove  abortive.  We  can  scarcely  con- 
ceive any  economic  use  to  which  glass 
which  goes  to  pieces  upon  receiving  a 
rough  surface  scratch — however  other- 
wise resistant — can  be  put  with  any  ad- 
vantage. Glass  sheets  or  plates  for  sky- 
lights, conservatories,  lighthouse  lan- 
terns, &c,  would  be  of  little  use  against 
hail  and  storms  if  a  fragment  of  grit 
lodged  upon  their  surfaces  would,  when 
struck  or  rubbed,  be  liable  to  cause  them 
to  fall  to  powder.  The  burglar  would 
find  this  toughened  glass  in  the  plate  of 
a  jeweler's  window  quite  a  boon  ;  and 
if,  too,  it  should  prove  ultimately  that 
this  glass  cannot  be  cut  evenly  and  read- 
ily by  the  ordinary  plate-glass  diamond, 
that  difficulty  alone  will,  we  apprehend, 
prove  a  bar  to  its  application  to  glazing 
purposes  upon  any  large  scale.  Nov 
would  there  even  seem  to  be  much  ad- 
vantage in  the  application  that  has  been 
suggested  to  watch-glasses,  which  are 
always  liable  to  be  scratched,  and  in 
which  a  pocketful  of  glass  dust  would 
be  no  improvement  upon  three  or  four 
large  fragments.  Nor,  indeed,  whether 
the  fact  be  that  M.  de  La  Bastie  has  ob- 
tained any  patents  or  not,  but  yet  relies 
on  making  a  secret  of  the  proper  tem- 


perature of  the  glass  and  of  the  precise 
composition  of  his  hydrocarbon  bath, 
omitting  the  apocryphal  temperature  ne- 
cessary in  the  air,  does  it  seem  to  us 
that  any  considerable  advantage  can 
accrue  to  him  as  a  discoverer  beyond  the 
fame  of  his  having  been  the  first  obser- 
ver of  some  facts  of  great  physical  in- 
terest. Any  one  financially  interested 
would  soon  find  out  within  what  limits 
of  temperature  the  process  answered 
best.  The  range  is  very  narrow,  for  if 
the  facts  be  truly  recorded,  the  tempera- 
ture of  the  glass  cannot  be  higher  than 
that  at  which  the  glass  softens  so  that 
the  object  would  lose  its  form,  nor  lower 
than  that  at  which  glass  begins  to 
assume  the  rigid  condition.  For  the 
glasses  of  wholly  earthy  bases,  such  as 
plate  and  crown,  or  white  Bohemian 
glass,  it  will  therefore  be  below  a  bright 
red,  approaching  a  yellow  heat  in  day- 
light, and  for  flint  or  other  lead  glasses 
below  a  dull  red.  The  total  reduction 
in  temperature  of  the  glass  produced  by 
immersion  in  the  bath  would  appear  to 
be  a  range  of  between  600  deg.  and 
800  deg.  Fah.  Again,  as  to  the  bath,  it 
would  be  futile  to  suppose  that  there  can 
be  any  chemical  action  between  its  ma- 
terial and  that  of  the  glass  quenched  in 
it.  The  effect,  whatever  its  nature, 
must  be  a  purely  physical  one,  depend- 
ent  mainly  upon  the  boiling  point  and 
degree  of  viscidity  of  the  liquid  ;  and 
we  cannot  but  suppose  also  that  these 
would  be  hit  upon  by  a  few  trials.  We 
cannot  but  think,  therefore,  that  M.  La 
Bastie  would  be  likely  to  obtain  a  far 
better  harvest  in  the  way  of  honestly-at- 
tained fame  were  he  fully  and  in  the 
most  exact  manner  to  detail  for  the  use 
of  men  of  science  every  part  of  his  very 
singular  discovery.  It  is  one  which  in 
its  scientific  aspects  is  likely  to  arrange 
itself  as  one  of  the  most  important  guid- 
ing lights  amidst  the  darkness  of  our 
ignorance  as  to  the  physical  changes 
which  takes  place  by  change  of  tempera- 
ture in  matter.  The  loose  speculations 
which  have  found  their  way  freely  into 
print,  and  pretend  to  offer  a  theory  to 
account  for  the  results  of  the  process, 
are  but  darkening  counsel  by  words 
without  knowledge,  while  even  the  facts 
to  be  accounted  for  remain  but  imper- 
fectly described  ;  let  us  have  these  and 
we  can  scarcely  doubt  that  some  of  the 


420 


van  nostrand's  engineering  magazine. 


competent  scientific  men  of  Europe 
— such  as  Fizeau  or  Jamin,  or  M.  Luy- 
nes,  who  appears  to  be  already  engaged 
in  the  investigation  in  France,  or  Stokes, 
3Iiller,  and  Clarke  in  our  own  country 
— will  be  induced  to  institute  and  care- 
fully conduct  such  trains  of  experiment 
as  may  throw  some  additional  light,  and, 
so  far  as  it  may  ■  go,  determinate  in 
character,  upon  these  phenomena,  con- 
necting them  firmly  with  known  physi- 
cal laws.  Such  experiments  must  be 
conducted  by  refined  methods  and  ap- 
paratus, and  with  a  previous  knowledge 
of  physical  optics  that  very  few  men, 
indeed,  in  any  country  possess.  Had 
Brewster  and  Faraday  been  alive  we 
should  already,  probably,  have  received 
from  them  much  light.  The  former 
showed  how  the  lines  of  strain,  both  of 
tension,  and  compression,  in  prisms  of 
glass,  produced  by  applied  mechanical 
force,  might  be  rendered  visible  by  the 
aid  of  polarized  light.  Analogous  meth- 
ods and  others  equally  refined,  which  we 
do  not  venture  to  suggest,  will  no  doubt 
be  employed  by  such  physicists  as  we 
have  named,  and  who  may  undertake 
this  promising  investigation.  But  cer- 
tainly no  light  will  be  thrown  upon  it — 
theoretic  or  practical  —  by  the  experi- 
ments of  the  character  of  those  said  to 
have  been  made  by  Mr.  Kircaldy.  We 
have  the  highest  respect  for  that  gentle- 
man as  a  faithful  recorder  of  well-made 
and  trust-worthy  experiments  upon  the 
resistance  of  materials  of  construction  to 
extraneous  forces  as  ordinarily  applied, 
but  it  is  no  disparagement  either  to  him 
or  to  the  apparatus  with  which  he  oper- 
ates, to  say  that  he  is  not  the  man  for 
any  such  delicate  and  far-reaching  re- 
search as  is  needed  to  throw  any  light 
upon  this  matter.  The  experiments 
stated,  in  the  above  lecture,  to  have 
been  made  by  him  upon  the  transverse 
resistance  to  static  strain  of  this  class 
are  far  from  accordant,  arising  in  part 
no  doubt  from  the  difficulties  already 
referred  to  as  besetting  all  such  experi- 
ments upon  a  body  so  rigid  as  glass;  but, 
probably  much  more  from  the  specimens 
submitted  to  him  not  being  all  alike  in 
resisting  power,  a  circumstance  which 
suggests  that  the  process  itself  may  be 
one  deficient  in  uniformity  of  result.  A 
lecturer  who  treats  of  a  subject  so  full 
of  difficulty  as   that  of   the  La   Bastie 


process  might  be  expected  to  be  equally 
certain  and  conversant  with  the  facts  he 
adduces,  and  it  certainly  is  surprising  to 
find  it  stated,  as  the  basis  for  a  some- 
what obscure  theory  of  the  Rupert's 
drop,  that  glass,  like  water,  possesses 
the  property  of  expanding  in  volume 
whilst  jessing  from  the  liquid  to  the 
solid  condition.  Water  and  bismuth 
are  the  only  two  bodies  now  known  to 
increase  in  volume  upon  consolidation, 
and  glass  certainly  does  not  expand 
when  becoming  solid  from  fusion,  nor  is 
it  necessary  to  call  in  any  such  condition 
to  account  for  the  phenomena  of  the 
Rupert's  drop,  which  was  ably  treated 
of  by  Dr.  Brewster,  although,  as  it  ap- 
pears to  us,  much  remains  before  the  re- 
markable phenomena  presented  by  these 
drops  can  be  said  to  be  completely  un- 
derstood. 

The  most  pertinent  and  valuable 
remarks  that  were  made  were  those 
of  Mr.  Hartley,  of  Sunderland,  during 
the  discussion  of  this  lecture.  His  view 
that  the  de  La  Bastie  glass  is  no  more 
than  a  Ruj)ert's  drop  in  another  form  is, 
probably,  in  the  main  true,  yet  it  pre- 
sents great  difficulties,  for  how  the  un- 
stable equilibrium  of  a  Rupert's  drop 
which  has  been  shown  to  depend,  as  one 
of  its  conditions,  upon  the  perfect  form 
of  equilibrium  given  to  the  drop  by  the 
mode  of  its  production,  can  exist  in  a 
flat  rectangular  plate,  still  less  in  other 
and  more  irregular  forms,  it  is  difficult 
to  understand. 


Signaling  on  the  German  Rail- 
avays.  —  Several  railway  companies  in 
Germany  are  experimenting  with  differ- 
ent systems  of  signaling,  their  interest 
in  the  matter  being  quickened,  not  by 
complaints  from  the  ladies,  who  have 
long  enjoyed  the  privilege  of  Damen- 
coupes,  but  by  the  number  of  fires  which 
took  place  last  winter  in  sleeping  car- 
riages. Electric  communication  is  found 
to  be  not  only  costly  but  untrustworthy, 
and  the  so-called  "  English"  system  of 
signaling  with  a  line  is  not  considered 
satisfactory.  In  short  trains  experiments 
are  being  made  with  a  cord,  which  is 
carried  by  a  ball  and  socket  holder  up 
to  the  steam-whistle. 

—  Iron. 


ON   MOLECULES. 


421 


ON  MOLECULES. 

From  "Engineering." 


The  interest  elicited  by  our  remarks 
upon  some  of  the  phases  assumed  by 
water  in  one  of  its  conditions,  induces 
us  to  place  before  our  readers  some 
points  suggested  by  the  subject,  and  to 
state  the  views  held  by  the  most  ad- 
vanced investigators  with  regard  to  the 
ultimate  form  of  water  and  matter  gen- 
erally, and  its  relation  to  the  vaporous 
or  gaseous  state.  The  subject  is  one 
that  demands  our  closest  attention,  for, 
upon  a  thorough  elucidation  and  appli- 
cation of  the  beautiful  hypothesis  as  to 
the  structure  of  matter,  which,  of  late, 
under  the  name  of  the  molecular  theory, 
has  been  so  earnestly  studied  and  so 
thoroughly  elaborated,  much  of  empiric 
practice  in  the  application  of  motive 
power  would  be  swept  away  with  a  bene- 
fit to  science  and  humanity  not  to  be 
lightly  estimated.  In  the  course  of  this 
article  we  shall,  in  the  interest  of.  junior 
students,  carefully  avoid  all  mathemati- 
cal formula,  and  present  the  subject  in 
its  barest  outlines,  that  he  who  runs  may 
read. 

It  is  possible  to  conceive  of  two  states 
in  which  matter  might  exist,  and  from 
the  times  of  the  ancient  Greek  philoso- 
pher down  to  the  present  day,  these  two 
states  have  formed  subjects  for  discus- 
sion— indeed,  our  most  modern  theory 
may  be  said  to  be  merely  a  greatly  im- 
proved form  of  one  propounded  ages 
ago  hy  Democritus,  and  in  its  essential 
conception  the  very  opposite  of  that  set 
forth  byAnaxagoras.  The  latter  taught 
that  all  matter  was  incapable  of  infinite 
division,  while  the  former  held  that, 
after  a  certain  extent  of  divisibility  had 
been  reached,  matter  could  be  no  longer 
subdivided,  and  the  small  particles  ar- 
rived at  called  atoms— literally  that 
which  cannot  be  cut — would  be  the 
minutest  possible  in  the  universe.  This 
is  now  the  almost  universally  received 
theory,  and  by  its  aid  certain  phenomena 
can  be  explained,  for  which  upon  no 
other  known  hypothesis  could  any  ex- 
planation be  suggested. 

The  term  atom  has  been  exclusively 
appropriated  by  the  chemist,  while  the 
mathematician   and    physicist   has   pre- 


ferred to  adopt,  or  share  with  him,  the 
word  molecule  to  signify  those  ultimate 
constituents  of  matter  upon  whose  mo- 
tions and  relations  depends  the  various 
states  of  all  bodies,  solid,  liquid  and 
gaseous  ;  their  temperature  ;  and  other 
properties. 

The  word  particle  is  also  freely  made 
use  of  as  involving  no  hypothesis,  and 
meaning  simply  a  small  part  of  anybody. 
Molecule  has  been  defined  by  Maxwell  as 
"  the  smallest  possible  portion  of  a  par- 
ticular substance;"  and,  again,  as  "that 
small  portion  of  the  substance  which 
moves  as  one  lump  in  the  motion  of  agi- 
tation." 

Every  substance  is  now  supposed  to  be 
composed  of  an  immense  number  of 
molecules,  which,  even  in  the  solid  state, 
are  never  entirely  at  rest,  and,  in  the 
gaseous,  are  in  a  state  of  perpetual  vio- 
lent commotion,  rushing  about  in  straight 
lines  in  all  directions  with  inconceivable 
rapidity  ;  and  it  is  this  perpetual  bom- 
bardment, as  it  has  been  called,  by  these 
little  particles  that  explains  the  known 
pressure  of  gas  on  the  walls  of  any  con- 
taining vessel,  the  incessant  impact  of 
the  molecules  producing  the  effect  of  one 
continual  pressure  just  as  upon  the  eye 
a  succession  of  rapid  flashes  of  light 
have  the  effect  of  one  continuous  flame. 
Of  course  the  molecules,  although  they 
are  supposed  to  be  separated  for  a  very 
considerable  distance  from  one  another, 
are  perpetually  meeting  and  rebounding, 
and  thus  their  velocity  is  interfered 
with,  but  there  is  a  certain  residuum  of 
speed,  left,  resulting  in  a  mean  velocity 
for  the  whole.  This  mean  velocity  indi- 
cates also  temperature,  and,  for  the  same 
substance  at  one  pressure,  the  same  mean 
velocity  is  always  accompanied  by  the 
same  temperature.  But  every  different 
substance  has  a  mean  velocity  of  its  own 
for  a  given  temperature,  and  these  have 
all  been  calculated,  such  is  the  extreme 
nicety  with  which  the  hypothesis  is  being 
worked  out.  Taking,  for  instance,  one 
of  the  constituents  of  water — hydrogen 
— in  the  form  of  gas  its  mean  velocity 
has  been  calculated  by  Joule  at  over  a 
mile  hi  one  second — a  speed  far  greater 


422 


VAN   NOSTRAND'S   ENGINEERING  MAGAZINE. 


than  anything  we  have  any  practical 
knowledge  of — far  above  that  obtained 
in  artillery  practice.  The  exact  velocity 
is  6,097  feet  per  second,  at  a  temperature 
of  32  deg.  Fah.,  and  at  the  ordinary 
pressure  of  the  atmosphere.  A  daring 
attack  has  been  made  upon  the  actual 
size  of  the  molecules  with  a  result  that 
has  every  element  of  probability  in  its 
favor.  Taking  the  theorem  of  Classius 
as  a  basis,  Thompson  has  calculated  that 
a  cubic  inch  of  gas  contains  1023  mole- 
cules, i.  e.,  a  hundred  thousand  million, 
million,  million  ;  and  he  deduced  from 
certain  optical  phenomena  in  connexion 
with  the  thickness  of  soap  bubbles,  from 
the  electrical  conductivity  of  metals,  and 
from  other  considerations,  that  the  di- 
ameter  of    a   molecule   was   about   the 

of  an  inch. 

500,000,000 

To  convey  some  idea  of  the  amount 
of  these  magnitudes  he  says  :  "  If  we 
conceive  a  sphere  of  water  as  large  as  a 
pea  magnified  to  the  size  of  the  earth, 
each  molecule  being  magnified  to  the 
same  extent,  the  magnified  structure 
would  be  coarser-grained  than  a  heap  of 
small  lead  shot,  but  less  coarse-grained 
than  a  heap  of  cricket  balls." 

It  will  be  observed  that  we  do  not 
specify  what  gas  this  is,  because  a  still 
further  development  of  the  theory  shows 
every  gas  at  a  given  temperature  and 
pressure  to  contain  the  same  number  of 
molecules,  having,  however,  different 
weights,  and  different  mean  velocities. 
But — and  here  comes  the  means  of  re- 
ducing the  theory  to  a  practical  issue — 
the  weights  and  the  velocities  so  counter- 
balance one  another  that  the  resulting 
energy  is  the  same  for  every  perfect  gas. 
For  this  argument  the  perfect  equality 
in  size  of  every  molecule  of  one  kind  of 
substance  is  assumed  ;  that  they  are  so 
equal  is,  however,  readily  proved.  Gra- 
ham has  shown  how  gases  can  be  sepa- 
rated by  diffusion  through  a  porous  sep- 
tum ;  but,  if  the  sizes  of  the  molecules 
of  our  gas  varied,  it  would  be  possible 
'by  successive  filtrations  to  get  different 
portions  of  the  gas  with  molecules  of 
different  sizes.  The  density  would  then 
become  unequal,  and  their  combining 
powers  different;  but  whether  this  sepa- 
ration is  looked  for  in  nature  or  by  the 
hand  of  man,  it  cannot  be  found.     Let 


hydrogen  be  taken  from  water,  from  a 
hydro-carbon,  or  from  a  fallen  meteor, 
its  properties,  energy,  and  density,  are 
always  alike  ;  and  so  with  all  gases.  A 
very  convincing  proof  of  the  molecular 
state  of  matter  may  be  found  by  taking 
a  cubic  inch  of  water,  and,  by  the  appli- 
cation of  heat,  converting  it,  in  a  closed 
vessel  of  one  cubic  foot  capacity,  into 
steam.  It  will  apparently  fill  it.  Now 
if  this  steam  were  an  expanded  solid  it 
would  fill  the  space  entirely  to  the  ex- 
clusion of  all  other  matter.  Does  it  so 
behave  ?  It  does  not.  In  the  first  place- 
the  result  is  little  interfered  with,  wheth- 
er the  air  is  first  exhausted  or  not  ;  for 
the  steam  can  be  made  to  fill  it  though 
the  air  be  there  ;  an  inch  of  ether  may 
be  added,  and  its  vapor  rises  and  fills 
the  space  as  though  nothing  were  there; 
an  inch  of  alchohol  could  be  similarly 
vaporized  as  though  nothing  were  pres- 
ent. The  same  thing  could  be  done  with 
other  volatile  substances  ;  and  we  could 
go  on  adding  liquid  after  liquid,  and 
evaporating  all  into  the  space  at  one 
time.  This  is  very  striking  proof  that 
the  liquid  in  vaporizing,  has  had  its  par- 
ticles widely  separated,  and  so  left  room 
for  other  particles  to  be  disseminated 
within  its  interestices.  This  position  is- 
still  further  strengthened  by  observation 
of  the  pressure  ;  each  liquid  exerts  a 
pressure  in  itself,  and  if  a  suitable  appa- 
ratus be  provided  to  receive  the  vapor- 
ized products  and  connected  with  a 
barometer,  it  will  be  found  that  the 
pressure  of  the  mixed  vapor  is  just  the 
sum  of  that  of  the  individual  vapors. 

Having,  now  indicated  the  state  of 
matter  in  the  form  of  gas,  that  of  liquids 
and  vapors  may  occupy  our  attention. 
In  a  liquid  the  various  motions  of  the 
molecules,  vibratory,  rotatory  and  rec- 
tilinear, exist  in  a  modified  form  ;  the 
rectilinear  is  slight,  while  the  other  two 
are  not  much  interfered  with.  If  heat 
be  applied  the  motion  of  translation  is 
increased  as  in  gases,  and,  at  certain 
temperatures,  different  for  most  sub- 
stances, vapor  begins  to  form.  Water 
gives  off  vapor  at  all  temperatures  ;  but 
this  is  not  the  case  with  all  bodies,  mer- 
cury, for  instance,  requiring  a  tempera- 
ture above  10  deg.  C.  before  it  vaporizes. 
The  dynamical  theory  of  heat  explains 
how  this  change  of  state  occurs.  The 
molecules   being   in   rapid   motion    and 


ON  MOLECULES. 


423 


tossed  about  in  all  directions  are  pre- 
vented on  all  points  but  the  surface  of 
the  liquid  from  escaping  ;  but  here  they 
meet  with  no  resistance  beyond  that 
mutual  attraction  which  exists  among 
the  molecules  in  the  liquid  state.  But 
at  the  surface  it  will  happen  that  some 
of  them,  by  a  combination  of  vibratory, 
rotatory  and  progressive  motions,  will  be 
ejected  with  sufficient  energy  to  carry 
them  out  of  the  sphere  of  the  attractive 
force  of  the  neighboring  molecules,  and 
they  then  assume  the  characteristics  of 
gas,  moving  with  the  velocity  described, 
and,  in  this  form  are  truly  particles  of 
vapor.  If  the  liquid  be  enclosed  in  some 
vessel,  these  vapor  molecules  in  their 
motion  of  translation  will  at  times  strike 
the  surface  of  the  liquid  and  become  im- 
prisoned through  the  attractive  force  of 
the  molecules,  to  be,  however,  replaced 
by  other  projected  molecules.  This 
process  will  continue,  and  the  difference 
between  the  number  of  molecules  sent 
out  by  the  liquid  and  those  caught  back 
again  becomes  less  and  less  till  equili- 
brium is  reached.  The  vapor  is  then 
said  to  be  saturated,  and  its  elasticity, 
under  the  circumstances,  at  its  greatest 
point ;  or,  in  other  words,  the  vapor  ex- 
erts its  maximum  tension  at  the  given 
temperature  and  pressure.  If  then  we 
attempt  to  decrease  the  volume  by  press- 
ure, a  portion  will  be  liquefied  according 
to  the  amount  of  pressure  ;  but  the  ten- 
sion will  remain  the  same.  If,  however, 
we  pursue  the  opposite  course  and  en- 
deavor to  increase  the  volume,  we  shall 
succeed,  and  the  tension  will  be  lessened; 
and  the  more  we  extend  the  volume  the 
more  exactly  do  we  find  it  proportional 
to  a  reduction  of  pressure  till  at  last  it 
conforms  to  Boyle's  law,  which  states 
that  in  perfect  gases  the  volume  is  ex- 
actly inversely  proportional  to  the  press- 
ure. 

But  this  want  of  accordance  of  vapors 
at  their  highest  state  of  tension  with 
gases  under  ordinary  conditions  of  press- 
ure, &c,  is  more  apparent  than  real,  for 
it  is  found  that  the  liquefiable  gases, 
such  as  carbonic  acid,  nitrous  oxyde,  &c, 
when  very  gi-eatly  compressed,  also  fail 
to  agree  with  Boyle's  law,  and  act  almost 
the  same  as  vapors.  It  must  not  be  for- 
gotten that  these  changes  of  volume 
produce  important  calorific  effects,  as 
will  readily  be  imagined  when  the  molec- 


ular action  is  mentally  followed.  The 
pressure  being  now  seen  to  be  simply  the 
sum  of  the  energies  of  a  multitude  of 
impacts,  it  follows  that  if  these  impacts 
take  place  upon  some  body  that  gives 
way  to  the  shock,  the  moving  force  of 
these  molecules  will  be  reduced  by  just 
so  much  as  the  body  gives  way  to  their 
violence;  that  is  to  say,  heat  or  molecular 
motion  will  be  converted  into  visible 
motion.  And  upon  experimental  in- 
quiry, such  is  the  case,  the  vapor  or  gas 
in  expanding  loses  heat,  and  if  the  ex- 
pansion be  great,  the  cold  produced  may 
be  most  severe.  On  the  other  hand, 
when  a  gas  is  compressed,  the  molecules, 
instead  of  losing  their  velocity,  have  an 
additional  quantity  imparted  to  them, 
and  the  predicted  and  observed  result  is 
a  manifestation  of  heat,  i.  e.,  motion  is 
converted  into  heat.  In  the  production 
of  steam  the  atmosphere  has  to  be  push- 
ed on  one  side  as  it  were,  or  the  piston 
has  to  be  forced  away  from  it  :  here 
again  heat  disappears,  and  is  rendered 
latent.  So  it  is  through  the  whole  range 
of  nature.  Where  heat  or  energy  is  lost 
sight  of  it  is  not  destroyed  ;  it  is  simply 
stored  up  for  future  use,  or  converted 
into  motion.  Physical  energy  of  every 
kind— chemical  action,  electrical  action 
— is  convertible  into  heat,  and,  as  Thomp- 
son has  pointed  out,  their  tendency  is 
continuously  in  that  direction.  "  There 
is  then  in  the  present  state  of  the  known 
world  a  tendency  towards  the  conversion 
of  all  physical  energy  into  the  form  of 
heat." 

Our  brief  survey  of  this  subject,  which 
possesses  such  a  close  and  wonderful  in- 
terest to  every  student  of  natural  phe- 
nomena, may  suitably  close  with  a 
shadowing  forth  of  the  result  which 
modern  speculation  and  experiment  in- 
evitable lead  to,  and  this  we  cannot  do 
more  explicitly  than  in  the  words  of 
Rankine,  which  we  extract  from  the 
Philosophical  Magazine  : 

"  Heat  moreover  tends  to  diffuse  itself 
uniformly  by  conduction  and  radiation 
until  all  matter  shall  have  acquired  the 
same  temperature."  , 

"  There  is  consequently.  Professor 
Thompson  concludes,  so  far  as  we  under- 
stand the  present  condition  of  the  uni- 
verse, a  tendency  towards  a  state  in 
which  all  physical  energy  will  be  in  the 
state  of  heat,  and  that  heat  so  diffused, 


424 


van  nostrand's  engineering  magazine. 


that  all  matter  will  be  at  the  same  tem- 
perature, so  that  there  will  be  an  end  of 
all  physicial  jmenomena. 

"  Vast  as  this  speculation  may  seem 


it  appears  to  be  soundly  based  on  experi- 
mental data,  and  to  represent  truly  the 
state  of  the  universe  so  far  as  we  know 
it." 


RIVERS  AND  MANUFACTORIES. 

From  "The  Engineer." 


One  of  the  most  difficult  legislative 
problems  in  existence  lies  in  framing 
good  laws  for  the  purification  of  a  manu- 
facturing country.  It  is  apparently  irri- 
jDOssible  to  draw  up  enactments  of  this 
kind  which  will  not  bear  hardly  on  large 
sections  of  the  community.  The  welfare 
of  the  few  should,  as  a  matter  of  course, 
be  abandoned  for  the  good  of  the  many; 
but  the  few  will  fail  to  accept  the  ne- 
cessity with  complaisance.  For  this 
reason,  the  utmost  care  should  be  taken 
to  dissever  the  operation  of  the  law  from 
any  appearance  of  hai-shness — by  no 
means  an  easy  task  to  perform.  But 
there  is  a  far  wider  and  deeper  question 
lying  beneath  the  surface  of  the  whole 
matter.  It  is  quite  within  the  range  of 
possibility  to  legislate  apparently  for 
the  good  of  the  many,  and  with  the  best 
intentions  possible,  and  yet  to  fail  to  at- 
tain the  object  sought.  And  it  is  to 
this  phase  of  the  question  that  we  wish 
to  direct  particular  attention. 

Those  who  have  devoted  any  thought 
to  the  progress  of  sanitary  legislation  in 
this  country  or  abroad,  can  scarcely 
have  failed  to  see  that  the  movement  in 
favor  of  the  purification  of  rivers  and 
the  disposal  of  sewage  is  a  comparatively 
new  thing  in  the  world.  Twenty-five 
years  ago  people  said  very  little  about 
sewage,  and  the  fact  that  a  river  was  not 
clean  called  forth  no  comments.  So  long 
as  sewage  was  got  out  of  a  town  and 
into  a  stream,  local  authorities  were 
quite  contented,  and  Parliament  took  no 
trouble  in  the  matter.  As  the  country 
grew  in  wealth  and  luxury,  and  the  de- 
sire for  comfort  augmented,  better  sys- 
tems for  cleaning  our  towns  and  our 
houses  sprang  into  existence,  and  sons 
regarded  with  horror  that  in  which 
their  fathers  saw  nothing  objectionable. 
This  was  partly  due  to  the  growth  of  re- 
finement in  the  nation,  and  the  feeling 
would  no  doubt  have  modified  the  course 


of  legislation  in  any  case.     But  a  more 
powerful  argument  operated  forcibly  to 
render  the  interference  of  Parliament  in 
sanitary  matters  essential.     Great  cities 
started  up  on  the  banks  of  streams,  and 
as  the  streams  received  all  the  refuse  of 
the  cities,  their  pollution  was  augmented 
until    it    became    intolerable    to   those 
who  dwelt   on  their  banks.     Then  the 
nation  begun  to  assert  that  the  rivers  of 
the    country   must   be   kept   pure  ;  and 
this  is  really  the  object  had  in  view  when 
sewage  irrigation  or  precipitation  is  em- 
ployed or   demanded.     The   great    sani- 
tary struggle  of  the  day  is,  in  fact,  to 
keep    our   rivers    unpolluted.      Now,   it 
never  was  disputed  until  within  a  com- 
paratively recent  period,  that  rivers  are 
the  great  cleansers  of  a  country  ;  and  to 
this  moment  it  is  almost  impossible  to 
see  how  any  substitute  for  their  opera- 
tion in  this  capacity  can  be  found.     So 
long  as  the  people  of  Great  Britain  con- 
fined their  attention  to  agricultural  and 
pastoral  pursuits  there  was   little   diffi- 
culty in  keeping  the  rivers  clean.     In  the 
first" place,  great  cities  are  impossible  in 
a  pastoral   country,    and   whatever  the 
population  might  be  as  a  whole,  the  im- 
purities to  be  disposed  of  proper  to  that 
population  would  be  diffused  over  a  large 
area,  and  no  concentration  of  filth  would 
exist.     But  Great  Britain   is  not  a  pasto- 
ral, or  agricultural,  but  a  manufacturing 
country.      Great  cities  have   come  into 
existence  within  her  shores,  and  sewage 
is  poured   into  her   streams,    in  certain 
localities,  in  such  volumes  that  oxydation 
and  precipitation  by  natural  causes  are 
quite   incompetent    to   keep    our   rivers 
pure.     Then  the  law  steps  in,  and  com- 
pels us  to  refrain  from  throwing  sewage 
into  our  rivers  ;  and  so,  instead  of  con- 
tinuing to  use  the  natural  cleansers  of 
the  country,   we  are  compelled  to  seek 
artificial  means  of  disposing  of  sewage. 
We  shall  not  enter  here  into  any  consid- 


RIVERS   AND   MANUFACTORmS. 


425 


eration  of  the  difficulties  which  attend 
this  operation — they  are  familiar,  no 
doubt,  to  the  greater  number  of  our 
readers  ;  nor  shall  we  deal  with  non- 
manufacturing  towns,  the  prosperity  of 
which  can  be  little  affected  in  any  way 
by  the  operation  of  sanitary  enactments. 
In  the  case  of  manufacturing  centres, 
however,  matters  assume  a  very  different 
aspect,  and  in  dealing  with  them  the  ut- 
most caution  is  essential  to  avoid  the 
passing  of  laws  which  may  either  prove 
a  dead  letter  or  cause  serious  injury  to 
the  property  of  our  manufacturers. 

If  the  worst  comes  to  the  worst,  the 
inhabitants  of  a  town  can  always  get  rid 
of  what  may  be  termed  pure  sewage.  So 
far  as  dwelling  houses  are  concerned,  all 
that  comes  from  them  may  be  turned  on 
to  the  land,  and  will  assist  to  grow  crops, 
and  promote  fertility.  But  not  so  with 
manufacturers.  It  is  quite  possible  to 
pollute  sewage,  and,  in  certain  cases,  the 
refuse  cast  by  manufacturers  into  sewers 
may  be  sufficiently  great  in  quantity  and 
deleterious  in  quality  to  render  large 
volumes  of  sewage  utterly  unfit  to  put 
upon  land  ;  and  even  if  the  evil  does  not 
attain  quite  to  this  point,  it  is  certain 
that  in  many  cases  the  quantity  of  sew- 
age is  impaired  by  the  refuse  mixed  with 
it.  The  spent  alkali,  for  example,  from 
paper  works,  requires  to  be  enormously 
diluted  before  it  can  be  put  upon  land 
without  destroying  grass.  It  would, 
perhaps,  be  possible,  under  certain  con- 
ditions, for  a  Local  Board,  to  prohibit 
manufacturers  from  pouring  certain  pro- 
ducts into  the  sewers  of  a  town.  For 
example,  let  it  be  supposed  that  the  sew- 
age of  a  town  is  rented  from  a  Local 
Board,  on  the  understanding  that  the 
sewerage  is  a  valuable  commodity.  If, 
then,  a  manufacturer  turns  in,  say,  a 
quantity  of  sulphuric  acid,  he  may  prac- 
tically render  the  sewerage  poisonous  to 
grass  for  the  time,  and  so  inflict  serious 
injury  on  the  tenant  of  the  sewage  farm. 
There  is  no  reason,  so  far  as  justice  is 
concerned,  why  the  Local  Board  should 
not,  in  such  a  case,  insist  that  the  manu- 
facturer must  not  pour  sulphuric  acid 
into  the  sewers.  Up  to  the  present  the 
poiut  has  hardly  been  raised,  because 
the  rainfall  and  sewage  have  not  been 
separated  ;  but  let  a  comparatively  small 
town,  with  a  few  large  paper  mills  or 
dye  works,  once  have  the  separate  system 


of  drainage,  and  send  only  concentrated 
sewage  on  to  an  irrigation  farm,  and 
complaints  would  quickly  be  heard.  In 
such  a  case,  what  is  the  wretched  manu- 
facturer to  do  ?  He  cannot  use  the  town 
drains,  and  he  must  not  use  the  river. 
The  reply  will  be  that  he  must  either  hit 
on  some  means  of  neutralizing  the  noxi- 
ous qualities  of  the  effluent  from  his 
works,  or  he  must  abandon  the  business 
altogether.  In  the  last  alternative,  thus 
stated,  we  have  the  objectionable  side  of 
sanitary  legislation.  In  a  word,  it  is 
possible  to  make  laws  which  will  ruin 
given  branches  of  trade.  Such  laws  are 
intended  for  the  good  of  the  many,  but 
although  they  may  promote  health  they 
may  be  inimical  to  wealth,  and  in  that 
case,  however  good  the  intentions  of  the 
law-makers  may  be,  the  practical  results 
of  the  operations  of  their  enactments 
will  be  most  unsatisfactory. 

It  is  not  difficult  to  cite  instances  in 
which  it  is  impossible  to  keep  streams 
pure  and  carry  on  certain  branches  of 
trade  at  the  same  time.  For  example, 
the  water  discharged  from  copper  mines 
is  Usually  excessively  bad,  and  no  means 
have  yet  been  discovered  of  rendering 
it  inoxious,  which  are  at  once  moderate 
in  cost  and  universally  applicable.  Some- 
thing may  be  done  under  certain  circum- 
stances, by  precipitating  the  copper  on 
iron  plate,  as  at  the  Amlwch  mines,  in 
North  Wales,  but  even  then  the  water 
discharged  from  the  settling  pits  is  des- 
tructive to  fish.  We  need  hardly  say  that 
it  cannot  be  put  upon  land.  There  is 
no  possible  means  of  disposing  of  it  but 
by  sending  it  into  the  nearest  river. 
The  result  of  an  enactment  that  the 
water  from  a  given  copper  mine  must 
not  go  into  a  river  would  be  that  the 
mine  must  be  closed.  Would  it  be  pru- 
dent to  enforce  the  law  in  such  cases ': 
Might  it  not  be,  altogether  better  for  the 
nation,  as  a  whole,  that  all  the  fish  in  a 
given  stream  should  be  killed,  and  that 
the  copper  mine  should  continue  in  oper- 
ation? We  shall  not  stop  to  answer 
the  question.  Those  who  advocate  the 
purification  of  our  streams  at  any  price 
are  very  fond  of  asserting  that  if  only 
manufacturers  will  but  try  they  can 
easily  purify  their  effluent,  and  pointing 
triumphantly  to  the  operation  of  the 
Alkali  Act,  they  say  that  what  can  be 
done   to  purify  the   air  cau  be   done  to 


426 


VAN  nostrand's  engineering  magazine. 


purify  the  water.  Now,  we  are  not 
arguing  that  manufacturers  should  be 
left  to  follow  their  own  sweet  will  and 
pollute  streams  as  they  please.  Our  ob- 
ject is  not  to  deprecate  sanitary  legis- 
lation, but  to  urge  caution  in  making  and 
putting  sanitary  laws  into  force.  The 
good  sense  of  the  country  may  be  relied 
on  to  a  great  extent  to  protect  trade  in- 
terests, but  it  is  not  all-powerful,  and 
nothing  would  tend  more  to  retard  pro- 
gress in  the  right  direction  than  first 
passing  severe  sanitary  laws  and  then 
enforcing  them  without  discrimination. 
In  spite  of  all  that  has  been  said  about 
the  purification  of  the  air,  even  those 
who  are  least  particular  will  agree  with 
us  that  the  atmosphere  of  Widness  is  not 
delicious.  To  make  the  air  of  this  town 
good  and  wholesome,  it  would,  as  mat- 
ters stand,  be  essential  to  shut  up  the 
chemical  works  for  which  the  place  is 
famous.  We  need  not  say  that  to  use 
the  law  for  such  a  purpose  would  be  un- 


justifiable and  impolitic  to  the  last  de- 
gree. Again,  what  would  become  of  the 
iron  trade  of  the  country  if  a  vigorous 
law  were  put  in  operation  to  compel  fur- 
naces to  consume  their  own  smoke  ? 
Yet  it  would  not  be  more  difficult  to 
make  iron  with  smokeless  furnaces  than 
it  is  to  avoid  the  pollution  of  rivers  by 
feltmakers,  dye  works,  chemical  works, 
or  paper  mills.  The  fact  appears  to  be 
that  it  is  utterly  impossible  in  a  manu- 
facturing region  to  enjoy  all  that  purity 
of  air  and  water  which  may  be  found  in 
agricultural  districts. 

It  is  proper  that  Parliament  should  in- 
terpose to  keep  the  pollution  of  our 
streams  and  our  atmosphere  within  rea- 
sonable limits,  but  the  existing  degree 
of  pollution  of  either  would  not  justify 
the  making  of  laws  which  might  cripple 
the  operations  of  the  manufacturers  to 
whom  Great  Britain  is  so  largely  in- 
debted for  her  prosperity. 


LIERNUR' S  IMPROVED  SYSTEM  OF  TOWN  DRAINAGE. 


From  "  Journal  of  Society  of  Arts." 


Public  opinion  is  daily  growing  strong- 
er and  stronger  in  favor  of  legislation 
to  prevent  or  lessen  the  scourge  of  dis- 
ease that  arises  from  defective  drain- 
age, and  to  stop  the  pollution  of  our 
streams.  It  is  particularly  fitting,  there- 
fore, that  through  the  medium  of  this 
Society  attention  should  be  drawn  to  a 
system  of  drainage  which,  it  is  averred, 
is  the  complete  solution  of  the  much 
vexed  problem,  sanitarily  and  technically, 
and  it  is  anticipated  financially  also. 

It  is  especially  fortunate  that  the  only 
part  of  the  Liernur  system,  the  practi- 
cability of  which  originally  admitted  of 
any  doubt,  has  now  been  extensively  in 
operation  upon  the  Continent  for  between 
three  and  four  years.  The  fact  that  it 
is  successful  in  the  highest  degree  will 
be  apparent  when  I  mention  that  every- 
where it  has  been  put  into  operation  it 
has  received  the  highest  approbation, 
testified  in  a  practical  way  by  its  exten- 
sion, and  that  amongst  the  evidence  that 
may  be  referred  to  are  such  reports  as 


those  of  the  Medical  Commission  ap- 
pointed by  the  Kingdom  of  Saxony,  the 
International  Medical  Congress  of  Vien- 
na, and  the  whole  of  the  twelve  Medical 
Inspectors  of  Holland.  These  last,  in  a 
report  to  the  Minister  of  the  Interior, 
declare  unanimously  that  "  sanitarily  and 
for  the  convenience  of  the  inhabitants,, 
the  Liernur  system  is  the  best  of  all  sys- 
tems hitherto  known."  This  favorable 
evidence  has  now  been  confirmed  by 
numerous  deputations  and  commissions 
from  England. 

My  object,  however,  is  not  to  string* 
together  such  evidence,  but  to  give  to 
the  Society  a  description  of  the  prin- 
ciples and  technical  details  of  the  sys- 
tem. 

The  end  and  object  of  sewerage  works 
is,  or  should  be,  to  remove  the  liquid 
refuse  of  a  town  in  such  a  way  that  there 
cannot  possibly  be  any  pollution,  by 
deleterious  matters,  of  soil,  air,  or 
stream,  and  in  such  a  way  that  no  offence 
is  given  to  sight  or  smell,  and  no  habits 


liernur' s  improved  system  of  town  drainage. 


427 


imposed  upon  the  people  which  are 
likely  to  be  neglected  by  even  the  lower 
orders  of  the  population. 

It  will  be  readily  admitted  that  the 
systems  in  use  in  this  country  cannot 
pass  the  standard  thus  laid  down.  The 
fault  of  all  of  them  is  that  in  one  great 
common  sewer  there  is  an  indescribable 
and  unmanageable  mixture  of  nastiness, 
which  pollutes  both  soil  and  atmosphere, 
and  which,  with  the  exception  of  those 
few  cases  where  effective  irrigation-farm- 
ing has  been  introduced,  pollutes  streams 
as  well.  Irrigation  has  been  pointed  to 
as  the  great  panacea  of  the  sewage  evil, 
forgetful  of  the  fact  that  it  leaves  un- 
touched the  two  great  evils  of  polluted 
air  and  soil,  which,  as  much  as  anything, 
affect  the  health  of  the  people. 

The  Liernur  system,  on  the  other  hand, 
is  founded  on  the  old  Napoleonic  maxim, 
"  Beat  the  enemy  in  detail " — "  Divide 
and  conquer."  In  other  words,  never  al- 
low any  nuisance  to  get  such  accumula- 
tive power  that  it  cannot  be  kept  under 
perfect  control. 

Primarily,  Captain  Liernur  lays  down 
the  principle  that  nothing  of  a  seriously 
polluting  character  should  ever  be  allow- 
ed to  enter  the  common  sewers.  For 
this  purpose  it  is  evident  that  not  only 
must  night-soil,  and  the  waste  refuse  of 
trade  be  kept  out,  but  also  the  fatty  and 
sedimentary  products  which  find  their 
way  down  kitchen  sinks,  and  the  detritus 
from  our  streets.  If  this  be  done,  it  is 
evident  that  the  sewer  water  by  itself, 
though  not  bright  and  sparkling,  will 
contain  in  it  no  materials  of  disease  to 
contaminate  either  soil  or  air,  and  will 
scarcely  be  dirtier  than  that  which  flows 
from  every  brooklet  in  the  country  after 
a  rainfall. 

To  keep  street  detritus  entirely  out  of 
sewers  it  is  necessary  that  the  gullies 
should  he  provided  with  apparatus  to 
detain  it.  Such  an  apparatus,  it  will  be 
seen  by  this  drawing,  consists  simply  in 
an  iron  bucket,  into  which  the  water, 
coming  from  the  street,  can  enter  only 
by  a  funnel,  and  from  which  it  can  only 
escape  into  the  sewer  by  filtering  up- 
wards through  a  thick,  loosely-woven 
straw  mat,  the  mud  in  suspension  being 
simply  cast  down  into  the  box. 

This  mud  can  be  easily  removed  by 
scavengers,  the  bucket  in  which  it  is 
contained  being  lifted  and  emptied  into 


a  cart.  According  to  the  pavement  em- 
ployed will  be  the  frequency  of  this 
emptying  process.  In  the  ideal  town  of 
which  I  am  speaking,  Captain  Liernur 
would  select  the  improved  wood  pave- 
ment, as  being  noiseless,  affording  a. 
good  foothold  for  the  horses,  offering  a 
free  scope  for  evaporation  and  percola- 
tion, and  as  being  easily  scavenged  by 
machinery.  On  such  a  pavement  the 
detritus  would  be  necessarily  small. 

To  those  who  would  advocate  letting 
the  mud  into  the  sewers  I  would  say,  re- 
member that  it  must  be  dealt  with  some- 
where, either  by  separating  it  from  the 
sewage  at  the  outfall,  or  dredging  it  out 
of  the  river.  Is  it  not  better,  therefore, 
to  deal  with  it  at  the  start,  and  prevent 
not  only  its  depositing,  choking  and  foul- 
ing in  the  sewers,  but  its  complicating 
the  sewage  problem  thereafter.  At  Bel- 
fast, for  instance,  they  have  periodically 
to  break  open  the  sewers  to  clean  out 
the  mud. 

Next,  it  is  requisite  to  keep  out  of  the 
sewers  all  the  waste  products  of  industry. 
For  this  purpose  it  is  absolutely  neces- 
sary that  legislation  should  compel  all 
manufacturers  to  clear  their  water  before 
passing  it  into  the  sewers.  The  reason 
for  this,  on  the  principle  "  divide  and 
conquer,"  is  obvious.  It  is  easier  to  deal 
with  substances  of  which  we  know,  or 
can  easily  ascertain  the  component  parts, 
and  the  different  variations  that  may  oc- 
cur, than  when  mixed  with  sewage  and 
waste  of  all  other  kinds.  In  the  latter 
case  it  becomes  an  indescribable  mixture 
no  man  can  master,  and  for  which  if  one 
day  a  golden  receipt  were  found,  the 
next  day's  variation  would  render  it  use- 
less. The  question  as  to  who  should 
bear  the  cost  of  separate  purification  is 
one  between  the  manufacturer  and  the 
authorities,  in  no  way  affecting  the  prin- 
ciple laid  down.  As  a  rule,  and  as  has 
now  been  found  out  by  practice  (see  the 
working  of  the  Alkali  Act  and  the  puri- 
fication of  dye  and  bleach  works,  as 
exemplified  by  Mr.  Thorn  at  the  Society's 
Rivers'  Pollution  Conference),  I  believe 
it  would  pay  the  manufacturer,  and  un- 
less legislation  compels  him  to  do  the 
work,  there  is  no  possible  solution  of  the 
sewage  problem. 

The  question  for  the  engineer  is,  how 
to  test  the  obedience  to  the  law.  Captain 
Liernur's  plan  is  simple.     On  the  drain- 


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VAN   NOSTRAND'S   ENGINEERING   MAGAZINE. 


age  pipe  from  the  factory  a  bend  is 
made,  in  which  some  of  the  water  flow- 
ing off  must  always  be  present.  From 
that  bend  to  the  surface  of  the  side  walk 
is  an  upright  pipe,  covered  by  a  lid. 
Through  this  pipe,  by  means  of  a  small 
hand-pump  six  inches  long,  the  inspector 
of  nuisances  can  at  any  time  take  a 
sample  for  analysis. 

The  sewage  problem  is  not  always 
complicated  by  the  question  of  manu- 
facturing refuse,  but  all  towns  have  in 
some  way  or  another  to  get  rid  of  human 
excrement,  which  is  the  most  dangerous, 
and  at  the  same  time  the  most  valuable, 
part  of  sewage.  That  it  is  absolutely 
necessary  for  sanitary  perfection  that  it 
be  kept  out  of  the  common  sewers  I 
think  no  one  will  deny,  if  its  separate 
collection  can  sanitarily  and  convenient- 
ly be  effected.  To  be  perfect,  such  col- 
lection involves  a  great  many  conditions, 
which  have  been  well  expressed  by  the 
Senior  Medical  Inspector  of  Holland.  A 
review  of  them  is  necessary  in  order  to 
understand  what  the  pneumatic  subdivi- 
sion of  the  Liernur  system  really  ac- 
complishes : 

"  In  the  first  place,  a  form  of  closet 
had  to  be  constructed  for  use  in  combina- 
tion with  this  system,  really  perfect  in  a 
sanitary  and  aesthetic  sense,  inoffensive 
to  sight  and  smell,  and  simple  and  cheap 
enough  for  all  classes  of  society,  includ- 
ing the  poorest  and  most  thoughtless, 
and  yet  permitting  to  the  rich  those 
luxuries  to  which  they  may  be  accustom- 
ed— qualities  which  the  water  closet,  as 
is  well  known,  does  not  possess. 

"  Secondly,  the  use  of  the  water  closet 
for  those  who  could  afford  the  expense 
of  it  and  desired  it,  had  to  remain  pos- 
sible. This  demand  has  been,  among 
many  others,  a  stumbling-block  to  the 
introduction  of  every  pail-closet  or  tub- 
closet  system  ever  known. 

"  Further,  no  laborers  had  to  enter  the 
houses,  nor  wagons  and  horses  to  be  seen 
in  the  street  to  remind  people  of  the 
work  of  removal,  and  thus  be  a  nuisance. 
The  work  had  to  be  accomplished  with- 
out necessarily  coming  to  the  knowledge 
of  any  one,  or  attracting  undue  atten- 
tion. 

"  But  there  is  another  point.  As  hy- 
giene prescribes  a  daily  removal  of  faecal 
matters  at  the  least,  the  work  had  to  re- 


main possible  from  a  financial  point  of 
view  ;  that  is,  a  great  many  closets  had 
to  be  emptied  by  but  one  single  opera- 
tion. This  involved  a  very  difficult 
problem  ;  one  closet  of  a  row  of  houses 
containing  much,  another  a  little,  and 
many,  perhaps,  nothing  at  all  ;  there 
were  resistances  to  be  overcome,  having 
the  greatest  differences,  by  the  applica- 
tion of  but  one  motive  power  at  one 
given  moment,  and  this  without  failure 
or  faltering.  And,  notwithstanding  this 
difficulty,  the  work  had  to  be  done  with- 
out requiring  a  complicated  mechanical 
apparatus.  Finally,  no  gases  could  be 
allowed  to  escape  during  or  after  the 
process.  The  pollution  of  the  soil  had 
to  be  absolutely  prevented,  and  all  dan- 
ger whatever  from  infection  avoided, 
without,  howevei*,  destroying  the  agri- 
cultural value  of  the  manure." 

To  the  conditions  above  stated  I  would 
add  another  most  important  one.  It  is, 
that  when  from  accident,  neglect,  or  as 
in  the  case  of  solitary  houses  from  con- 
venience, the  emptying  process  does  not 
take  place  daily,  the  material  must  be  so 
confined  that  in  no  way  can  anything 
escape  to  contaminate  air  or  soil.  And 
further,  I  would  add,  that  the  fatty  and 
sedimentary  products  of  kitchen  sinks, 
which  are  the  same  in  substance  as  faecal 
matter,  with  this  difference  that  they  are 
not  by  several  days  so  far  on  the  road  to 
decomposition,  should  also  be  removed 
under  similar  conditions  to  faecal  matter. 
In  Holland,  where  these  matters  find 
their  way  fresh  into  the  canals  at  once, 
and  form  good  food  for  the  fish,  they 
will  not  trouble  to  adopt  the  Liernur 
system  of  collecting  them,  but  in  this 
country  it  is  desirable  to  exclude  them 
from  the  sewers  for  two  reasons.  First, 
that  in  time  they  would  give  off  organic 
matter  in  solution  and  be  polluting;  and 
secondly,  that  their  valuable  manurial 
qualities  would  be  lost  to  the  town. 

Captain  Liernur's  pneumatic  subdivi- 
sion for  the  collection  of  excrement  and 
sink  refuse  is  the  most  novel  part  of  his 
plan  of  town  drainage,  for  although  the 
other  subdivisions  have  many  novel 
features  and  improvements,  it  was  the 
only  part  about  which,  previous  to  its 
being  tried,  there  .could  be  any  doubt  as 
to  its  being  technically  possible.  These 
doubts  have  now  been  removed  by  four 


liernur's  improved  system  of  town  drainage. 


420 


years  of  successful  operation.  As  re- 
marked by  the  Senior  Medical  Inspector 
of  Holland,  "  it  is  due  to  the  inventor  to 
state  that  the  works  executed  by  him  in 
Amsterdam  and  Leyden  show  that  he 
has  overcome  all  the  difficulties  com- 
pletely ; "  and  the  Director  of  Public 
Works  supports  this  by  stating  that 
"  never  has  there  been  in  the  history  of 
applied  science  an  invention  which  has 
come  to  such  perfection  ■  in  so  short  a 
time  as  the  Liernur  system." 

I  will  now  draw  your  attention  for  a 
while  to  the  technical  details  of  the 
pneumatic  system. 

Any  large  town  would  be  divided  into 
districts  of  from  250  to  1,000  acres  ac- 
cording to  local  circumstances.  Each 
district  would  be  separate  and  as  inde- 
pendent from  any  other  as  if  it  were  an 
isolated  town.  Each  such  district  is 
again  divided  into  small  drainage  com- 
plexes or  areas  varying  from  10  to  50 
acres,  also  according  to  local  circum- 
stances. Each  of  these  little  drainage 
areas  is  provided  with  one  air-tight  cast- 
iron  tank,  built  in  sections  so  as  to  be 
easily  enlarged,  and  with  spherical  ends 
to  resist  atmospheric  pressure.  This 
tank,  which  for  distinction  sake  I  call  a 
street  tank,  is  placed  at  a  convenient 
spot,  generally  where  two  or  more  streets 
meet,  and  about  three  feet  under  the 
pavement.  From  the  tank  along  the 
several  streets  extend  air-tight  cast-iron 
main  pipes  five  inches  in  diameter,  each 
perfectly  separate  and  independent  of 
each  other.  These  pipes  are  connected 
by  branches  with  the  closets  of  the 
houses,  and  are  preferably  placed  in  the 
rear,  so  as  to  prevent  as  much  as  possible 
the  tearing  up  of  pavements,  and  to  get 
at  closets  by  the  shortest  route. 

It  will  be  understood  that  if  a  vacuum 
is  made  in  the  street  tank,  a  motive 
power  is  stored  up,  which  can  be  let 
loose  upon  any  given  street  pipe,  and 
will  literally  suck  towards  the  tank  the 
contents  of  the  closet  pipes.  A  new 
vacuum  can  then  be  created,  and  the 
emptying  into  the  tank  be  completed. 

The  question  then  occurs,  how  is  the 
vacuum  made,  and  how  are  the  contents 
of  the  tank  removed.  To  this  I  must 
answer  that  while  the  system  is  being  put 
into  operation,  that  is  before  the  central 
pumping  station  and  its  connections  are 
complete,  both  the  vacuum  and  empty- 


ing processes  are  the  operation  of  a  mov- 
able air-pump  engine  and  an  air-tight 
tender,  which  once  a  day  visit  the  street 
tank  for  the  purpose.  This  mode  is 
merely  temporary,  and  enables  the  sys- 
tem to  be  begun  in  any  number  of 
places  at  the  same  time  without  incon- 
venience. It  is  largely  used  in  Bohemia, 
where  the  system  is  extensively  in  opera- 
tion in  barracks  and  large  factories,  the 
demand  for  the  manure  in  its  undiluted 
fluid  c6nditionfor  the  cultivation  of  beet 
being  very  great,  the  price  given  being 
equivalent  to  8s.  per  head  per  annum. 
Even  this  temporary  method  is  without 
any  annoyance  to  sight  or  smell.  Pro- 
fessor Volger  says,  speaking  of  the 
works  at  Prague  : 

"  I  have  repeatedly  witnessed  the 
operation  with  real  pleasure.  Once  an 
elegantly  dressed  lady  with  her  servant 
came  close  to  me,  and  I  noticed  how  she 
stooped  down  over  the  mouths  of  the 
reservoir,  watching  carefully,  with  warm 
hearted  interest,  the  various  manoeuvres, 
without  the  slightest  idea  of  the  loath- 
some substance  which  was  being  hand- 
led." 

The  traveling  air-pump,  engine  and 
tender,  however  good  as  a  temporary 
measure,  are  undesirable  as  a  perma- 
nence, nor  do  they  form  part  of  the  sys- 
tem when  complete.  A  central  station 
is  chosen  in  which  are  erected  two  or 
three  air-pump  engines,  the  aggregate 
horse-power  being  only  what  is  required 
for  working  purposes,  and  the  division 
into  two  or  three  engines  being  for  con- 
venience in  case  of  cleaning,  repairs,  or 
accident.  Under  the  building  are  air- 
tight cast-iron  reservoirs,  in  which  the 
engines  maintain  a  vacuum  of  about 
three  -  fourths  atmospheric  pressure. 
From  the  reservoirs  are  laid,  by  the 
most  direct  routes,  air-tight  pipes,  called 
central  pipes,  also  five  inches  in  diame- 
ter, passing  by,  and  by  a  couple  of  con- 
nections communicating  with,  each  street 
tank.  One  connection  is  with  the  top  of 
the  tank,  and  by  it  air  only  can  be  suck- 
ed out.  The  other  connection  goes 
down  into  the  well  of  the  tank  so  as  to 
suck  up  its  contents  and  remove  them 
to  the  central  reservoirs. 

The  operation,  then,  is  the  following  ; 
The  air-pump  in  the  central  building 
maintains  during  the  day  a  vacuum  in 


430 


VAN  nostrand's  engineering  magazine. 


the  reservoirs  underneath,  and  in  the 
whole  length  of  the  central  pipes  con- 
nected therewith.  Patrols  of  two  men 
each  parade  the  district  like  turnkeys. 
Coming  to  a  street  tank  they  open  the 
lids,  by  which  access  it  given  to  the 
cocks  which  shut  off  each  pipe  from  the 
tank.  One  man  fixes  his  key  upon  the 
cock  connecting  the  central  or  vacuum 
pipe  with  the  tank,  and  the  other  has  his 
vipon  the  cock  belonging  to  one  of  the 
street  main  pipes  leading  to  the  houses. 
The  moment  the  first  man  turns  his  key 
he  opens  the  connection  between  the 
central  station  and  the  tank,  the  air  con- 
tained in  which  is  at  once  exhausted, 
and  a  vacuum  established,  the  extent  of 
which  is  indicated  by  a  small  vacuum 
meter.  He  then  shuts  the  cock,  while 
the  other  man,  by  turning  his  key,  lets 
loose  the  force  upon  one  of  the  pipes 
leading  by  its  branches  to  the  houses. 
This  action  repeated  once  or  twice  brings 
the  faecal  matter  into  the  tank.  In  Am- 
sterdam, for  instance,  there  are  as  many 
as  138  houses  whose  closet  pipes  are  thus 
cleaned  out  at  once.  In  the  same  way  a 
second,  third  and  fourth  pipe,  each 
leading  to  different  streets,  may  be  dealt 
with,  and  the  whole  faecal  products  of 
the  little  drainage  complex  belonging  to 
the  tank  be  thus  collected  in  it.  Before 
leaving  the  tank  the  matter  must  be 
despatched  to  the  central  station,  and 
this  is  done  by  simply  opening  the  sec- 
ond connection  of  the  vacuum  pipe, 
which  dips  into  the  well  of  the  tank, 
when  all  the  matter  is  at  once  sucked 
up  and  dispatched  towards  the  central 
station. 

So  the  men  patrol  the  district  from 
tank  to  tank,  simply  turning  a  few  cocks ; 
and  such  is  the  wonderful  simplicity  and 
ingenuity  displayed  by  the  inventor, 
that,  with  the  exception  of  these  cocks, 
which  are  of  the  simplest  possible  con- 
struction, and  can  be  taken  up  and  ex- 
amined at  a  moment's  notice,  there  is 
nothing  movable,  or  which  could  get 
out  of  order,  in  the  whole  system  of 
pipes,  from  and  including  the  closet  to 
the  reservoirs  of  the  central  building. 

The  theoretical  difficulties  to  be  over- 
come were  great — some  closets  would  be 
much  farther  off  from  the  tanks  than 
others,  and  some  might  have  received 
no  material  during  the  day,  and  other 
unequal  quantities.     It  might  be  imag- 


ined, therefore,  that  by  reason  of  these 
variations  the  vacuum  might  be  destroy- 
ed and  the  emptying  process  prevented. 
To  explain  why  this  is  not  the  case,  I 
must  first  tell  you  what  cannot  be  done. 
It  is  impossible  to  propel  liquid  any 
great  distance  through  a  horizontal  pipe 
by  air  pressure.  The  piston  of  air 
would  break  through  the  column  of 
water,  cast  it  down  on  the  lower  segment 
of  the  pipe,  and  passing  over  would 
destroy  the  vacuum.  It  is  evident,  there- 
fore, that  Captain  Liernur  could  not  use 
horizontal  pipes.  What,  however,  can 
easily  be  done,  is  to  raise  fluids  verti- 
cally, as  in  a  pump,  and  bring  them  to 
the  top  of  an  inclined  plane,  down  which 
they  will  flow  by  their  own  gravity  ; 
consequently,  all  Captain  Liernur's  pneu- 
matic pipes  are  a  succession  of  wave 
lines,  being  composed  of  inclines  vary- 
ing from  1  in  5  to  1  in  250  before  the 
street  tanks  are  reached,  according  as 
the  fluidity  of  the  matter  increases.  I 
may  here  say,  that  before  reaching  the 
street  tanks,  and  even  where  water  clos- 
ets are  not  used,  the  matter  is  reduced, 
by  the  powerful  action  of  the  atmos- 
pheric shock,  to  a  consistency  resembling 
that  of  the  thinnest  of  chocolate.  Now, 
Captain  Liernur  gives  to  every  branch 
pipe  from  the  houses  to  any  one  street 
main  the  same  aggregate  of  vertical 
risers,  breaking  them  up  to  hop  over  an 
intervening  gas  or  water  pipe,  or  accord- 
ing to  convenience.  Now,  a  pump  can 
never  empty  all  the  water  contained  in 
the  receptacle  pumped  from.  There  is  a 
minimum  that  it  can  never  remove.  In 
the  same  way  in  these  risers,  which  act 
like  pumps,  there  must  always  remain  a 
minimum  quantity  of  fluid  just  sufficient 
to  fill  the  riser.  In  a  state  of  rest  this 
minimum  is  partly  in  the  riser  and  part- 
ly in  the  lower  end  of  the  gradient  of 
the  pipe,  forming  a  complete  lock-off  of 
one  gradient  from  another,  and  a  perfect 
resistance  to  the  vacuum  being  destroyed 
even  though  any  particular  pipe  may 
have  received  no  additions  since  last  the 
emptying  process  took  place.  The  best 
example  I  could  give  of  this  would  be 
to  take  two  branches  from  one  main  pipe, 
and  opposite  one  another  as  in  the  rough 
sketch.  Suppose  the  riser  to  be  in  each 
case  one  foot  and  the  branch  100  feet 
long,  with  a  gradient  of  1  in  100  ;  the 
branch  on  the  right  leads,  we  will  say, 


liernur' s  improved  system  of  town  drainage. 


431 


to  the  house  of  a  small  family,  produc- 
ing one  foot  of  fluid  matter,  or  just 
enough  to  fill  the  riser,  and  that  on  the 
right  to  a  barrack,  where  more  than  a 
hundred  times  as  much  may  be  expect- 
ed. We  have,  therefore,  in  the  barrack 
pipe  a  mass  filling  both  pipe  and  riser, 
and  ready,  on  the  the  slightest  force,  to 
discharge  into  the  main  or  street  pipe. 
On  the  other  hand,  in  the  branch  pipe  of 
the  small  family,  there  is  the  minimum 
quantity  collected  at  the  foot  of  the 
riser.  The  sucking  action  is  now  put  in 
operation  in  the  main  pipe.  What  is 
the  result  ?  The  pressure  of  the  atmos- 
phere begins  to  act,  and  the  barrack 
pipe  rapidly  discharges  into  the  main 
pipe,  while  the  smaller  quantity  is  sim- 
ply climbing  up  the  riser,  and"  before  it 
has  got  to  the  top  of  the  riser  to  be  in  a 
position  to  discharge,  all  the  surplus 
quantity  in  the  barrack  pipe  has  gone, 
and  that  which  is  left  is  simply  equal  to 
that  minimum  which,  as  I  said  before, 
cannot  be  withdrawn.  In  this  way  the 
fullest  pipe  always  begins  to  discharge 
first,  the  next  more  full  waiting  for  it, 
and  so  on,  until  the  minimum  is  reached, 
when  simply  air  breaks  through.  It  is 
thus  that  Captain  Liernur  turns  natural 
laws  to  his  own  purposes,  and  contrives 
that  the  minimum  quantity  gives  the 
maximum  resistance,  and  the  maximum 
quantity  the  minimum  resistance. 

As  I  mentioned  before,  one  of  the 
great  advantages  of  the  pneumatic  sys- 
tem is  that  it  does  not  forbid  the  use  of 
the  water  closet  to  those  unwilling  to 
give  up  the  use  of  Ithat  expensive  and 
oftentimes  troublesome  luxury.  As, 
however,  all  the  water  added  has  here- 
after to  be  got  rid  of,  Captain  Liernur 
stipulates  that,  if  economy  is  to  be 
studied,  it  is  absolutely  necessary  to  have 
a,  form  of  closet,  of  which  there  are 
several  known,  which  only  allows  of  a 
limited  quantity  of  water  being  used. 
His  own  improved  water  closet,  of  which 
a  quart  of  water  is  and  must  be  used  at 
■each  sitting,  independent  of  the  will  of 
the  individual,  has  been  greatly  admired, 
as  being  simple  in  construction,  and  not 
likely  to  get  out  of  order,  or  to  allow  of 
freezing  in  winter.  It  would  take  up 
too  much  of  your  time  to  describe  this, 
■especially  as  I  wish  to  draw  your  atten- 
tion to  the  Liernur  closet  without  water. 
This  is  intended  for  the  working  classes, 


who  cannot  afford  the  more  expensive 
luxury,  and  who  would  abuse  it  if  they 
had  it.  These  form  75  to  80  per  cent, 
of  our  population,  and  the  Liernur  closet 
suitable  for  them  has  been  declared  to 
be  as  inoffensive  as  the  ordinary  Eng- 
lish water  closet,  and,  but  for  the  preju- 
dice existing  in  favor  of  that  conven- 
ience, as  well  fitted  for  the  rich  as  for 
the  poor. 

The  pneumatic  privy  has  no  movable 
mechanism  at  all,  and  is  used  without 
any  water  for  flushing.  The  excreta  falls 
into  the  bottom  of  a  deep  funnel,  but 
the  size  and  position  of  the  seat  opening 
is  so  arranged,  and  the  shape  of  the  fun- 
nel is  so  made,  that  the  extreme  area  in 
which  the  excreta  can  fall  is  practically 
as  much  limited  as  would  be  the  case  in 
an  ordinary  chamber-pot.  The  effect  is 
that  the  excreta  falls  and  is  collected  in 
a  pocket  below  of  but  small  compass, 
without  touching  the  sides  of  the  funnel, 
offering  to  the  air  a  surface  of  only  five 
inches.  The  pocket  referred  to  is  one 
arm  of  a  short  bent  tube  or  syphon  trap, 
discharging  in  a  soil-pipe.  This  dis- 
charge is  effected  by  the  weight  of  the 
excreta,  fluids  and  solids,  themselves, 
each  new  deposit  forcing  the  former  out. 
Thus  the  older  matter  is  automatically 
shut  off  from  further  communication 
with  the  outer  air,  and  it  being  well 
known  that  no  fermentation  capable  of 
generating  elements  dangerous  to  health 
takes  place  within  the  first  thirty  hours 
after  production,  it  is  evident  that  the 
small  surface  of  fresh  substances  ex- 
posed to  the  air  could  at  the  utmost  onlv 
throw  off  offensive  gases.  To  carry 
these  off,  however,  each  funnel  is  in  the 
upper  part  made  double,  the  space  be- 
tween being  provided  with  a  two-inch 
ventilating  pipe  placed  close  under  the 
seat  and  leading  to  the  outside  of  the 
roof  of  the  house,  and  furnished  on  top 
with  a  so-called  Wolpert's  air-sucker. 
This  little  contrivance,  scarcely  known 
in  this  country,  is  very  simple,  having 
no  movable  parts  whatever,  but  is  singu- 
larly effective  ;  the  slightest  and  almost 
imperceptible  motion  of  air  (which  in 
towns  is  never  quite  still)  causes  an  up- 
ward current  in  the  pipe.  The  i*esult  is 
that  when  the  lid  is  removed  from  the 
seat  opening  a  current  of  air  strikes  at 
once  downwards  into  the  funnel.  From 
this  it  is  evident  that  under  no  eircuni- 


432 


VAN  nostrand's  engineering  magazine. 


stances  can  an  offensive  smell  escape 
from  the  funnel  into  the  apartment.  The 
funnel  itself  being  of  a  dark  color,  it 
throws  no  reflected  light  on  the  excreta 
below.  It  is  plain,  therefore,  that  there 
can  be  nothing  to  offend  either  the  sense 
of  sight  or  the  sense  of  smell,  and  this 
is  all  that  can  be  expected  from  the  best 
water  closet. 

Attention  must  be  called  to  the  fact 
that  the  pocket  of  the  soil  pipe  into 
which  the  overflow  of  the  privy  funnel 
proper  takes  place  is  also  ventilated. 
This  pocket,  being  a  bent  tube  discharg- 
ing into  the  branch-pipe,  is  the  real  re- 
ceptacle from  which  the  faecal  matter  is 
permanently  removed  ;  all  the  same, 
whether  it  belongs  to  the  water-closet 
or  the  pneumatic  privy  of  the  system. 
The  pipe  provided  for  the  ventilation  al- 
luded to  serves  at  the  same  time  for  ad- 
mitting the  atmospheric  air  for  the  pneu- 
matic process.  Hence  such  air  does  not 
enter  through  the  seat  opening,  nor  is 
the  matter  in  the  closet  itself  removed 
by  pneumatic  force. 

I  have  now  to  describe  how  it  is  that 
the  sedimentary  products  of  the  kitchen 
sinks  are  separated  from  the  rest  of  the 
house  water,  and  carried  off  by  the 
pneumatic  pipes.  That  they  are  thus 
separated  is  due  to  an  exceedingly  in- 
genious apparatus  Captain  Liernur  em- 
ploys for  separating  them  from  the 
household  water  running  off  to  the  com- 
mon sewer.  It  is  a  trap  placed  at  some 
suitable  spot  in  the  open  air,  into  which 
all  the  kitchen  and  household  water  on 
its  way  to  the  sewer  discharges.  In 
order  to  flow  off  into  the  sewer,  all  this 
water  must  pass  upward  through  a  close 
grating,  which  acts  as  a  strainer.  The 
sediment  is  thus  thrown  down  into  a 
sort  of  pocket,  which  stands  in  commu- 
nication with  the  privy  soil-pipe.  When 
now  the  pneumatic  blast  takes  place,  the 
pocket  of  the  sink  is  cleaned  simul- 
taneously with  the  closet  pipes,  the  air 
to  do  this,  which  enters  through  grating, 
blowing  it  clean  at  the  same  time. 

Before  coming  to  the  treatment  of  the 
matter  collected,  at  the  central  station, 
I  wish  to  say  a  few  words  as  to  the 
remedies  for  accidents  and  stoppages. 
Remember  that  the  motto  of  the  system 
is  "  divide  and  conquer,"  and  see  how 
this  is  carried  out  in  every  detail.  To 
prevent  foreign  substances  being  thrown 


down   and   stopping  up   the   pipes,  the 
throat  of  the  privy  funnel  you  will  see 
is  made  narrower  than  the  pipes  are,  so 
that    theoretically    everything    passing 
the  throat  will  go  further,  and  the  most 
extraordinary  things  do  go  through  in 
practice.     As  a  further  precaution   the 
closet  syphon  is  crossed  by  an  iron  bar, 
dividing  it  into  two  equal  spaces.     Any- 
thing that  is  small  enough  to  go  through 
will  never  create  any  stoppage.     Larger 
articles  simply  stop  up  the  closet  itself, 
and  give   the  person  who  transgressed 
the  trouble  of  removing  them,  a  lesson 
found  in  Holland  amongst  the  poorest 
people   to   be   quite  effectual.     Further 
each  branch  pipe  from  a  house  is  provid- 
ed with  a  stop  cock  accessible  to  the  offi- 
cials,  by  which  any  house  can  at   any 
time  be  shut  off  from  the  rest  of   the 
system.     Presuming  a  stoppage  possible, 
the   whole   pneumatic   power   could  be 
concentrated   on    any   particular   house 
pipe.     Such  things  as  leakages  again  do 
not   occur,   and  if  they  did  they  would 
be  closed  up  by  the  earth  or  substances 
drawn  in  by  the  suction  power.     In  fact 
it  would  be  impossible  to  keep  a  leak 
open  even  if  desired.     But  what  would 
be  done  in  case  of  breakage,  is  an  in- 
quiry I   have   heard,  and  the  answer  is 
that  one  would  do  the  same  as  if  a  water 
pipe  burst — Mend  it !     There  is  this  dif- 
ference, however,  between  the  two  cases, 
a  water  pipe  is  so  much  more  likely  to 
break  as  the  pressure  is  outwards.      In 
the  pneumatic  pipes  the  pressure  is  in- 
wards, quite  a  different  thing.     Suppos- 
ing, however,  a  pipe  did  unaccountably 
break,  a  thing  that  has  not  occurred  in 
experience  in  the  shifty  and  uncertain 
soil  of  Holland,  how  far  would  it  affect 
the  system  ?     If  in  the  house,  the  repair 
could  be  made  at  once  with  or  without 
shutting  off  the  house.     If  in  the  branch- 
es or  main  pipe,  it  could  at  the  utmost 
affect  the  houses  upon  that  pipe.     Now 
on  account  of  the  risers,  the  pneumatic 
pipes  never  need  be  deeply  laid  ;  below 
frost  depth,  that  is  about  three  feet,  is 
quite  sufficient,  so  there  is  no  difficulty 
there.     A  more   serious  affair  would  be 
the  breaking  of  one  of  the  central  pipes 
communicating  the  vacuum  to  the  street 
tanks.     This  could  not  fail  to  be  discov- 
ered,  localized   and    repaired    at   once. 
Suppose,  however,  an  extreme  case,  in 
which  the  repair  could  not  be  effected 


lternttr's  improved  system  of  town  drainage. 


433 


for  a  whole  week.  Then  there  are  two 
ways  open.  You  can  go  back  for  the 
time  to  the  movable  air-pump,  or  you 
can  simply  not  perform  the  emptying 
process  for  a  week  instead  of  daily  as 
required  by  the  system.  This  delay  has 
often  taken  place  at  Amsterdam  through 
the  intentional  negligence  of  an  opponent 
of  the  system  who  was  in  authority. 
Remember  it  is  the  pipes  only,  not  the 
closets  which  are  emptied  by  pneumatic 
force,  and  there  is  room  in  the  pipes  for 
a  week's  product.  Indeed,  in  applying 
the  system  to  isolated  houses  on  the  out- 
skirts of  a  town  or  in  the  country,  with- 
out any  tanks  or  street  pipes,  the  closet 
pipes  are  only  intended  to  be  emptied 
once  a  week. 

In  case  any  one  should  think  that  fer- 
mentation would  set  in  in  the  closed 
pipes  during  that  period,  I  may  mention 
that  the  Dutch  authorities  tried  the  ex- 
periment for  thirteen  months,  and  found 
no  change. 

I  have  especially  dwelt  upon  the 
chance  of  accidents  and  their  effect  upon 
the  system,  as  I  have  found  the  subject 
quite  a  bugbear  in  the  eyes  of  many. 

I  have  now  to  describe  what  is  to  be 
done  with  the  matter  collected  at  the 
central  reservoir,  namely,  its  conversion 
into  poudrette.  This  part  of  the  Liernur 
system  has  not  yet  been  tested  on  a  large 
scale,  although  the  practicability  of  it 
has  been  sufficiently  proved  both  by  ac- 
tual trial  and  by  experience  in  sugar-re- 
fining, in  which  a  similar  process  is  car- 
ried on. 

It  is  a  well  ascertained  fact,  that  of 
the  heat  contained  in  the  steam  of  a  high 
pressure  engine,  employed  in  working 
the  air-pump  engine  for  collecting  the 
matter,  but  7  to  8  per  cent,  are  convert- 
ed into  power,  the  remaining  92  per  cent, 
escaping  with  the  exhaust  steam.  It  is 
this  steam,  superheated  by  being  passed 
through  a  Green's  economizer,  and  made 
dry  again,  that  Captain  Liernur  uses  for 
the  drying  process.  It  is  conducted 
through  pipes  in  an  upright  hermetically 
closed  boiler,  into  which  the  fluid  man- 
ure, after  being  mixed  with  a  little  sul- 
phuric acid,  is  conducted,  and  in  which 
by  the  heat  thus  imparted  a  rapid  boiling 
takes  place.  This  is  assisted  by  the  fact 
that  a  partial  yacuum  exists  in  the  boil- 
er on  account  of  the  vapors  of  the 
evaporation  being  condensed  in  another 
Vol.  Xm.— No.  5—28 


receptacle.  This  other  receptacle  is  en- 
gaged in  the  second  or  drying  pro- 
and  consists  of  a  hollow  drum  of  thin  reel 
copper,  fifteen  feet  long,  and  two  feet  in 
diameter.  This  drum  revolves  in  a 
trough  of  the  already  thickened  matter, 
and  is  itself  placed  in  a  hermetically 
closed  vessel,  in  which  a  vacuum  is  main- 
tained. What  with  the  heat  imparted 
to  the  drum  from  the  inside  by  the  va- 
pors from  the  first  boiling  which  pass 
through  it,  and  the  vacuum  outside,  the 
thin  layer  of  fsecal  matter  it  takes  up  is 
thoroughly  dried  in  the  course  of  one 
revolution,  and  is  scraped  off  by  a  fixed 
knife,  falling  in  little  shavings  into  a  box 
below. 

Now,  whatever  manurial  ingredients 
there  are  in  the  sewage  must  be  in  the 
poudrette,  the  air,  or  the  vapors.  They 
cannot  be  in  the  vapors,  for  these  come 
out  as  pure  distilled  water,  nor  in  the  ah*, 
for  a  vacuum  is  maintained  in  the  vessel; 
therefore  they  must  all  be  in  the  poud- 
rette. 

As  the  poudrette  has  not  yet  taken  its 
place  as  an  article  of  commerce,  I  will 
not  enter  into  any  estimates  as  to  the 
revenue  to  be  derived  from  its  sale.  I 
would  merely  point  out  that  it  is  the 
pure  undiluted  material,  in  a  strong  con- 
centrated state,  and  capable  of  being 
stored  for  any  length  of  time,  and  that 
I  firmly  believe  that  in  a  town  moder- 
ately densely  populated  the  revenue 
would  be  sufficient  not  only  to  cover  the 
annual  expenses  but  to  pay  the  interest 
of,  and  redemption  on,  the  cost  of  the 
works.  In  other  words,  that  the  pneu- 
matic system  would  practically  cost  the 
ratepayers  nothing. 

For  a  similar  reason  I  will  make  no 
estimates  of  cost,  as  this,  as  in  all  drain- 
age works,  varies  immensely,  according 
to  local  circumstances. 

The  sanitary  view  of  the  pneumatic 
system  is  best  described  in  the  following- 
sentences  from  the  account  by  the  Senior 
Medical  Inspector  of  Holland  : 

"Sanitaky. — The  excreta  are,  from 
the  moment  the  closets  are' emptied  to 
the  moment  when  the  process  is  finished 
and  they  are  converted  into  dry  powder, 
absolutely  deprived  of  all  chance  of  do- 
ing harm,  being  locked  up  from  first  to 
last  in  air-tight  vessels.  The  powder  it- 
self is  harmless,  because  fermentation  in 


434 


VAN  NOSTRAND  S  ENGINEERING   MAGAZINE. 


a  dry  state  is  impossible.  The  water  of 
the  excreta  has  also  become  harmless, 
because  being  driven  out  by  evaporation 
and  condensed  again  (the  vapor  passes 
through  an  ordinary  condenser),  it  re- 
turns to  the  public  streams  as  distilled, 
and  consequently,  pure  water.  And  the 
gaseous  products  of  the  evaporation, 
perhaps  still  containing  germs  of  disease, 
are  blown  by  the  air-pump  engine,  with 
the  rest  of  the  air  sucked  up  out  of  the 
tubes  and  pipes,  into  the  fire  place  of  the 
boiler,  and  there  are  completely  burned. 
No  matter,  therefore,  how  infectious  the 
excreta  may  have  been,  their  power  to 
work  evil  is  stopped  forever." 

In  support  of  this,  I  may  add  that  offi- 
cial statements  at  Leyden  aver  that  the 
district  where  the  system  is  applied  was 
formerly  noted  for  the  prevalence  of 
typhoid  and  diphtheria,  and  that  these 
diseases  have  now  disappeared  entirely. 
Similar  evidence  is  given  by  the  Amster- 
dam authorities. 

Having  described  the  pneumatic  sub- 
division of  the  Liernur  system,  I  must 
now  shortly  state  how  Captain  Liernur 
would  provide  for  the  ordinary  drain- 
age, as  distinct  from  the  sewerage,  if  the 
town  were  perfectly  virgin  in  this  re- 
spect. This  part  of  the  system  is  of  less 
interest  in  England,  because  most  of  our 
towus  are  sewered,  or  at  any  rate  have 
the  rudiments  of  sewers,  which  they 
would  be  unlikely  to  displace  for  his  im- 
proved sewers.  In  their  case  he  would 
simply  apply  the  pneumatic  system,  and, 
If  they  liked,  his  mode  of  removing 
street  detritus,  thus  relieving  the  sewers 
of  all  dangerous  matter.  But  in  a  town 
■entirely  new  as  to  drainage,  he  would 
never  adopt  the  present  system,  by 
which  not  only  is  great  cost  incurred, 
but  pollution  of  soil  rendered  unavoid- 
able. He  would  construct  the  ordinary 
sewers  of  vitrified  earthenware,  so  as  to 
be  practically  impervious,  and  then  no- 
thing would  get  either  in  or  out  except 
through  the  proper  channels.  To  pro- 
vide for  the  drainage  of  the  subsoil,  for 
which  at  present  the  common  sewer 
serves  by  its  porosity,  he  would  follow 
the  farmer's  plan  of  laying  agricultural 
drain-pipes,  these  emptying  at  intervals 
into  the  ordinary  sewer  below.  These 
subsoil  drains  would  be  laid  so  as  to  keep 
the  subsoil  water  permanently  at  its  low- 


est level,  thus  preventing  the  fluctua- 
tions, which  cause  the  alternate  inhaling 
and  exhaling  by  the  earth  of  the  atmos- 
phere. The  sanitary  results  of  such  fluc- 
tuations are  thus  described  by  Dr.  Alfred 
Carpenter  : 

"  In  a  porous  soil,  which  easily  allows 
of  the  rise  and  fall  of  the  water-line,  an 
amount  of  air  finds  entrance  and  exit 
equal  in  volume  to  the  quantity  of  water 
which  occupies  the  interstices  of  the 
earth.  If  the  soil  is  impure  from  cess- 
pool soakage  and  other  sewage  abom- 
inations, the  air  drawn  into  those  inter- 
stices, as  the  water-line  falls,  becomes 
naturally  loaded  with  the  results  of  sew- 
age decomposition.  As  the  water-line 
rises  this  air  is  expelled  and  adulterates 
the  purer  atmosphere  above.  If  the 
area  is  an  inhabited  one,  much  of  this 
finds  its  way  into  the  basements  of  the 
houses  built  upon  such  a  foundation  (it 
gets  out  more  easily  there),  and  the  in- 
habitants naturally  suffer  from  the 
effects  of  foul  air.  If  the  subsoil  is 
drained  by  sewer  pipes,  and  the  latter 
are  not  ventilated  in  the  most  efficient 
manner,  another  evil  also  arises.  The 
sewers  which  were  pervious,  and  allowed 
leakage  into  the  subsoil  of  both  air  and 
water,  which  passed  downwards,  are  now 
sealed  to  some  extent,  and  all  sewer 
gases  find  their  way  into  the  houses  di- 
rect. But  this  is  not  all.  The  rise  of 
the  water-line  is  attended  by  certain 
evils.  Typhoid,  and  its  allied  diseases, 
become  prevalent,  but  as  the  water-line 
falls  again,  another  set  of  diseases  be- 
come prevalent  also,  the  intermittent 
class  — ague,  neuralgia,  rheumatic  dis- 
orders, are  rife.  It  is  found  in  ague 
districts  that  the  drying,  which  naturally 
follows  upon  the  fall  of  the  water-line, 
is  accompanied  by  epidemics  of  inter- 
mittent fever  and  its  allies,  with  all 
those  acute  sufferings  which  are  called 
tic,  brow  ague,  megrims,  et  id  genus 
omne.  So  it  becomes  the  interest  of  the 
inhabitants  of  such  a  district  to  keep  the 
water  line  as  nearly  as  possible  at  the 
same  level,  for  its  rise  or  fall  is  always 
followed  by  damage  to  public  health." 

Besides  the  sanitary  advantages,  there 
are  technical  advantages  which  effect 
such  a  saving  in  cost  that  these  subsoil 
drains,  and  the  sewers,  proper,  can  be 


HEAT   ABSORBED   BY   EXPANSION. 


435 


constructed  for  about  as  much  as  the 
present  imperfect  system.  The  sewers 
are  made  much  smaller  without  fear  of 
"bursting,  even  when  full,  because  of  the 
permanent  pressure  outside  of  the  higher 
subsoil  water.  The  current  in  them  will 
at  all  times  be  more  swift,  and  hence 
more  cleansing  in  its  action,  and  if  the 
water  contained  in  them,  deprived  by 
Captain  Liernur's  plans  of  putrescrible 
matter  and  manufacturing  waste,  be 
allowed,  without  further  treatment,  to 
enter  streams,  his  sewers  can  take  the 
most  direct  route  to  the  nearest  water 
course,  thus  saving  the  enormous  expense 
of  huge  main  and  intercepting  sewers 
now  so  much  used  to  carry  the  whole 
of  the  sewage  out  of  town. 


The  above  description  of  the  Liernur 
system  is  necessarily  brief  and  imperfect. 
Any  one  wishing  for  minuter  details,  I 
would  refer  to  a  long  technical  account 
written  by  me  in  the  Sanitary  Record oi 
21st  November,  1874. 

In  conclusion,  letme  say  that  to  strang- 
ers to  the  system  a  number  of  theoreti- 
cal objections  will  be  sure  to  arise,  the 
answer  to  which  is  that  in  practice  they 
do  not  arise.  The  subject,  however,  is 
of  such  paramount  importance  for  Eng- 
land, that  a  Government  official  inquiry 
into  the  system  is  very  desirable.  In 
this  I  am  sure  every  one  will  agree  with 
me,  if,  as  I  hope,  in  the  preceding  re- 
marks &  prima  facie  case  has  been  made 
out. 


HEAT  ABSORBED  BY  EXPANSION. 

By  S.  W.  ROBINSON,  Professor  of  Mechanical  Engineering,  and  Teacher  in  Physics  in  the  Illinois  Industrial 

University. 

Written  for  Van  Nostrand's  Magazine. 


An  article  in  the  March  number  of  the 
Magazine,  by  Professor  H.  S.  Carhart, 
of  the  Northwestern  University,  indi- 
cates, as  well  as  intelligence  which  has 
come  to  the  ears  of  the  writer  regarding 
the  Professor's  experiments,  that  he  is 
doing  good  work  in  the  line  of  College 
Physical  Experiments.  Those  interested 
in  Western  institutions  of  learning  are 
glad  to  realize  the  fact  that  experimenta- 
tion as  a  means  of  demonstration  in  edu- 
cational classes  is  so  widespread  as  to 
have  reached  some  of  our  Western  uni- 
versities. 

Though  Professor  Carhart  deserves 
much  credit  for  his  fine  experiments  of 
a  high  order,  yet  we  fear  that  he  has  al- 
lowed himself  to  get  a  little  off  of  the 
right  track  in  his  reasoning,  as  set  forth 
in  the  article  above  referred  to,  reason- 
ing which  the  writer  has  waited  several 
months  to  see  set  aright,  and  which,  it 
is  thought,  ought  not  to  go  uncorrected. 

I  have,  however,  only  one  point  to 
call  particular  attention  to,  and  that  is 
in  regard  to  the  performance  of  exter- 
nal work  by  the  expanding  gas  while  the 
receiver  is  being  exhausted  by  the  air 
pump.     The  Professor  supposes,  doubt- 


less by  oversight,  that  in  such  an  experi- 
ment the  operator  performs  the  external 
work  of  expansion  of  the  gas  in  the  re- 
ceiver, by  his  own  effort  in  lifting  the 
piston  from  the  gas,  a  position  probably 
more  readily  taken,  on  account  of  an- 
other seeming  explanation  of  the  dis- 
appearance of  heat. 

When  the  piston  is  raised  by  the 
operator,  what  constitutes  the  effort  ? 
The  pressure  of  the  air  upon  the  top  of 
the  piston  must  be  lifted.  What  does 
it  ?  The  pressure  of  the  gas  beneath 
the  piston,  together  with  the  lift  exerted 
by  the  pumpman.  In  exhausting  a  re- 
ceiver, the  first  stroke  will  be  accom- 
plished with  less  effort  than  a  stroke  near 
the  completion  of  the  exhaustion,  if  a 
plain  single  acting  cylinder  is  used. 
Why?  Because  the  gas  in  the  first 
stroke,  having  a  greater  pressure,  per- 
forms more  of  the  work  of  raising  the 
piston  against  the  constant  pressure  of 
the  outside  atmosphere.  In  other  word  s, 
the  gas  in  the  receiver  does  perform  ex- 
ternal work,  and,  so  long  as  any  gas  re- 
mains in  the  receiver,  continues  to  aid 
the  operator.  If  the  gas  in  the  receiver 
were  prevented,  by  a  stop-cock  or  other- 


436 


VAN  NOSTRAND'S   ENGINEERING   MAGAZINE. 


wise,  from  entering  the  cylinder  while 
the  piston  is  raised,  the  operator  would 
perform  the  whole  work  of  lifting  the 
atmosphere,  and  the  effort,  it  is  readily 
seen,  would  be  greater  with  the  form  of 
pump  supposed,  than  if  the  gas  were  al- 
lowed to  enter  the  cylinder  freely. 
When  the  gas  is  excluded  from  the  cyl- 
inder as  the  piston  is  raised,  and  retain- 
ed in  a  fixed  elevated  position,  produc- 
ing a  complete  vacuum  beneath,  what 
occurs  by  opening  the  stop-cock  ?  The 
reply  is  :  "  why,  the  gas,  of  course,  now 
performs  no  external  work."  Still  the 
receiver  will  be  found  cooled  as  before. 
Examine  the  cylinder  of  the  pump.  It 
is  heated.  And  this  heating  will  exactly 
neutralize  the  cooling.  The  gas  in  the 
receiver  performs  work,  external  to  that 
remaining  in  it,  by  ejecting  a  portion 
into  the  cylinder,  this  work  being  stored 
in  the  moving  particles  of  gas.  As  they 
collide  against  the  interior  of  the  cylin- 
der, heat  is  generated,  and  just  enough, 
when  the  particles  have  come  to  rest,  to 
represent  by  that  heat  the  work  of  ex- 
pansion having  taken  place  in  the  receiv- 
er. This  is  in  fact  nothing,  but  the 
famous  experiment  of  Gay  Lussac,  and 
Dr.  Joule.  See  Tyndall,  Heat  as  a  Mode 
of  Motion,  p.  89.  Maxwell's  Text  Book 
on  Meat,  &c.     In  the  exhaustion  of  a 


receiver  by  an  air  pump,  if  there  were  no 
external  pressure,  as  of  air,  to  be  over- 
come, the  piston  would  need  to  be  held 
back  to  prevent  its  rising  too  rapidly. 
In  other  words,  the  piston  would  under 
these  circumstances  raise  some  certain 
weight.  This  is  the  very  external  work 
which  the  gas  must  perform,  and  which 
of  course  must  cool  it,  as  indicated  by 
the  pile. 

Again  the  refrigeration  of  the  receiver 
can  hardly  be  due,  to  any  great  extent, 
to  the  motion  produced  among  the  part- 
icles of  gas,  because  this  motion,  in  the 
receiver  itself,  must  be  insignificant.  If 
not  for  the  first  quarter  stroke,  that  of  the 
succeeding  quarter  strokes  must  be,  be- 
cause here  the  cooling  after  the  first 
could  be  due  only  to  the  difference  of  the 
motion  in  succeeding  quarter  strokes. 
Also  the  motion  of  the  gas  in  the  re- 
ceiver, caused  by  so  slight  a  disturbance 
as  produced  simply  by  the  departure  of 
a  portion  of  the  gas,  must  involve  an 
amount  of  work  extremely  insignificant 
when  compared  with  the  raising  of  the 
weight  as  above  mentioned.  We  must 
therefore  conclude  that  the  refrigeration 
is  due  for  very  nearly  its  entire  amount, 
and  when  the  gas  in  the  receiver  has 
come  to  rest  after  the  pump  strokes,  to 
its  entire  amount,  to  external  work. 


BALANCED  VALVES  IN  LOCOMOTIVES. 


From  "The  Engineer." 


Many  and  varying  estimates  have  been 
made  concerning  the  power  wasted  in 
overcoming  thefriction  of  slide  valves,and 
probably  on  no  subject  has  there  been  a 
greater  diversity  of  opinion.  It  has  been 
assumed  on  the  one  hand  that  as  much  as 
one-fourth  of  the  power  of  an  engine  is 
thus  wasted,  and  those  who  hold  this 
doctrine  point  triumphantly  to  broken 
and  bent  valve  spindles  as  so  many  proofs 
that  they  are  right,  and  that  their 
judgment  is  sound;  others  maintain  that 
the  loss  of  power  is  nominal,  and  they 
adduce  as  evidence  that  they  are  right, 
link  motions  and  eccentrics  which  have 
run  for  years  almost  without  wear.  The 
truth  is,  that  neither   party  accurately 


expresses  the  facts.  It  is  not  to  be  dis- 
puted that  slide  valves  do  work  with  a 
good  deal  of  friction,  and  so  waste  power 
when  unbalanced ;  but  it  is  quite  certain 
that  they  can  never  waste  one-fourth  of 
the  whole  force  of  an  engine.  Scores 
of  balanced  valves  are  in  the  market  now, 
or  have  been,  and  many  of  the  systems  of 
balancing,  or  taking  off  the  pressure 
from  the  backs  of  the  valves,  have  been 
adopted  with  success  in  marine  and  sta- 
tionary engines,  but  none  appear  to  have 
given  satisfactory  results  with  locomo- 
tives. 

In  this  country  there  is,  unfortunately, 
not  so  complete  and  thorough  an  inter- 
change of  ideas  among  locomotive  super- 


BALANCED   VALVES   IN   LOCOMOTIVES. 


437 


intendents  as  is  desirable,  and  matters  are 
not  much  better  in  the  United  States. 
There,  however,  exists  the  Master  Me- 
chanics' Association,  and  that  society 
appears  to  be  doing  really  good  work,  by 
appointing  committees  to  investigate  cer- 
tain questions  and  obtain  answers  from 
various  railroads  concerning  the  exper- 
ience of  the  locomotive  superintendents. 
One  of  the  most  recent  subjects  discussed 
has  been  the  efficiency  of  various  systems 
of  balanced  slide  valves  as  applied  to 
locomotive  engines.  The  results  of  the 
inquiry  are  instructive.  Fourteen  loco- 
motive superintendents  have  replied  to 
the  questions  of  the  Valve  Gear  Com- 
mittee. These  replies  go,  on  the  whole, 
to  show  that  no  satisfactory  valve  has  yet 
been  produced,  and  that  nothing  is  better 
than  the  ordinary  slide  valve.  Some  of 
the  valves  are  well  known,  others  but 
little  known  in  this  country.  The  evidence 
concerning  them  is  easily  summarized  ; 
thus  Mr.  Hayes,  of  the  Flint  and  Pere 
Marquette  Railway,  tried  Richardson's 
valve,  which  he  ran  for  two  months  or 
about  5,000  miles.  The  valve  seats  were 
in  good  condition,  but  the  valve  leaked 
badly  and  was  removed.  The  ordinary 
valves  spared  the  seats  just  as  much  in 
running  the  same  distance.  Mr.  Taylor, 
of  the  Old  Colony  Railway,  tried  no  fewer 
than  five  varieties  of  balanced  valves, 
and  pronounces  them  all  worthless.  Mr. 
Thompson,  of  the  Eastern  Railroad,  has 
used  Adams'  valves — well  known  in  this 
country— with  good  results.  The  ordi- 
nary slide  valves  in  his  engines  required 
repairing  after  45,000  miles;  the  Adams' 
valve  ran  66,000  miles.  On  the  Terre 
Haute  and  Indianapolis  line,  balanced 
valves  have  been  tried  with  a  moderate 
amount  of  success.  In  the  course  of  the 
discussion  which  followed  the  presenta- 
tion of  the  report,  it  became  apparent  that 
the  general  current  of  opinion  was  against 
balanced  valves,  because  they  gave  no 
advantage  with  the  increased  cost  and 
complication. 

It  is  certain  that  when  large  valves  are 
used,  as  in  marine  engines,  some  arrange- 
ment must  of  necessity  be  adopted  to 
take  the  pressure  off  the  back,  and  it  can 
hardly  be  disputed  that  if  a  satisfactory 
device  could  be  employed  with  locomo- 
tives a  decided  advantage  would  be  gain- 
ed; but  the  device  has  yet  to  be  obtained, 
and  a  wide  field  for  invention  still  remains 


unexplored.  As  regards  saving  of  power, 
the  question  may  resolve  itself  into  a  mat- 
ter of  economy  of  fuel.  Now,  all  the 
evidence  obtained  in  America  goes  to 
show  that  no  saving  of  fuel  whatever  is 
realized  by  even  the  best  balanced  valves 
tried.  But  the  question  may  be  regarded 
from  a  totally  different  point  of  view. 
A  balanced  valve  renders  the  handling 
of  an  engine  easy,  and  saves  wear  and 
tear,  not  only  in  the  valve  and  cylinder 
faces,  but  throughout  the  entire  valve 
motion.  Some  of  the  American  locomo- 
tive superintendents  stated  that  with  bal- 
anced valves  the  reduction  of  friction  was 
so  great  that  the  reversing  lever  would 
remain  in  any  position  in  which  it  was 
placed,  although  the  detent  was  not  in  a 
notch  in  the  sector.  But  there  was  also 
testimony  to  show  that  the  valves  which 
worked  thus  easily  were  all  liable  to  blow 
through,  and  that  some  of  them  blew  so 
badly  that  their  use  actually  increased  the 
consumption  of  steam.  It  does  not  appear 
that  any  of  the  speakers  were  acquainted 
with  Beattie's  valve,  as  used  on  our  South 
Western  Railway  with  great  success;  but 
this  can  hardly  be  called  a  balanced  valve, 
closely  resembling,  as  it  does  in  practice, 
the  old  "  long  D  "  used  by  Watt.  One 
proposal  came  out  during  the  discussion 
which  is  well  worth  attention.  It  is  that 
valves  and  seats  should  have  chilled  faces. 
It  does  not  appear  to  us  that  any  difficulty 
would  be  met  with  in  carrying  out  this 
system  of  construction.  It  is  eminently 
simple,  and  the  excessive  hardness  of  a 
chilled  surface  is  well  known.  The  ex- 
perience of  one  of  the  speakers  is  worth 
notice.  Mr.  Jackman,  of  the  Chicago, 
Alton,  and  St.  Louis  line,  tried  a  device 
which  we  shall  allow  him  to  describe  in 
his  own  words  : 

"  We  are  using  now,  on  three  or  four 
engines,  another  thing,  and  I  want  to 
state  what  it  is  so  that  every  one  can 
take  advantage  of  it.  We  plane  out  a 
groove  on  the  bearing  surface  of  the 
valve  of,  say,  f  in.  in  width,  by  almost 
the  length  of  the  valve,  leaving  the  ends 
inside,  then  drill  a  little  hole  ^in.  at  each 
end  down  into  that  place  and  put  the 
valve  in.  The  first  time  I  tried  that 
was  four  months  ago,  I  think.  When  the 
engine  went  out  from  the  shop  the  man 
who  took  her  out  says,  '  She  blows  ;  I 
think  we  shall  have  to  take  these  valves 
out  and  replace  them.'     So  I  had  a  new 


438 


VAN    NOSTRAND'S   ENGINEERING  MAGAZINE. 


set  of  valves,  all  fitted  exactly  every  way, 
so  as  to  just  lift  the  cover  off  and  replace 
those  we  had  grooved  out  with  the 
others. 

After  that  I  let  the  man  run  her 
on  passenger  trains.  I  put  the  air  hrake 
on  her  and  put  her  into  the  hands  of  one 
of  our  very  good  runners,  and  ran  a  pas- 
senger train  between  Bloomington  and 
Chicago — one  of  our  heavy  trains — and 
after  he  had  run  her  two  or  three  times 
he  came  to  me  and  said,  'What  in  the 
world  did  you  do  to  the  valves  of  that 
engine  ?  I  used  to  run  that  engine  before 
you  put  her  in  order  on  a  freight,  and 
she  is  an  entirely  different  engine  now  ; 
what  did  you  do  to  the  valves  ? '  I  said 
we  did  not  do  anything.  '  Why  certainly 
you  have  done  something,  for  the  engine 
don't  handle  as  she  used  to  handle.'  Then 
I  told  him  just  what  we  had  done — that 
we  had  cut  those  grooves,  and  he  said 
the  engine  handled  a  great  deal  better 
and  a  great  deal  easier.  He  had  run  the 
engine  previously  a  great  deal,  and  he 
discovered  it  without  knowing  anything 
about  what  had  been  done,  so  that  I  rather 
came  to  the  conclusion  that  there  was 
really  some  merit  in  those  grooves.  The 
only  difficulty  there  can  be  in  it  is  this. 
At  a  certain  point  you  may  have  what 
steam  will  blow  through  this  £in.  hole 
down  into  the  steam  port.  That  may  be 
a  disadvantage,  but  there  is  only  a  certain 


time  during  the  stroke  of  the  engine  that 
that  can  take  place.  During  the  other 
part  of  the  stroke  you  have  what  steam 
goes  through,  and  from  this  fin.  by  14in. 
or  15in.  port,  to  lift  up  on  the  valve  and 
take  that  much  weight  off  the  surface. 
I  wanted  to  state  this  fact,  and  state  what 
this  engineer  said  abont  it.  On  the 
strength  of  that  experience  I  have  put 
the  same  thing  into  three  or  four  engines 
since  with  pretty  good  results.  It  has 
not  been  more  than  four  months  since 
the  experiment  began,  so  I  cannot  tell 
you  what  the  result  will  be  finally,  but 
I  simply  suggest  it  to  the  Convention. 
It  is  a  simple,  easy  thing  to  try,  and 
any  one  can  try  it,  for  I  do  not  think 
there  is  any  patent  on  it." 

It  is  not  very  easy  to  see  why  this 
groove  gave  good  results,  and  we  must 
rest  content  with  Mr.  Jackman's  verdict. 
In  our  opinion,  balancing  valves  will 
scarcely  accomplish  the  required  end  in 
the  case  of  locomotives  ;  and  inventors 
would  do  well  to  devote  their  attention 
to  the  production  of  some  species  of 
piston  valve  which  will  accomplish  what 
is  required.  To  produce  such  a  valve 
under  the  conditions  is  not  an  easy  task> 
but  the  success  which  has  attended  Mr. 
Beattie  in  dealing  with  outside  cylinder 
engines  may  serve  to  stimulate  others 
to  grapple  with  engines  with  inside  cylin- 
ders. 


THE  BEHAVIOR  OF  FLUID,  WITH  SPECIAL  REFERENCE  TO 
THE  RESISTANCE  OF  SHIPS.*      • 


From  "Iron." 


By  the  term  "  resistance"  I  mean  the 
opposing  force  which  a  ship  experiences 
in  its  progress  through  the  water.  Con- 
sidering the  immense  aggregate  amount 
of  power  expended  in  the  propulsion  of 
ships  ;  or,  in  other  words,  in  overcoming 
the  resistance  of  ships,  I  trust  you  will 
look  favorably  on  an  attempt  to  eluci- 
date the  causes  of  this  resistance.  It  is 
true  that  improved  results  in  shipbuild- 
ing have  been  obtained  through  accumu- 
lated experience  ;  but  it  unfortunately 
happens  that  many  of  the  theories  by 

*  Avpaper  read  before  the  Mechanical  Section  of  the 
British  Association  by  W.  Froude,  C.  E. 


which  this  experience  is  commonly  inter- 
preted, are  interwoven  with  fundamen- 
tal fallacies,  which,  passing  for  princi- 
ples, lead  to  mischievous  results  when 
again  applied  beyond  the  limits  of  actual 
experience.  The  resistance  experienced 
by  ships  is  but  a  branch  of  the  general 
question  of  the  forces  which  act  on  a 
body  moving  through  a  fluid,  and  has 
within  a  comparatively  recent  period 
been  placed  in  an  entirely  new  light  by 
what  is  commonly  called  the  theory  of 
stream-lines. 

It  is  convenient  to  consider  first  the 
case   of  a  completely  submerged  body 


THE   BEHAVIOR   OF   FLUID. 


439 


moving  in  a  straight  line  with  iiniform 
speed  through  an  unlimited  ocean  of 
fluid.  A  fish  in  deep  water,  a  subma- 
rine motive  torpedo,  a  sounding-lead 
while  descending  through  the  water,  if 
moving  at  uniform  speed,  are  all  exam- 
ples of  the  case  I  am  dealing  with.  It  is 
a  common  but  erroneous  belief  that  a 
body  thus  moving  experiences  resistance 
to  its  onward  motion  by  an  increase  of 
pressure  on  its  head  end,  and  a  diminu- 
tion of  pressure  on  its  tail  end.  It  is 
thus  supposed  that  the  entire  head  end 
of  the  body  has  to  keep  on  exei'ting 
pressure  to  drive  the  fluid  out  of  the 
way,  to  force  a  passage  for  the  body, 
and  that  the  entire  tail  end  has  to  keep 
on  exerting  a  kind  of  suction  on  the  fluid 
to  induce  it  to  close  in  again — that  there 
is,  in  fact,  what  is  termed  plus  pressure 
throughout  the  head  end  of  the  body  and 
minus  pressure  or  partial  vacuum 
throughout  the  tail  end. 

This  is  not  so  ;  the  resistance  to  the 
progress  of  the  body  is  not  due  to  these 
causes.  The  theory  of  stream-lines  dis- 
closes to  us  the  startling,  but  true  propo- 
sition, that  a  submerged  body,  if  moving 
at  a  uniform  speed,  through  a  perfect 
fluid,  would  encounter  no  resistance 
whatever.  By  a  perfect  fluid,  I  mean  a 
fluid  which  is  free  from  viscosity,  or 
quasi-sodidity,  and  in  which  no  friction 
is  caused  by  the  sliding  of  the  particles 
of  the  fluid  past  one  another,  or  past  the 
surface  of  the  body.  The  property 
which  I  describe  as  "  quasi-solidity" 
must  not  be  confused  with  that  which 
persons  have  in  their  minds  when  they 
use  the  term  "  solid  water."  When  the 
people  in  this  sense  speak  of  water  as 
being  "  solid,"  they  refer  to  the  sensation 
of  solidity  experienced  on  striking  the 
water-surface  with  the  hand,  or  to  the 
reaction  encountered  by  an  oar-blade  or 
propeller.  What  I  mean  by  "  quasi-solid- 
ity," is  the  sort  of  stiffness  which  is  con- 
spicuous in  tar  or  liquid  imid  ;  and  this 
property  undoubtedly  exists  in  water, 
though  in  a  very  small  degree.  But  the 
sensation  of  solid  reaction  which  is  en- 
countered by  the  hand  or  the  oar-blade, 
is  not  in  any  way  due  to  this  property, 
but  to  the  inertia  of  the  water  :  it  is  in 
effect  this  inertia  which  is  erroneously 
termed  solidity  ;  and  this  inertia  is  pos- 
sessed by  the  perfect  fluid,  with  which 
we    are   going   to  deal,  as   fully  as  by 


water.  Nevertheless,  it  is  true,  I  am 
presently  going  to  show  you,  that  the 
perfect  fluid  would  offer  no  resistance  to 
a  submerged  body  moving  through  it  at 
a  steady  speed.  It  will  be  seen  that  the 
apparent  contradiction  in  term-  which  I 
have  just  advanced  is  cleared  up  by  the 
circumstance,  that  in  the  one  case  we  are 
dealing  with  steady  motion,  and  in  the 
other  case  with  the  initiation  of  motion. 
The  proposition  that  the  motion  of  a 
body  through  a  perfect  fluid  is  unre- 
sisted, or,  what  is  the  same  thing,  that 
the  motion  of  a  perfect  fluid  past  a  body 
has  no  tendency  to  push  it  in  the  direc- 
tion in  which  the  fluid  is  flowing,  is  a 
novel  one  to  many  persons  ;  and  to  such 
it  must  seem  extremely  startling.  It 
arises  from  a  general  principle  of  fluid 
motion,  which  I  shall  presently  put  be- 
fore you  in  detail,  namely,  that  to  cause 
a  perfect  fluid  to  change  its  condition  of 
flow  in  any  manner  whatever,  and  ulti- 
mately to  return  to  its  original  condition 
of  flow,  does  not  require,  nay,  does  not 
admit  of,  the  expenditure  of  any  power, 
whether  the  fluid  be  caused  to  flow  in  a 
curved  path,  as  it  must  do  in  order  to 
get  round  a  stationary  body  which  stands 
in  its  way,  or  to  flow  with  altered  speed, 
as  it  must  do  in  order  to  get  through  the 
local  contraction  of  channel  which  the 
presence  of  the  stationary  body  practi- 
cally ci'eates.  Power,  it  may  indeed  be 
said,  is  first  expended,  and  force  ex- 
erted to  communicate  certain  motions  to 
the  fluid  ;  but  that  same  power  will  ulti- 
mately be  given  back,  and  the  force 
counterbalanced,  when  the  fluid  yields 
up  the  motion  which  has  been  communi- 
cated to  it,  and  returns  to  its  original 
condition. 

Assume  a  pipe  bent,  and  its  ends 
joined  so  as  to  form  a  complete  circular 
ring,  and  the  fluid  within  it  running  with 
velocity  round  the  circle.  This  fluid,  by 
centrifugal  force,  exercises  a  uniform, 
outward  pressure  on  every  part  of  the 
uniform  curve ;  and  this  is  the  only 
force  the  fluid  can  exert.  This  pressure 
tends  to  tear  the  ring  asunder,  and  causes 
a  uniform  longitudinal  tension  on  each 
part  of  the  ring,  in  the  same  manner  as 
the  pressure  within  a  cylindrical  boiler 
makes  a  uniform  tension  on  the  shell  of 
the  boiler.  Now,  in  the  case  of  fluid  run- 
ning round  within  rings  of  various  diam- 
eter, just  as  in  the  case  of  railway  trains 


440 


VAN  nostrand's  engineering  magazine. 


running  round  curves  of  various  diam- 
eter, if  the  velocity  along  the  curve  re- 
main the  same,  the  outward  pressure  on 
each  part  of  the  circumference  is  less,  in 
proportion  as  the  diameter  becomes 
greater  ;  but  the  circumferential  tension 
of  the  pipe  is  in  direct  proportion  to  the 
pressure  and  to  the  diameter  ;  and  since 
the  pressure  has  been  shown  to  be  in- 
versely as  the  diameter,  the  tension  for 
a  given  velocity  will  be  the  same,  what- 
ever be  the  diameter.  Thus,  if  we  take 
a  ring  of  double  diameter,  if  the  velocity 
is  unchanged,  the  outward  pressure  per 
lineal  inch  will  be  halved ;  but  this 
halved  pressure,  acting  with  the  double 
diameter,  will  give  the  same  circumfer- 
ential tension.  Now  this  longitudinal 
tension  is  the  same  at  every  part  of  the 
ring  ;  and  if  we  cut  out  a  piece  of  the 
ring  and  supply  the  longitudinal  tension 
at  the  ends  of  the  piece,  by  attaching 
two  straight  pipes  to  it  tangentially,  and 
if  we  maintain  the  flow  of  the  fluid 
through  it,  the  curved  portion  of  the 
pipe  will  be  under  just  the  same  strains 
as  when  it  formed  part  of  the  complete 
ring.  It  will  be  subject  merely  to  a 
longitudinal  tension ;  and  if  the  pipe 
thus  formed  be  flexible,  and  fastened  at 
the  ends,  the  flow  of  fluid  through  it  will 
not  tend  to  disturb  it  in  any  way. 
Whatever  be  the  diameter  of  the  ring- 
out  of  which  the  piece  is  assumed  to  be 
cut,  and  whatever  be  the  length  of  the 
segment  cut  out  of  it,  we  have  seen  that 
the  longitudinal  tension  will  be  the  same 
if  the  fluid  be  moving  at  the  same 
velocity  ;  so  that  if  we  piece  together 
any  number  of  such  bends  of  any  lengths 
and  any  curvatures  to  form  a  pipe  of 
any  shape,  such  pipe,  if  flexible  and  fast- 
ened at  the  ends  will  not  be  disturbed 
by  the  flow  of  fluid  through  it  ;  and  the 
equilibrium  of  each  portion  and  of  the 
whole  of  the  combined  pipe  will  be 
satisfied  by  a  uniform  tension  along  it. 
-Further,  if  the  two  ends  of  the  pipe  are 
in  the  same  straight  line,  pointing  away 
from  one  another,  since  the  tensions  on 
the  ends  of  the  pipes  are  equal  and  op- 
posite, the  flow  of  the  fluid  through  it 
does  not  tend  to  push  it  bodily  endways. 
This  is  the  point  which  it  was  my  object 
to  prove  ;  but  in  the  course  of  this  proof 
there  has  incidentally  appeared  the  j 
further  proposition  that  a  flexible,  tortu- 
ous pipe,  if  fastened  at  the  ends,  will  not 


tend  to  be  disturbed  in  any  way  by  the 
flow  of  fluid  through  it.  This  proposi- 
tion may  to  some  persons  seem  at  first 
sight  to  be  so  paradoxical  as  to  cast 
some  doubt  on  the  validity  of  the  reason- 
ing which  has  been  used  ;  but  the  pro- 
position is  neveitheless  true,  as  can  be 
proved  by  a  closely  analogous  experi- 
ment, as  follows  :— Imagine  the  ends  of 
the  flexible  tortuous  pipe  to  be  joined  so 
as  to  form  a  closed  figure  ;  there  will 
then  be  no  need  for  the  imaginary 
fastenings  at  the  ends,  since  each  end  will 
supply  the  fastening  to  the  other.  Then 
substitute  for  the  fluid  flowing  round 
the  circuit  of  the  pipe  a  flexible  chain, 
,  running  in  the  same  path.  In  this  case 
|  the  centrifugal  f orees  of  the  chain  run- 
|  ning  in  its  curved  path  are  similar  to 
;  those  of  the  fluid  flowing  in  the  pipe  ; 
[  and  the  longitudinal  tension  of  the  chain 
1  represents  in  every  particular  the  longi- 
tudinal tension  on  the  pipe.  As  a  sim- 
ple form  of  this  experiment,  if  a  chain 
be  set  rotating  at  a  very  high  velocity 
over  a  pulley,  it  will  be  seen  that  the 
centrifugal  forces  do  not  tend  to  disturb 
the  path  of  the  running  chain  ;  and,  in- 
deed, the  velocity  being  extremely  great, 
the  forces,  in  fact,  tend  to  preserve  the 
path  of  the  chain  in  opposition  to  any 
disturbing  cause.  On  the  other  hand, 
if  by  sufficient  force  we  disturb  it  from 
its  path,  it  tends  to  retain  the  new  fig- 
ure which  has  been  thus  imposed  upon 
it.  The  stream  of  fluid  in  the  tortuous 
flexible  pipe  would  behave  in  a  strictly 
analogous  manner. 

[Here  the  author  clearly  illustrated 
his  propositions  by  means  of  elaborate 
diagrams.] 

As  streams  approach  a  body,  their 
first  act  is  to  broaden,  and  consequently 
to  lose  velocity,  and  therefore,  as  we 
know,  to  increase  in  quasi-hydrostatic 
pressure.  Presently  they  again  begin  to 
narrow,  and  therefore  quicken,  and  di- 
minish in  pressure,  until  they  pass  the 
middle  of  the  body,  by  which  time  they 
have  become  narrower  than  in  their 
original  undisturbed  condition,  and  con- 
sequently have  a  greater  velocity  and 
less  pressure  than  the  undisturbed  fluid. 
After  passing  the  middle  they  broaden 
again  until  they  become  broader  than  in 
their  original  condition,  and  therefore 
have  less  velocity  and  greater  pressure 
than  the  undisturbed  fluid.     Finally,  as 


THE  BEHAVIOR   OF   FLUID. 


441 


they  recede  from  the  body  they  narrow- 
again,  until  they  ultimately  resume  their 
original  dimension,  velocity,  and  press- 
ure. Thus,  taking  the  pressure  of  the 
surrounding  undisturbed  fluid  as  a  stand- 
ard, we  have  an  excess  of  pressure  at 
both  the  head  and  stern  ends  of  the 
body,  and  a  defect  of  pressure  along  the 
middle. 

We  will  now  consider  what  will  be  the 
result  of  substituting  an  ocean  of  water 
for  an  ocean  of  perfect  fluid.  The  dif- 
ference between  the  behavior  of  water 
and  that  of  the  theoretically  perfect 
fluid  is  twofold,  as  follows  : — First.  The 
particles  of  water,  unlike  those  of  a  per- 
fect fluid,  exert  a  drag  or  fractional  re- 
sistance upon  the  surface  of  the  body  as 
they  glide  along  it.  This  action  is  com- 
monly termed  surface-friction,  or  skin- 
friction  ;  and  it  is  so  well-known  a  cause 
of  resistance  that  I  need  not  say  any- 
thing further  on  this  point,  except  this, 
that  it  constitutes  almost  the  whole  of 
the  resistance  experienced  by  bodies  of 
tolerably  easy  shape  traveling  under 
water  at  any  reasonable  speed.  Secondly. 
The  mutual  frictional  resistance  exper- 
ienced by  the  particles  of  water  in  mov- 
ing past  one  another,  combined  with  the 
almost  imperceptible  degree  of  viscosity 
which  water  possesses,  somewhat  hinders 
the  necessary  stream-line  motions,  alters 
their  nice  adjustment  of  pressures  and 
velocities,  and  thus  defeats  the  balance 
of  stream-like  forces  and  induces  resist- 
ance. 

This  action,  however,  is  imper- 
ceptible in  forms  of  fairly  easy  shape. 
On  the  other  hand,  angular  or  very 
blunt  features  entail  considerable  resist- 
ance from  this  cause,  because  the  stream- 
line distortions  are  in  such  cases  abrupt, 
and  degenerate  into  eddies,  thus  causing 
great  difference  of  velocity  between  ad- 
jacent particles  of  water,  and  great  conse- 
quent friction  between  them.  "Dead 
water,"  in  the  wake  of  a  ship  with  a  full 
run,  is  an  instance  of  this  detrimental 
action. 

So  far  we  have  dealt  with  submerged 
bodies  only  ;  we  will  now  take  the  case 
of  a  ship  traveling  at  the  surfaee  of  the 
water.  But  first,  let  us  suppose  the  sur- 
face of  the  water  to  be  covered  with  a 
sheet  of  rigid  ice,  and  the  ship  cut  off 
level  with  her  water-line,  so  as  to  travel 
beneath  the   ice,  floating,  however,   ex- 


actly in  the  same  position  as  before.     As 
the  ship  travels  along,    the    stream-like 
motions  will  be  the  same  as  for  a  sub- 
merged body,  of  which  the  ship  may  be 
regarded   as   the   lower    half ;  and   the 
ship  will  move  without  resistance,  except 
that  due  to  surface-friction  and  mutual 
friction  of   the  particles.      The  stream- 
like motions  being  the  same  in  character 
as  those  we  have  been  considering,  we 
shall  still  have  at  each  end  an  excess  of 
pressure  which  will  tend  to  force  up  the 
sheet  of  ice,  and  along  the  side  we  shall 
have  defect  of  pressure  tending  to  suck 
down  the  sheet  of  ice.     If,  now,  we  re- 
move the  ice,  the  water  will  obviously 
rise  in  level  at  each  end,  so  that  excess 
of  hydrostatic  head  may  afford  the  nec- 
essary  reaction    against   the    excess   of 
pressure  ;  and  the  water  will  sink  by  the 
sides,  so  that  defect  of  hydrostatic  head 
may  afford  reaction  against  the  defect  of 
pressure.     The    hills   and  valleys    thus 
formed   in   the   water   are,   in   a   sense, 
waves  ;  and,  though  originating  in  the 
stream-like  forces-  of  the  body,  yet  when 
originated,  they  come  under  the  domin- 
ion of  the  ordinary  laws  of  wave-motion, 
and,  to  a  large  extent,  behave  as  inde- 
pendent waves.    The  consequences  which 
result  from  this  necessity  are  most  intri- 
cate ;  but   the   final   upshot   of   all  the 
different   actions    which    take    place   is 
plainly  this — that  the  ship  in  its  passage 
along  the  surface  of  the  water  has  to  be 
continually   supplying  the  waste    of  an 
attendant  system  of  waves,  which  from 
the  nature  of  their  constitution  as  inde- 
pendent waves,  are  continually  diffusing 
and   transmitting    themselves    into   the 
surrounding  water,  or,  where  they  form 
what  is  called  broken  water,  crumbling 
away  into  froth.     Now,  waves  represent 
energy,  or  work  done  ;  and  therefore  all 
the    energy   represented   by   the  waves 
wasted  from  the  system  attending  the 
ship,  is  so  much  work  done  by  the  pro- 
pellers or  tow-ropes  which  are  urging  the 
ship.     So  much  wave-energy  wasted  per 
mile  of  travel,  is  so  much  work  done  per 
mile  ;    and  so  much  work  done  per  mile 
is  so  much  resistance.     The  actions  in- 
volved in  this  cause  of  resistance,  which 
is   sometimes    termed    "Wave-genesis/" 
are    so    complicated   that   no    extensive 
theoretical  treatment  of  the  subject  can 
be  usefully  attempted.     All  that  can  be 
known  about  this  subject  must,  for  the 


442 


VAN  nostrand's  engineering  magazine. 


present,  I  believe,  be  sought  by  direct 
experiment. 

Having  thus  briefly  described  the  sev- 
eral elements  of  a  ship's  resistance,  I 
will  proceed  to  draw  your  attention 
more  particularly  to  certain  resulting 
considerations  of  practical  importance. 
Do  not,  however,  suppose  that  I  shall 
venture  on  dictating  to  shipbuilders 
what  sort  of  ships  they  ought  to  build  ; 
I  have  so  little  experience  of  the  practi- 
cal requirements  of  ship-owners,  that  it 
would  be  presumptuous  in  me  to  do  so  ; 
and  I  could  not  venture  to  condemn  any 
feature  in  a  ship  as  a  mistake,  when,  for 
all  I  know,  it  may  be  justified  by  some 
practical  object  of  which  I  am  ignorant. 
For  these  reasons,  if  I  imply  that  some 
particular  element  of  form  is  better  than 
some  other,  it  will  be  with  the  simple 
object  of  illustrating  the  application  of 
principles,  by  following  which  it  would 
be  possible  to  design  a  ship  of  given  dis- 
placement to  go  at  given  speed,  with 
minimum  resistance,  in  smooth  water — 
in  fact,  to  make  the  best  performance  in 
a  "  measured  mile"  trial. 

I  have  pointed  out  that  the  cause  of 
resistance  to  the  motion  of  a  ship  through 
the  water  are  : — first,  surface-friction  ; 
secondly,  mutual  friction  of  the  particles 
of  water  (and  this  is  only  practically 
felt  when  there  are  features  sufficiently 
abrupt  to  cause  eddies);  and  thirdly, 
wave-genesis.  I  have  also  shown  that 
these  are  the  only  causes  of  resistance. 
I  have  shown  that  a  submerged  body, 
such  as  a  fish,  or  torpedo,  traveling  in  a 
perfect  fluid,  would  experience  no  resist- 
ance at  all  ;  that  in  water  it  experiences 
practically  no  resistance  but  that  due  to 
surface-friction  and  the  action  of  eddies  ; 
and  that  a  ship  at  the  surface  experiences 
no  resistance  in  addition  to  that  due 
to  these  two  causes,  except  that  due  to 
the  waves  she  makes.  I  have  done  my 
best  to  make  this  clear  ;  but  there  is  an 
idea  that  there  exists  a  form  of  resist- 
ance, a  something  expressed  by  the  term 
^  "direct  head-resistance,"  which  is  inde- 
pendent of  the  above-mentioned  causes. 
This  idea  is  so  largely  prevalent,  of  such 
long  standing,  and  at  first  sight  so 
plausible,  that  I  am  anxious  not  to  leave 
any  misunderstanding  on  the  point. 

Lest,  then,  I  should  not  have  made 
my  meaning  sufficiently  clear,  I  say  dis- 
tinctly,  that   the  notion  of  head-resist- 


ance, in  any  ordinary  sense  of  the  word, 
or  the  notion  of  any  opposing  force  due 
to  the  inertia  of  the  water  on  the  area  of 
the  ship's  way,  a  force  acting  upon   and 
measured  by  the  area  of  midship  section 
is,  from  beginning  to  end,  an  entire  de- 
lusion.    No  such  force  acts  at  all,  or  can 
act.     ISTo  doubt,  if  two  ships  are  of  pre- 
cisely similar  design,  the  area  of  midship 
section  may  be  used  as  a  measure  of  the 
resistance,  becauoe  it  is  a  measure  of  the 
size  of  the  ship  ;  and  if  the  ships  were 
similar  in  every  respect,  so  also  would 
the  length  of  the  bowsprit,  or  the  height 
of  the  mast,  be  a  measure  of  resistance, 
and  for  just  the  same  reason.     But  it  is 
an   utter   mistake  to  suppose  that  any 
part   of   a   ship's  resistance  is  a  direct 
effect  of  the  inertia  of  the  water  which 
has  to  be  displaced  from  the  area  of  the 
ship's  way.     Indirectly  the  inertia  causes 
resistance  to  a  ship  at  the  surface,  be- 
cause the  pressure  due  to  it  makes  waves. 
But  to  a  submerged  body,  or  to  the  sub- 
merged portion  of  a  ship  traveling  be- 
neath rigid  ice   no   resistance  whatever 
will   be   caused   by   the   inertia   of  the 
water  which  is  pushed  aside.     And  this 
means  that,  if  we  compare  two  such  sub- 
merged bodies,  or  two  such  submerged 
portions  of  ships  traveling  beneath  the 
ice,  as  long  as  they  are  both  of  sufficiently 
easy  shape  not  to  cause  eddies,  the  one 
which  will  make  the  least  resistance   is 
the  one  which  has  the  least  skin  surface, 
though  it  have  twice  or  thrice  the  area 
of  midship  section  of  the  other. 

The  resistance  of  a  ship,  then,  practi- 
cally consists  of  three  items — namely, 
surface-friction,  eddy-resistance,  and 
wave-resistance.  Of  these  the  first- 
named  is,  at  least  in  the  case  of  large 
ships,  much  the  largest  item.  In  the 
Greyhound,  a  bluff  ship  of  1100  tons, 
only  170  feet  long,  and  having  a  thick 
stem  and  sternposts,  thus  making  consid- 
erable eddy-resistance,  and  at  ten  knots 
visibly  making  large  waves,  the  surface- 
friction  was  58  per  cent,  of  the  whole 
resistance  at  that  speed  ;  and  there  can 
be  no  doubt  that  with  the  long  iron 
ships  now  built,  it  must  be  a  far  greater 
proportion  than  that.  Moreover,  the 
Greyhound  was  a  coppered  ship,  and 
most  of  the  work  of  our  iron  ships  has 
to  be  done  when  they  are  rather  foul, 
which  necessarily  increases  the  surface - 
friction  item.     The    second  item  of  re- 


PINE   TIMBER. 


443 


sistance,  namely,  the  formation  of  ed- 
dies, is,  I  believe,  imperceptible  in  ships 
as  finely  formed  as  most  modern  iron 
steamships.  Thick  square-shaped  stems 
and  stern-posts  are  the  most  fruitful 
source  of  this  kind  of  resistance.  The 
third  item  is  wave-resistance.  On  this 
point,  as  we  have  seen,  the  stream-line 
theory  rather  suggests  tendencies,  than 
supplies  quantitative  results,  because, 
though  it  indicates  the  nature  of  the 
forces  in  which  the  waves  originate,  the 
laws  of  such  wave-combinations  are  so 
very  intricate  that  they  do  not  enable  us 
to  predict  what  waves  will  actually  be 
formed  under  any  given  conditions. 

There  are,  however,  some  rules,  I  will 
not  call  them  principles,  which  have  to 
some  extent  been  confirmed  by  experi- 
ment. At  a  speed  dependent  on  her 
length  and  form,  a  ship  makes  a  very 
large  wave-resistance.  At  a  speed  not 
much  lower  than  this,  the  wave-resist- 
ance is  considerably  less,  and  at  low 
speeds  it  is  insignificant.  Lengthening 
the  entrance  and  run  of  a  ship  tends  to 
decrease  the  wave-resistance  ;  and  it  is 
better  to  have  no  parallel  middle  body, 
but  to  devote  the  entire  length' of  the 
ship  to  the  entrance  and  run,  though  in 
this  case  it  be  necessary  to  increase  the 
midship  section  in  order  to  get  the  same 
displacement  in  a  given  length.  With 
a  ship  thus  formed,  with  fair  water-lines 
from  end  to  end,  the  speed  at  which 
wave-resistance    is    accumulating    most 


rapidly,  is  the  speed  of  an  ocean  wave, 
the  length  of  which,  from  crest  to  crest, 
is  about  that  of  the  ship  from  end  to 
end.  I  have  said  we  may  practically 
dismiss  the  item  of  eddy-resistance. 
The  problem,  then,  to  be  solved  in  de- 
signing a  ship  of  any  given  size,  to  go 
at  a  given  speed  with  the  least  resistance, 
is  to  so  form  and  proportion  the  ship 
that  at  the  given  speed  the  two  main 
causes  of  resistance,  namely,  surface- 
friction  and  wave-resistance,  when  added 
together,  may  be  a  minimum.  In  order 
to  reduce  wave-resistance  we  should 
make  the  ship  very  long.  On  the  other 
hand,  to  reduce  the  surface-friction  we 
should  make  her  comparatively  short,  so 
as  to  diminish  the  surface  of  wetted 
skin.  Thus,  as  commonly  happens  in 
such  problems,  we  are  endeavoring  to 
reconcile  conflicting  methods  of  improve- 
ment ;  and  to  work  out  the  problem  in 
any  given  case,  we  require  to  know  ac- 
tual quantities.  We  have  sufficient  gen- 
eral data  from  which  the  skin-resistance 
can  be  determined  by  simple  calculation ; 
but  the  data  for  determining  wave-resist- 
ance must  be  obtained  by  direct  experi- 
ments upon  different  forms  to  ascertain  its 
value  for  each  form.  Such  experiments 
should  be  directed  to  determine  the  wave- 
resistance  of  all  varieties  of  water-line, 
cross  section,  and  proportion  of  length, 
breadth  and  depth,  so  as  to  give  the 
comparative  results  of  different  forms  as 
well  as  the  absolute  result  for  each. 


PINE  TIMBER.* 

By  Mb.  C.  GRAHAM  SMITH. 
From  "  Engineering." 


Wood,  which  not  a  great  time  back 
was  one  of  the  principal  materials  of 
construction,  has  now  been  replaced  to 
so  great  an  extent  by  iron,  that  timber 
does  not  receive  the  attention  from  en- 
gineering students  which  it  did  in  the 
youth  of  our  older  members. 

Excepting  for  foundation  piles,  small 
roofs,  and  railway  platforms,  it  is  sel- 
dom employed  in  this  country  for  what 
may  be  termed  permanent  engineering 
structures.  Still,  as  many  of  us  stu- 
dents will  probably  be  engaged  on  work 

*  Read  before  the  students  of  the  Institution  of  Civil 
Engineers. 


in  new  countries,  the  development  of 
which  is,  to  a  great  extent,  dependent  on 
a  proper  employment  of  its  resources 
among  which  timber  generally  occupies 
a  position  by  no  means  unimportant,  and 
as  this  material  is  so  highly  appreciated 
by  the  contractor  for  staging,  temporary 
bridges,  and  other  appliances  necessary 
in  the  carrying  out  of  large  engineering 
contracts,  the  author  trusts  his  remarks 
may  prove  of  value. 

Where  speed  in  execution  is  the  point 
above  all  others  to  be  attained,  timber, 
unless  in  exceptional  cases,  is  the  mate- 
rial to  employ  ;  for  even  in  this  country 


444 


van  nostrand's  engineering  magazine. 


a  wooden  structure  may  be  put  up  in  the 
time  occupied  in  rolling  plates,  and  mak- 
ing templates  for  a  more  permanent  one 
of  iron. 

Pine  timber,  one  of  the  most  abundant 
and  useful  of  all  woods,  is  found  in  one 
species  or  another  nearly  all  over  North 
America,  and  the  countries  bordering  on, 
or  in  the  vicinity  of,  the  Baltic  Sea. 

Yellow,  white,  red  and  pitch  pine,  as 
also  white  and  black  spruce,  are  import- 
ed from  North  America  ;  that  from  the 
Baltic  is  invariably  known  as  fir  timber, 
and  is  usually  named  after  the  district 
or  country  in  which  it  is  grown. 

The  yellow  and  white  pines  of  America, 
although  botanically  different,  are,  in 
practice,  looked  upon  as  the  same  tim- 
ber. It  is  not  considered  so  durable  as 
the  Baltic  fir  when  exposed  to  the  weath- 
er in  this  country,  but  in  its  native  land 
it  seems  to  answer  well  ;  for  the  bridge 
over  the  Delaware  at  Trenton,  was  con- 
structed with  this  timber  in  1804,  and 
the  Pennsylvania  Railroad  Company 
have  only  now,  seventy  years  after  its 
erection,  considered  it  advisable  to  re- 
place it  by  an  iron  structure.  A  cargo 
of  this  timber  will  consist  of  balks  vary- 
ing in  length  from  20  ft.  to  60  ft., 
and  40  to  80  cubic  feet  in  content,  the 
average  scantling  being  about  16  in.  by 
16  in.,  and  short  logs  maybe  had  exceed- 
ing 26  in.  by  26  in.,  but  this  is  an  excep- 
tional size  which  commands  a  high  price. 
If  the  balks  composing  a  lot  of  this  tim- 
ber have  an  average  content  of  65  cubic 
feet,  it  may  be  bought  at  the  market 
rate  ;  and  if  1^  per  cent,  be  added  for 
each  5  ft.  above  65  ft.  and  up  to  80  cubic 
feet,  a  very  fair  approximation  to  the 
value  of  the  wood  will  be  obtained.  It 
is  much  in  request  for  pattern  making, 
and  other  purposes  requiring  a  soft,  non- 
resinous,  and  easily  worked  wood  ;  and 
has  a  good  quality  of  retaining  its  form 
when  subjected  to  heavy  working 
strains. 

The  red  pine  of  America,  so  named 
from  its  color,  is  slightly  harder  than  the 
yellow,  and  when  exposed  to  damp  is 
more  durable.  This,  although  an  easily 
worked  wood,  is  not  used  for  such  pur- 
poses as  pattern  making  on  account  of 
its  liability  to  twist  and  split,  but  when 
of  good  quality  it  is  an  excellent  wood 
for  masts  and  spars,  being  straight  grain- 
ed and  tolerably  free  from  knots.     It  is 


imported  in  balks  up  to  50  ft.  in  length, 
and  generally  about  40  cubic  feet  in  con- 
tent; the  approximate  extra  value  for  each 
5  ft.  above  this  size  is  l\  per  cent,  up  to 
50  cubic  feet.  The  average  scantling  is 
10  in.  by  10  in.,  but  it  may  be  had  in 
small  quantities  from  13  in.  to  14  in. 
square. 

Pitch  pine,  obtained  from  the  South- 
ern States  of  North  America,  is  disting- 
uished by  the  extremely  large  quantities 
of  resin  which  it  contains,  and  the  dis- 
tinctive character  of  its  annual  rings.  In 
point  of  strength  it  is  superior  to  yellow 
pine  and  Baltic  fir  to  an  extent  of  about 
30  per  cent.,  and  is  more  durable  than 
the  former  in  positions  subject  to  alter- 
nate wetness  and  dryness,  but  in  a  warm 
moist  atmosphere  it  will  very  quickly 
rot  ;  when  totally  immersed  in  water  or 
buried  underground  it  is  supposed  to  be 
surpassed  in  durability  by  Baltic  fir,  al- 
though its  use  in  these  positions  is  of  too 
recent  a  date  for  this  to  be  borne  out 
by  experience.  On  account  of  the  large 
amount  of  resin  which  this  wood  contains 
it  will  not  take  paint,  neither  is  it  con- 
sidered a  nice  wood  to  work  ;  for  these 
reasons  and  on  account  of  its  dearness, 
it  has  not  been  much  used  excepting  in 
the  balk  and  by  joiners  for  stairs  and 
flooring  boards.  It  is  imported  in  balks 
averaging  16  in.  X  16  in.  and  varying  in 
length  from  40  ft.  to  70  ft.  The  market 
average  is  about  80  cubic  feet,  and  the 
approximate  extra  value  for  each  5  ft. 
above  this  is  l£  per  cent,  up  to  100  cubic 
feet ;  but  special  sizes  up  to  150  cubic 
feet  may  be  obtained  at  high  prices. 
There  now  being  large  quantities  in  the 
market  its  price  is  considerably  reduced, 
and  it  is  consequently  coming  very  much 
more  into  use. 

American  white  and  black  spruce,  dis- 
tinguished by  the  color  of  its  bark,  is  a 
species  of  white  wood  which  forms  a 
good  tough  material  for  temporary  work; 
but  should  not  be  used  in  permanent 
situations,  as  it  shrinks,  warps,  cracks, 
and  is  very  liable  to  rot  when  exposed 
to  warmth  or  damp.  This  timber  is  im- 
ported in  deals  which  are  used  for  joists 
in  inferior  houses,  also  in  balks  varying 
from  30  cubic  feet  to  50  cubic  feet  in 
content,  but  more  frequently  in  unbark- 
ed  round  logs,  9  in.  to  12  in.  in  diameter 
at  the  butt,  and  varying  in  length  from 
20  ft.  to  50  ft.  ;  it  is  much  used  for  ship 


PINE   TIMBER. 


445 


spars  and  other  analogous  purposes,  in 
which  case  the  bark  is  generally  left  on 
until  the  wood  is  cut  up  for  use,  this  is 
said  to  preserve  it  from  the  rot  and 
otherwise  improve  it  ;  but  when  exposed 
to  the  weather  it  will  not  last  more  than 
five  or  six  years  unless  kept  properly 
painted  or  varnished. 

Baltic  fir  contains  no  small  quantity 
of  resin  and  is  somewhat  similar  in  ap- 
pearance and  texture  to  pitch  pine.  It 
is  slightly  stronger,  tougher,  and  when 
used  in  this  country  more  durable  than 
American  yellow  pine.  The  color  of  this 
wood  is  dependent  on  the  climate  and 
soil  in  which  it  is  grown,  and  varies 
from  light  yellow  to  red,  but  when 
named  by  color  considerable  ambiguity 
is  caused,  as  in  England  it  is  designated 
either  red  or  yellow  according  to  local 
custom.  It  is  an  excellent  material  when 
employed  in  dry  and  well  ventilated  situ- 
ations, or  when  completely  underground 
or  water  ;  still  like  most  other  woods 
it  does  not  answer  well  in  damp  situa- 
tions to  which  the  air  has  access.  Memel 
is  considered  to  be  the  most  durable  of 
the  whole  pine  class  ;  balks  of  this  tim- 
ber as  well  as  those  from  Riga,  Sweden 
and  Norway,  do  not  much  exceed  14 
in.  X  14  in.  X  40  ft.  in  length,  but  this  size 
may  be  obtained  at  the  market  rate. 
The  timber  from  the  north-western  pro- 
vinces of  Prussia,  may  be  had  from  18 
in.  to  20  in.  square  and  50  ft.  in  length 
without  much  additional  cost  ;  but  in 
order  that  there  may  be  little  sap  wood 
and  the  logs  be  made  as  parallel  as  pos- 
sible, it  is  usually  cross  cut  into  lengths 
varying  from  20  ft.  to  30  ft. 

In  newly  sawn  pine  timber  the  sap 
and  heart  wood  are  generally  very  clear- 
ly defined;  and  when  the  balks  are  lying 
in  the  yard  the  quantity  of  sap  wood 
may  be  roughly  estimated  in  the  early 
morning,  as  the  dew  will  cause  it  to  have 
a  moist  appearance  whilst  the  more  ma- 
tured timber  will  be  quite  dry. 

The  Baltic  spruce  is  not  so  tough  as 
that  obtained  from  America,  but  is  gen- 
erally considered  to  be  more  durable  ; 
still  there  is  little  choice  between  them, 
both  being  equally  unfit  for  any  perma- 
nent work  unless  thoroughly  seasoned 
and  kept  perfectly  dry,  but  not  warm. 
This  timber  is  largely  imported  from 
Norway,  and  being  often  45  ft.  or  more 
in  length  and  only  8  in.  or  9  in.  in  diam- 


eter at  its  thickest  part,  is  extensively 
used  for  scaffold  poles,  ladders  and  mine 
props. 

In  the  building  trade  there  are  certain 
favorite  scantlings  for  joists,  planks, 
roof  spars,  and  other  portions  of  a  struc- 
ture ;  merchants,  therefore,  frequently 
ship  a  cargo  of  pine  or  spruce  cut  into 
planks,  deals  and  battens  of  these  sizes. 
Planks,  deals  and  battens  are  usually  11 
in.,  9  in.  and  V  in.  in  width  respectively, 
by  2j  in.  to  3  in.  in  thickness,  and  some- 
times they  are  cut  4  in.,  but  this  is  an 
exceptional  size;  although  latterly  many 
have  been  imported  6  in.  thick  and  des- 
ignated the  "  double  deal."  One  great 
advantage  to  be  derived  from  employing 
this  foreign  cut  timber  is  that  it  is  very 
much  more  seasoned  than  when  import- 
ed in  whole  logs. 

Many  instance  of  wooden  structures 
having  stood  centuries  might  be  given, 
were  it  not  well  known  that  the  durabil- 
ity of  properly  seasoned  matured  timber 
is  beyond  computation,  when  employed 
in  those  situations  to  which  it  is  by  na- 
ture adapted.  Unfortunately  the  demand 
for  timber  is  so  great  that  it  is  felled  at 
improper  seasons,  and  consequently,  on 
its  arrival  in  this  country,  is  often  full 
of  sap,  and  sometimes  rot  will  be  found 
to  have  set  in;  and  this  latter  evil  is  not 
unfrequently  propitiated  after  its  arrival 
by  its  being  stored  on  undrained  waste 
ground  fully  exposed  to  the  influence  of 
this  humid  atmosphere,  and  so  badly  or 
closely  piled  that  there  is  no  ventilation 
whatever. 

Trees  for  timber  should  be  felled  whilst 
the  sap  is  not  in  circulation,  that  is  a 
month  or  six  weeks  after  they  have  be- 
gun to  cast  their  foliage.  Stripping  the 
bark  in  the  spring  and  felling  the  trees 
in  the  autumn  or  winter  is  stated  by 
some  authorities  to  harden  the  sap  wood 
and  make  it  firm  and  durable  ;  whilst 
others  consider  this  treatment  to  shorten 
the  life  of  timber,  and  render  it  very 
liable  to  rot.  These  remarks  do  not  ap- 
ply to  pine  timber,  as  it  is  an  evergreen, 
and  the  circulation  of  the  sap  is  still  a 
point  to  be  decided  by  botanists  ;  al- 
though practical  men  usually  consider  it 
to  be  less  active  during  the  winter 
months,  when  pine  and  fir  are  mostly 
felled;  but  so  far  as  the  author  can  learn 
this  time  is  chosen  merely  on  account  of 
the  convenience  it  affords  for  transport- 


446 


VAN  NOSTRAND'S   ENGINEERING   MAGAZINE. 


ing  the  timber  to  the  banks  of  the  fresh- 
ets, sometimes  a  distance  of  20  or  30 
miles  over  marshy  ground,  which,  unless 
frozen,  would  not  sustain  the  weight  of 
the  horses. 

In  Australia  the  bushmen  live  in  what 
are  termed  gunyahs  ;  these  are  simply 
roughly  formed  huts  covered  with  sheets 
of  bark  stripped  from  gum  trees,  the 
usual  practice  being  to  cut  a  ring  of  bark 
some  5  ft.  or  6  ft.  in  height  from  the 
trunks  of  those  trees  nearest  at  hand  ; 
the  tree  dies,  and  the  author  can  testify 
to  the  wood  becoming  hard  and  dry 
throughout  in  a  very  short  space  of  time. 
This  little  piece  of  bush  life  has  been  in- 
troduced as  giving  matter  for  discussion, 
the  process  of  "  ringing  "  appearing  to 
have,  under  some  circumstances,  suffi- 
cient merits  to  sanction  its  more  extend- 
ed application.  If  the  bark  be  severed 
shortly  after  the  leaves  have  begun  to 
shoot  they  must  depend  for  nourishment 
on  the  sap  already  within  the  tree, 
which,  through  the  medium  of  the  bark, 
will  be  more  or  less  exhausted  from  all 
parts  of  the  timber  ;  whereas  if  the  tree 
be  stripped  of  its  bark  the  wood  will 
simply  be  dried  by  the  influence  of  the 
atmosphere.  This  method  will  not  an- 
swer with  American  pine,  as  the  author 
has  been  informed  that  trees  killed  by 
this  or  other  means,  when  left  standing 
in  that  country,  will,  in  the  space  of 
from  8  to  12  months,  be  full  of  worms, 
which  seem  to  form  directly  under  the 
bark. 

Seasoning  timber  has  from  the  earliest 
dates  commanded  much  attention,  and 
numerous  methods  have  been  proposed 
for  superseding  nature;  among  the  prin- 
cipal of  these  are  water  seasoning,  boil- 
ing and  steaming.  Water  seasoning 
may  be  resorted  to  when  dealing  with 
small  scantlings,  but  with  large  balks  it 
is  of  little  service,  as  the  time  occupied 
in  penetrating  to  any  depth  is  very  con- 
siderable. Small  timber  treated  in  this 
way  is  not  liable  to  warp  or  crack,  the 
drying  being  carried  on  equally  from  the 
exterior  to  the  interior  ;  and  as  the  tim- 
ber is  said  to  season  more  rapidly,  timber 
ponds  are  considered  by  some  to  be  nec- 
essary appendages  to  a  timber  yard. 
Most  foreign  pine  wood  undergoes  this 
process  to  some  extent,  as  when  felled  it 
is  put  into  the  freshets  and  carried  by 
them  to  the  rivers,  where  it  is  made  into 


rafts  sometimes  four  or  five  balks  deep, 
and  taken  to  a  port  for  shipment,  so  be- 
ing afloat  from  four  to  six  months. 

The  time  required  for  seasoning  may 
be  curtailed  one-third  by  boiling  or 
steaming,  but  this  must  not  be  carried 
to  excess,  or  the  strength  and  elasticity 
of  the  wood  will  be  much  reduced  ;  it  is 
not,  therefore,  considered  advisable  to 
continue  the  process  longer  than  from 
50  to  75  minutes  for  each  inch  in  thick- 
ness, the  exact  time  being  determined  by 
the  nature  of  the  wood.  In  shipbuild- 
ing .  this  system  is  resorted  to,  as  the 
timber  when  hot  may  be  bent  to  almost 
any  curve,  and  it  is  supposed  to  be  a 
preventive  against  splitting,  warping  and 
the  dry  rot. 

The  generally  accepted,  although  not 
fully  determined,  theory  on  which  the 
success  of  these  systems  depends,  is  that 
the  sap  is  dissolved,  and  thus  a  better 
circulation  effected  ;  and  Mr.  Sagismund 
Beer  has  found  that  this  is  greatly  ex- 
pedited by  boiling  the  timber  in  a  solu- 
tion of  borax,  and  afterwards  washing  it 
in  hot  water.  Freshly  imported  timber 
of  small  size  when  treated  by  this  pro- 
cess is  fully  shrunk,  dried,  and  rendered, 
at  the  small  cost  of  4d.  or  5d.  per  cubic 
foot,  ready  for  use  in  the  course  of  a  few 
weeks  ;  still  it  is  to  be  feared  that  this 
method  will  not  be  found  so  efficacious 
when  dealing  with  large  scantlings,  as 
the  boiling  is  continued  about  six  hours 
for  each  inch  in  thickness,  whereby  the 
elasticity  of  the  exterior  fibres  of  the 
timber  must  be  impaired,  and  it  is  on 
these  that  the  strength  of  wood  mainly 
depends  when  used  as  struts  and  beams. 
It  is  said  that  these  difficulties  are  got 
over  by  injecting  the  solution  of  borax 
under  pressure,  and  as  some  experiments 
on  large  sizes  of  timber  will  probably  be 
carried  out  under  the  author's  supervision 
the  results  will  be  placed  at  the  disposal 
of  the  Institution,  even  should  these  pre- 
conceived opinions  prove  erroneous. 

Where  time  is  not  of  first  importance 
there  is  nothing  like  good  dry  fresh  air 
for  obtaining  sound  and  durable  timber ; 
deals  and  planks  are  much  sought  after 
when  seasoned  under  cover  in  this  way. 

The  time  occupied  in  seasoning  timber 
depends  so  much  on  circumstances  that 
it  cannot  be  reduced  to  any  rule  of 
thumb  ;  the  same  may  be  said  of  the 
weight  lost  during   the  process,   which 


PINE   TIMBER. 


447 


varies  with  each  species  of  timber  and 
must  not  be  taken  at  one-fifth  or  one- 
sixth  as  stated  by  some  authorities  ;  for 
instance  pitch  pine  will  not  lose  much 
more  than  one-fortieth  of  its  weight, 
whilst  English  oak  and  yellow  pine  will 
sometimes  be  reduced  as  much  as  one- 
fourth. 

Fresh  air  is  also  one  of  the  best  pre- 
ventives against  the  rot  ;  which  is  caused 
by  the  fermentation  of  the  sap  and  is  of 
two  kinds.  The  "  wet  rot"  caused  by 
alternate  wetness  and  dryness,  and  the 
"  dry  rot"  by  insufficient  ventilation. 

Many  nostrums  have  been  brought 
forward  for  its  cure,  but  as  they  have 
proved  of  no  practical  use  time  will  not 
now  be  taken  up  by  referring  to  them  ; 
when  once  the  rot  sets  in  unless  it  be 
entirely  cut  away  from  the  more  sound 
timber  the  whole  will  be  destroyed. 

Nature  in  addition  supplies  other  des- 
troying elements,  among  which  are  sea- 
worms,  and  in  tropical  climates  white 
ants,  the  latter  of  which  have  been 
known  to  honey-comb  the  sleepers  at  one 
end  of  a  line  of  railway  before  the  other 
was  completed  ;  but  when  the  railway 
is  once  finished  their  ravages  are  at  an 
end,  for  they  will  not  attack  timber  sub- 
ject to  continuous  vibration. 

The  most  destructive  sea-worms  are 
the  Teredo  navalis  and  the  IAmnoria 
terebans ;  the  former  species,  which  is 
commonly  known  as  the  ship-worm, 
seems  to  be  a  development  of  the  vege- 
tation which  attaches  itself  to  timber, 
for  it  enters  the  wood  by  the  smallest 
possible  hole  and  remains  therein,  in- 
creasing in  size  as  it  proceeds  ;  it  is  often 
found  the  length  of  one's  finger,  and  it 
is  said  to  have  reached  3  ft.  in  length 
and  f  in.  in  diameter.  The  latter  species 
consists  of  small  creatures  seldom  more 
than  \  in.  in  length,  still  they  do  fully 
as  much  mischief  as  their  larger  compan- 
ions. From  the  experiments  of  Mr. 
Stevenson  at  the  "  Bell  Rock,"  it  would 
appear  that  all  kinds  of  pine  wood  are 
completely  destroyed  by  the  Limnora 
terebans  in  periods  of  time  varying  from 
one  and  a  half  to  four  and  a  half  years. 
"  Kyanizing,"  "  Burnetizing,"  "  Creo- 
soting,"  and  other  methods  have  been 
adopted  for  preserving  timber  ;  but  as 
creosoting  is  now  generally  employed,  to 
the  exclusion  of  the  other  more  expensive 
processes,  in  most  situations  not  especial- 


ly liable  to  fire  or  where  its  odor  is  not 
objectionable,  it  will  alone  here  be  con- 
sidered. Timber  to  be  creosoted  is  put 
into  large  iron  cylinders  in  which  a  vac- 
uum is  maintained  for  a  period  governed 
by  the  quality,  scantling  and  condition 
of  the  wood  ;  by  this  means  the  sap  is 
withdrawn,  when  its  place  is  supplied 
by  creosote,  extracted  from  coal  tar,  in 
which  it  exists  to  the  extent  of  from  20 
to  23  per  cent.  ;  this  is  forced  into  the 
pores  of  the  timber  under  a  pressure  of 
from  100  lb.  to  180  lb.  per  square  inch. 
Yellow  pine  may  be  impregnated  with 
12  or  more  pounds  of  creosote  per  cubic 
foot,  but  10  lb.  is  the  quantity  usually 
specified  ;  and  in  order  to  get  thorough 
work  all  timber  should  be  weighed  both 
before  and  after  the  operation.  Nomin- 
al creosoting  is  practiced  to  no  little  ex- 
tent ;  the  vacuum  is  often  left  on  for 
too  short  a  time,  or  perhaps  not  put  on 
at  all,  the  wood  is  consequently  creosot- 
ed only  f  in.,  or  an  inch  in  depth  from 
the  surface  ;  and  should  it  not  be  pro- 
perly seasoned,  sap  is  confined  to  the  in- 
terior and  the  wood  rendered  most  liable 
to  decay.  This  has  in  fact  much  the 
same  effect  as  painting,  smoking,  or  char- 
ring, none  of  which  should  be  resorted 
to  until  the  wood  is  thoroughly  season- 
ed ;  it  is  often  desirable  to  leave  posts 
or  framed  structures  exposed  to  the 
weather  for  a  year  or  more  before  paint- 
ing them.  Creosoting  pine  timber  with 
10  lb.  per  cubic  foot  costs,  without  in- 
cluding wear  and  tear  of  plant,  about 
5^d.  per  cubic  foot  ;  it  reduces  its  trans- 
verse strength  fully  one-eighth,  but  at 
the  same  time  renders  it  very  durable 
and  protects  it  to  a  great  extent  against 
the  white  ant  and  sea-worms  ;  but  for 
what  length  of  time  timber  thus  prepar- 
ed will  stand  the  attacks  of  the  latter, 
has  not  yet  been  definitely  determined. 
Mr.  Stevenson  states  that  at  Invergordon 
and  other  places  the  worm  eats  freely 
thoroughly  creosoted  timber ;  but  at 
Ostend  creosoted  timber  was  at  the  end 
of  seven  years  untouched,  whilst  that 
uncreosoted,  but  otherwise  under  pre- 
cisely similar  circumstances,  was  com- 
pletely perforated  by  the  Teredo  in  two 
years  ;  and  many  like  instances  might 
be  given.  Mr.  Rendal,  in  giving  evi- 
dence before  the  Leith  Harbor  Commis- 
sioners, limits  the  life  of  creosoted  tim- 
ber submerged  in  that  port  to  20  years; 


448 


VAN  nostrand's  engineering  magazine. 


if  this  be  so  a  step  in  the  right  direction 
has  been  made,  for  Mr.  Stevenson  found 
that  the  Limnoria  terebans  began  to  at- 
tack even  greenheart  when  submerged 
nineteen  years ;  and  at  Wick  Harbor 
and  Salem  in  the  Sound  of  Mull  this 
timber  was  found  to  be  attacked  after 
being  submerged  only  four  years. 

Galileo  was  among  the  first  to  investi- 
gate the  strength  of  wooden  beams  on 
purely  mathematical  principles  ;  and, 
like  many  later  investigators,  after  em- 
ploying the  higher  mathematics  to  an 
unlimited  extent,  arrived  at  conclusions 
incompatible  with  practice.  To  use 
Tredgold's  words,  "  fortunately  that  pre- 
cision so  essential  to  the  philosopher  is 
not  absolutely  necessary  to  the  architect 
and  engineer,"  consequently  simple  for- 

bcP 
mulre,  such  as  W=C-y,  may  be  resort- 
ed to  in  practice.  These  formulas  are 
generally  deduced  from  actual  experi- 
ment in  the  manner  somewhat  as  fol- 
lows :  If  a  beam  of  b  inches  in  breadth, 
d  inches  in  depth,  and  L  feet  clear  span, 
breaks  with  a  weight  W  in  cwts.  applied 
at  the  centre,  it  is  not  difficult  to  deter- 
mine in  what  ratio  the  strength  of  an- 
other beam  of  the  same  material  will 
vary  ;  if  the  breadth  be  double  it  is  at 
once  evident  that  its  strength  is  doubled, 
if  its  length  be  double  its  strength  is 
practically  halved,  and  if  its  depth  be 
double  its  strength  will  be  increased 
four  times  ;  for  these  reasons  the  sec- 
tional areas  in  tension  and  compression, 
as  well  as  the  distance  apart  of  their 
centres  of  gravity  are  doubled,  conse- 
quently the  moment  of  resistance  of  the 
beam  is  increased  four  times,  and  simi- 
larly by  using  any  other  depth  it  will  be 
found  that  this  moment  varies  as  the 
square  of  the  depth.  The  breaking 
weight,  therefore,  varies  directly  as  the 
breadth  and  square  of  the  depth,  and  in- 
versely as  the  length,   therefore  W  a 

bcP 

-y- .     Now  it  is  well  known  that  the  ad- 

hesion  of  the  particles  or  fibres  to  one 
another  affect  the  strength  of  a  beam, 
to  an  extent  which  can  only  be  determin- 
ed by  introducing  an  unknown  quantity ; 

bd* 
W   therefore   becomes   equal  to   C  -^- , 

JL 

where  C  is  the  unknown,  but  nearly  con- 
stant, quantity,  the  value  of  which  can 


be  ascertained  only  by  actual  experiment. 
But  since  the  strengths  of  no  two  beams 
of  the  same  timber  and  scantlings  are 
precisely  the  same,  it  follows  that  no 
two  constants  will  be  equal  in  value  ; 
this  accounts,  to  some  extent,  for  the 
variety  of  scantlings  employed  for  one 
and  the  same  purpose.  A  short  time 
since  a  warehouse  floor  gave  way,  and 
the  engineers  employed  on  opposite 
sides  of  the  law  action  which  ensued  had 
little  difficulty,  by  using  the  extremes  of 
constants,  in  making  their  calculations 
suit  the  wishes  of  their  respective  clients. 
The  floor  was  thus  shown  on  good 
authority  to  be  at  the  same  time  both 
amply  strong  and  too  weak  ;  under 
these  circumstances  the  only  course  to 
pursue  was  to  call  in  an  independent 
witness,  who  not  being  content  to  accept 
a  constant  which  might  at  any  time  be 
disputed,  had  a  beam  from  the  floor  in 
question  tested,  deduced  a  constant  from 
the  result,  and  gave  his  evidence  accord- 
ingly. As  the  quality  of  timber  varies 
very  considerably,  even  in  the  same 
cargo,  before  employing  it  in  work  of 
any  magnitude,  one  or  more  average 
samples  should  be  tested,  and  a  constant 
deduced  on  which  all  calculations  for  the 
strength  of  the  timber  may  be  based, 
This  method  is  pursued  by  Mr.  Lyster. 
engineer-in-chief  to  the  Mersey  Docks, 
and  Harbor  Board  ;  and  as  it  has  been 
his  practice  for  many  years  past,  he  is 
now  in  possession  of  some  very  valuable 
results,  a  few  of  which,  by  his  kind  per- 
mission, are  put  before  you  in  the 
Addenda. 

The  experiments  given  have  been  se- 
lected on  account  of  their  being,  so  far 
as  the  author  can  learn,  the  largest 
scantlings  ever  tested.  The  constants 
of  Tredgold,  Barlow,  and  others  were 
obtained  by  testing  small  pieces  of  tim- 
ber, in  selecting  which  it  has  evidently 
gone  against  the  conscience  of  the  inves- 
tigators to  take  those  cross-grained  and 
containing  knots ;  but  timber  of  any 
size  has  always  more  or  less  of  these 
blemishes,  consequently  their  constants 
give  a  strength  to  timber  which  cannot 
be  attained  in  actual  work.  On  refer- 
ring to  the  Addenda  it  will  be  found 
that  (Experiment  No  I.)  a  best  selected 
Memel  fir  beam  13^-  in.  by  13  J  in.  with 
10  ft.  6  in.  clear  span  practically  gave 
way  with  a  distributed  load  of  56  tonsr 


PINE   TIMBER. 


449 


and  finally  broke  down  with  61  tons  ; 
whilst  the  distributing  breaking  weight 
of  this  beam  found  by  employing  the 
constant  for  Menael  given  by  Tredgold 
is  114  tons,  and  by  that  of  Barlow  120 
tons  ;  similar  results  will  be  obtained  if 
the  remaining  experiments  be  compared 
with  the  same  or  other  authorities. 

Constants  deduced  from  testing  large 
pieces  of  timber  will  be  found  in  the 
Addenda,  and  it  is  the  author's  opinion 
that  these  will  give  results  approximat- 
ing very  closely  to  ordinary  practice  ; 
should  this  meeting  take  a  similar  view 
there  will  be  little  difficulty  in  deducing 
from  them  other  constants  for  beams 
loaded  or  supported  in  any  way  what- 
ever ;  or  even  for  columns  which  are  of 
such  proportions  that  they  give  way 
wholly  by  flexure. 

The  deflection  of  timber  which  is  to 
be  used  in  a  permanent  structure  need 
hardly  be  considered,  so  long  as  factors 
of  safety  of  eight  or  ten  are  adhered  to, 
for  up  to  one-fifth  of  the  breaking  load 
it  is  certainly  not  excessive. 

In  conclusion  it  may  be  well  to  state 
that  the  author  has  based  his  remarks 
mostly  on  experience  gained  whilst 
studying  under  Mr.  Lyster  ;  and  he 
hopes  they  will  harmonize  with  those  of 
his  fellow-students. 

Addenda. 

The  accuracy  of  the  following  results 
is  beyond  question  ;  for  the  experiments 
were  carried  out  in  accordance  with  in- 
struction from  the  engineer  to  the  Mer- 
sey Dock  Board  under  the  supervi- 
sion of  the  resident  engineer  at  Birken- 
head. 

The  tests  by  hydraulic  machinery  were 
made  at  the  Birkenhead  Chain  Test 
Works  belonging  to  the  Dock  Board. 
This  machinery  is  so  arranged  that  it  is 
checked  by  three  separate  and  independ- 
ent appliances,  all  of  which  were  accu- 
rately adjusted.  Firstly,  by  a  lever  and 
dial,  the  lever  being  actuated  by  a  small 
metal  ram  worked  direct  from  the  press- 
ure on  the  cylinders  of  the  strain  being- 
registered  on  the  dial.  Secondly,  by 
dead  weights  lifted  by  a  small  ram  which 
is  also  worked  direct  from  the  pressure 
in  the  cylinders.  And  lastly,  by  dead 
weighted  levers  working  on  knife  edge 
centres  up  to  100  tons.  The  machinery 
was  constructed  by  Sir  William  Arni- 
Vol.  XIII.— No.  5—29 


strong  and  Co.'  and  is  fully  up  to  their 

usual  standard  of  workmanship. 

The   constants  deduced  or  given  are 

intended  to  be  employed  in  the  formula 

C  b  d2 
W= — =: —    where    W  =  the    breaking 

weight  at  centre  in  cwts.,  5=breadth  in 
inches,  d= depth  in  inches,  and  L= clear- 
span. 

No.  I. 

Experiment  with  two  best  selected 
Memel  fir  beams  13^  in.  wide,  13^  in. 
deep,  and  10  ft.  6  in.  clear  span.  Both 
beams  were  cut  from  the  same  balk  and 
placed  12  ft.  apart  centre  to  centre,  the 
space  between  them  being  bridged  with 
railway  metals,  upon  which  pig  iron  was 
loaded  until  .the  beams  broke. 

The  following;  observations  were  taken : 


Load 

Deflection. 

Distrib- 

uted on 
the  Two 
Beams. 

Beam 

cut  from 

Butt. 

Beam 

cut  from 

Top. 

Remarks. 

Tons. 

In. 

In. 

40.2 

.10 

.12 

59.6 

.31 

.27 

75.2 

.37 

.51 

97.3 

1.12 

1.45 

j  First  fracture  ob- 

(          served. 

f  The       deflection 

111.7 

J   not  taken  as  the 
j  beams  hadcrush- 

122.0 

Broke. 

Broke. 

[_       ed  at  ends. 

The  distributed  breaking  load  on  each 

122 

of  the  above  beams  is,  therefore, =  61 

2 

tons,  which  is  equivalent  to  30.5  tons  ap- 
plied at  the  centre. 

WL 


C: 


30.5X20X10.5 


6405 
2460 


13.5X13.5X13.5 
Therefore  C  =  2.60. 

No.  II. 

Experiment  with  two  Quebec  yelloAv 
pine  beams  14  in.  wide,  15  in.  deep,  and 
10  ft.  6  in.  clear  space.  Both  beams 
were  cut  from  the  same  log  and  tested 
in  precisely  the  same  manner  as  No.  I. 

The  following;  observations  were  taken  - 


450 


VAN   NOSTRAND'S   ENGINEERING   MAGAZINE. 


Summary  of  Timber  Experiments  Nos.  I.  to  V. 


Species  of  Timber. 

Scantling. 

Clear 
Span. 

Num- 
ber of 
Beams 
Tested. 

Average 
Break-load 
applied  at 

Centre. 

Average 
valve  of 
Cin  W= 
bd 

Remarks. 

Baltic  Memel  fir 

Quebec  yellow  pine . . 
Baltic  fir  (average). . . 
Pitch  pine 

In.      In. 
Il?ixl3i 

14  xl5 

6   xl2 

6   xl2 

6   xl2 

14  xl5 

14   xl5 

Ft.  In. 
10  6 
10  6 
12  3 
12  3 
12  3 
10  6 
10  6 

2 
2 

2 
2 

2 
2 
2 

Tons. 
SO.  50 
30.50 

9.50 
10.35 

800 
60.00 
36.00 

2.60 
2.03 
2.70  1 
2.93    1 

2.27    y 
4.00    | 
2.40  J 

Distributed  Load. 
C  Load  applied  at 

American  red  pine. . . 
Pitch  pine • 

J  centre   by   means 
1       of  hydraulic 

Quebec  yellow  pine. . 

(_      machinery. 

Deflection. 

Load  Dis- 

tributed on 
the  Two 

Practically 

Remarks . 

Beams. 

the  same  on 
both  Beams. 

Tons. 

Inches. 

26.6 

.18 

57.0 

.29 

69.6 

.39 

83.0 

.66 

102.0 

.87 

First  fracture  observ'd 

122.0 

Broke. 

0: 


The  beam  cut  from  the  top  end  of  the 
log  broke  down  bodily. 

The  distributed  breaking  load  on  each 

122 
of  the  beams  is,  therefore,  —  =61  tons, 

which  is  equivalent  to  30.5  tons  applied 
at  the  centre. 

WL 
~  bcF 

_30.5  X  20  X  10.5_6404 
_     14X15X15     _ 3150 
Therefore  C=2.03. 

No.  m. 

Experiment  to  ascertain  the  relative 
strength  of  Baltic  fir,  pitch  pine,  and 
American  red  pine.  Beams  6  in.  wide, 
12  in.  deep,  and  12  ft.  3  in.  clear  bear- 
ing. The  ends  of  the  logs  were  placed 
in  stirrups,  and  the  load  applied  at  the 
centre  by  means  of  hydraulic  machin- 
ery. 

The  following  observations  were  taken : 


.2  6 
a.  a 

03 


Tons 
3.0 
5.0 
7.5 

8.0 

8.5 

10.0 

10.2 

10.5 


Baltic  Fir. 


Deflection. 


So 
o3  sz 


In. 

.29 
.56 

.87 
Broke 


In. 
.37 
.60 

1.11 

1.93 

Broke 


Pitch  Pine. 


Deflection. 


e  6 


In. 

.11 

.28 

.53 

.78 
Broke 


S  6 

03  Jz 


In. 

.38 
.61 

.97 

1.31 

Broke 


Red  Pine. 


Deflection. 


a  d 

02^ 


In. 
.43 
.70 

Broke 


•5/* 
S  d 

03  Jz 


In. 
.37 

.61 

1.94 
Broke 


Baltic  Fir. — Average  breaking  weight 
applied  at  centre 


8.5  +  10.5 


=  9.5  tons.     C= 


WL 


bd" 


Therefore 

9.5X20X12.25 


C= 


2327 


6X12X12 


-  = =  2.70. 

864 


Pitch  Pine. — Average  breaking  weight 
applied  at  centre 

10.2+10.5 


10.35  tons. 


Therefore 

10.35X20X12.25 


C  = 


2536 


6X12X12 


864 


=  2.93. 


American  Red  Pine. — Average  break- 
ing weight  applied  at  centre 

7.5  +  8.5 
=  8  tons. 


TELFORD   AND   MACADAM   ROADWAY   PAVEMENT. 


451 


ThereforeC= 


8X20X12.25 


6X12X12 
No.  IV. 


I960      „  n. 

■ =2.27. 

864 


Experiment  with  two  pitch  pine  beams 
cut  from  the  same  log  14  in.  wide,  15  in. 
deep,  and  10  ft.  6  in.  clear  bearing. 
Tested  by  hydraulic  machinery  in  the 
same  manner  as  No.  III. 

The  following  observations  were  taken : 


Deflection. 

Load 

applied 

at 

Beam 

Beam 

Centre. 

cut  from 

cut  from 

Butt. 

Top. 

Tons. 

Inches. 

Inches. 

10.0 

-02 

.05 

20.0 

.22 

.27 

30.0 

.36 

.41 

40.0 

.49 

.61 

50. 0 

.72 

.93 

59.2 

Broke . 

60.0 

1.14 

In  testing  the  beam  cut  from  the  butt 
of  the  log,  the  strain  was  slacked  off  at 
60  tons,  and  on  account  of  being  again 
put  on  rather  too  suddenly  the  beam 
broke  with  57.5  tons,  but  there  can  be 
very  little  doubt  but  that  60  tons  is  very 
near  the  breaking  weight  of  the  speci- 
men. 

WL 


60X20X10.5      12,600 


14X15X15 


3150 


Therefore  C  =  4. 


No.  V. 

Experiment  with  two  Quebec  yellow 
pine  beams,  cut  from  different  logs,  14 
in.  wide,  15  in.  deep,  and  10  ft.  6  in. 
clear  span.  Tested  by  hydraulic  ma- 
chinery in  the  same  manner  as  No.  III. 

The  following  observations  were  taken : 


Load 
applied 

at 
centre. 

Deflection. 

Sample 
No.  1. 

Sample 
No.  2. 

Remarks. 

Tons. 
10.0 
20.0 
30.0 
34.0 
38.3 

Inches. 
.14 
.44 
.56 

Broke. 

Broke. 

Deflection  of  sam- 
ple No.  2  not 
taken. 

Average  breaking  weight   applied  at 
centre 

38.3  +  34 


C 


2 
WL 


=  36  tons. 


bd3 
_36X20X16.5 


7560 


14X15X!5        3150 
Therefore  C=2.40. 

From  a  careful  study  of  many  experi- 
ments on  both  large  and  small  scantlings 
of  timber,  and  taking  into  consideration 
that  sap  wood  is  generally  more  or  less 
present  in  most  beams,  the  author  would 
advise  that  the  following  constants  be 
employed  in  ordinary  work  :  Baltic  fir 
when  of  best  quality  2.6,  when  second 
rate  2.3  ;  Canadian  yellow  pine  2.2  ; 
pitch  pine  2.4  ;  and  American  red  pine 
2.3. 


TELFORD  AND  MACADAM  ROADWAY  PAVEMENT. 

By  A.  P.  STORKS,  Jr.,  C.  E. 
Written  for  Van  Nostrand's  Engineering  Magazine. 


In  the  construction  of  a  Telford  and 
Macadam  Roadway  Pavement,  the  first 
consideration  must  be  given  to  the  selec- 
tion of  the  materials  which  are  to  be 
used.  This  is  a  question  of  the  greatest 
importance,  for  with  poor  materials  it  is 
impossible  to  construct  a  good  and  dur- 
able  pavement.      The   location   of    the 


proposed  work  must  decide  which  of  the 
different  materials  of  which  it  is  proper 
to  construct  such  a  pavement  may  be 
used.  The  hardest  and  most  durable  rock 
that  can  be  procured  without  too  large 
an  expense  is  always  the  most  desirable. 

MATERIALS. 

For   the   "Telford"   foundation,   any 


452 


VAN   NOSTRAND'S   ENGINEERING   MAGAZINE. 


rock  which  is  not  too  easily  crushed  or 
decomposed  by  the  action  of  water,  may 
be  used.  Of  those  which  are  found 
most  common,  trap  rock  and  gneiss  are 
the  best  adapted  to  this  use  ;  they  are 
easily  sledged  to  the  required  shape  and 
size,  and  are  very  durable.  A  few  weeks 
since,  a  Telford  pavement  of  this  mate- 
rial, which  had  been  in  use  for  five 
years,  was  examined,  and  not  the  least 
signs  of  decomposition  could  be  discov- 
ered. 

For  broken  stone,  or  Macadam,  or  road 
metal,  as  it  is  sometimes  called,  a  hard 
and  tough  material  is  required,  such  as 
green  stone,  trap  rock,  hard  lime  stone, 
or  slag  from  iron  furnaces. 

For  the  surfacing  or  binding  of  the 
Macadam,  clean  sharp  gravel  or  the  screen- 
ings of  the  broken  stone  may  be  used. 
The  latter  can  be  surfaced  with  less 
rolling,  and  retains  moisture  for  a  longer 
time  when  sprinkled,  and,  therefore,  has 
the  preference. 

CROSS    SECTION. 

Before  the  materials  selected  for  the 
pavement  can  be  prepared,  the  cross 
section  of  the  pavement  must  be  decided 
upon.  This  must  be  governed  by  the 
kind  and  amount  of  traffic  it  is  required 
to  carry.  If  this  is  constant  and  heavy, 
a  thick  pavement  is  reqired  ;  if  there  is 
to  be  but  little  travel  over  it,  as  upon  a 
country  road,  a  much  thinner  pavement 
will  be  all  that  is  necessary. 

For  city  use,  where  the  traffic  is  heavy, 
a  Telford  foundation  8  inches  in  thickr 
ness  is  laid,  and  covered  with  10  inches 
of  broken  stone.  Telford,  on  the  Holy- 
head roads  in  England,  laid  upon  a  level 
road  had  a  foundation  of  from  4  to  7 
inches  in  thickness,  placing  the  smaller 
stones  at  the  side  or  gutter,  and  the 
larger  ones  in  the  centre,  thus  giving 
the  surface  a  crown  from  the  gutter  to 
the  centre.  In  Germany,  upon  the  Govern- 
ment roads,  the  foundation  is  laid  from 
8  to  12  inches  in  thickness,  and  when 
the  pavement  is  laid  across  marsh  lands, 
two  courses  of  foundation  are  laid,  one 
upon  the  other,  each  of  them  12  inches 
in  thickness,  and  upon  this  the  road 
metal  is  placed. 

For  an  ordinary  highway  or  turnpike, 
a  Telford  foundation  6  inches  thick, 
with  6  inches  of  Macadam  upon  it,  thor- 
oughly rolled   and   surfaced,    affords   a 


perfect  protection  to  the  road  bed,  and 
is  therefore  all  that  is  required. 

In  all  eases,  whatever  may  be  the 
thickness  of  the  pavement  laid,  the  sur- 
face must  be  so  formed,  that  the  water 
falling  upon  it  will  run  to  either  side, 
when  it  will  be  conducted  by  the  gutter 
to  the  side  drains  or  sewers,  and  by  them 
removed  from  the  road.  If  this  crown 
is  too  great,  the  water  flowing  across  the 
pavement  rapidly  will  form  gutters  and 
destroy  the  surface  ;  this  must  be  care- 
fully avoided.  A  crown  of  1  in  60  for 
a  pavement  over  60  feet  in  width,  and  1 
in  30  for  one  of  less  width,  will  be  found 
suitable.  Upon  a  steep  grade  a  larger 
crown  is  required  than  upon  a  light  one, 
to  prevent  the  surface  water  from  flow- 
ing too  far  down  the  grade  and  over  the 
surface  of  the  road,  before  reaching  the 
gutter.  The  crown  should  take  the  form 
of  the  arc  of  a  circle.  Experience  has 
shown,  that  when  the  surface  of  a  pave- 
ment is  made  to  pitch  in  a  straight  line 
from  the  centre  of  the  roadway  to  either 
gutter,  that  passing  vehicles  are  inclined 
to  keep  near  the  gutter,  and  by  constant 
use  this  portion  of  the  road  is  worn 
down  more  rapidly  than  the  rest,  and  a 
hollow  is  formed  in  the  surface  which 
retains  the  water,  and  prevents  it  from 
flowing  into  the  gutter  ;  and  causes  it 
to  take  a  new  channel  for  itself  in  the 
roadway. 

ROAD    BED. 

Like  any  other  structure,  a  pavement 
must  have  a  firm  foundation  upon  which 
to  rest,  or  it  will  be  worthless.  The 
road  bed  must  be  carefully  prepared;  all 
rock  must  be  removed  to  a  sufficient 
depth  to  allow  6  inches  of  earth  between 
it  and  the  Telford.  All  boulders  which 
appear  on  the  surface  must  be  removed, 
and  the  holes  thus  made  filled  with  earth 
and  well  rammed.  Any  soft  loam  or 
decayed  vegetable  matter  should  be  re- 
placed by  good  firm  material.  The  road 
bed  should  be  shaped  to  the  crown  which 
the  pavement  will  have  when  completed, 
and  the  whole  surface  well  rolled  with 
an  iron  road  roller,  of  not  less  than  two 
tons  in  weight,  drawn  by  horses. 

Care  must  be  taken  to  drain  the  road 
bed  thoroughly,  so  that  neither  natural 
springs  nor  surface  water  shall  cause  the 
earth  of  which  it  is  formed  to  become 
soft  or  spongy.     The  road  bed  should  be 


TELFORD   ATsTD   MACADAM   ROADWAY   PAVEMENT. 


453 


raised  from  2  to  4  inches  above  the  re- 
quired grade  (after  making  allowance  for 
the  thickness  of  the  pavement)  to  allow 
for  settlement  caused  by  the  heavy  roll- 
ers, with  which  the  Macadam  is  rolled, 
forcing  the  Telford  into  the  road  bed, 
and  the  packing  of  the  materials  of 
which  it  is  formed. 

TELFORD   FOUNDATION. 

Upon  the  road  bed  is  laid  the  Telford 
foundation.  This  may  be  constructed  of 
any  good  firm  rock,  which  may  be  con- 
venient to  the  work  and  easily  procured. 
The  material  used  in  New  York  City 
for  this  purpose  is  gneiss  rock,  which  is 
found  in  large  quantities  upon  the  island. 
Its  abundance  and  consequent  cheapness 
recommend  it  ;  and  experience  has  prov- 
ed it  to  be  equal  to  any  kind  of  stone 
for  a  foundation.  Care  is  taken  to  select 
a  quality  that  does  not  contain  too  much 
mica,  and  which  is  firm  and  sound. 

The  rock  which  has  been  selected  for 
the  foundation  or  "  Telford,"  is  broken 
with  sledges  to  the  required  size.  The 
rule  is  that  the  stones  should  have  a 
base  of  not  more  than  80  or  less  than  12 
square  inches,  and  a  depth  of  a  little 
more  than  the  required  thickness  of  the 
foundation  when  completed.  These 
stones  are  set  in  courses  with  their  bases 
on  the  road  bed  and  their  greatest  length 
extending  across,  and  at  right  angles  to 
the  centre  line  of  the  road.  The  ends  of 
each  stone  are  clipped  square  so  as  to 
present  as  great  a  surface  as  possible  to 
the  adjoining  stones,  in  order  to  form  as 
strong  a  bond  as  possible.  Each  course 
must  be  laid  so  as  to  break  joints  with 
the  one  laid  before  it ;  the  stones  must 
be  set  plumb,  rather  than  at  right  angles 
to  the  grade  line;  this  is  done  so  that  the 
weight  of  passing  vehicles  may  be  re- 
ceived and  transferred  to  the  road  bed, 
without  forcing  the  stones  from  their 
positions. 

The  pavement  is  then  thoroughly 
wedged  by  forcing  small  pieces  of  stone 
into  all  the  interstices.  This  is  done 
with  an  iron  bar  about  4  feet  long  and 
l£  inch  in  diameter,  which  is  furnished 
with  a  wedge  shape  point,  and  a  round 
flat  head  about  2£  inches  in  diameter. 
With  the  point  of  the  bar  the  stones  are 
forced  apart,  and  into  the  spaces  thus 
formed  smaller  stones  are  driven  with 
the  head  of  the  bar.     When  this  wedd- 


ing is  done  thoroughly,  a  good  founda- 
tion for  the  Macadam  is  secured.  Any 
projecting  points  are  then  removed  from 
the  surface  of  the  "  Telford,"  by  break- 
ing them  off  with  a  small  hand  hammer; 
this  is  called  clipping.  Any  loose  stone 
remaining  upon  the  surface,  are  either 
removed  or  broken  to  about  the  size  of 
the  Macadam,  which  is  to  be  placed 
upon  the  road. 

The  object  of  this  foundation  is  two- 
fold. 1st,  It  is  the  means  of  distributing 
the  weight  or  pressure  which  is  applied 
to  the  surface  of  the  road,  over  a  large 
area  of  road  bed,  and  thus  preventing 
any  possibility  of  the  pavement  sinking 
and  becoming  uneven.  2d,  It  serves  as 
a  drain  for  any  water  that  would  other- 
wise collect  under  the  pavement,  and 
prevents  it  from  softening  or  otherwise 
injuring  the  road  bed. 

MACADAM    OR   ROAD   METAL. 

This  "  Telford  foundation  "  is  covered 
with  broken  stone,  called  "  Macadam  " 
or  "  road  metal,"  to  a  thickness  of  from 
6  to  12  inches.  This  course  receives  all 
of  the  wear  caused  by  the  traffic,  and 
defective  construction  here  will  increase 
very  largely  the  amount  of  labor  and 
materials  required  to  keep  the  road  in 
repair,  and  the  greatest  care  must  be  ex- 
ercised in  the  selection  of  the  material 
and  the  manner  in  which  they  are  ap- 
plied. The  road  metal  must  be  made  of 
a  tough  and  hard  substance.  Basaltic 
and  trap  rocks,  and  especially  those 
which  contain  a  large  percentage  of 
hornblende  are  the  best. 

Neither  granite,  nor  any  rock  which 
contains  quartz,  feldspar  or  mica,  in  any 
considerable  quantities,  should  be  used. 
They  are  easily  crushed,  and  such  as  con- 
tain feldspar  are  soon  decomposed  by 
the  action  of  the  weather. 

The  greater  the  specific  gravity,  the 
firmer  the  grain,  and  in  trap  rocks,  the 
more  decidedly  blue  the  color,  the  tough- 
er and  more  durable  is  the  rock. 

When  trap  rock  has  a  coarse  grain 
and  is  of  a  brownish  color,  it  will  crush 
easily,  and  decay  when  exposed  to  the 
action  of  the  weather.  More  or  less  of 
this  material  is  found  upon  the  surface 
of  all  beds  of  trap  rock,  but  should 
never  be  used  for  metaling  a  road. 

The  rock  selected  is  broken  by  hand 
or  machine  to  the  required  size.     In  this 


454 


van  nostrand's  engineering  magazine. 


city  the   specifications   are  as   follows  : 

"The  stone  to  be  of  trap  rock,  of  a 
sound,  hard  and  durable  quality,  entire- 
ly free  from  soft,  disintegrated,  or  other 
stone  that  can  be  easily  crushed,  to  be 
broken  to  a  uniform  size,  so  as  to  pass 
through  a  ring  of  from  1^  inches  to  2 
inches  in  diameter,  and  to  be  screened 
free  from  dust  and  dirt." 

Macadam  required  that  "all  stones 
should  be  broken  by  hand  into  angular 
fragments."  When  a  large  quantity  of 
stone  is  to  be  used,  it  is  almost  impos- 
sible to  get  it  broken  by  hand  to  the  re- 
quired size  as  rapidly  as  it  is  wanted. 

To  make  it  profitable,  the  men  em- 
ployed must  be  paid  by  the  yard,  and 
in  order  to  increase  their  wages  they 
will  leave  the  stone  too  large.  Nearly 
all  of  the  broken  stone  used  in  this  city, 
is  broken  from  the  spawls  taken  from 
the  "Trap  Block"  quarries  on  the  west 
of  the  Hudson  River  opposite  the  city. 

Machines  now  in  use,  known  as  the 
"  Improved  Blake  Crushers,"  break  the 
rock  into  "  angular  fragments "  suffi- 
ciently uniform,  and  to  any  desired  sizet 

Hand  broken  stone  require  less  rolling 
to  pack  them  than  machine  broken  stone, 
but  when  once  packed  they  make  equally 
durable  pavements. 

All  hand  broken  stones  should  be 
handled  with  forks  made  for  the  purpose, 
before  they  are  placed  upon  the  road, 
in  order  to  free  them  from  dirt  and 
dust. 

Machine  broken  stones  should  be  pass- 
ed over  a  scum  to  separate  from  them 
all  dust  and  fine  stone,  which  is  formed 
in  the  breaking.  This  fine  material  or 
"  scummings  "  may  be  used  to  advantage 
for  the  binding  or  surfacing  of  the  road. 

The  broken  stone  is  spread  upon  the 
Telford  foundation  in  two  layers  or 
courses  of  from  3  to  6  inches  in  thick- 
ness. The  first  layer  is  rolled  until  it 
ceases  to  settle,  and  is  firm  as  the  roller 
passes  over  it.  The  second  layer  is  then 
added  and  rolled  until  it  presents  a 
smooth  surface. 

On  the  first  Telford  and  Macadamized 
roads  built  in  this  city,  broken  stone  of 
gneiss  was  used  for  the  first  layer,  but  it 
proved  to  be  as  expensive  as  trap,  and 
was  much  inferior  to  it.  When  the  sec- 
ond layer  was  rolled  the  soft  stone  be- 
neath would  crush  to  a  powder.  The 
use  of  it  has  since  been  discontinued. 


Two  layers  of  broken  trap,  each  S 
inches  in  thickness,  make,  when  rolled, 
nearly  a  solid  mass  10  inches  in  thick- 
ness, making  with  the  Telford  founda- 
tion, as  laid  in  New  York,  a  pavement 
18  inches  in  thickness,  which  is  nearly 
impervious  to  water,  and  is  not  disturb- 
ed by  frost.  The  frost  often  penetrates 
the  earth  for  some  distance  below  the 
bottom  of  the  pavement,  but  it  never 
heaves  it. 

During  the  present  winter  (18*74  and 
1875),  I  made  an  examination  of  a  number 
of  different  pieces  of  this  pavement,  and 
found  in  every  case  that  the  frost  had 
penetrated  the  road  bed  for  a  depth  of 
from  9  to  18  inches,  and  thai  the  inter- 
stices in  the  Telford  foundation  were 
filled  with  ice,  but  in  not  a  single  instance 
was  the  pavement  disturbed  by  the  frost 
coming  out  of  the  ground. 

The  rolling  of  the  broken  stone,  and 
the  furnishing  of  the  surface,  is  done 
with  heavy  iron  rollers  moved  by  either 
steam  or  horse-power. 

A  sufficient  number  of  sprinkling  carts- 
are  provided  to  keep  the  stones  thorough- 
ly wet  during  the  process  of  rolling.. 
This  causes  them  to  pack  more  rapidly 
than  when  they  are  dry. 

SURFACING   AND   ROLLING. 

When  the  second  layer  of  broken  stone 
has  been  rolled  so  that  it  presents  a. 
smooth  surface,  it  is  thoroughly  wet,  and 
a  thin  layer,  about  one-half  an  inch  in 
thickness  of  clean  sharp  gravel,  or  what 
is  preferable,  screenings  and  clips  of 
trap  rock,  is  spread  over  it,  and  rolled, 
a  second  layer  is  spread  of  the  same  ma- 
terial, and  so  on,  until  the  water  from 
the  carts  ceases  to  penetrate  the  pave- 
ment, but  is  held  up  on  the  surface,  or, 
in  other  words,  the  surf  ace  is  "puddled." 

During  all  of  this  process  of  rolling, 
the  pavement  must  be  kept  thoroughly 
saturated  with  water.  When  the  sur- 
face is  puddled  the  heavy  rollers  are  re- 
moved, and  a  road  roller,  weighing  two 
tons,  which  is  drawn  by  horses,  keeps 
the  surface  smooth  until  it  is  thoroughly 
dry.  The  road  is  then  ready  to  be 
thrown  open  to  traffic. 

Where  the  grades  are  not  greater  than 
1  in  15,  steam  rollers  made  by  Aveling 
&  Porter,  England,  are  generally  used 
on  the  city  work — these  weigh  about  15 
tons.     On  any  grade  over  1  in  15,  large 


TELFORD   AND   MACADAM   ROADWAY   PAVEMENT. 


455 


iron  rollers,  weighing  about  8  tons,  and 
drawn  by  8  horses,  are  used. 

DRAINING. 

Drains  or  receiving  basins  should  be 
built  at  a  distance  of  not  more  than  300 
feet  apart,  to  take  the  water  which  is 
collected  in  the  gutters  away  from  the 
road. 

When  this  cannot  be  done,  and  the 
water  has  to  be  carried  a  greater  dis- 
tance by  the  gutter,  or  when  the  grade 
is  greater  than  1  in  40,  concrete  gutters 
should  be  laid.  For  this  purpose,  1  part 
cement,  2  parts  clean  sharp  sand,  and  6 
parts  clean  broken  stone,  are  mixed  to- 
gether. Sufficient  water  is  then  added 
to  bring  the  mass  to  a  proper  consist- 
ency. 

The  Macadam  is  removed  for  a  dis- 
tance of  2  feet  from  the  curb,  to  a 
depth  of  6  inches,  the  trench  thus  form- 
ed is  thoroughly  wet,  and  filled  with  the 
concrete,  which  is  settled  with  a  wooden 
rammer  until  it  is  flushed.  This  forms 
a  gutter  which  cannot  be  washed  away 
by  the  water,  and  adds  but  a  very  small 
amount  to  the  cost  of  the  road,  and  will 
save  a  great  deal  both  in  maintenance 
and  repairs. 

When  no  curb  is  laid  at  the  sides  of 
the  roadway,  a  gutter  made  of  trap 
block  or  cobble  stones  is  desirable,  this 
prevents  any  portion  of  the  pavement 
from  working  out  to  the  sides  of  the 
road. 

MAINTENANCE. 

A  Telford  and  Macadam  road  must 
be  properly  "  maintained  "  or  "  kept  up." 
If  this  is  done  thoroughly  from  the  start 
the  cost  of  repairs  of  the  road  will  be 
very  much  reduced.  In  fact,  a  road  that 
is  well  and  thoroughly  maintained,  needs 
very  little  repairing,  for  it  is  never  out 
of  order. 

Fresh  materials  must  be  added  in  small 
quantities,  as  they  are  needed,  to  keep 
the  road  to  its  proper  cross  section. 
Any  small  holes,  ruts,  loose  stone,  or 
other  imperfections  must  be  filled  or  re- 
moved; this  requires  the  constant  care  of 
industrious  and  trusty  men. 

A  road  should  be  divided  into  sections 
of  not  more  than  a  quarter  of  a  mile  in 
length.  At  or  about  the  centre  of  each 
section  should  be  a  small  quantity  of 
broken  stone  and  gravel,  to  be  used  as  it 
is  required  upon   the   section  ;  and  also 


a  place  where  all  droppings,  or  other  ma- 
terial taken  from  the  surface  of  the  road, 
may  be  deposited. 

One  man  can  take  care  of  from  four 
to  twelve  such  sections.  The  number 
depends  upon  the  width  of  the  road  and 
the  amount  of  traffic  over  it. 

When  a  pavement  is  new,  small  stones 
will  "prick  up."  These  must  be  removed, 
and  the  hole  formed  filled  with  gravel. 
Any  accumulation  of  mud  or  dust  must 
be  removed  by  scraping.  This  can  be 
done  just  after  a  shower,  when  the  road 
is  wet,  to  the  best  advantage.  The  road 
must  not  be  scraped  too  clean,  a  cover- 
ing of  £  inch  in  thickness  of  the  dust 
which  is  formed  by  the  wear  of  the  road 
metal  protects  the  surface  of  the  pave- 
ment, and  when  it  is  kept  moist,  as  it 
should  be,  makes  the  road  smoother  for 
the  passing  vehicles,  and  less  trying  to 
the  horses  driven  over  it. 

When  the  stones  of  which  the  pave- 
ment is  composed  become  bare,  a  very 
thin  layer  of  clean  sharp  gravel  should 
be  spread  over  it.  It  is  not  necessary  to 
roll  this,  the  wheels  of  passing  vehicles 
soon  form  it  into  a  smooth  surface. 
When  it  becomes  necessary  to  raise  the 
road,  to  its  original  cross  section,  the 
surface  should  be  "raised"  with  short 
picks,  so  that  new  material  placed  upon 
it  will  when  rolled  form  a  perfect  bond 
with  the  old  material. 

The  rolling  is  best  done  with  heavy 
rollers,  but  if  these  are  not  convenient, 
the  action  of  the  wheels  passing  over 
the  thin  coat  of  stone  will  in  time  serve 
the  same  purpose.  The  surface  of  the 
road  must  be  kept  moist,  but  not  wet,  if 
it  becomes  too  dry  the  stones  lose  their 
bond,  and  the  road  becomes  rough  ;  and 
too  much  water  will  soften  the  surface. 
and  in  time  will  form  ruts.  Both  of  these 
evils  must  be  carefully  avoided. 

The  following  data  are  the  result  of 
careful  experiments,  and  will  be  of  great 
value  and  convenience  in  making  esti- 
mates for,  or  in  the  construction  and 
maintenance  of,  a  Telford  and  Macadam- 
ized roadway  pavement  : 

One  man's  labor  for  10  hours  is  equiva- 
lent to  the  following  items  : 
2  cubic  yards  of  stone  sledged  for  Tel- 
ford pavement. 
8  cubic  yards  of  stone  loaded   and  un- 
loaded from  wao-on. 


456 


VAN   NOSTRAND'S   ENGINEERING   MAGAZINE. 


35  square   yards  8  in.  Telford  pavement 

laid. 
31  square   yards  8  in.  Telford  pavement 

wedged. 
60  square   yards  8  in.  Telford  pavement 

clipped. 
1 J  to  2  cubic  yards  trap  rock  broken  from 

quarry  spawls. 
16  cubic  yards  broken  stone   or  gravel 

spread  on  road. 

A  gang  of    men  for   paving  Telford 
pavement  should  be  devised  as  follows  : 

1  man  paving  to  every  6  ft.  in  width  of 

pavement. 
1  man  wedging  to  every  5  ft.  in  width 

of  pavement. 
1  man  clipping  to  every  10  feet  in  width 

of  pavement. 

A  steam  roller  requires 
1  steam  engineer. 
1  laborer  or  wheelman. 
1  water  cart. 
1  watchman. 


Aveling  &  Porter's  15  ton  road  roller 
will  consume  per  day  : 

^  to  £  ton  of  coal. 

■h  gal.  oil. 

ft-  lbs.  cotton  waste. 

Will  roll  and  finish  151  square  yards 
pavement. 

Each  steam  roller  should  be  attended 
by: 

2  sprinkling  carts. 

3  road  men   to  keep  the  surface  of  the 

road  to  the  required  shape,  and  to 
spread  gravel. 

Maintenance  : 

1  2-horse  monitor  will  sprinkle  in  the 
city,  when  water  is  convenient,  32,- 
000  square  yards  road. 

1  1-horse  cart  will  sprinkle  14,000  squai'e 
yards. 

1  man  will  keep  30,000  square  yards  of 
pavement  free  from  stones  and  drop- 
pings where  the  travel  is  constant. 


THE  ORIGIN  AND  GROWTH  OF  ENGINEERING  SCIENCE. 

Inaugural  Address  of  Sir  JOHN  HAWKSHAW,  F.  K.  S.,  before  the  British  Association. 
Condensed  from  report  in  "  Nature." 


To  those  on  whom  the  British  Asso- 
ciation confers  the  honor  of  presiding 
over  its  meetings,  the  choice  of  a  subject 
presents  some  difficulty. 

The  Presidents  of  Sections,  at  each 
annual  meeting,  give  an  account  of  what 
is  new  in  their  respective  departments  ; 
and  essays  on  science  in  general,  though 
■desirable  and  interesting  in  the  earlier 
years  of  the  Association,  would  be  less 
appropriate. 

Past  Presidents  have  already  discours- 
ed on  many  subjects,  on  things  organic 
and  inorganic,  on  the  mind  and  on  things 
perhaps  beyond  the  reach  of  mind,  and 
I  have  arrived  at  the  conclusion  that 
humbler  themes  will  not  be  out  of  place 
on  this  occasion. 

I  propose  in  this  Address  to  say  some- 
thing of  a  profession  to  which  my  life- 
time has  been  devoted — a  theme  which 
cannot  perhaps  be  expected  to  stand  as 
high  in  your  estimation  as  in  my  own, 


and  I  may  have  some  difficulty  in  making- 
it  interesting  ;  but  I  have  chosen  it  be- 
cause it  is  a  subject  I  ought  to  under- 
stand better  than  any  other.  I  propose 
to  say  something  on  its  origin,  its  work, 
and  kindred  topics. 

Rapid  as  has  been  the  growth  of 
knowledge  and  skill  as  applied  to  the 
art  of  the  engineer  during  the  last  cen- 
tury, we  must,  if  we  would  trace  its 
origin,  seek  far  back  among  the  earliest 
evidences  of  civilization. 

In  early  times,  when  settled  commu- 
nities were  few  and  isolated,  the  oppor- 
tunities for  the  interchange  of  knowledge 
were  scanty  or  wanting  altogether. 
Often  the  slowly  accumulated  results  of 
the  experience  of  the  wisest  heads  and 
the  most  skillful  hands  of  a  community 
were  lost  on  its  downfall.  Inventions 
of  one  period  were  lost  and  found  again. 
Many  a  patient  investigator  has  puzzled 
his  brain  in  trying  to  solve  a  problem 
which  had  yielded  to  a  more  fortunate 


ORIGIN   AND   GROWTH   OF   ENGINEERING   SCIENCE. 


457 


laborer  in  the  same  field  some  centuries 
before. 

The  ancient  Egyptians  had  a  knowl- 
edge of  Metallurgy,  much  of  which  was 
lost  during  the  years  of  decline  which 
followed  the  golden  age  of  their  civiliza- 
tion. The  art  of  casting  bronze  over 
iron  was  known  to  the  Assyrians,  though 
it  has  only  lately  been  introduced  into 
modern  metallurgy  ;  and  patents  were 
granted  in  1609  for  processes  connected 
with  the  manufacture  of  glass,  which 
had  been  practised  centuries  before.  An 
inventor  in  the  reign  of  Tiberius  devised 
a  method  of  producing  flexible  glass, 
but  the  manufactory  of  the  artist  was 
totally  destroyed,  we  are  told,  in  order 
to  prevent  the  manufacture  of  copper, 
silver,  and  gold  from  becoming  depre- 
ciated. 

Again  and  again  engineers  as  well  as 
others  have  made  mistakes  from  not 
knowing  what  those  had  done  who  have 
gone  before  them,  and  have  had  the 
same  difficulties  to  contend  with.  In 
the  long  discussion  which  took  place  as 
to  the  practicability  of  making  the  Suez 
Canal,  an  early  objection  was  brought 
against  it  that  there  was  a  difference  of 
32|  feet  between  the  level  of  the  Red 
Sea  and  that  of  the  Mediterranean.  La- 
place at  once  declared  that  such  could 
not  be  the  case,  for  the  mean  level  of 
the  sea  was  the  same  on  all  parts  of  the 
globe.  Centuries  before  the  time  of 
Laplace  the  same  objection  had  been 
raised  against  a  project  for  joining  the 
waters  of  these  two  seas.  According  to 
the  old  Greek  and  Roman  historians,  it  j 
was  a  fear  of  flooding  Egypt  with  the 
waters  of  the  Red  Sea  that  made  Darius, 
and  in  later  times  again  Ptolemy,  hesi- 
tate to  open  the  canal  between  Suez  and 
the  Nile.  Yet  this  canal  was  made,  and 
was  in  use  some  centuries  before  the 
time  of  Darius. 

Strabo  tells  us  that  the  same  objection 
that  the  adjoining  seas  were  of  different 
levels,  was  made  by  his  engineers  to 
Demetrius,  who  wished  to  cut  a  canal 
through  the  Isthmus  of  Corinth  some 
two  thousand  years  ago.  But  Strabo 
dismisses  at  once  this  idea  of  a  difference 
of  level,  agreeing  with  Archimedes  that 
the  force  of  gravity  spreads  the  sea 
equally  over  the  earth. 

When  knowledge  in  its  higher 
branches   was  confined  to  a  few,  those 


who  possessed  it  were  often  called  upon 
to  perform  many  and  various  services 
for  the  communities  to  which  they  be- 
longed ;  and  we  find  mathematicians 
and  astronomers,  painters  and  sculptors. 
and  priests  called  upon  to  perform  the 
duties  which  now  pertain  to  the  profes- 
sion of  the  architect  and  the  engineer. 
And  as  soon  as  civilization  had  advanced 
so  far  as  to  admit  of  the  accumulation 
of  wealth  and  power,  then  kings  and 
rulers  sought  to  add  to  their  glory  while 
living  by  the  erection  of  magnificent 
dwelling-places,  and  to  provide  for  their 
aggrandizement  after  death  by  the 
construction  of  costly  tombs  and  tem- 
ples. Accordingly  we  soon  find  men  of 
ability  and  learning  devoting  a  great 
part  of  their  time  to  building  and  archi- 
tecture, and  the  post  of  architect  became 
one  of  honor  and  profit.  In  one  of  the 
most  ancient  quarries  of  Egypt  a  royal 
high  architect  of  the  dynasty  of  the 
Psammetici  has  left  his  pedigree  sculp- 
tured on  the  rock,  extending  back  for 
twenty-three  generations,  all  of  whom 
held  the  same  post  in  succession  in  con- 
nection with  considerable  sacerdotal 
offices. 

As  there  were  in  these  remote  times 
officers  whose  duty  it  was  to  design  and 
construct,  so  also  there  were  those 
whose  duty  it  was  to  maintain  and  re- 
pair the  royal  palaces  and  temples.  In 
Assyria,  700  years  before  our  era,  as  we 
know  from  a  tablet  found  in  the  palace 
of  Sennacherib  by  Mr.  Smith,  there  was 
an  officer  whose  title  was  the  Master  of 
works.  The  tablet  I  allude  to  is  inscrib- 
ed with  a  petition  to  the  king  from  an 
officer  in  charge  of  a  palace,  requesting 
that  the  master  of  works  may  be  sent  to 
attend  to  some  repairs  which  were  much 
needed  at  the  time. 

Under  the  Roman  Empire  there  was 
almost  as  great  a  division  of  labor  in 
connection  with  building  and  design  as 
now  exists.  The  great  works  of  that 
period  were  executed  and  maintained  by 
an  army  of  officers  and  workmen,  who 
had  special  duties  assigned  to  each  of 
them. 

Passing  by  those  early  attempts  at  de- 
sign and  construction  which  supplied 
the  mere  wants  of  the  individual  and  the 
household,  it  is  to  the  East  that  we 
must  turn  if  we  would  find  the  earliest 
works   which   display   a   knowledge    of 


458 


VAN   NOSTRAND'S   ENGINEERING   MAGAZINE. 


engineering.  Whether  the  knowledge 
of  Engineering,  if  we  may  so  call  it, 
possessed  by  the  people  of  Chaldsea  and 
Babylonia  was  of  native  growth  or  was 
borrowed  from  Egypt  is,  perhaps,  a 
question  which  cannot  yet  be  answered. 
Both  people  were  agricultural,  dwelling 
on  fertile  plains,  intersected  by  great 
rivers,  with  a  soil  requiring  water  only 
to  enable  it  to  bring  forth  inexhaustible 
crops.  Similar  circumstances  would 
create  similar  wants,  and  stimulate  to 
action  similar  faculties  to  satisfy  them. 
Apart  from  the  question  of  priority  of 
knowledge,  we  know  that  at  a  very  early 
period,  some  four  or  five  thousand  years 
ago  at  least,  there  were  men  in  Mesopo- 
tamia and  Egypt  who  possessed  consider- 
able mechanical  knowledge,  and  no  little 
skill  in  hydraulic  engineering.  Of  the 
men  themselves  we  know  little  ;  happily, 
works  often  remain  when  the  names  of 
those  who  conceived  and  executed  them 
have  long  been  forgotten.     . 

It  has  been  said  that  architecture  had 
its  origin  not  only  in  nature,  but  in 
religion  ;  and  if  we  regard  the  earliest 
works  which  required  mechanical  knowl- 
edge and  skill,  the  same  may  be  said  of 
engineering.  The  largest  stones  were 
chosen  for  sacred  buildings,  that  they 
might  be  more  enduring  as  well  as  more 
imposing,  thereby  calling  for  improve- 
ment and  invention  of  mechanical  con- 
trivances, to  assist  in  transporting  and 
elevating  them  to  the  position  they  were 
to  occupy  ;  for  the  same  reason  the 
hardest  and  most  costly  materials  were 
chosen,  calling  for  further  improvement 
in  the  metal  forming  the  tools  required 
to  work  them.  The  working  of  metals 
was  further  perfected  in  making  images 
of  the  gods,  and  in  adorning  with  the 
more  precious  and  ornamental  sorts  the 
interior  and  even  external  parts  of  their 
shrines. 

The  earliest  buildings  of  stone  to 
which  we  can  assign  a  date  with  any 
approach  to  accuracy,  are  the  pyramids 
of  Gizeh.  To  their  builders  they  were 
sacred  buildings,  even  more  sacred  than 
their  temples  or  temple  palaces.  They 
were  built  to  preserve  the  royal  remains, 
until,  after  a  lapse  of  3,000  years,  which 
we  have  reason  to  believe  was  the  period 
assigned,  the  spirit  which  had  once  ani- 
mated the  body  should  re-enter  it.  Al- 
thoxigh     built     5,000    years     ago,    the 


masonry  of  the  Pyramids  could  not  be 
surpassed  in  these  days  ;  all  those  who 
have  seen  and  examined  them,  as  I  my- 
self have  done,  agree  in  this  ;  moreover,. 
the  design  is  perfect  for  the  purpose  for 
which  they  were  intended,  above  all  to 
endure.  This  building  of  pyramids  in 
Egypt  continued  for  some  ten  centuries,, 
and  from  60  to  70  still  remain,  but  none 
are  so  admirably  constructed  as  those  of 
Gizeh.  Still,  many  contain  enormous 
blocks  of  granite  from  30  to  40  feet 
long,  weighing  more  than  300  tons,  and 
display  the  greatest  ingenuity  in  the  way 
in  which  the  sepulchral  chambers  are 
constructed  and  concealed. 

The  genius  for  dealing  with  large 
masses  in  building  did  not  pass  away 
with  the  pyramid  builders  in  Egypt,  but 
their  descendants  continued  to  gain  in 
mechanical  knowledge,  judging  from  the 
enormous  blocks  which  they  handled 
with  precision.  When  the  command  of 
human  labor  was  unlimited,  the  mere 
transport  of  such  blocks  as  the  statue  of 
Rameses  the  Great,  for  instance,  which 
weighed  over  800  tons,  need  not  so 
greatly  excite  our  wonder ;  and  we 
know  how  such  blocks  were  moved  from 
place  to  place,  for  it  is  shown  on  the 
wall  paintings  of  tombs  of  the  period 
which  still  remain. 

But  as  the  weight  of  the  mass  to  be 
moved  is  increased,  it  becomes  no  longer 
a  question  of  only  providing  force  in  the 
shape  of  human  bone  and  muscle.  In. 
moving  in  the  last  century  the  block 
which  now  forms  the  base  for  the  statue 
of  Peter  the  Great,  at  St.  Petersburg, 
and  which  weighs  1,200  tons,  force  could, 
be  applied  as  much  as  was  wanted,  but 
great  difficulty  was  experienced  in  sup- 
porting it,  and  the  iron  balls  on  which 
it  was  proposed  to  roll  the  block  along 
were  crushed,  and  a  harder  metal  had  to 
be  substituted.  To  facilitate  the  trans- 
port of  material,  the  Egyptians  made 
solid  causeways  of  granite  from  the  Nile 
to  the  Pyramids  ;  and  in  the  opinion  of 
Herodotus,  who  saw  them,  the  cause- 
ways were  more  wonderful  works  than 
the  Pyramids  themselves. 

The  Egyptians  have  left  no  record  of 
how  they  accomplished  a  far  more  diffi- 
cult operation  than  the  mere  transport 
of  weight — that  is,  how  they  erected 
obelisks  weighing  more  than  400  tons. 
Some  of  these  obelisks  must  have  been. 


ORIGIN   AND   GROWTH   OF   ENGINEERING   SCIENCE. 


459' 


lifted  vertically  to  place  them  in  position, 
as  they  were  by  Fontana  in  Rome  in 
later  times,  when  the  knowledge  of 
mechanics,  we  know,  was  far  advanced. 

The  practice  of  using  large  blocks  of 
stone  either  as  monoliths  or  as  forming 
parts  of  structures  has  existed  from  the 
earliest  times  in  all  parts  of  the  world. 

The  Peruvians  used  blocks  weighing 
from  15  to  20  tons,  and  fitted  them  with 
the  greatest  nicety  in  their  cleverly  de- 
signed fortifications. 

In  India  large  blocks  were  used  in 
bridges  when  the  repugnance  of  Indian 
builders  to  the  use  of  the  arch  rendered 
them  necessary,  or  in  temples,  where,  as 
in  the  Temple  of  the  Sun  at  Orissa, 
stones  weighing  from  20  to  30  tons  form 
part  of  the  pyramidal  roof  at  a  height 
of  from  70  to  80  feet  from  the  ground. 
Even  as  late  as  the  last  century,  Indians, 
without  the  aid  of  machinery,  were  using 
blocks  of  granite  above  40  feet  long  for 
the  doorposts  of  the  gateway  of  Sering- 
ham,  and  roofing  blocks  of  the  same 
stone  for  a  span  of  21  feet. 

At  Persepolis,  in  the  striking  remains 
of  the  palaces  of  Xerxes  and  Darius, 
more  than  one  traveler  has  noted  the 
great  size  of  the  stones,  some  of  which 
are  stated  to  be  55  feet  long  and  6  to  10 
feet  broad. 

So  in  the  Greek  temples  of  Sicily, 
many  of  the  blocks  in  the  upper  parts  of 
the  temples  are  from  10  to  20  tons 
weight. 

The  Romans,  though  they  did  not 
commonly  use  such  large  stones  in  their 
own  constructions,  carried  off  the  largest 
obelisks  from  Egypt  and  erected  them 
at  Rome,  where  more  are  now  to  be 
found  than  remain  in  Egypt.  In  the 
temples  of  Baalbek,  erected  under 
Roman  rule,  perhaps  the  largest  stones 
are  to  be  found  which  have  been  used 
for  building  since  the  time  of  the  Pha- 
raohs. The  terrace  wall  of  one  of  the 
temples  is  composed  of  three  courses  of 
stones,  none  of  which  are  less  than  30 
feet  long  ;  and  one  stone  still  lies  in  the 
quarry  squared  and  ready  for  transport, 
which  is  70  feet  long  and  14  feet  square, 
and  weighs  upwards  of  1,135  tons,  or 
nearly  as  much  as  one  of  the  tubes  of 
the  Britannia  Bridge. 

I  have  not  mentioned  dolmens  and 
menhirs,  rude  unhewn  stones  often 
weighing  from  30  or  40  tons,  which  are 


found  from  Ireland  to  India,  and  from 
Scandinavia  to  the  Atlas,  in  Africa.  To 
transport  and  erect  such  rude  masses  re- 
quired little  mechanical  knowledge  or 
skill,  and  the  operation  has  excited  more 
wonder  than  it  deserves.  Moreover, 
Fergusson  has  gone  far  to  show  that  the 
date  assigned  to  many  of  them  hitherto 
has  been  far  too  remote  ;  most,  and 
possibly  all,  of  those  in  northern  and 
western  Europe  having  been  erected, 
since  the  time  of  the  Roman  occupation. 
And  to  this  day  the  same  author  shows 
that  menhirs,  single  stones  often  weigh- 
ing over  20  tons,  are  erected  by  hill 
tribes  of  India  in  close  proximity  to 
stone  buildings  of  elaborate  design  and 
finished  execution,  erected  by  another 
race  of  men. 

For  whatever  purpose  these  vast  stones- 
were  selected — whether  to  enhance  the 
value  or  to  prolong  the  endurance  of  the 
buildings  of  which  they  formed  a  part — 
the  tax  on  the  ingenuity  of  those  who 
moved  and  placed  them  must  have  tend- 
ed to  advance  the  knowledge  of  me- 
chanical appliances. 

The  ancient  Assyrians  and  Egyptians 
had  possibly  more  knowledge  of  mechan- 
ical appliances  than  they  are  generally 
credited  with.  In  the  wall  paintings 
and  sculptures  which  show  their  mode  of 
transporting  large  blocks  of  stone,  the 
lever  is  the  only  mechanical  power  rep- 
resented, and  which  they  appear  to  have 
used  in  such  operations  ;  nor  ought  we 
to  expect  to  find  any  other  used,  for,, 
where  the  supply  of  human  labor  was 
unlimited,  the  most  expeditious  mode  of 
dragging  a  heavy  weight  along  would 
be  by  human  power  ;  to  have  applied 
pulleys  and  capstans,  such  as  would  now 
be  employed  in  similar  undertakings, 
would  have  been  mere  waste  of  time.  In 
some  countries,  even  now,  where  manual 
labor  is  more  plentiful  than  mechanical 
appliances,  large  numbers  of  men  are 
employed  to  transport  heavy  weights, 
and  do  the  work  in  less  time  than  it 
could  be  done  with  all  our  modern 
mechanical  appliances.  In  other  opera- 
tions, such  as  raising  obelisks,  or  the 
large  stones  used  in  their  temple  palaces. 
where  human  labor  could  not  be  applied 
to  such  advantage,  it  is  quite  possible 
that  the  Egyptians  used  mechanical 
aids.  On  one  of  the  carved  slabs  which 
formed  part  of  the  wall  panelling  of  the 


460 


VAN   NOSTRAND'S   ENGINEERING   MAGAZINE. 


palace  of  Sardanapalus,  which  was  built 
about  930  years  before  our  era,  a  single 
pulley  is  clearly  shown,  by  which  a  man 
is  in  the  act  of  raising  a  bucket — prob- 
ably drawing  water  from  a  well. 

It  has  sometimes  been  questioned 
whether  the  Egyptians  had  a  knowledge 
of  steel.  It  seems  unreasonable  to  deny 
them  this  knowledge.  Iron  was  known 
at  the  earliest  times  of  which  we  have 
any  record.  It  is  often  mentioned  in  the 
Bible,  and  in  Homer  ;  it  is  shown  in  the 
early  paintings  on  the  walls  of  the  tombs 
;at  Thebes,  where  butchers  are  represent- 
•ed  as  sharpening  their  knives  on  pieces 
of  metal  colored  blue,  which  were  most 
probably  pieces  of  steel.  Iron  has  been 
found  in  quantity  in  the  ruined  palaces 
■of  Assyria  ;  and  in  the  inscriptions  of 
that  country  fetters  are  spoken  of  as 
having  been  made  of  iron,  which  is  also 
so  mentioned  in  connection  with  other 
metals  as  to  lead  to  the  supposition  that 
it  was  regarded  as  a  base  and  common 
metal.  Moreover,  in  the  Great  Pyramid 
a  piece  of  iron  was  found  in  a  place 
were  it  must  have  lain  for  5,000  years. 
The  tendency  of  iron  to  oxydize  must 
render  its  preservation  for  any  long 
period  rare  and  exceptional.  The  qual- 
ity of  iron  which  is  now  made  by  the 
native  races  of  Africa  and  India  is  that 
which  is  known  as  wrought  iron  ;  in 
ancient  times,  Dr.  Percy  says  the  iron 
which  was  made  was  always  wrought 
iron.  It  is  very  nearly  pure  iron,  and 
a  very  small  addition  of  carbon  would 
convert  it  into  steel.  Dr.  Percy  says 
the  extraction  of  good  malleable  iron  di- 
rectly from  the  ore  "  requires  a  degree  of 
skill  very  far  inferior  to  that  which  is 
implied  in  the  manufacture  of  bronze." 
And  there  is  no  great  secret  in  making 
steel ;  the  natives  of  India  now  make  ex- 
cellent steel  in  the  most  primitive  way, 
which  they  have  practised  from  time 
immemorial.  "When  steel  is  to  be  made, 
the  proportion  of  charcoal  used  with  a 
given  quantity  of  ore  is  somewhat  larger, 
and  the  blast  is  applied  more  slowly 
than  when  wrought  iron  is  the  metal  re- 
quired. Thus,  a  vigorous  native  work- 
ing the  bellows  of  skin  would  make 
wrought  iron  where  a  lazy  one  would 
have  made  steel.  The  only  apparatus 
required  for  the  manufacture  of  the 
finest  steel  from  iron  ore  is  some  clay 
for   making   a  small   furnace   four   feet 


high,  and  from  one  to  two  broad,  some 
charcoal  for  fuel,  and  a  skin  with  a  bam- 
boo tuyere  for  creating  the  blast. 

The  supply  of  iron  in  India  as  early  as 
the  fourth  and  fifth  centuries  seems  to 
have  been  unlimited.  The  iron  pillar  of 
Delhi  is  a  remarkable  work  for  such  an 
early  period.  It  is  a  single  piece  of 
wrought  iron  50  feet  in  length,  and  it 
weighs  not  less  than  17  tons.  How  the 
Indians  forged  this  large  mass  of  iron 
and  other  heavy  pieces  which  their  dis- 
trust of  the  arch  led  them  to  use  in  the 
construction  of  roofs,  we  do  not  know. 
In  [the  temples  of  Orissa  iron  was  used 
in  large  masses  as  beams  or  girders  in 
roof -work  in  the  thirteenth  century. 

The  influence  of  the  discovery  of  iron 
on  the  progress  of  art  and  science  cannot 
be  over-estimated.  India  well  repaid 
any  advantage  which  she  may  have  de- 
rived from  the  early  civilized  communi- 
ties of  the  West  if  she  were  the  first  to 
supply  them  with  iron  and  steel. 

An  interesting  social  problem  is  afford- 
ed by  a  comparison  of  the  relative  con- 
ditions of  India  and  this  country  at  the 
present  time.  India,  from  thirty  to  forty 
centuries  ago,  was  skilled  in  the  manu- 
facture of  iron  and  cotton  goods,  which 
manufacturers,  is  less  than  a  century, 
have  done  so  much  for  this  country.  It 
is  true  that  in  India  coal  is  not  so  abun- 
dant or  so  universally  distributed  as  in 
this  country.  Yet,  if  we  look  still  fur- 
ther to  the  East,  China  had  probably 
knowledge  of  the  use  of  metals  as  soon 
as  India,  and  moreover  had  a  boundless 
store  of  iron  and  coal.  Baron  Richtho- 
fen,  who  has  visited  and  described  some 
of  the  coal-fields  of  China,  believes  that 
one  province  alone,  that  of  Southern 
Shanshi,  could  supply  the  world  at  its 
present  rate  of  consumption  for  several 
thousand  years.  The  coal  is  near  the 
surface,  and  iron  abounds  with  it. 
Marco  Polo  tells  us  that  coal  was  uni- 
versally used  as  fuel  in  the  parts  of 
China  which  he  visited  towards  the  end 
of  the  fourteenth  century,  and  from 
other  sources  we  have  reason  to  believe 
it  was  used  there  as  fuel  2,000  years 
ago.  But  what  progress  has  China  made 
in  the  last  ten  centuries  ?  A  great 
future  is  undoubtedly  in  store  for  that 
country  ;  but  can  the  race  who  now 
dwell  there  develop  its  resources,-  or 
must  they  await  the  aid  of  an  Aryan 


ORIGIN   AND   GROWTH   OF   ENGINEERING   SCIENCE. 


461 


race  ?  Or  is  anything  more  necessary 
than  a  change  of  institutions,  which 
might  come  unexpectedly,  as  in  Japan  ? 

The  art  of  extracting  metals  from 
the  ore  was  practised  at  a  very  early 
date  in  this  country.  The  existence 
long  ago  of  tin  mines  in  Cornwall,  which 
are  so  often  spoken  of  by  classical 
writers,  is  well  known  to  all.  That  iron 
was  also  extracted  from  the  ore  by  the 
ancient  Britons  is  most  probable,  as  it 
was  largely  used  for  many  purposes  by 
them  before  the  Roman  conquest.  The 
Romans  worked  iron  extensively  in  the 
Weald  of  Kent,  as  we  assume  from  the 
large  heaps  of  slag  containing  Roman 
coins  which  still  remain  there.  The 
Romans  always  availed  themselves  of 
the  mineral  wealth  of  the  countries 
which  they  conquered,  and  their  mining 
operations  were  often  carried  out  on  the 
largest  scale,  as  in  Spain,  for  instance, 
where  as  many  as  forty  thousand  miners 
were  regularly  employed  in  the  mines  at 
New  Carthage. 

Coal,  which  was  used  for  ordinary 
purposes  in  England  as  early  as  the 
ninth  century,  does  not  appear  to  have 
been  largely  used  for  iron  smelting  until 
the  eighteenth  century,  though  a  patent 
was  granted  for  smelting  iron  with  coal 
in  the  year  1611.  The  use  of  charcoal 
for  that  purpose  was  not  given  up  until 
the  beginning  of  this  century,  since 
which  period  an  enormous  increase  in 
the  mining  and  metallurgical  industries 
has  taken  place  ;  the  quantity  of  coal 
raised  in  the  United  Kingdom  in  1873 
having  amounted  to  127  million  tons, 
and  the  quantity  of  pig  iron  to  upwards 
of  6-J  million  tons. 

The  early  building  energy  of  the  world 
was  chiefly  spent  on  the  erection  of 
tombs,  temples,  and  palaces. 

While,  in  Egypt,  as  we  have  seen,  the 
art  of  building  in  stone  had  5,000  years 
ago  reached  the  greatest  perfection,  so 
in  Mesopotamia  the  art  of  building  with 
brick,  the  only  available  material  in  that 
country,  was  in  an  equally  advanced 
state  some  ten  centuries  later.  That 
buildings  of  such  a  material  have  lasted 
to  this  day  shows  how  well  the  work 
was  done  ;  their  ruinous  condition  even 
now  is  owing  to  their  having  served  as 
quarries  for  the  last  three  or  four  thou- 
sand years,  so  that  the  name  of  Nebiichad- 
nezzar,   apparently  one  of  the  greatest 


builders  of  ancient  times,  is  as  common 
on  the  bricks  of  many  modern  towns  in 
Persia  as  it  was  in  old  times  in  Babylon. 
The  labor  required  to  construct  the 
brick  temples  and  palaces  of  Chaldsea 
and  Assyria  must  have  been  enormous. 
The  mound  of  Koyunjik  alone  contained 
14-^  million  tons,  and  represents  the  labor 
of  10,000  men  for  twelve  years.  The 
palace  of  Sennacherib,  which  stood  on 
this  mound,  was  probably  the  largest 
ever  built  by  any  one  monarch,  contain- 
ing as  it  did  more  than  two  miles  of 
walls,  panelled  with  sculptured  alabaster 
slabs,  and  twenty-seven  portals,  formed 
by  colossal  bulls  and  sphinxes. 

The  pyramidal  temples  of  Chaldaea  are 
not  less  remarkable  for  the  labor  be- 
stowed on  them,  and  far  surpass  the 
buildings  of  Assyria  in  the  excellence  of 
their  brickwork. 

The  practice  of  building  great  pyra- 
midal temples  seems  to  have  passed  east- 
wards to  India  and  Burmah,  where  it 
appears  in  buildings  of  a  later  date,  in 
Buddhist  topes  and  pagodas  ;  marvels 
of  skill  in  masonry,  and  far  surpassing 
the  old  brick  mounds  of  Chaldoea  in 
richness  of  design  and  in  workmanship. 
Even  so  late  as  this  century  a  king  of 
Burmah  began  to  build  a  brick  temple 
of  the  old  type,  the  largest  building, 
according  to  Fergusson,  which  has  been 
attempted  since  the  Pyramids. 

The  mere  magnitude  of  many  of  these 
works  is  not  so  wonderful  when  we  take 
into  account  the  abundance  of  labor 
which  those  rulers  could  command. 
Countries  were  depopulated,  and  their 
inhabitants  carried  off  and  made  to  labor 
for  the  conquerors.  The  inscriptions  of 
Assyria  describe  minutely  the  spoils  of 
war  and  the  number  of  captives  ;  and 
in  Egypt  we  have  frequent  mention 
made  of  works  being  executed  by  the 
labor  of  captive  peoples.  Hepodotus 
tells  us  that  as  many  as  360,000  men 
were  employed  in  building  one  palace 
for  Sennacherib.  At  the  same  time  it 
must  .  not  be  forgotten  that  the  very 
character  of  the  multitude  would  de- 
mand from  some  one  the  skill  and  brain  to 
organize  and  direct,  to  design  and  plan 
the  Avork. 

It  would  be  surprising  if  men  who 
were  capable  of  undertaking  and  suc- 
cessfully completing  unproductive  works 
of  such  magnitude  did  not  also  employ 


462 


van  nostrand's  engineering  magazine. 


their  powers  on  works  of  a  more  use" 
ful  class.  Traces  still  remain  of  such 
works  ;  enough  to  show,  when  compared 
with  the  scanty  records  of  the  times 
which  have  come  down  to  us,  that  the 
prosperity  of  such  countries  as  Egypt 
and  Mesopotamia  was  not  wholly  depend- 
ant on  war  and  conquest,  but  that  the 
reverse  was  more  likely  the  case,  and 
that  the  natural  capabilities  of  those 
countries  were  greatly  enlarged  by  the 
construction  of  useful  works  of  such 
magnitude  as  to  equal,  if  not  in  some 
cases  surpass,  those  of  modern  times. 

Egypt  was  probably  far  better  irri- 
gated in  the  days  of  the  Pharaohs  than 
it  is  now.  To  those  unacquainted  with 
the  difficulties  which  must  be  met  with 
and  overcome  before  a  successful  system 
of  irrigation  can  be  carried  out,  even  in 
countries  in  which  the  physical  conditions 
are  favorable,  it  may  appear  that  noth- 
ing more  is  required  than  an  adequate 
supply  of  unskilled  labor.  Far  more 
than  this  was  required  :  the  Egyptians 
had  some  knowledge  of  surveying,  for 
Eustathius  says  they  recorded  their 
marches  on  maps  ;  but  such  knowledge 
was  probably  in  those  days  very  limited, 
and  it  required  no  ordinary  grasp  of 
mind  to  see  the  utility  of  such  extensive 
works  as  were  carried  out  in  Egypt  and 
Mesopotamia,  and,  having  seen  the  util- 
ity, to  successfully  design  and  execute 
them.  To  cite  one  in  Egypt — Lake 
Moeris,  of  which  the  remains  have  been 
explored  by  M.  Linant,  was  a  reservoir 
made  by  one  of  the  Pharaohs,  and  sup- 
plied by  the  flood  waters  of  the  Nile. 
It  was  150  square  miles  in  extent,  and 
was  retained  by  a  bank  or  dam  60  yards 
wide  and  10  high,  which  can  be  traced 
for  a  distance  of  thirteen  miles.  This 
reservoir  was  capable  of  irrigating  1,200 
square  miles  of  country.  No  work  of 
this  class  has  been  undertaken  on  so  vast 
;a  scale  since,  even  in  these  days  of  great 
works. 

The  prosperity  of  Egypt  was  in  so 
great  a  measure  dependent  on  its  great 
river,  that  we  should  expect  that  the 
Egyptians,  a  people  so  advanced  in  art 
and  science,  would  at  an  early  period 
have  made  themselves  acquainted  with 
its  regime.  We  know  that  they  care- 
fully registered  the  height  of  the  annual 
rise  of  its  waters  ;  such  registers  still 
remain  inscribed  on   the   rocks   on   the 


banks  of  the  Nile,  with  the  name  of 
the  king  in  whose  reign  they  were 
made.  The  people  of  Mesopotamia 
were  equally  observant  of  the  regime  of 
their  great  rivers,  and  took  advantage  in 
designing  their  canals  of  the  different 
periods  in  the  rising  of  the  waters  of  the 
Tigris  and  Euphrates.  A  special  officer 
was  appointed  in  Babylon,  whose  duty 
it  was  to  measure  the  rise  of  the  river  ; 
and  he  is  mentioned  in  an  inscription 
found  in  the  ruins  of  that  city,  as  record- 
ing the  height  of  the  water  in  the  Tem- 
ple of  Bel.  The  Assyrians,  who  had  a 
far  more  difficult  country  to  deal  with, 
owing  to  its  rocky  and  uneven  surface, 
showed  even  greater  skill  than  the  Baby- 
lonians in  forming  their  can  Is,  tunnel- 
ing through  rock,  and  building  dams  of 
masonry  across  the  Euphrates.  While 
the  greater  number  of  these  canals  in 
Egypt  and  Mesopotamia  were  made  for 
the  purpose  of  irrigation,  others  seem  to 
have  been  made  to  serve  at  the  same 
time  for  navigation.  Such  was  the  canal 
which  effected  a  junction  between  the 
Mediterranean  and  the  Red  Sea,  which 
was  a  remarkable  work,  having  regard 
to  the  requirements  of  the  age  in  which 
it  was  made.  Its  length  was  about 
eighty  miles  ;  its  width  admitted  of  two 
triremes  passing  one  another.  At  least 
one  of  the  navigable  canals  of  Baby- 
lonia, attributed  to  Nebuchadnezzar,  can 
compare  in  extent  with  any  work  of  later 
times.  I  believe  Sir  H.  Rawlinson  has 
traced  the  canal  to  which  I  allude 
throughout  the  greater  part  of  its  course, 
from  Hit  on  the  Euphrates  to  the  Per- 
sian Gulf,  a  distance  of  between  four  and 
five  hundred  miles.  It  is  a  proof  of  the 
estimation  in  which  such  works  were 
held  in  Babylonia  and  Assyria,  that, 
among  the  titles  of  the  god  Vul  were 
those  of  "Lord  of  Canals,"  and  "The 
Establisher  of  Irrigation  Works." 

The  springs  of  knowledge  which  had 
flowed  so  long  in  Babylonia  and  Assyria 
were  dried  up  at  an  early  period.  With 
the  fall  of  Babylon  and  destruction  of 
Nineveh  the  settled  population  of  the 
fertile  plains  around  them  disappeared, 
and  that  which  was  desert  before  man 
led  the  waters  over  it  became  desert 
again,  affording  a  wide  field  for,  and  one 
well  worthy  of,  the  labors  of  engineers 
to  come. 

Such  was   not  the  case  with   Egypt. 


ORIGIN   AND   GROWTH   OF   ENGINEERING   SCIENCE. 


463 


Long  after  the  period  of  its  greatest 
prosperity  was  reached,  it  remained  the 
fountain  head  from  whence  knowledge 
flowed  to  Greece  and  Rome.  The  Phil- 
osophers of  Greek  and  those  who,  like 
Archimedes,  were  possessed  of  the  best 
mechanical  knowledge  of  the  time,  re- 
paired to  Egypt  to  study  and  obtain  the 
foundation  of  their  knowledge  from 
thence. 

Much  as  Greece  and  Rome  were  in- 
debted] to  Egypt,  it  will  probably  be 
found,  as  the  inscribed  tablets  met  with 
in  the  mounds  of  Assyria  and  Chaldsea 
are  deciphered,  that  the  latter  civiliza- 
tions owe,  if  not  more,  at  least  as  much, 
to  those  countries  as  to  Egypt.  This  is 
the  opinion  of  Mr.  Smith,  who,  in  his 
work  describing  his  recent  interesting 
discoveries  in  the  East,  says  that  the 
classical  nations  "borrowed  far  more 
from  the  valley  of  the  Euphrates  than 
that  of  the  Nile." 

In  the  science  of  astronomy,  which  in 
these  days  is  making  such  marvellous 
discoveries,  Chaldaea  was  undoubtedly 
preeminent.  Among  the  many  relics  of 
these  ancient  peoples  which  Mr.  Smith 
has  recently  brought  to  this  country  is  a 
portion  of  a  metal  astrolabe  from  the 
palace  of  Sennacherib,  and  a  tablet  on 
which  is  recorded  the  division  of  the 
heavens  according  to  the  four  seasons, 
and  the  rule  for  regulating  the  inter- 
calary month  of  the  year.  Not  only  did 
the  Chaldaeans  map  out  the  heavens  and 
arrange  the  stars,  but  they  traced  the 
motion  of  the  planets,  and  observed  the 
appearance  of  comets  ;  they  fixed  the 
signs  of  the  zodiac,  and  they  studied 
the  sun  and  moon  and  the  periods  of 
eclipses. 

But  to  return  to  that  branch  of  knowl- 
edge to  which  I  wish  more  particularly 
to  draw  your  attention,  as  it  grew  and 
spread  from  east  to  west,  from  Asia  over 
Europe.  Of-  all  nations  of  Europe  the 
Greeks  were  most  intimately  connected 
with  the  civilization  of  the  East.  A 
■maritime  people  by  the  nature  of  the 
land  they  lived  in,  colonization  followed 
as  a  matter  of  course  on  the  tracks  of 
itheir  trading  vessels  ;  and  thus,  more 
than  any  other  people,  they  helped  to 
spread  Eastern  knowledge  along  the 
shores  of  the  Mediterranean,  and  through- 
•out  the  shores  of  Europe. 

The  early  constructive  works  of  Greece, 


till  about  the  seventh  century  b.  c,  form 
a  strong  contrast  to  those  of  its  more 
prosperous  days.  Commonly  called  Pel- 
asgian,  they  are  more  remarkable  as  en- 
gineering works  than  admirable  as  those 
which  followed  them  were  for  architec- 
tural beauty.  Walls  of  huge  unshapely 
stones — admirably  fitted  together,  how- 
ever— tunnels  and  bridges  characterize 
this  period.  In  Greece,  during  the  few 
and  glorious  centuries  which  followed, 
the  one  aim  in  all  construction  was  to 
please  the  eye,  to  gratify  the  sense  of 
beauty  ;  and  in  no  age  was  that  aim 
more  thoroughly  and  satisfactorily  at- 
tained. 

In  these  days,  when  sanitary  questions 
attract  each  year  more  attention,  we  may 
call  to  mind  that  twenty-three  centuries 
ago  the  city  of  Agrigentum  possessed  a 
system  of  sewers,  which,  on  account  of 
their  large  size,  were  thought  worthy  of 
mention  by  Diodorus.  This  is  not,  how- 
ever, the  first  record  of  towns  being 
drained;  the  well  known  Cloaca  Maxima, 
which  formed  part  of  the  drainage  sys- 
tem of  Rome,  was  built  some  two  centu- 
ries earlier,  and  great  vaulted  drains 
passed  beneath  the  palace  mounds  of  un- 
bui'nt  brick  at  Nimrod  and  Babylon  ; 
and  possibly  we  owe  the  preservation  of 
many  of  the  interesting  remains  found 
in  the  brick  mounds  of  Chaldsea  to  the 
very  elaborate  system  of  pipe  drainage 
discovered  in  them,  and  described  by 
Loftus. 

Whilst  Pelasgian  art  was  being  super- 
seded in  Greece,  the  city  of  Rome  was 
founded  in  the  eighth  century  before 
our  era  ;  and  Etruscan  art  in  Italy,  like 
the  Pelasgian  art  in  Greece,  was  slowly 
merged  in  that  of  an  Aryan  race.  The 
Etruscans,  like  the  Pelasgians  and  the 
old  Egyptians,  were  Turanians,  and  re- 
markable for  their  purely  constructive  or 
engineering  works.  Their  city  walls  far 
surpass  those  of  any  other  ancient  race, 
and  their  drainage  works  and  .tunnels 
are  most  remarkable. 

The  only  age  which  can  compare  with 
the  present  one  in  the  rapid  extension  of 
utilitarian  works  over  the  face  of  the 
civilized  world,  is  that  during  which  the 
Romans,  an  Aryan  race,  as  we  are,  were 
in  power.  As  Fergusson  has  said,  the 
mission  of  the  Aryan  races  appears  to 
be  to  pervade  the  world  with  useful  and 
industrial  arts.     That  the  Romans  adorn- 


464 


VAN   NOSTRAND'S   ENGINEERING   MAGAZINE. 


ed  their  bridges,  their  aqueducts,  and 
their  roads  ;  that  with  a  sound  knowl- 
edge of  construction  they  frequently 
made  it  subservient  to  decoration,  was 
partly  owing  to  the  mixture  of  Etruscan 
or  Turanian  blood  in  their  veins,  and 
partly  to  their  great  wealth,  which  made 
them  disregard  cost  in  their  construction, 
and  to  their  love  of  display. 

It  would  be  impossible  for  me  to  do 
justice  to  even  a  small  part  of  the 
engineering  works  which  have  survived 
fourteen  centuries  of  strife,  and  remain 
to  this  day  as  monuments  of  the  skill, 
the  energy,  and  ability  of  the  great 
Roman  people.  Fortunately,  their  works 
are  more  accessible  than  those  of  which 
I  have  spoken  hitherto,  and  many  of  you 
are  probably  already  familiar  with  them. 

Conquerors  of  the  greater  part  of  the 
civilized  world,  the  admirable  organiza- 
tion of  the  Romans  enabled  them  to 
make  good  use  of  the  unbounded  re- 
sources which  were  at  their  disposal. 
Yet,  while  the  capital  was  enriched,  the 
development  of  the  resources  of  the 
most  distant  provinces  of  the  empire  was 
never  neglected. 

War,  with  all  its  attendant  evils,  has 
often  indirectly  benefited  mankind.  In 
the  long  sieges  which  took  place  during 
the  old  wars  of  Greece  and  Rome,  the 
inventive  power  of  man  was  taxed  to 
the  utmost  to  provide  machines  for 
attack  and  defence.  The  ablest  mathe- 
maticians and  philosophers  were  pressed 
into  the  service,  and  helped  to  turn  the 
scale  in  favor  of  their  employers.  The 
world  has  to  regret  the  loss  of  more  than 
one,  who,  like  Archimedes,  fell  slain  by 
the  soldiery  while  applying  the  best 
scientific  knowledge  of  the  day  to  de- 
vising means  of  defence  during  the  siege. 
In  these  days,  too,  science  owes  much  to 
the  labors  of  engineers  and  able  men, 
whose  time  is  spent  in  making  and  im- 
proving guns,  the  materials  composing 
them,  and  armor  plates  to  resist  them, 
or  in  studying  the  motion  of  ships  of 
war  in  a  seaway. 

The  necessity  for  roads  and  bridges 
for  military  purposes  has  led  to  their 
being  made  where  the  necessary  stimu- 
lus from  other  causes  was  wanting  ;  and 
so  means  of  communication,  and  the  in- 
terchange of  commodities,  so  essential 
to  the  prosperity  of  any  community, 
have   thus  been  provided.      Such   was 


the  case  under  the  Roman  Empire.  Sor 
too,  in  later  times  the  ambition  of  Na  - 
poleon  covered  France  and  the  countries 
subject  to  her  with  an  admirable  system 
of  military  roads.  At  the  same  time,  we 
must  do  Napoleon  the  justice  of  saying 
that  his  genius  and  foresight  gave  a 
great  impetus  to  the  construction  of  all 
works  favorable  to  commercial  progress. 
So,  again,  in  this  country  it  was  the  re- 
bellion of  1745,  and  the  want  felt  of 
roads  for  military  purposes,  which  first 
led  to  the  construction  of  a  system  of 
roads  in  it  unequaled  since  the  time  of 
the  Roman  occupation.  And  lastly,  in 
India,  in  Germany,  and  in  Russia,  more 
than  one  example  could  be  pointed  out 
where  industry  will  benefit  by  railways 
which  have  originated  in  military  pre- 
cautions rather  than  in  commercial  re- 
quirements. 

But  to  return  to  Rome.  Roads  fol- 
lowed the  tracks  of  her  legions  into  the 
most  distant  provinces  of  the  empire. 
Three  hundred  and  seventy-two  great 
roads  are  enumerated,  together  more 
than  48,000  miles  in  length,  according 
to  the  itinerary  of  Antoninus. 

The  water  supply  of  Rome  during  the 
first  century  of  our  era  would  suffice  for 
a  population  of  seven  millions,  supplied 
at  the  rate  at  which  the  present  popula- 
tion of  London  is  supplied.  This  water 
was  conveyed  to  Rome  by  nine  aque- 
ducts ;  and  in  later  years  the  supply 
was  increased  by  the  construction  of 
five  more  aqueducts.  Three  of  the  old 
aqueducts  have  sufficed  to  supply  the- 
wants  of  the  city  in  modern  times. 
These  aqueducts  of  Rome  are  to  be 
numbered  among  her  grandest  engineer- 
ing works.  Time  will  not  admit  of  my 
saying  anything  about  her  harbor  works 
and  bridges,  her  basilicas  and  baths, 
and  numerous  other  works  in  Europe, 
in  Asia,  and  in  Africa.  Not  only  were 
these  works  executed  in  a  substantial 
and  perfect  manner,  but  they  were  main- 
tained by  an  efficient  staff  of  men  divid- 
ed into  bodies,  each  having  their  special 
duties  to  perform.  The  highest  officers 
of  state  superintended  the  construction 
of  works,  were  proud  to  have  their 
names  associated  with  them,  and  con- 
structed extensive  works  at  their  own 
expense. 

Progress  in  Europe  stopped  with  the 
fall     of    the    Roman   Empire.     In    the 


ORIGIN   AND   GROWTH   OF   ENGINEERING   SCIENCE. 


465 


fourth  and  succeeding  centuries  the  bar- 
barian hordes  of  Western  Asia,  people 
who  felt  no  want  of  roads  and  bridges, 
swept  over  Europe  to  plunder  and  des- 
troy. 

With  the  seventh  century  began  the 
rise  of  the  Mohammedan  power,  and  a 
partial  return  to  conditions  apparently 
more  favorable  to  the  progress  of  indus- 
trial art,  when  widespread  lands  were 
.•again  united  under  the  sway  of  power- 
ful rulers.  Science  owes  much  to  Arab 
scholars,  who  kept  and  handed  on  to  us 
the  knowledge  acquired  so  slowly  in 
ancient  times,  and  much  of  which  would 
have  been  lost  but  for  them.  Still,  few 
useful  works  remain  to  mark  the  supre- 
macy of  the  Mohammedan  power  at  all 
comparable  to  those  of  the  age  which 
preceded  its  rise. 

A  great  building  age  began  in  Europe 
in  the  tenth  century,  and  lasted  through 
the  thirteenth.  It  was  during  this  peri- 
od that  these  great  ecclesiatical  build- 
ings were  erected,  which  are  not  more  re- 
markable for  artistic  excellence  than  for 
boldness  in  design. 

While  the  building  of  cathedrals  pro- 
gressed on  all  sides  in  Europe,  works  of 
utilitarian  character,  which  concern  the 
engineer,  did  not  receive  such  encourage- 
ment, excepting  perhaps  in  Italy. 

From  the  twelfth  to  the  thirteenth 
centuries,  with  the  revival  of  the  arts 
and  sciences  in  the  Italian  republics, 
many  important  works  wei'e  undertaken 
for  the  improvement  of  the  rivers  and 
harbors  of  Italy.  In  1481  canal  locks 
were  first  used  ;  and  some  of  the  earliest 
of  which  we  have  record  were  erected 
by  Leonardo  da  Vinci,  who  would  be 
remembered  as  a  skillful  engineer  had  he 
not  left  other  greater  and  more  attract- 
ive works  to  claim  the  homage  of  pos- 
terity. 

The  great  use  that  has  since  been 
made  of  this  simple  means  of  transfer- 
ring floating  vessels  from  one  water 
level  to  another,  in  connection  not  only 
with  inland  navigation,  but  in  all  the 
great  ports  and  harbors  of  the  world, 
renders  it  all  the  more  deserving  of  re- 
mark. 

In  India,  under  the  Moguls,  irrigation 
works,  for  which  they  had  a  natural 
aptitude,  were  carried  on  during  these 
centuries  with  vigor,  and  more  than  one 
•emperor  is  noted  for  the  numerous  great 
Vol.  XIII.— No.  5—30 


works  of  this  nature  which  he  carried 
out.  If  the  native  records  can  be  trust- 
ed, the  number  of  hydraulic  works  un- 
dertaken by  some  rulers  is  surprising. 
Tradition  relates  that  one  king  who 
reigned  in  Orissa  in  the  twelfth  centurj 
made  one  million  tanks  or  reservoirs, 
besides  building  sixty  temples,  and 
erecting  numerous  other  works. 

In  India,  the  frequent  overflow  of  the 
great  rivers,  and  the  periodical  droughts, 
which  rendered  irrigation  necessary,  led. 
to  extensive  protective  works  being  un- 
dertaken at  an  early  period  ;  but  as 
these  works  have  been  maintained  by 
successive  rulers,  Mogul  and  Moham- 
medan, until  recent  times,  and  have  not 
been  left  for  our  inspection,  deserted 
and  useless  for  3,000  years  or  more,  as 
is  often  the  case  in  Egypt  and  Mesopo- 
tamia, there  is  more  difficulty  in  ascer- 
taining the  date  of  such  works  in  India. 

Works  of  irrigation  were  among  the 
earliest  attempts  at  engineering  under- 
taken by  the  least  civilized  inhabitants 
in  all  parts  of  the  world.  Even  in  Aus- 
tralia, where  savages  are  found  as  low 
as  any  in  the  scale  of  civilization,  traces 
of  irrigation  works  have  been  found  ; 
these  works,  however,  must  be  taken  to 
show  that  the  natives  were  once  some- 
what more  civilized  than  we  now  find 
them.  In  Feejee,  our  new  possession, 
the  natives  occasionally  irrigate  their 
land,  and  have  executed  a  work  of  a 
higher  class,  a  canal  some  two  mile* 
long  and  sixty  feet  wide,  to  shorten  the 
distance  passed  over  by  their  eonoes. 
The  natives  of  New  Caledonia  irrigate 
their  fields  with  great  skill.  In  Peru, 
the  Incas  excelled  in  irrigation  as  in 
other  great  and  useful  works,  and  con- 
structed most  admirable  underground 
conduits  of  masonry  for  the  purpose  of 
increasing  the  fertility  of  the  land. 

It  is   frequently  easier  to  lead  water 
where    it   is    wanted   than  to   check   its 
irruption  into  places  where  its  presence 
|  is  an  evil,  often  a  disaster.     For  centu- 
I  ries   the    existence    of   a   large   part   of 
[  Holland    has    been    dependent    on    the 
skill   of  man.     How   soon   he  began  in 
that  country  to  contest  with  the  sea  the 
'  possession  of  the  land  we  do  not  know, 
j  but  early  in  the  twelfth   century   dvkes 
i  were  constructed  to  keep  back  the  ocean. 
I  As   the   prosperity    of   the    country    in- 
creased with  the  great  extension  of  its 


466 


VAN   NOSTRAND'S   ENGINEERING   MAGAZINE. 


commerce,  and  land  became  more  valua- 
ble and  necessary  for  an  increasing  pop- 
ulation, very  extensive  works  were  un- 
dertaken. Land  was  reclaimed  from 
the  sea,  canals  were  cut,  and  machines 
were  designed  for  lifting  water.  To  the 
practical  knowledge  acquired  by  the 
Dutch,  whose  method  of  carrying  out 
hydraulic  works  is  original  and  of  native 
growth,  much  of  the  knowledge  of  the 
present  day  in  embanking,  and  drain- 
ing, and  canal  making  is  due.  The 
North  Holland  Canal  was  the  largest 
navigable  canal  in  existence  until  the 
Suez  Canal  was  completed  ;  and  the 
Dutch  have  just  now  nearly  finished 
making  a  sea  canal  from  Amsterdam  to 
the  North  Sea,  which,  though  not  equal 
to  the  Suez  Canal  in  length,  will  be  as 
great  in  width  and  depth,  and  involves 
perhaps  larger  and  more  important 
works  of  art.  This  country  was  for 
many  years  beholden  to  the  Dutch  for 
help  in  carrying  out  hydraulic  works. 
In  the  seventeenth  century  much  fen 
land  in  the  eastern  counties  was  drained 
by  Dutch  labor,  directed  by  Dutch  engi- 
neers, among  whom  Sir  Cornelius  Ver- 
muyden,  an  old  campaigner  of  the  Thirty 
Years'  War  and  a  colonel  of  horse  under 
Cromwell,  is  the  most  noted. 

While  the  Dutch  were  acquiring  prac- 
tical knowledge  in  dealing  with  water, 
and  we  in  Britain  among  others  were 
benefiting  by  their  experience,  the  disas- 
trous results  which  ensued  from  the  in- 
undations caused  by  the  Italian  rivers  of 
the  Alps  gave  a  new  importance  to  the 
science  of  hydraulics.  Some  of  the 
greatest  philosophers  of  the  seventeenth 
century — among  them  Torricelli,  a  pupil 
of  Galileo, — were  called  upon  to  advise 
and  to'superintend  engineering  works;  nor 
did  they  confine  themselves  to  the  con- 
struction of  preventive  works,  but  thor- 
oughly investigated  the  condition  per- 
taining to  fluids  at  rest  or  in  motion, 
and  gave  to  the  world  a  valuable  series 
of  works  on  hydraulics  and  hydraulic 
engineering,  which  form  the  basis  of 
our  knowledge  of  these  subjects  at  the 
present  day. 

Some  of  the  best  scientific  works 
(prior  to  the  nineteenth  century)  on 
engineering  subjects  we  owe  to  Italian 
and  French  writers.  The  writings  of 
Belidor,  an  officer  of  artillery  in  France 
in  the  seventeenth  century,  who  did  not, 


however,  confine  himself  to  military 
subjects,  drew  attention  to  engineering 
questions.  Not  long  after  their  appear- 
ance, the  Fonts  et  Chausees  were  estab- 
lished, which  has  maintained  ever  since 
a  body  of  able  men  specially  educated 
for,  and  devoted  to,  the  prosecution  of 
industrial  works. 

The  impulse  given  to  road-making  in. 
the  early  part  of  the  last  century  soon 
extended  to  canals  and  means  for  facili- 
tating locomotion  and  transport  gener- 
ally. Tramways  were  used  in  connec- 
tion with  mines  at  least  as  early  as  the 
middle  of  the  seventeenth  century,  but 
the  rails  were,  in  those  days,  of  wood. 
The  first  iron  rails  are  said  to  have  been; 
laid  in  this  country  as  early  as  1738  ; 
after  which  time  their  use  was  gradually 
extended,  until  it  became  general  in 
mining  districts. 

By  the  beginning  of  this  century  the 
great  ports  of  England  were  connected 
by  a  system  of  canals  ;  and  new  harbor 
works  became  necessary,  and  were  pro- 
vided to  accommodate  the  increase  of 
commerce  and  trade,  which  improved' 
means  of  internal  transport  had  render- 
ed possible.  It  was  in  the  construction 
of  these  works  that  our  own  B rind  ley 
and  Smeaton,  Telford  and  Rennie,  and 
other  engineers  of  their  time,  did  so 
much. 

But  it  was  not  untill  the  steam-en- 
gine, improved  and  almost  created  by 
the  illustrious  Watt,  became  such  a  po- 
tent instrument,  that  engineering  works 
to  the  extent  they  have  since  been  car- 
ried out  became  possible  or  necessary. 
It  gave  mankind  no  new  faculty,  but  it 
at  once  set  his  other  faculties  on  an  em- 
inence, from  which  the  extent  of  hfe 
future  operations  became  almost  unlim- 
ited. 

Water-mills,  wind-mills,  and  horse- 
machines  were  in  most  cases  superseded,. 
Deep  mines,  before  only  accessible  by 
adits  and  water  levels,  could  at  once  be 
reached  with  ease  and  economy.  Lakes- 
and  fens  which,  but  for  the  steam-engine,, 
would  have  been  left  untouched,  were 
drained  and  culti vated. 

The  slow  and  laborious  toil  of  hands 
and  fingers,  bone  and  sinew,  was  turned 
to  other  employments,  where,  aided  by 
ingenious  mechanical  contrivances,  the 
produce  of  one  pair  of  hands  was  multi- 
plied a  thousand-fold,  and  their  cunning 


ORIGIN   AND   GROWTH    OF   ENGINEERING    SCIENCE. 


467 


extended  until  results  marvelous,  if  you 
consider  them,  were  attained.  Since 
the  time  of  Watt  the  steam-engine  has 
exerted  a  power,  made  conquests,  and 
increased  and  multiplied  the  material 
interests  of  this  globe  to  an  extent  which 
it  is  scarcely  possible  to  realize. 

But  while  Watt  has  gained  a  world- 
wide, well-earned  fame,  the  names  of 
those  men  who  have  provided  the  ma- 
chines to  utilize  the  energies  of  the 
steam-engines  are  too  often  forgotten. 
Of  their  inventions  the  majority  of  man- 
kind know  little.  They  worked  silently 
at  home,  in  the  mill,  or  in  the  factory, 
observed  by  few.  Indeed,  in  most  cases 
these  silent  workers  had  no  wish  to  ex- 
pose their  work  to  public  gaze.  Were 
it  not  so,  the  factory  and  the  mill  are 
not  places  where  people  go  to  take  the 
air.  How  long  in  the  silent  night  the 
inventors  of  these  machines  sat  and  pon- 
dered ;  how  often  they  had  to  cast  aside 
some  long-sought  mechanical  movement 
and  seek  another  and  a  better  arrange- 
ment of  parts,  none  but  themselves  could 
ever  know.  They  were  unseen  workers, 
who  succeeded  by  rare  genius,  long 
patience,  and  indomitable  perseverance. 
More  ingenuity  and  creative  mechan- 
ical genius,  is  perhaps  displayed  in  ma- 
chines used  for  the  manufacture  of  tex- 
tile fabrics  than  by  those   used  in  any 

.  other  industry.  It  was  not  until  late  in 
historical  times  that  the  manufacture  of 
such  fabrics  became  established  on  a 
large  scale  in  Europe.  Although  in 
China  man  was  clothed  in  silk  long  ago, 
and  although  Confucius,  in  a  work  writ- 
ten 2,300  years  ago,  orders  with  the 
greatest  minuteness  the  rules  to  be  ob- 
served in  the  production  and  manufac- 
ture of  silk,  yet  it  was  worth  nearly  its 
weight  in  gold  in  Europe  in  the  time  of 
Aurelian,  whose  empress  had  to  forego 
the  luxury  of  a  silk  gown  on  account  of 
its  cost  ?  Through  Constantinople  and 
Italy  the  manufacture  passed  slowly 
westwards,  and  was  not  established  in 
France  until  the  sixteenth  century,  and 
arrived  at  a  still  later  period  in  this 
country.     It   is   related   that  James  V. 

had  to  borrow  a  pair  of  silk  hose  from 
the  Earl  of  Mar,  in  order  that  he  might 
not,  as  he  expressed  it,  appear  as  a  scrub 
before  strangers. 

So  cotton,  of  which  the  manufacture 

in    India    dates    from   before   historical 


times,  had  scarcely  by  the  Christian  era 
reached  Persia  and  Egypt.  Spain  in  the 
tenth  and  Italy  in  the  fourteenth  cen- 
tury manufactured  it,  but  Manchester, 
which  is  now  the  great  metropolis  of 
the  trade,  not  until  the  latter  half  of 
the  seventeenth  century. 

Linen  was  worn  by  the  old  Egyptian-. 
and  some  of  their  linen  mummy  clothe 
surpass  in  fineness  any  linen  fabrics  made 
in  later  days.  The  Babylonians  wore 
linen  also  and  wool,  and  obtained  a  wide- 
spread fame  for  skill  in  workmanship  and 
beauty  in  design. 

In  this  country  wool  once  formed  the 
staple  for  clothing.  Silk  was  the  first 
rival,  but  its  costliness  placed  it  beyond 
the  reach  of  the  many.  To  introduce  a 
new  material  or  improved  machine  into 
this  or  other  countries  a  century  or  more 
ago  was  no  light  undertaking.  Invent- 
ors and  would-be  benefactors  alike,  ran 
the  risk  of  loss  of  live.  Loud  was  the 
outcry  made  in  the  early  part  of  the 
eighteenth  century  against  the  introduc- 
tion of  Indian  cottons  and  Dutch  cali- 
coes. 

Until  1738,  in  which  year  the  improve- 
ments in  spinning  machinery  were  be- 
gun, each  thread  of  worsted  or  cotton 
wool  had  been  spun  between  the  fingers 
in  this  and  all  other  countries.  Wyatt, 
in  1738,  invented  spinning  by  rollers  in- 
stead of  fingers,  and  his  invention  was 
further  improved  by  Arkwright.  In 
1770  Hargreaves  patented  the  spinning- 
jenny,  and  Crompton  the  mule  in  1775. 
a  machine  which  combined  the  advan- 
tages of  the  frames  of  both  Hargreave-: 
and  Arkwright.  In  less  than  a  century 
after  the  first  invention  by  Wyatt. 
double  mules  were  working  in  Manches- 
ter with  over  2,000  spindles.  Improve- 
ments in  machines  for  weaving  were  be- 
gun at  an  earlier  date.  In  1579  a  rib- 
bon loom  is  said  to  have  been  invented 
at  Dantzic,  by  which  from  four  to  six 
pieces  could  be  woven  at  one  time,  but 
the  machine  was  destroyed  and  the  in- 
ventor lost  his  life.  In  1800  Jacquard's 
most  ingenious  invention  was  brought 
into  use,  which,  by  a  simple  mechanical 
operation,  determines  the  movements  of 
the  threads  which  form  the  pattern  in 
weaving.  But  the  greatest  discovery 
in  the  art  of  weaving  was  wrought  by 
Cartwright's  discovery  of  the  power 
loom,  which  led  eventually  to  the  sub- 


468 


VAN   NOSTRAND'S   ENGINEERING    MAGAZINE. 


stitution  of  steam  for  manual  labor,  and 
enabled  a  boy  with  a  steam  loom  to  do 
iifteen  times  the  work  of  a  man  with  a 
hand  loom. 

Steamboats,  the  electric  telegraph, 
and  railways,  are  more  within  the  cog- 
nizance of  the  world  at  large,  and  the 
progress  that  has  been  made  in  them  in 
little  more  than  one  generation  is  better 
known  and  appreciated. 

It  is  not  more  than  forty  years  since 
one  of  our  scientific  men,  and  an  able 
one  too,  declared  at  a  meeting  of  this 
Association  that  no  steamboat  would 
ever  cross  the  Atlantic  ;  founding  bis 
statement  on  the  impracticability,  in  his 
view,  of  a  steamboat  carrying  sufficient 
coal,  profitably,  I  presume,  for  the  voy- 
age. Yet,  soon  after  this  statement  was 
made,  the  Sirius  steamed  from  Bristol 
to  New  York  in  seventeen  days,  and 
was  soon  followed  by  the  Great  Western, 
-which  made  the  homeward  passage  in 
thirteen-and-a-half  days  ;  and  with  these 
voyages  the  era  of  steamboats  began. 
Like  most  important  inventions,  that  of 
the  steamboat  was  a  long  time  in  assum- 
ing a  form  capable  of  being  profitably 
utilized  ;  and  even  when  it  had  assumed 
such  a  form,  the  objections  of  commer- 
cial and  scientific  men  had  still  to  be 
overcome. 

The  increase  in  the  number  of  steam- 
boats since  the  time  when  the  Sirius 
-first  crossed  the  Atlantic  has  been  very 
great.  Whereas  in  1814  the  United 
Kingdom  only  possessed  two  steam  ves- 
sels, of  together  456  tons  burden,  in  1872 
-there  were  on  the  register  of  the  United 
Kingdom  3,662  steam  vessels,  of  which 
the  registered  tonnage  amounted  to 
over  a  million  and  a  half  of  tons,  or  to 
nearly  half  the  whole  steam  tonnage  of 
the  world,  which  did  not  at  that  time 
greatly  exceed  three  million  tons. 

As  the  number  of  steamboats  has 
largely  increased,  so  also  gradually  has 
their  size  increased  until  it  culminated 
in  the  hands  of  Brunei  in  the  Great 
Eastern. 

A  triumph  of  engineering  skill  in  ship- 
building, the  Great  Eastern  has  not 
been  commercially  so  successful.  In 
this,  as  in  many  other  engineering  prob- 
lems, the  question  is  not  how  large  a 
thing  can  be  made,  but  how  large,  hav- 
ing regard  to  other  circumstances,  it  is 
]     -per  at  the  time  to  make  it. 


If,  as  regards  the  dimensions  of  steam- 
boats, we  have  at  present  somewhat 
overstepped  the  limits  in  the  Great 
Eastern,  much  still  remains  to  be  done 
in  perfecting  the  form  of  vessels,  wheth- 
er propelled  by  steam  or  driven  by  the 
force  of  the  wind.  A  distinguished 
member  of  this  Association,  Mr.  Froude, 
has  now  for  some  years  devoted  himself 
to  investigations  carried  on  with  a  view 
to  ascertain  the  form  of  vessel  which 
will  offer  the  least  resistance  to  the 
water  through  which  it  must  pass.  So 
many  of  us  in  these  days  are  called  up- 
on to  make  journeys  by  sea  as  well  as 
by  land,  that  we  can  well  appreciate  the 
value  of  Mr.  Fronde's  labors,  so  far  aa 
they  tend  to  curtail  the  time  which  we 
must  spend  on  our  ocean  journeys  ;  and 
we  should  all  feel  grateful  to  him  if 
from  another  branch  of  his  investiga- 
tions, which  relates  to  the  rolling  of 
ships,  it  should  result  that  the  move- 
ment in  passenger  vessels  could  be  re- 
duced. 

As  improvements  in  the  form  of  the  hull 
are  effected,  less  power — that  is,  lew 
fuel — will  be  required  to  propel  the  ves- 
sel through  the  water  for  a  given  dis- 
tance. Great  as  have  been  the  improve- 
ments effected  in  marine  engines  to  thii 
end,  much  still  remains  to  be  done. 
Wolf's  compound  engine,  so  long  over- 
looked, is,  with  some  improvements,- 
being  at  last  applied.  Whereas  the 
consumptiou  of  fuel  in  such  vessels  a§ 
the  Himalaya  used  to  be  from  5  to  6  lbs, 
of  fuel  per  effective  horse-power,  it  has 
been  reduced,  by  working  steam  more 
expansively  in  vessels  of  a  later  date,  to 
2  lbs.  Yet,  comparing  this  with  the 
total  amount  of  energy  of  2  lbs.  of  coal, 
it  will  be  found  that  not  a  tenth  part  of 
the  power  is  obtained  which  that  amount 
of  coal  would  theoretically  call  into  ac- 
tion. 

There  is  no  more  remarkable  instance 
of  the  rapid  utilization  of  what  was  in 
the  first  instance  regarded  by  most  men 
as  a  mere  scientific  idea,  than  the  adop- 
tion and  extension  of  the  electric  tele- 
graph. 

Those  who  read  Odier's  letter  written 
in  1773,  in  which  he  made  known  his 
idea  of  a  telegraph  which  would  enable 
the  inhabitants  of  Europe  to  converse 
with  the  Emperor  of  Mogul,  little 
thought   that  in  less  than  a  century  a 


ORIGIN   AND   GROWTH    OF   ENGINEERING   SCIENCE. 


409 


•onversation  between  persons  at  points 
«o  far  distant  would  be  posssible.  Still 
less  did  those  who  saw  in  the  following 
year  messages  sent  from  one  room  to 
another  by  Lesage  in  the  presence  of 
Friedrich  of  Prussia,  realize  that  they 
had  before  them  the  germ  of  one  of  the 
most  extraordinary  inventions  among 
the  many  that  will  render  this  century 
famous. 

I  should  weary  you  were  I  to  follow 
the  slow  steps  by  which  the  electric  tele- 
graph of  to-day  was  brought  to  its  pres- 
ent state  of  efficiency.  In  the  present 
eentury  few  years  have  passed  without 
sew  workers  appearing  in  the  field  ; 
dome  whose  object  was  to  utilize  the 
new-found  power  for  the  benefit  of  man- 
kind, others— and  their  work  was  not 
the  least  important  in  the  end — whose 
object  was  to  investigate  magnetism  and 
electrical  phenomena  as  presenting  scien- 
tific problems  still  unsolved.  Galvani, 
Volta,  Oersted,  Arago,  Sturgeon,  and 
Faraday,  by  their  labors,  helped  to 
made  known  the  elements  which  render- 
ed it  possible  to  construct  the  electric 
telegraph.  With  the  battery,  the  elec- 
tric coil,  and  the  electro-magnet,  the 
elements  were  complete,  and  it  only  re- 
mained for  Sir  Charles  Wheatstone  and 
others  to  combine  them  in  a  useful  and 
practically  valuable  form.  The  inven- 
tions of  Alexander,  Steinheil,  and  those 
of  similar  nature  to  that  of  Sir  Charles 
Wheatstone,  were  made  known  at  a  later 
date  in  the  same  year,  which  will  ever 
be  memorable  in  the  annals  of  tele- 
graphy. 

The  first  useful  telegraph  was  con- 
structed upon  the  Blackwall  Railway  in 
1838,  Messrs.  Wheatstone's  and  Cooke's 
instruments  being  employed.  From 
that  time  to  this  the  progress  of  the 
electric  telegraph  has  been  so  rapid, 
that  at  the  present  time,  including  land 
lines  and  submarine  cables,  there  are  in 
use  in  different  parts  of  the  world  not 
lees  than  400,000  miles  of  telegraph. 

Among  the  numerous  inventions  of 
late  years,  the  outomatic  telegraph  of 
Mr.  Alexander  Bain,  of  Dr.  Werner 
Siemens,  and  of  Sir  Charles  Wheatstone, 
are  especially  worthy  of  notice.  Mr. 
Bain's  machine  is  cheifly  used  in  the 
United  States,  that  of  Dr.  Werner  Sie- 
mens in  Germany.  In  this  country  the 
machine  invented  by  Sir  Charles  Wheat- 


stone, to  whom  telegraphy  owes  so 
much,  is  chiefly  employed.  By  his  ma- 
chine, after  the  message  has  been  punch- 
ed out  in  a  paper  ribbon  by  one  machine 
on  a  system  analogous  to  the  dot  and 
dash  of  Morse,  the  sequence  of  the  cur- 
rents requisite  to  transmit  the  message 
along  the  wire  is  automatically  determin- 
ed in  a  second  machine  by  this  perforat- 
ed ribbon.  This  second  operation  is  an- 
alogous to  that  by  which  in  Jacquard's 
loom  the  motions  of  the  threads  requisite 
to  produce  the  pattern  is  determined  by 
perforated  cards.  By  Wheatstone's  ma- 
chine errors  inseparable  from  manual 
labor  are  avoided  ;  and  what  is  of  even 
more  importance  in  a  commercial  point 
of  view,  the  time  during  which  the  wire 
is  occupied  in  the  transmission  of  a  mes- 
sage is  considerably  diminished. 

By  the  application  of  these  automatic 
systems  to  telegraphy,  the  speed  of 
transmission  has  been  wonderfully  accel- 
erated, being  equal  to  200  words  a 
minute,  that  is,  faster  than  a  shorthand 
writer  can  transcribe  ;  and,  in  fact, 
words  can  now  be  passed  along  the 
wires  of  land  lines  with  a  velocity 
greater  than  can  be  dealt  with  by  the 
human  agency  at  either  end. 

Owing  partly  to  the  retarding  effects 
of  induction  and  other  causes,  the  speed 
of  transmission  by  long  submarine  ca- 
bles is  much  smaller.  With  the  cable 
of  1858  only  1\  words  per  minute  were 
got  through.  The  average  with  the  At- 
lantic cable,  Dr.  C.  W.  Siemens  informs 
me,  is  now  seventeen  words,  but  twenty- 
four  words  per  minute  can  be  read. 

One  of  the  most  striking  phenomena 
in  telegraphy  is  that  known  as  the  du- 
plex system,  which  enables  messages  to 
be  sent  from  each  end  of  the  same  wire 
at  the  same  time.  This  simultaneous 
transmission  from  both  ends  of  a  wire 
was  proposed  in  the  early  days  of  tele- 
graphy, but,  owing  to  imperfect  insula- 
tion, was  not  then  found  to  be  practic- 
able ;  but  since  then  telegraphic  wires 
have  been  better  insulated,  and  the  sys- 
.tem  is  now  becoming  of  great  utility,  as 
it  nearly  doubles  the  capacity  for  work 
of  every  wire. 

Of  railways  the  progress  has  been 
enormous,  but  I  do  not  know  that  in  a 
scientific  point  of  view  a  railway  is  so 
marvelous  in  its  character  as  the  elec- 
tric  telegraph.      The   results,    however,. 


470 


VAN   NOSTRAND'S   ENGINEERING   MAGAZINE. 


of  the  construction  and  use  of  railways 
are  more  extensive  and  widespread,  and 
their  utility  and  convenience  brought 
home  to  a  larger  portion  of  mankind.  It 
has  come  to  pass,  therefore,  that  the 
name  of  George  Stephenson  has  been 
placed  second  only  to  that  of  James 
Watt ;  and  as  men  are  and  will  be  esti- 
mated by  the  advantages  which  their 
labors  confer  on  mankind,  he  will  remain 
in  that  niche,  unless  indeed  some  greater 
luminary  shotfld  arise  to  outshine  him. 
The  merit  of  George  Stephenson  con- 
sisted, among  other  things,  in  this,  that 
he  saw  more  clearly  than  any  other  en- 
gineer of  his  time  the  sort  of  thing  that 
the  world  wanted,  and  that  he  per- 
severed in  despite  of  learned  objectors 
with  the  firm  conviction  that  he  was 
right  and  they  were  wrong,  and  that 
there  was  within  himself  the  power  to 
demonstrate  the  accuracy  of  his  convic- 
tions. 

We  who  live  in  these  days  of  roads 
and  railways,  and  can  move  with  a  fair 
degree  of  comfort,  speed,  and  safety, 
almost  where  we  will,  can  scarcely  real- 
ize the  state  of  England  two  centuries 
ago,  when  the  years  of  opposition  which 
preceded  the  era  of  coaches  began  ; 
when,  as  in  1662,  there  were  but  six 
stages  in  all  England,  and  John  Cross- 
dell,  of  the  Charterhouse,  thought  there 
were  six  too  many  ;  when  Sir  Henry 
Herbert,  a  member  of  the  House  of 
Commons,  could  say,  "  If  a  man  were  to 
propose  to  carry  us  regularly  to  Edin- 
burgh in  coaches  in  seven  days,  and 
bring  us  back  in  seven  more,  should  we 
not  vote  him  to  Bedlam  ?" 

In  spite  of  short-sighted  opposition, 
coaches  made  their  way  ;  but  it  was  not 
till  a  century  later,  in  1784, — and  then  I 
believe  it  was  in  this  city  of  Bristol — 
that  coaches  were  first  established  for 
the  conveyance  of  mails.  Those  here 
who  have  experienced,  as  I  have,  what 
the  discomforts  were  of  long  journeys 
inside  the  old  coaches,  will  agree  with 
me  that  they  were  very  great  ;  and  I 
believe,  if  returns  could  be  obtained  of" 
the  accidents  which  happened  to  coaches, 
it  would  be  found  that  many  more  peo- 
ple were  injured  and  killed  in  proportion 
to  the  number  that  traveled  by  that 
mode  than  by  the  railways  of  to-day. 

No  sooner  had  our  ancestors  settled 
<";  >wn  with  what  comfort  was  possible  in 


their  coaches,  well  satisfied  that  twelve 
miles  an  hour  was  the  maximum  speed 
to  be  obtained  or  that  was  desirable, 
than  they  were  told  that  steam  convey- 
ance on  iron  railways  would  supersede 
their  "  present  pitiful"  methods  of  con- 
veyance. Such  was  the  opinion  of 
Thomas  Gray,  the  first  promoter  of 
railways,  who  published  his  work  on  a 
general  iron  railway  in  1819.  Gray  was 
looked  on  as  little  better  than  a  mad- 
man. 

Railways  add  enormously  to  the 
national  wealth.  More  than  twenty-five 
years  ago  it  was  proved  to  the  satisfac- 
tion of  a  committee  of  the  House  _  of 
Commons,  from  facts  and  figures  which 
I  then  adduced,  and  the  Lancashire  and 
Yorkshire  Railway,  of  which  I  was  the 
engineer,  and  which  then  formed  the 
principal  railway  connection  between 
the  populous  towns  of  Lancashire  and 
Yorkshire,  effected  a  saving  to  the  public 
using  the  railway  of  more  than  the 
whole  amount  of  the  dividend  which  was 
received  by  the  proprietors.  These  cal- 
culations were  based  solely  on  the 
amount  of  traffic  carried  by  the  railway, 
and  on  the  difference  between  the  rail- 
way rate  of  charge  and  the  charges  by 
the  modes  of  conveyance  anterior  to 
railways.  No  credit  whatever  was  taken 
for  the  saving  of  time,  though  in  Eng- 
land preeminently  time  is  money. 

Considering  that  railway  charges  on 
many  items  have  been  considerably  re- 
duced since  that  day,  it  may  be  safely 
assumed  that  the  railways  in  the  British 
Islands  now  produce,  or  rather  save  to 
the  nation,  a  much  larger  sum  annually 
than  the  gross  amount  of  all  the  divi- 
dends payable  to  the  proprietors,  with- 
out at  all  taking  into  account  the  benefit 
arising  from  the  saving  in  time.  The 
benefits  under  that  head  defy  calcula- 
tion, and  cannot  with  any  accuracy  be 
put  into  money  ;  but  it  would  not  be  at 
all  over-estimating  this  question  to  say 
that  in  time  and  money  the  nation  gains 
at  least  what  is  equivalent  to  10  per 
cent,  on  all  the  capital  expended  on 
railways.  I  do  not  urge  this  on  the 
part  of  railway  proprietors,  for  they  did 
not  embark  in  these  undertakings  with  a 
view  to  the  national  gain,  but  for  the 
expected  profit  to  themselves.  Yet  it  is 
as  well  it  should  be  noted,  for  railway 
proprietors  appear   sometimes  by  some 


ORIGIN   AND   GROWTH   OF   ENGINEERING   SCIENCE. 


471 


people  to  be  regarded  in  the  light  of 
public  enemies. 

It  follows  from  these  facts  that  when- 
ever a  railway  can  be  made  at  a  cost  to 
yield  the  ordinary  interest  of  money,  it 
is  in  the  national  interest  that  it  should 
be  made.  Further,  that  though  its  cost 
anight  be  such  as  to  leave  a  smaller  divi- 
dend than  that  to  its  proprietors,  the 
loss  of  wealth  to  so  small  a  section  of 
■the  community  will  be  more  than  supple- 
mented by  the  national  gain,  and  there- 
fore there  may  be  cases  where  a  Govern- 
ment may  wisely  contribute  in  some  form 
to  undertakings  which,  without  such 
aid,  would  fail  to  obtain  the  necessary 
support, 

Mr.  Bramwell,  when  presiding  over 
Tthe  Mechanical  Section  at  Brighton, 
drew  attention  to  the  waste  of  fuel. 

Dr.  Siemens,  in  an  able  lecture  he  de- 
livered by  request  of  the  Association  to 
the  operative  classes  at  the  meeting  at 
Bradford,  pointed  out  the  waste  of  fuel 
In  special  branches  of  the  iron  trade,  to 
which  he  has  devoted  so  much  atten- 
tion. 

He  showed  on  that  occasion  that,  in 
the  ordinary  re-heating  furnace,  the  coal 
•  consumed  did  not  produce  the  twentieth 
part  of  its  theoretical  effect,  and  in  melt- 
ing steel  in  pots  in  the  ordinary  way 
not  more  than  one-seventieth  part  ;  in 
melting  one  ton  of  steel  in  pots  about 
2|-  tons  of  coke  being  consumed.  Dr. 
Siemens  further  stated  that,  in  his  re- 
generative gas  furnace,  one  ton  of  steel 
was  melted  with  12  cwt.  of  small  coal. 

Mr.  Lowthian  Bell,  who  combines 
-chemical  knowledge  with  the  practical 
experience  of  an  ironmaster,  in  his  Presi- 
dential address  to  the  members  of  the 
Iron  and  Steel  Institute  in  1873,  stated 
that,  with  the  perfect  mode  of  with- 
drawing and  utilizing  the  gases  and  the 
improvement  in  the  furnaces  adopted  in 
the  Cleveland  district,  the  present  make 
•of  pig-iron  in  Cleveland  is  produced 
with  3£  million  tons  of  coal  less  than 
would  have  been  needed  fifteen  years 
Ago  ;  this  being  equivalent  to  a  saving 
of  45  per  cent,  of  the  quantity  formerly 
used.  He  shows  by  figures,  Avith  which 
he  has  favored  me,  that  the  calorific 
power  of  the  waste  gases  from  the  fur- 
naces is  sufficient  for  raising  all  the 
steam  and  heating  all  the  air  the  fur- 
naces require. 


It  has  already  been  stated  that  by 
working  steam  more  expansively,  either 
in  double  or  single  engines,  the  consump- 
tion of  fuel  in  improved  modern  en- 
gines compared  with  the  older  forms; 
may  be  reduced  to  one-third. 

All  these  reductions  still  fall  far  short 
of  the  theoretical  effect  of  fuel  which 
may  be  never  readied.  Mr.  Lowthian 
Bell's  figures  go  to  show  that  in  the  in- 
terior of  the  blast  furnace,  as  improved 
in  Cleveland,  there  is  not  much  more  to 
be  done  in  reducing  the  consumption  of 
fuel  ;  but  much  has  already  been  done, 
and  could  the  reductions  now  attainable, 
and  all  the  information  already  acquired 
be  universally  applied,  the  saving  in 
fuel  would  be  enormous. 

If  I  have  pointed  out  that  we  do  not 
avail  oui*selves  of  more  than  a  fractional 
part  of  the  useful  effects  of  fuel,  it  is 
not  that  I  expect  we  shall  all  at  once 
mend  our  ways  in  this  respect.  Many 
cases  of  waste  arise  from  the  existence 
of  old  and  obsolete  machines,  of  bad 
forms  of  furnaces,  of  wasteful  grates, 
existing  in  most  dwelling-houses  ;  and 
these  are  not  to  be  remedied  at  once, 
for  not  everyone  can  afford,  however 
desirable  it  might  be,  to  cast  away  the 
old  and  adopt  the  new. 

In  looking  uneasily  to  the  future  sup- 
ply and  cost  of  fuel,  it  is,  however, 
something  to  know  what  may  be  done 
even  with  the  application  of  our  present 
knowledge  ;  and  could  we  apply  it  uni- 
versally to-day,  all  that  is  necessary  for 
trade  and  comfort  could  probably  be  as 
well  provided  for  by  one-half  the  present 
consumption  of  fuel ;  and  it  behoves 
those  who  are  beginning  to  build  new 
mills,  new  furnaces,  new  steamboats,  or 
new  houses,  to  act  as  though  the  price 
of  coal  which  obtained  two  years  ago 
had  been  the  normal  and  not  the  abnor- 
mal price. 

"  Whence  and  whither,"  is  an  aphor- 
ism which  leads  us  away  from  present 
and  plainer  objects  to  those  which  are 
more  distant  and  obscure  ;  whether  we 
look  backwards  or  forwards,  our  vision 
is  speedily  arrested  by  an  impenetrable 
veil. 

On  the  subjects  I  have  chosen  you 
will  probably  think  I  have  traveled 
backwards  far  enough.  I  have  dealt  to 
some  extent  with  the  present. 

The  retrospect,  however,  may  by  use- 


472 


VAN   NOSTRAND'S   ENGINEERING   MAGAZINE. 


ful  to  show  what  great  works  in  former 
ages. 

Some  things  have  been  better  done 
than  in  those  earlier  times,  but  not  all. 

In  what  we  choose  to  call  the  ideal 
we  do  not  surpass  the  ancients.  Poets 
and  painters  and  sculptors  were  as  great 
in  former  times  as  now  ;  so,  probably, 
were  the  mathematicians. 

In  what  depends  on  the  accumulation 
of  experience,  we  ought  to  excel  our 
forerunners.  Engineering  depends  large- 
ly on  experience  ;  nevertheless,  in  future 
times,  whenever  difficulties  shall  arise  or 
works  have  to  be  acomplished  for  which 
there  is  no  precedent,  he  who  has  to 
perform  the  duty  may  step  forth  from 
any  of  the  walks  of  life,  as  engineers 
have  not  unfrequently  hitherto  done. 

The  marvelous  progress  of  the  last 
two  generations  should  make  everyone 
cautious  of  predicting  the  future.  Of 
engineering  works,  however,  it  may  be 
said  that  their  practicability  or  imprac- 
ticability is  often  determined  by  other 
elements  than  the  inherent  difficulty  in 
the  works  themselves.  Greater  works 
than  any  yet  achieved  remain  to  be 
accomplished — not  perhaps  yet  awhile. 
Society  may  not  yet  require  them  ;  the 
world  could  not  at  present  afford  to  pay 
for  them. 

The  progress  of  engineering  works,  if 
we  consider  it,  and  the  expenditure 
upon  them,  has  already  in  our  time 
been  prodigious.  One  hundred  and 
sixty  thousand  miles  of  railway  alone, 
put  into  figures  at  20,000/.  a  mile, 
amounts  to  3,200  million  pounds  sterling  ; 
add  400,000  miles  of  telegraph  at  100/.  a 
mile,  and  100  millions  more  for  sea 
canals,  docks,  harbors,  water  and  sani- 
tary works  constructed  in  the  same 
period,  and  we  get  the  enormous  sum  of 
3,340  millions  sterling  expended  in  one 
generation  and  a  half  on  what  may  un- 
doubtedly be  called  useful  works. 

The  wealth  of  nations  may  be  impair- 
ed by  expenditure  on  luxuries  and  war  ; 
it  cannot  be  diminished  by  expenditure 
on  works  like  these. 

As  to  the  future,  we  know  we  cannot 
create  a  force  ;  we  can,  and  no  doubt 
shall,  greatly  improve  the  application  of 
those  with  which  we  are  acquainted. 
What  are  called  inventions  can  do  no 
more    than    this,  yet  how  much  every 


day  is  being  done  by  new  machines  and' 
instruments. 

The  telescope  extended  our  vision  to 
distant  worlds.  The  spectroscope  ha? 
far  outstripped  that  instrument,  by  ex- 
tending our  powers  of  analysis  to  regions' 
as  remote. 

Postal  deliveries  were  and  are  great 
and  able  organizations,  but  what  are 
they  to  the  telegraph  ? 

Need  we  try  to  extend  our  vision  into 
futurity  farther?  Our  present  knowl- 
edge, compared  to  what  is  unknown 
even  in  physics,  is  infinitesimal.  We 
may  never  discover  a  new  force — yetr 
who  can  tell  ? 

REPORTS  OF  ENGINEERING  SOCIETIES. 

American  Society  of  Civil  Engineers. — 
The  last  issue  of  the  "  Transactions"  con- 
tains papers  and  discussions  of  the  Annual 
Convention  not  before  published. 

On  Pumping  Engines  by  W.  M.  Roberts,. 
D.  M.  Greene  and  J.  H.  Harlow  ;— On  Com- 
pound Engines  by  J.  W.  Hill  ; — On  Kails  by 
A.  L.  Holley,  W.  Metcalf  and  W.  W.  Evans  ; 
—On  Railway  Signals,  C.  H.  Fisher,  J.  D. 
Steele,  W.  P.  Shinn  and  C.  Paine  ;— On  Rapid 
Transit  in  large  cities  ; — by  R.  H.  Buel,  C.  fl. 
Fisher,  J.  D.  Steele  and  W.  H.  Searles. 

The  present  issue  contains  also  a  detailed- 
account  of  the  failure  of  the  Brainerd  Bridge, 
with  suggestions  as  to  the  cause. 


IRON  AND  STEEL  NOTES. 

Use  of  Rail  Ends  in  Blast  Fuknaces. — 
Heyrowsky  says  that  there  are  different 
methods  for  using  rail  ends  in  the  Bessemer 
process,  and  that  it  is  acknowledged  that  20- 
to  25  per  cent,  can  be  introduced  into  the 
Bessemer  retort  without  any  objection.  An- 
other use  has  lately  been  tried  with  success  at 
the  Zeltweg  blast  furnace,  and  as  Zeltweg 
possesses  a  large  balance  of  rail  ends  this  work 
is  very  important,  The  production  of  the  fur- 
nace heretofore  has  been  4,600  cwt.  of  grey 
Bessemer  pig  per  week  ;  now  it  is  5,400  cwt. 
This  difference  of  800  cwt.  corresponds  exact- 
ly to  the  quantity  of  rail  ends  used.  In  like 
manner,  instead  of  rail  ends,  grey  and  even 
white  cast  iron  could  be  used  without  dimin- 
ishing the  economical  results.  — Mining  Journal, 

Remarkably  Large  Yield  of  Pig  Iron  by 
a  Charcoal  Furnace.— From  a  recent 
number  of  the  Marquette  Mining  Journal  we 
take  the  following  statement  of  the  work  done 
by  Bay  furnace,  No.  2,  at  Onota,  Michigan^ 
during  the  month  of  August  last :  Number 
of  gross  tons  of  pig  iron  made,  1,109| ;  average 
make  per  day,  35.78  tons  ;  highest  daily  yield, 
Aug.  20th,  41|  tons  ;  lowest  daily  yield,  Aug, 
7th,  31  tons  ;  yield  on  the  first  day  of  tbe- 
month,  35  tons  ;  yield  on  the  last  day  of  the 
month,  36  tons  ;  average  yield  of  the  ore,  60. 31 


IRON    AND   STEEL   NOTES. 


473 


per  cent. ;  number  of  bushels  of  charcoal  used 
to  the  ton  of  iron  101.98  ;  total  number  of 
charges  in  the  month,  3,770  ;  total  number  of 
pounds  of  ore  charged,  4,120,550  ;  total  num- 
ber of  bushels  of  charcoal  used,  113,100.  The 
iron  was  of  the  following  gra  les  :  No.  1, 
91 5i  tons;  No.  2,  185£  tons,  and  No.  3,  8| 
tons  :  total,  l,109j  gross  tons.  During  the 
seven  days  beginning  on  the  19th  and  ending 
on  the  25th,  276^  gross  tons  were  made,  which 
is  believed  to  be  the  largest  week's  make  yet 
attained  by  a  charcoal  furnace.  This  furnace 
is  45  feet  high,  and  9i  feet  across  the  bosh. 
H.  S.   Pickands  is  Superintendent. — Bulletin. 

REVOLUTION  IN  THE  PRODUCTION  AND  TREAT- 
MENT of  Iron  and  Steel. — One  of  the 
most  important  patents  which  have  ever  been 
granted  for  the  production  of  iron  and  steel 
will  be  found,  says  Capital  and  Labor,  in  that 
recently  granted  to  Messrs.  Samuel  R.  Smyth 
and  Joseph  Simpson,  of  No.  58  Fountain- 
street,  Manchester.  This  patent  commences 
with  an  exhaust  vacuum  furnace,  and  its  opera- 
tions extend  to  the  manufacture  of  the  finest 
productions  in  iron  and  steel.  It  is,  however, 
so  complete  in  its  character  that  portions  can 
be  applied  to  existing  blast  furnaces,  Bessemer 
converters,  or  Siemens'  furnaces.  Masses  of 
metal  of  twenty-five  tons  in  weight  can  be 
treated  at  one  time  in  the  patentees'  patent 
metal  receiver,  which  forms  an  important 
feature  in  the  invention.  In  it  the  molten 
metal  can  be  purified  and  refined  into  any 
quality  of  iron,  or  it  may  be  converted  into 
steel.  The  cost  of  producing  iron  or  steel  of 
any  quality  by  means  of  this  patent  process  is 
enormously  reduced.  By  the  use  of  the  pat- 
entees' '  comparatively  inexpensive  exhaust 
vacuum  furnace  the  metal  can  be  smelted  with- 
out the  necessity  of  providing  blast  engines, 
and  it  is  never  allowed  to  cool  from  that  point 
until  it  has  been  manipulated  into  a  finished 
production.  In  the  manufacture  of  steel  the 
purifying  process  (which  only  occupies  a  few 
minutes)  enables  steel  to  be  produced  from 
Cleveland,  Lincolnshire,  or  Northamptonshire 
iron,  or  even  from  cinder  pig,  because  the 
objectionable  metalloids  in  the"  iron  are  either 
removed  or  rendered  quite  innocuous  by  the 
use  of  the  compounds  applied  by  the  patentees 
in  their  apparatus.  The  iron  being  thus  puri- 
fied and  refined,  steel  can  be  produced  there- 
from, by  their  process,  without  the  use  of 
spiegeleisen,  In  applying  the  process  to  Bes- 
semer convertors  or  to  Siemens'  furnaces  it 
may,  however,  be  necessary  to  use  a  small 
amount  of  spiegel.  In  working  this  invention 
throughout  it  is  a  notable' feature  that  solid 
fuel  only  comes  once  into  contact  with  the 
metal.  The  gases  from  the  coal  are  stored  in 
a  gasholder,  and,  along  with  those  evolved  in 
the  vacuum  smelting  furnace,  they  are  used  in 
heating  the  furnaces  for  the  further  manipula- 
tion of  the  metal.  By  this  means  all  the  com- 
bustible properties  in  the  coal  are  made  use  of, 
and  after  the  gases  have  supplied  all  the  car- 
bonic oxyde  necessary  for  completing  the  fur- 
ther stages  of  production.  It  is,  lastly,  used 
for  raising  the  steam  required  in  the  boilers 
on  the  premises.     By  this  means  the  consump- 


tion of  fuel  is  reduced  to  the  lowest  minimum 
possible.  By  the  patentees'  method  of  treat- 
ment any  weight  of  charge  of  metal  can  be 
purified  and  refined  at  once,  and  converted 
into  steel  if  desired.  The  metal  can  also  bt 
held  in  its  molten  state  in  the  patent  metal  re 
ceiver  for  any  length  of  time  which  may  be 
desired,  without  any  waste  of  material,  inas- 
much as  the  metal  can  be  oxydized  or  de- 
oxydized.  carbonized  or  de-earbonized  in  the 
metal  receiver  any  number  of  times  at  the  will 
of  the  manipulator.  By  this  process  also  a- 
plate,  casting,  or  forging  of  any  weight  can  be 
produced  without  any  laminations,  because  irt- 
the  metal  receiver  every  atom  of  the  metal 
will  be  of  perfect  evenness  of  quality,  ductility, 
and  density.  This  important  invention  is  the 
result  of  years  of  careful  examination  and 
study,  and  the  practical  results  which  have 
been  obtained  by  the  application  of  the  inven- 
tion to  adequate  quantities  of  metal  are  such 
as  to  justify  even  more  sanguine  statements 
that  are  made  herein. 

MECHANICAL  AlDS  TO  PUDDLING. — We  note 
that  ironmasters,  who  are  not  experi- 
menting with  rotary  furnaces,  are  still  casting 
about  for  a  means  of  puddling  their  iron  with 
as  little  manual  labor  as  is  practicable.  The 
difficulties  arising  out  of  the  want  of  enough- 
puddlers  sufficiently  skilled  to  do  their  work 
properly,  is  driving  the  finished  iron  trade  in 
most  parts  of  the  kingdom  to  seek  mechanical 
aid,  which  they  would  otherwise  not  be  anx- 
ious about.  When  men  have  once  set  up  a 
plan,  there  is  a  pardonable  reluctance  to  inter- 
fere with  it,  so  long  as  it  can  be  made  to  serve 
the  purpose  for  which  it  was  originally  design- 
ed. Single-hand  puddling  furnaces  were  weli 
enough  when  the  demand  for  iron  was  less 
than  now,  or  when  men  were  more  abundant 
in  proportion  to  the  demand;  but  now  that  the 
aggregate  of  the  requirements  of  the  iron-con- 
suming world  is  vast,  and  puddlers  are  scarce,, 
it  becomes  a  necessity  that  a  method  of  mak- 
ing finished  iron  in  its  early  stages  should  be 
adopted  by  which  a  larger  quantity  than  here- 
tofore may  be  got  out  in  the  same  time.  More- 
over, such  is  now  the  competition  in  the  manu- 
facture of  iron,  both  at  home  and  abroad,  that 
rigid  economy  must  be  enforced.  Where, 
therefore,  ironmasters  are  not  prepared  to 
adopt  revolving  machinery,  they  are  seeking- 
out  and  adopting  the  best  form  of  double  fur- 
nace, worked  in  part  by  machinery,  and  pos- 
sessing a  heating  chamber  for  warming  the 
pig  iron  before  it  is  thrown  into  the  puddling 
furnace.  One  such  furnace  is  known  in  York- 
shire as  the  "Joe  Pickles''  furnace — Mr.  Pick- 
les having  been  a  millwright  in  the  service  of 
the  Kirkscall  Iron  Company,  by  whom  the  fur- 
nace is  made.  There  is  nothing  remarkably 
striking  about  it,  but  practical  men  are  giving 
increased  attention  to  it,  and  it  is  now  being 
adopted  outside  Yorkshire.  The  furnace  has 
an  opening  on  each  side,  so  that  two  men  can 
be  simultaneously  employed  upon  it.  In  & 
double  furnace  of  this  description  the  back 
wall,  with  all  its  cost  of  fettling  and  frequent 
repairing,  is  dispensed  with,  and  by  reducing: 
the  area  to  be  heated  there  is  economy  in  the- 


474 


VAN    NOSTRAND  S   ENGINEERING    MAGAZINE. 


consumption  of  fuel.  The  pigs  are  heated  in 
a  chamber  on  each  side  of  the  flue.  The  pud- 
dling machine  consists  of  a  frame  fastened  to 
the  outer  plates  of  the  furnace.  Upon  this 
frame  is  fixed  a  small  steam  engine,  which  is 
arranged  so  as  to  move  a  beam  up  and  down. 
From  each  end  of  this  beam  a  crank  is  worked, 
having  at  its  proximity  a  forked  swivel,  and 
in  this  the  rabble  or  tool  is  fixed.  The  verti- 
cal movement  of  the  beam  gives  a  horizontal 
motion  to  one  end  of  the  crank  to  which  the 
tool  is  attached,  so  that  instead  of  the  puddler 
or  underhand  having  to  work  the  iron  while  it 
is  in  a  fluid  state  the  machine  does  it,  and  all 
the  workmen  have  to  do  is  to  change  the  rab- 
ble when  it  becomes  too  hot,  and  replace  it 
with  a  cold  one.  By  lifting  it  out  of  the  swiv- 
el fork,  this  is  done  without  stopping  the  ma- 
chine. The  arrangement  is  such  that  the  tool 
working  on  one  side  of  the  furnace  cannot 
come  into  contact  with  the  tool  working  on  the 
opposite  side,  for  as  the  one  is  going  into  the 
furnace  on  one  side  the  other  is  making  its 
outward  stroke,  and  while  one  is  working  at 
the  fire  end  of  the  furnace  the  other  is  work- 
at  the  fire-bridge  end.  By  an  ingenious  con- 
trivance the  machine  causes  the  tool  to  work 
four  strokes  in  each  jamb  before  it  returns  on 
its  journey  across  the  furnace.  The  advant- 
age of  this  will  be  seen  when  it  is  considered 
that  the  tool  must  pass  over  the  middle  of  the 
furnace  twice  to  reach  alternately  each  jamb 
once.  The  furnace  has  water  boshes  around 
it  to  prevent  the  fettling  from  working  out  so 
rapidly  as  under  the  old  arrangement  of  the 
single  furnace.  Messrs.  E.  P.  &  W.  Baldwin, 
who  have  finished  ironworks  at  Stourport,  and 
Dudley,  and  Wolverhampton,  are  those  who 
have  most  recently  adopted  the  "Joe  Pickles" 
furnace  we  have  described. — Engineer. 


RAILWAY  NOTES. 

J  ANUFACTURE      OF     STEEL      IN     FRANCE. — 

iYl  France,  which  at  one  time  was  reputed 
incapable  of  making  steel,  has  made  it  at  the 
following  rates  for  the  last  twelve  years  : — In 
1863,  1800  tons  ;  1864,  6700 ;  1865,  9700  ;  1866, 
10,800  ;  1867,  19,900  ;  1868,  42.600  ;  1869,  52,- 
400  ;  1870,  90,000  ;  1871,  110,000  ;  1872,  138,- 
500  ;  1873,  167,000  ;  1874,  217,000  tons.  This 
extraordinary  development  of  French  metal- 
lurgy is  encouraging  to  those  interested  in 
French  industry. 

AN  experiment  is  being  made  with  wooden 
rails  on  a  portion  of  the  Muncy  Creek 
Railroad,  an  unfinished  line  of  forty  miles,  in 
Lycoming  County,  Pa.  U.S.  Mr.  H.  R.  Mehrl- 
ing,  the  superintendent,  has  recently  had  700 
ft.  of  track  laid  on  a  curve  just  beyond  Muncy 
Creek,  and  it  has  been  found  to  answer  the 
purpose  much  better  than  was  anticipated. 
The  rails  are  of  sugar  maple,  7  in.  by  4 in.,  and 
about  12ft.  in  length.  The  ties  are  laid  down 
in  the  ordinary  way,  notched,  and  the  rails  let 
into  them  about  4  in.  They  are  then  keyed 
firmly  with  wooden  wedges  driven  on  the 
sides,  which  makes  the  track  very  solid  and 
firm.  The  locomotive  and  heavy  cars  have 
&een  passed  over  this  experimental  track  at 


different  rates  of  speed,  and  it  has  been  found 
to  work  admirably,  and  give  every  assurance 
of  success.  The  cost  of  laying  wooden  rails, 
manufactured  out  of  this  hard  material — that 
becomes  almost  as  solid  as  bone  when  seasoned 
— is  450  dols.  per  mile.  Iron  costs  4000  dols. 
per  mile.  No  iron  spikes  are  required,  as  the 
rails  are  secured  with  wooden  wedges,  and  the 
cost  of  track-laying  is  about  the  same  as  put- 
ting down  iron.  These  wooden  tracks  have 
been  tried  at  different  places  in  the  United 
States,  and  invariably  been  found  to  work 
well.  The  highest  rate  of  speed  for  locomotives 
to  pass  over  them  with  safety  has  been  fixed 
at  sixteen  miles  per  hour,  but  even  if  this  rate 
were  reduced  to  twelve  or  to  ten  miles,  the 
saving  in  expense  would  more  than  compensate 
for  the  reduction  in  speed.  It  has  also  been 
shown  by  experiment  that  these  wooden  rails 
will  last,  ordinarily,  from  three  to  four  years, 
which  is  another  important  item  to  be  taken 
in  consideration. 

A  brilliant  experiment  in  railway  warfare 
has  been  conducted  by  Major-General  Sir 
Charles  Reid  at  Meean  Meer.  The  Pioneer  of 
India  says  its  object  was  to  test  how  guns  and 
troops  could  be  conveyed  to  or  from  any  point 
of  a  railway  line,  independently  of  railway 
platforms  and  the  usual  accessories  for  the 
loading  of  heavy  material.  The  General's 
method,  described  in  a  Calcutta  contemporary, 
was  as  follows  : — Doors,  constructed  to  swing 
downwards,  were  opened  in  the  front  and  rear 
of  each  wagon  of  a  railway  train.  With  all 
its  doors  down,  the  train  became  a  long  con- 
tinuous platform,  with  high  sides.  At  either 
end  of  this  train  was  a  low  truck  containing  a 
pair  of  iron  girders  which  could  be  readily  run 
out,  covered  with  planks,  and  converted  into  a 
sloping  platform.  Accordingly,  at  daybreak, 
half  a  battery  of  horse  artillery  was  marched 
to  the  spot.  The  order  was  given  to  lower  . 
the  doors  and  girders.  The  horses  were 
brought  in  at  one  end  of  the  train,  and  placed 
head  to  head,  in  their  separate  trucks,  while 
the  guns  and  the  carriages  were  run  up  on  the 
girders  at  the  other  ;  the  artillerymen  were 
distributed  in  second  class  carriages  ;  finally, 
the  girders  and  doors  were  pulled  up,  the  en- 
gine was  attached,  and  away  went  the  half- 
battery  on  its  expedition,  in  36  minutes  after 
its  arrival  on  the  spot.  After  a  run  of  some  : 
minutes  the  train  stopped  at  a  place  where 
there  was  a  raised  embankment,  about  half  a 
mile  from  a  level  crossing.  The  doors  and 
platforms  were  thrown  down  ;  the  horses 
went  out  at  one  end,  and  the  Armstrong  guns 
at  another,  and  in  less  time  than  seven  minutes 
the  first  gun  opened  fire  from  the  embankment. 
It  took  only  45  minutes  from  the  time  the 
train  stopped  to  limber  the  guns,  each  of 
which  was  pulled  by  six  horses,  and  to  reach 
the  level  crossing  in  full  force  and  complete 
order. 


ENGINEERING  STRUCTURES. 

Several  civil  engineers,  engaged  with  the 
surveys  for  a  water  conduit  from  Touja  to 
Bougie,  have  made  a  very  interesting  and  im- 
portant discovery.      A  mountain  which  was 


ORDNANCE   AND   NAVAL. 


475 


-situated  in  the  proposed  line  of  the  conduit 
was  to  be  tunneled  for  a  length  of  500  yards  ; 
and  in  searching  for  the  most  suitable  place 
the  engineer  discovered  an  ancient  tunnel  6  ft. 
8  in.  in  height,  and  19  ft.  7  in.  in  circumference. 
It  is  supposed  that  this  is  the  same  tunnel 
mentioned  in  an  epigraph  found  at  Lambeoc, 
according  to  which  the  tunnel  was  built  in  the 
reign  of  Antoninus  Pius,  the  plans  being  pre- 
pared by  a  veteran  of  the  Third  Legion,  named 
Nonius  Datus.  Finding  works  like  this  after 
a  time  of  2000  years,  we  cannot  but  be  greatly 
astonished  at  the  power,  energy,  and  genius  of 
a  nation  which  produced,  with  the  limited 
•  means  available  at  those  times,  such  gigantic 
structures. 

Wonderful  Engineering. — Anyone  desir- 
ing to  obtain  any  idea  of  the  stupendous 
accomplishments  of  railroad  engineering 
should  spend  a  few  days  in  Tehachape  Pass, 
investigating  the  operations  of  the  Southern 
Pacific  Railroad  Company.  About  twenty 
miles  of  that  road  is  a  succession  of  cuts,  fills 
and  tunnels.  Within  this  distance  there  are 
thirteen  tunnels,  ranging  from  1100  feet  to  a 
few  yards  in  length.  For  the  greater  portion 
of  the  way  the  road  bed  is  cut  through  solid 
granite.  The  elevation  is  so  great  from  the 
present  terminus  of  the  road,  at  Caliente,  to 
Tehachape  Valley,  that  the  first  mile  and  a  half 
out  of  Caliente  is  attained  by  laying  down 
eight  miles  of  track.  Higher  up  in  the  pass 
the  road  runs  through  a  tunnel,  encircles  the 
hill,  and  passes  a  few  feet  above  the  tunnel. 
After  completely  encircling  the  hill,  and 
-going  half  around  again,  the  track  doubles  on 
itself  like  a  closely  pursued  hare,  and  after 
running  several  miles  in  the  opposite  direction, 
strikes  up  the  canon.  This  circling  and 
doubling  is  for  grade.  Once  the  track  crosses 
the  pass,  and  this  involves  the  building  of  a 
long  and  very  high  bridge.  We  doubt  if  a 
more  difficult  and  expensive  piece  of  engineer- 
ing was  encountered  in  the  building  of  the 
Central  Pacific  over  the  Sierras  than  that  with 
which  the  Southern  Pacific  is  now  struggling 
in  Tehachape  Pass.  Another  tremendous  piece 
of  work  is  the  San  Fernando  tunnel,  which, 
when  completed,  will  be  over  a  mile  and  a 
half  in  length,  and  in  places  over  1000  feet  be- 
neath the  surface.  Yet  the  company  will 
accomplish  this  great  work,  and  run  cars 
through  from  San  Francisco  to  Los  Angeles  by 
the  first  of  next  July.  All  the  force  that  can 
be  used  is  kept  at  work  on  the  San  Fernando 
tunnel.  In  the  Tehachape  Pass  5000  men  are 
employed,  and  the  force  is  being  increased  at 
the  rate  of  1000  Chinamen  per  week. — Los 
_Anpeie-i  (Oal.)  Herald. 


ORDNANCE  AND  NAVAL. 

The  work  with  the  81-ton  gun,  if  it  had  been 
less  important  than  others,  has  been  of  a 
more  interesting  character  than  any  of  its  pre- 
decessors. In  the  first  place  the  gun  had  to  be 
lifted  into  its  carriage,  and  it  remained  to  be 
seen  if  it  was  properly  adjusted.  Of  this  the 
officials  entertained  no  doubt  from  the  care 
with    which    every  part  of    both    gun    and 


carriage  had  been  made  to  scale.  The  gun 
was  lifted  just  as  other  guns  are,  by  rop< 
slings  passed  under  its  arms,  or  trunnions,  and 
so  well  had  their  proper  position  been  calcu- 
lated that  the  monster  hung  in  an  exact  hori- 
zontal line  evenly  balanced.  The  work  of 
transferring  it  to  its  place  on  the  carriage  occu- 
pied only  a  few  minutes,  and  it  fitted,  as  an- 
ticipated, with  perfect  accuracy  everywhere. 
Then  came  the  more  serious  task  of  removing 
it  down  to  or  towards  the  butts,  and  for  this 
work  the  locomotive  which  waits  on  the  Royal 
gun  factories,  and  is  called  the  "  Gunner,'' 
was  brought  into  requisition.  This  locomo- 
tive, though  much  more  powerful  than  the 
little  engines  which  run  about  the  Royal  Ar- 
senal on  the  narrow  gauge,  is  not  half  the  size 
of  the  ordinary  railway  locomotives,  and 
doubts  had  been  expressed  as  to  its  being  equal 
to  the  duty  required  of  it.  Indeed,  when  it 
was  first  set  to  pull  the  great  Juggernaut-like 
car  along  the  railroad  it  was  utterly  unable  to 
move  it.  Again  and  again  the  engine  made 
the  attempt,  occasionally  moving  the  wheels 
an  inch  or  two,  but  more  often  pulling  up 
dead,  or  snapping  in  twain  the  great  hawsers 
by  which  it  was  attached.  The  character  of 
the  railway  line  had  much  to  do  with  this 
failure  ;  it  was  laid  down  a  good_  many  years 
ago  for  very  different  work.  It  is  rough  and 
irregular,  and,  moreover,  it  rises  at  first  on  a 
slight  incline.  By  the  help  of  lifting  jacks, 
handspikes,  and  a  rope  attached  to  a  station- 
ary engine  in  one  of  the  workshops,  the  carri- 
age was  coaxed  on  for  about  a  hundred  yards, 
but  the  120  tons  of  dead  weight  resting  upon 
its  twelve  wheels  all  packed  close  together  was 
slow  to  move,  and  it  was  feared  that  the 
attempt  must  be  given  up  for  the  day,  or  some 
other  expedient  adopted.  It  occurred,  however, 
to  some  one  to  harness  on  a  couple  of  the 
small  locomotives  in  front  of  their  larger 
brother,  as  the  narrow  and  broad  gauge  lines- 
run  together.  This  proved  the  solution 
of  the  difficulty,  for  the  three  engines  moved 
the  burden  quite  easily,  to  the  surprise  of  al- 
most everybody,  the  additional  power  lent  by 
the  little  engines  being  to  all  appearance 
ridiculously  small.  A  stoppage,  however, 
took  place  shortly  before  reaching  the  canal 
which  separates  the  practice  ground  from  the 
rest  of  the  arsenal,  and  it  was  decided  to  defer 
crossing  the  bridge  until  to-day.  Beyond  the 
canal  is  the  worst  part  of  the  line,  as  it  runs 
along  an  embankment  down  a  steep  incline, 
which  has  on  one  occasion  given  way. 

Torpedo  Boat  for  the  Austrian  Govern- 
ment.—Messrs.  J.  Thornycroft,  of 
Chiswick,  have  just  completed  a  steam  torpedo 
launch  for  the  Austro-Hungarion  Government. 
A  trial  of  this  boat  took  "place  on  Saturday 
last,  the  11th  hist,,  on  the  Thames  below  Lon- 
don Bridge.  At  the  trial  trip  there  were  on 
board,  besides  the  builders  of  the  vessels  : 
Baron  Spaun,  Naval  Attache.  Austro-Hunga- 
rian  Embassy  ;  the  "\  ieomte  de  la  Jour  du 
Pin,  Naval  Attache,  French  Embassy  ;  and 
Mr.  Schneider,  Chief  Engineer,  Austrian  Navy. 
A  start  was  made  a  little  below  the  Thames 
Ironworks  at  eleven  minutes  past  twelve,  and 


476 


van  nostrand's  engineering  magazine. 


the  hour's  run  finished  at  Lower  Hope  Reach,  | 
below  Gravesend,  at  eleven  minutes  past  one 
O'clock.     During  the  run  the  number  of  revo- 
lutions was  taken  by  Mr.  Schneider  and  Mr. 
Walker,  chief  draughtsman  at  Messrs.  John  I.  ; 
Thornycroft  and  Company's,  and  was  found 
to  be  exactly  24,700.     The  vessel  was  then  run  | 
up  to  Long  Reach,  and  run  six  times  over  the 
measured  knot  there,    when   the  number  of 
revolutions  of  the  engines  required  to  do  one 
knot  was  found  to  be  1357.     The  number  of 
revolutions    done    during  the    hour  (24,700), 
divided  by  the  number  required   to  do  one  j 
knot  (1357),  gave  the  number  of  knots  done  in 
the  hour  as  18,202,  a  result  which  is  certainly 
most  satisfactory. 

On  the  way  up  to  London  the  vessel  was  run  ; 
past  a  small  schooner  at  a  speed  of  ten  knots, 
and  a  dummy  torpedo  was  launched  against  j 
her  side.     The  torpedo  struck   the  schooner 
amidships  at  about  6  ft.  or  7  ft.   below  the  j 
water  level,   and  had  it  been  filled  with  its ! 
charge    of    dynamite    (25  lb.),   the  schooner 
would  undoubtedly  have  gone  to  the  bottom. 
The  torpedo  gear  on  this  vessel  consists  of  two  j 
poles  38  ft.  long,  one  on  either  side,  and  so  } 
arranged  that  an  attack  may  be  made  directly  ! 
ahead  of  the  boat,  in  which  case  the  boat  must  j 
he  stopped  and  backed  off  her  enemy  imme- ! 
diately  after  the  explosion  ;  or  on  the  broad- 
side,  when  the  boat  may  be  kept  going  ahead 
all  the  time,  and  so  saving  the  time   which 
would  be  otherwise  lost  in  stopping  and  back-  \ 
ing.     The  dimensions   of  the  torpedo  launch 
are  : — Length,  67  ft. ;  beam,  8  ft.  6  in. ;  and  the 
speed  guaranteed  by  the  builders  wa3  fifteen 
knots. — Engineer. 

1  — i 

BOOK  NOTICES 

Iveson's  Horse  Power  Diagram.     London  : 
E.   &  F.  N.  Spon.     For   sale  by  D.  Van 
Nostrand.     Price  $4.25. 

This  is  a  folding  chart  to  facilitate  calcula- 
tions of  horse  power  of  engines,  when  the 
ordinary  data  are  given. 

The  results  are  found  by  line  illustrations  on 
finely  engraved  charts. 

CLIMATE  AND  TlME  FN  THEIR  GEOLOGICAL 
Relations.  By  James  Croll.  New 
York  :  D.  Appleton  &  Co.     Price  $2.50. 

Mr.  Croll  has  set  forth  his  views  at  various 
times  in  the  Philosophical  Magazine  and  other 
British  journals. 

He  is  a  vigorous  writer,  and  has  earned  a 
right  to  respectful  attention  by  his  varied 
labors  as  a  geologist. 

The  principal  topic  of  the  present  work  is 
the  change  in  temperature  of  the  earth's  sur- 
face during  geological  ages,  the  evidence  of 
which  we  find  in  the  coal  and  drift  forma- 
tions. 

The  illustrations,  consisting  largely  of  color- 
ed charts,  are  very  good. 

Hand  Book  for  Charcoal  Burners.  By 
G.  Svedelius,  translated  from  the  Swed- 
ish by  R.  B.  Anderson,  A.  M.  New  York  : 
John  Wiley  &  Son.    Price  $1.50. 

We  presume  this  treatise  may  be  considered 
of  some  value  in  some  part  of  this  country, 


though  we  don't  exactly  know  where.     Judg 
ing  from  the  preface,  the  chief  reason  for  the= 
original  publication  in  Sweden  was  a  Govern- 
ment Prize  of  six  hundred  and  fifty-six  rix- 
dollars. 

The  author  certainly  made  a  good  deal  of 
one  of  the  simplest  operations  in  the  world 
The  minuteness  with  which  the  details  of  the- 
manual  labor  is  described  is  equaled  by  noth- 
ing we  know  of  except  instructions  for  croch- 
eting and  needlework. 

Charcoal  makers,  who  desire  to  know  how 
elaborate  a  process  they  are  engaged  in,  should 
possess  themselves  of  this  work. 

A    Manual    op    Metallurgy.      By    W*t 
Henry  Greenwood,  F.C.S.     Volume  2. 
New  York  :    G.  P.  Putnam's  Sons.     For  sale 
by  Van  Nostrand.     Price  $1.50. 

The  subjects  treated  in  this  volume  are  the 
extraction  severally  of  Copper,  Lead,  Zinc, 
Mercury,  Silver,  Gold,  Nickel,  Cobalt,  and 
Aluminum  from  their  respective  ores. 

The  work  is  systematic,  giving  the  naturai 
history  of  the  different  native  compounds  of 
these  metals,  and  also  their  chemical  constitu- 
tion. 

The  reader  is  cautioned  in  the  preface  not 
to  expect  such  a  description  of  the  details  of 
metallurgical  operations  as  only  the  larger 
works  can  contain  ;  the  author  only  attempts 
to  give  such  explanations  as  are  generally  re- 
ceived of  the  scientific  principles  upon  which 
the  processes  are  based.  This  he  seems  to  have 
satisfactorily  accomplished. 

PROBLEMS    IN    STONE    CUTTING.       By   S.    ED- 
WARD Warren,  C.E.     New  York:   Joha 
Wiley  &  Son 

Prof.  Warren's  works  are  so  well  known, 
that  we  need  not  enlarge  upon  their  general 
excellence.  From  such  inspection  as  we  have 
been  able  to  make  of  this  work,  we  should 
say  it  was  equal  to  the  best  of  the  professor's 
previous  books. 

We  know  of  nothing  so  acceptable  just  now 
as  this  book.  Having  been  called  upon  dur- 
ing the  last  season  to.  reoommend  such  a  book 
as  a  supplement  to  a  course  in  descriptive 
geometry,  we  were  obliged  to  recommend 
parts  of  two  or  three  expensive  works  as  th& 
only  way  of  fulfilling  the  requirements.  This 
new  work  of  Prof.  Warren's  would  have  an- 
swered completely  to  the  demand. 

With  his  usual  precision  of  classification,  the. 
author  divides  his  problems  into  four  classes; 
viz: 

I.  Plane-sided  structures. 
II.  Structures  containing  developable  sur- 
faces. 

Ill    Structures  containing  warped  surfaces. 

IV.  Structures  containing  double  curved 
surfaces. 

Tin  folding  plates  illustrate  the  work,  con- 
taining seventy-three  separate  figures. 

The  Mechanical  Engineer:  His  Prepara- 
tion and  His  Work.     An  address  to  the 
graduating  class  of  Stevens'  Institute.     By  R. 
H.   Thurston,  A.  M.    C.  E.     New  York:   D. 
Van  Nostrand.    Price  50  cts. 
It  is  well  that  this  able  address  is  put  in  a 


BOOK    NOTICES. 


477 


-form  to  reach  beyond  the  circle  for  whom 
alone  it  was  originally  prepared.  At  the  re- 
quest of  the  hearers,  it  was  published  in  neat 
pamphlet  form. 

The  address  may  be  read  with  profit  by 
young  and  old  of  other  professions  than  that 
of  mechanical  engineer. 

The  professor  first  details  the  nature  of  the 
studies  pursued,  and  sets  forth  the  advantages 

.■of  the  culture  derived  from  each,  then  gives 
some  exceedingly  practical  advice  in  regard  to 
the  use  of  the  acquired  talents  in  their  profes- 

.  ^ional  career. 

It  is  not  a  farewell  speech  of  the  ordinary 
academy  or  college  type,  but  widely  different 
ib  many  respects,  and  naturally  so,  inasmuch 
as  the  graduates  to  whom  it  was  addressed  had 
presumably  adopted  a  profession,  and  were 
entitled  to  advice  regarding  its  duties.  It  is 
certain  that  no  one  was  better  fitted  to  advise 
them  than  their  talented  professor  of  mechan- 
ical enffineering. 

The  Past  and  Future  op  Geology.  By 
Joseph  Prestwich,  F.  R.  8. ,  F.  G.  8.  (An 
inaugural  address.)  London:  McMillan  &  Co. 
For  sale  by  I>.  Van  Nostrand.     Price  $1.00. 

From  so  eminent  a  source,  an  essay  on  the 
subject  of  Geological  discovery  is  exceedingly 
Taluable.  Of  course,  the  question  of  internal 
3ieat  receives  a  large  share  of  attention. 

Several  well  executed  diagrams,  illustrating 
-€he  distribution  in  time,  of  organic  life,  adorn 
the  book  and  convey  a  surprising  amount  of 
information  at  a  glance. 

J  exton's  Pocket-Book  for  Boiler-Makers 
and  Steam"  Users.  By  M.  J  Sexton. 
'London:  E.  &  F.  N.  Spon.  For  sale  by  D. 
Tan  Nostrand.     Price  $2.00. 

This  is  substantially  a  table  book  of  weights 
and  dimensions  of  parts  of  a  boiler.  But  brief 
treatises  on  the  care  and  management  of  boilers 
are  interpolated  between  the  separate  tables. 

The  book  is  neatly  made,  after  the  manner 
of  the  smaller  table-books — opening  length- 
wise— is  pretty  well  illustrated  with  wood-cuts, 
and  moreover  is  furnished  with  blank  leaves 
at  different  places  throughout  the  book — a  plan 
worth  following  in  all  similar  works. 

On  the  Strength  op  Cement.  By  John 
Grant,  C.E.  London:  E.  &  F.  N.  Spon. 
For  sale  by  D.  Van  Nostrand.     Price  $4.25. 

This  work  gives  detailed  description  of  ex- 
periments upon  the  strength  of  cements;  but 
chiefly  on  Portland  cement,  used  in  the  south- 
ern main  drainage  works  of  London.  The 
volume  is  a  reprint  of  papers  read  before  the 
Institution  of  Civil  Engineers  on  two  separate 
occasions:  December,  1865,  and  April,  1871. 

Besides  the  results  of  many  experiments 
carefully  tabulated,  the  plates  afford  valuable 
information  to  engineers  respecting  the  con- 
struction of  sewers  of  various  sizes. 

Homes  and  How  to  make  them — Illus- 
trvted  homjes.  by  c.  c.  gardner. 
Boston :  James  K.  Osgood  &  Co.  For  sale  by 
D.  Van  Nostrand.     Price  $2.00. 

These  unique  volumes  ought  to  be  widely 
read.  They  are  designed  primarily  for  those 
■who  are  about  to  build,  or  who  have  friends 


S 


soliciting  advice  about  building  houses;  but 
they  may  be  read  with  pleasure  and  profit  by 
any  who  delight  in  lively  pictures  of  home 
life  amid  people  who  are  altogether  humin, 
mostly  witty,  and  in  every  way  agreeable  to 
meet  as  the  author  presents  them. 

They  are  worth  careful  reading  as  samples 
of  successful  presentation  of  a  semi-technical 
subject  in  a  delightful  way. 

rPiiE  Journal  of  the  Iron  and  Steel  Insti- 

I      tute.  Part  1.    London:  E.  &  F.  N.  Spon. 

For  sale  by  D.  Van  Nostrand.     Price  $3.75. 
Among  the  papers  of  this  new  volume,  the 

more  important  are: 

The  Ores  of  Iron  in  their  Geological  Relations. 
By  Warrington  Smith,  F.R.S. 

Notes  of  a  visit  to  Coal  and  Iron  Works  of  the 
United  States.  By  I.  Lowthian  Bell, 
F.R.S. 

The  Sum  of  Heat  utilized  in  Smelting  Cleve- 
land Ironstone.     (Same  author.) 

The  Manufacture  of  Bessemer  Steel  in  Bel- 
gium.    By  M.  Julien  Deby. 

Reports  of  Iron  and  Steel  Industries  in  the 
United  Kingdom  and  in  Foreign  Coun- 
tries. 

The  Works  op  E.  Verdet:  Cours  de  Phys- 
iquie.  2  vols.  Leg  ons  D'Optique  Physi- 
que. 2  vols.  Conferences  de  Physique.  2 
vols.  Theorie  Mecanique  de  Chaleur.  2  vols. 
Notes  et  Memoires.  1  vol.  Paris  :  Victor 
Masson. 

Nothing  in  the  way  of  wood-cut  illustration 
or  typography  can  be  finer  than  is  exhibited 
in  these  works  of  Verdet. 

The  volumes  average  something  over  500 
pages  each.  To  illustrate  the  Cours  de  Physi- 
que alone  there  are  516  wood-cuts. 

In  Physical  Optics  this  work  is  the  most  ex- 
tensive with  which  we  are  acquainted.  All 
are  standard  works. 

A  New  Method  of  Obtaining  the  Differ- 
entials of  Functions.  By  Prof.  J. 
Minot  Rice,  of  United  States  Navy,  and  Prof. 
W.  Woolsey  Johnson,  of  St.  John's  College. 
Revised  edition.  New  York  :  D.  Van  Nos- 
trand.    Price  50  cts. 

The  authors  of  this  little  essay  advocate  a 
return  to  the  method  of  fluxions,  which  has 
been  almost  abandoned  by  modern  instructors. 

The  method  of  presenting  the  subject  is  cer- 
tainly clear,  and  to  the  mathematical  student 
attractive.  Whether  the  beginner  rinds  diffi- 
culty in  accepting  the  doctrine  of  limits  or  not, 
he  will  certainly  reap  benefit  from  a  study  of 
this  little  treatise. 

An  Elementary  Treatise  on  Steam  and 
the  Steam  Engine.  By  D.  Kinvear 
Clark,  C.  E.  London  :  Lockwood  &  Co. 
1875.  For  sale  by  D.  Van  Nostrand.  Price 
$1.40. 

We  have  here,  recast,  one  of  the  series  of 
practical  works,  presenting  in  a  cheap  and 
generally  reliable  form  the  elements  and  prin- 
ciples of  science  and  art,  and  kno-vn  as 
Weale's.  The  present  work  is  adapted  from 
Mr.  John  SewelFs  elementary  treatise  on  steam, 
the  portions  of  that  treatise,  useful  in  its  day, 
which  time  and  discovery  have  rendered  obso- 


478 


van  nostrand' s  engineering  magazine. 


lete,  teeing  replaced  by  matter  more  directly 
interesting  to  the  steam  engineer.  Other  sub- 
jects, such  as  the  mechanical  theory  of  heat, 
unknown  at  the  first  publication  of  the  work, 
are  introduced  for  the  first  time,  as  well  as  the 
more  important  of  the  numerous  improvements 
that  the  steam  engine  has  received  in  the  in- 
terval. The  historical  notice  of  steam  and  the 
steam  engine,  by  Mr.  Sewell,  is  retained  un- 
altered, although  susceptible  of  considerable 
improvement.  At  all  events,  such  an  obvious 
blunder  as  the  representation  of  the  goddess 
Isis  as  a  male  divinity,  and  the  change  of  the 
termination  of  her  name  to  suit  the  change  of 
sex,  might  have  been  corrected.  In  the  prac- 
tical portion  every  essential  part  of  the  sub- 
ject is  treated  of  competently  and  in  a  popular 
style  ;  while  there  are  also  given  numerous 
and  useful  tables  illustrating  the  capacities  of 
boilers,  and  the  properties  of  fuel  and  steam. 

i^NGrNEERiNG  Papers.  ByC.  Graham  Smith, 
!i    Stud.  Inst,  C.  E.     Spon,   London.     1875. 
For  sale  by  D..  Van  Nostrand.     Price  |2.00. 

This  little  work  is  a  reprint  of  three  papers 
on  mortar,  practical  ironwork,  and  retaining 
walls.  The  first  two  were  read  before  the  In- 
stitute of  Civil  Engineers,  and  each  obtained 
a  Miller  prize.  The  third  was  read  before  the 
Edinburgh  and  Leith  Engineers'  Society.  We 
are  pleased  to  see  these  papers  put  together  in 
a  convenient  and  accessible  form,  for  they  are 
very  practical  in  their  character,  and  contain 
a  good  deal  of  useful  information.  The  paper 
on  mortar  is  probably  the  best  available  treat- 
ise in  the  English  language  on  the  subject. 
That  on  practical  ironwork  is  valuable,  be- 
cause it  deals  with  the  subject  in  a  way  hardly 
ever  employed  by  other  authors.  Mr.  Smith 
says  little  or  nothing  about  strains,  but  he  gives 
numerous  practical  hints  about  the  way  iron 
structures  should  be  designed  and  put  togeth- 
er ;  and  in  a  species  of  appendix  to  the  paper 
he  very  properly  calls  attention  to  a  fact  too 
often  overlooked — namely,  that  what  are  term- 
ed "fancy"  sizes  and  sections  of  iron  always 
command  a  fancy  price.  The  designer  should 
always  endeavor  to  work  with  marketable  ma- 
terials ;  but  the  student  will  search  most  books 
in  vain  before  he  can  discover  what  sizes  of 
iron  are  and  what  are  not  easily  to  be  had  at 
ordinary  prices.  The  paper  on  retaining  walls 
is  simply  and  clearly  written,  but  it  does  not 
contain  much  that  is  very  novel  ;  indeed,  so 
much  has  been  written  about  retaining  walls, 
that  it  is  impossible  to  say  anything  new  on 
the  subject.  We  can  recommend  Mr.  Smith's 
little  book,  especially  to  the  younger  members 
of  the  profession. — Engineering. 

Designing  Valve  Gearing.  By  E.  J.  Cowl 
ing  Welch,  M.  I.  M.  E.  E.  &  F.  N. 
Spon.  For  sale  by  D.  Van  Nostrand.  Price 
$2.00. 

This  is  a  most  useful  text  book,  and  some- 
thing of  the  kind  has  long  been  a  desideratum 
among  draughtsmen  and  engineers.  Valve 
oearing  constitutes  a  rather  difficult  and  per- 
plexing problem,  and  the  solution  offered  by 
scientific  men  in  formulated  results,  is  to  the 
ordinary  engineer  only  more  perplexing  still. 
Mr.  Welch  has  conferred  on  the  profession  a  | 


great  boon  in  this  little  book,  in  which  he 
elucidates  all  the  problems  connected  with  the 
subject  in  as  simple  a  geometrical  manner  as 
possible  In  his  opening  chapter  he  gives  the 
geometrical  basis,  viz.,  the  31st  Proposition  in 
the  3d  Book  of  Euclid,  on  which  his  diagram- 
matic investigation  depend.  He  then  treats  of 
the  easjr  method  in  which  the  relative  travel  of 
crank,  eccentric  tumbler  and  slide  valve  may 
at  any  moment  of  "the  stroke  be  compared, 
and  afterwards  proceeds  to  treat  of  lap  and 
lead,  and  adjustment  of  ordinary  slide  and  ex 
pansion  valves,  for  any  ratio  of  cut-off.  His 
further  chapters  on  variable  expansion  valves, 
and  on  Stephenson's,  Gooch's  and  Allan's  link 
motion,  are  admirable,  and  invaluable  to  the 
engineer  and  draughtsman,  who  would  wish 
to  rise  superior  to  the  ignoble,  but  too  frequent 
plan  of  valve  designing  by  trial  and  model. 
There  are  but  one  or  two  little  points  in  this 
most  admirable  text-book  which  we  could  wish 
altered  for  the  better.  The  diagrams  are  ex- 
cellent, and  sufficiently  numerous,  but  the  mat- 
ter is  too  heavily  printed  without  break  for 
convenient  and  comprehensive  reading.  The- 
system  of  paragraphs,  and  special  results  being 
placed  in  separate  lines,  render  such  matter  of 
much  easier  perusal  and  comprehension.  Fur- 
ther, the  book  can  scarcely  be  read  with  inter 
est  for  general  information.  It  is  simply  a. 
series  of  propositions,  since  there  is  seldom 
half  a  dozen  lines  without  reference  to  the 
diagrams.  The  diagrams  are  frequently  not 
on  the  page  in  which  they  are  being  constantly 
referred  to,  and  thus  destroy  all  chance  of  con 
secutive  reading.  The  book  must  be  labori- 
ously studied,  like  a  book  of  geometry,  but, 
nevertheless,  is  so  well  worth  that  study  that 
we  most  heartily  recommend  it  to  all  who  may 
have  valve  gearing  to  design. 

The  Present  Practice  of  Sinking  and 
Boring  Wells,  &c.  By  Ernest  Spon. 
London  :  E.  and  F.  Spon.  1875.  For  sale 
by  D .  Van  Nostrand .     Price  $3. 00. 

When  the  pollution  of  our  rivers  by  manu- 
facturing processes  and  the  sewerage  of 
large  towns  has  risen  to  such  a  pitch  that  leg- 
islative measures  are  necessary  to  prevent, 
widespread  epidemical  disease,  it  seems  high 
time  that  some  steps  should  be  taken  to  obtain 
the  supply  of  water  for  drinking  purposes  from 
some  less  feculent  source.  And  it  is  not  only 
in  populous  and  manufacturing  districts  that 
such  a  precaution  is  necessary.  In  agricultural 
districts  most  of  the  supply  is  drawn  from 
surface  drainage  or  shallow  wells,  both  be- 
coming more  and  more  unsafe  owing  to  the 
increasing  practice  of  dressing  pasture  as  well 
as  arable  land  with  manure  to  an  extent  un- 
known but  a  few  years  ago.  Under  these- 
circumstances  it  is  well  that  deep  in  the  bow- 
els of  the  earth,  especially  in  those  countries 
where  a  wholesome  supply  is  most  difficult  to 
obtain  at  or  near  the  surface,  there  exist  vast 
reservoirs  of  the  pure  element,  which  the  im- 
proved engineering  appliances  of  these  days 
enable  us  to  reach,  and  which,  as  in  Liverpool,. 
South  London  and  elsewhere,  have  already 
been  to  a  considerable  extent  utilized.  To 
teach  us  to  tap  these  stores  in  the  best  and 


BOOK    NOTICES. 


479 


most  economical  way  is  the  object  of  Mr. 
Spon's  book.  Suitability  of  site  for  a  deep 
well  depends  mainly  upon  three  considerations. 
First,  there  is  the  capacity  and  lie  of  the  water- 1 
bearing  strata,  next,  the  extent  of  its  outcrop,  i 
and,  third,  the  amount  of  rainfall  over  the  : 
area  of  the  outcrop.  The  presence  and  posi- 
tion of  faults  in  the  strata  is  another  impor- 
tant element.  Springs  depend  upon  the  rain- 
fall, and  that  they  sometimes  appear  independ- 
ent of  it  is  owing  to  the  extent  of  the  subter- 
raneous accumulations  which  they  drain.  In 
deep  wells  where  the  water  is  collected  from  a 
surface  much  above  the  level  of  the  well,  the 
water,  when  tapped,  especially  at  first,  often 
rises  with  great  force  and  to  a  considerable 
height.  The  secondary  and  tertiary  forma- 
tions, the  last  especially,  from  the  alternations 
it  presents  of  loose,  sandy  permeable  strata 
with  impervious  rocks  and  clay,  are  the  most 
suitable  for  deep  well-boring.  Some  of  the 
primary  formations  also  are  water  bearing ; 
but  from  the  more  general  presence  in  them  of 
bituminous,  or  other  mineral  impurities,  they 
are  less  suitabe  for  water  supply.  The  chalk 
— a  secondary  formation — is  the  great  water- 
bearing stratum  for  the  larger  portion  of  the 
south  of  England.  The  greensand  underneath 
it  also  contains  vast  supplies.  In  the  mid- 
dandsand  northern  counties  again,  the  Permian 
and  triassic  formations  yield  immense  quanti- 
ties of  water,  and  supply  Coventry,  Birming- 
ham, and  other  large  towns,  copiously.  Mr. 
Spon  gives  formula?  by  which  to  estimate  the 
probable  supply  in  each  case,  furnishing  also 
much  varied  and  useful  information  applica- 
ble to  numerous  localities,  which  he  follows 
up  with  an  exhaustive  practical  exposition  of 
the  art  and  mystery  of  well-sinking,  profusely 
illustrated,  but  through  which  it  is  difficult  to 
follow  him  without  the  aid  of  his  diagrams. 
We  notice,  however,  no  allusion  to  any  of  the 
numerous  forms  of  diamond  drill  which  have 
become  so  indispensable  in  all  boring  opera- 
tions. 

Some  interesting  information  is  given 
regarding  the  districts  already  supplied  by 
wells  in  the  strata  above  referred  to.  From 
the  lower  Permian  sandstone  large  quantities 
of  water  are  pumped  for  the  use  of  Sunder- 
land and  many  neighboring  towns  and  villa- 
ges. This  supply,  calculated  to  reach  five 
millions  of  gallons  a  day,  is  obtained  from  an 
area  of  fifty  square  miles  overlying  the  coal 
measures.  Coventry  is  supplied  with  750,000 
gallons  a  day  from  two  bore-holes  driven  from 
the  bottom  of  the  reservoir  into  the  new  red 
sandstone,  the  water  rising  at  the  rate  of  700 
gallons  a  minute.  The  wells  of  the  Tranmere, 
Birkenhead  and  Wirral  Waterworks  yield  to- 
gether about  four  millions  of  gallons  a  day, 
drawn  from  the  trias.  Two  million  gallons  of 
the  water  used  in  Birmingham  comes  from  the 
new  red  sandstone.  Crewe,  Leamington,  and 
Liverpool  are  supplied  from  the  same  form- 
ation. In  1850  the  yield  of  one  of  the  bore- 
holes in  the  last-named  town  was  nearly  a  mil- 
lion gallons  in  the  twenty-four  hours.  The 
Goldstone  wells,  from  which  Brighton  is  sup- 
plied, are  in  the  chalk,  and  each  yields  about 
3,000,000  gallons  daily. 


traite  t.heorique  et  practique  de  la. 
Fabrication  du  fer  et  de  L'acier, 
accompagneduin  expose  des  ameliorations 
dont  elle  est  susceptible  principalement 
en  Belgiojje  par  B.  Valerius.  Deuxieme 
edition  originaleFrancaise.  Royal  8vo,  paper, 
with  folio  Atlas  plates.  Paris,  1875.  For  sale 
by  D.  Van  Nostrand.     Price  $30.00. 

This  is  the  work  of  Prof.  Benoit  Valerius,, 
who  died  May  30,  1873,  now  published  from 
his  MSS,  and  with  considerable  additions,  by 
his  brother,  Prof.  II.  Valerias,  of  the  Univer- 
sity of  Ghent.  The  text  of  this  elaborate 
work  forms  a  volume  of  852  pages,  royal  8vo_ 
The  plates  are  in  portfolio,  large  quarto,  and 
35  in  number,  and  are  the  finest  as  well  as  the 
most  extensive  series  of  drawings  upon  the 
subject  that  have  ever  been  issued.  Those 
covering  the  subject  of  roll  turning  are  particu- 
larly noticeable  in  their  elaborate  character 
and  fineness  of  execution. 

Applied  Science.  Part  1.  Geometry  on 
Paper.  Part  2.  Solidity,  Weight  and 
Pressure.  By  Edward  Sang.  London :  E.  & 
F.  N.  Spon.  For  sale  by  D .  Van  Nostrand. 
Price  each  $1.25. 

These  two  books  are  smaller  than  might  be 
expected  from  their  titles,  but  small  as  they 
are,  they  are  quite  '  disproportionate,  on  the 
side  of  bulk,  to  the  amount  of  valuable  infor- 
mation they  contain. 

Part  1  is  a  collection  of  examples  in  Plane 
Geometry,  in  which  the  pupil  is  advised  to 
use  very  rude  instruments;  the  diagrams  sug- 
gest home-made  ones. 

Part  2  makes  similar  suggestions  in  regard 
to  Solid  Geometry,  but  adds  chapters  on  Cube 
Root,  Strains  and  the   Steel  Yard.     The  ap- 
pearance of  these  apparent  incongruities  is  ex- 
plained by  the  author's  opinion  expressed  in 
the  preface,  that  the  study  of  practical  geom- 
j  etry  must  lead  us  to  examine  all  the  physical 
i  properties  of  matter  which  can  influence  our 
j  measurements  or  aid  us  in  conducting  them. 

A  Treatise  on  the  Origin,  Proper  Pre- 
vention, and  Cure  of  Dry  Rot  in  Tim- 
i  ber.     By  Thomas  Allen  Britton.     London :. 
IE.  &  F.  N.  Spon.  For  sale  by  D.  Van  Nostrand. 
Price  $3.00. 

Although  the  chief  title  of  the  book  limit? 
I  it  to  a  consideration  of  dry  rot  in  timber,  the 
author  has  by  no  means  confined  himself  to  a 
consideration  of  this  subject,  but  has  devoted 
|  the  greater  portion  of  the  volume  to  the  de- 
i  scriptions  of  various  established  processes  of 
seasoning  and  preserving  timber  and  wooden 
I  structures,  of  the  destruction  of  this  marerial 
in  hot  climates,  and  of  the  decay  of  furniture, 
wood-carvings,   &c.     The  first  chapters,  it  is 
!  true,  after  the   introductory  remarks  on  the 
j  nature  and  properties  of  timber,  deal  with  the 
j  question  of  dry  rot,  and  besides  describing  its 
!  general  characteristics  and  results,  quote  many 
authorities  and  give  several  illustrations  bear- 
ing on  the  subject.     Taken  altogether  the  infor- 
mation is  scarcely  so  complete  as  that  con- 
i  taiued  in  the  article  published  by  us  last  week 
(see  ante  page  151),  and  based  upon  the  excel- 
lent treatise  of  M.  Bourseul.     After  some  con- 
sideration on  the  subject  of  felling  and  cutting 


480 


VAN   NOSTRAND'S   ENGINEERING   MAGAZINE. 


timber,  the  author  proceeds  with  lengthy  de- 
scriptions of  various  seasoning  processes. 
Amongst  them  are  Davison  and  Symington's 
desiccation  method,  Bethell's  drying  stoves, 
introduced  between  1848  and  lb63,  Langton's 
patent  for  the  extraction  of  sap,  Kyan's  bi- 
chloride of  mercury  process,  the  creosote  treat- 
ment of  Mr.  John  Bethell,  Boucherie's  sul- 
phate of  copper  method,  and  many  others  tried 
in  this  country  and  abroad. 

Coming  back  then  to  a  subject  more  apropos 
to  the  title  of  the  book,  the  author  gives  us  a 
chapter  "on  the  means  of  preventing  dry  rot 
in  modern  houses,  and  the  causes  of  their  de- 
cay." And  under  this  heading  we  come  sud- 
denly to  a  receipt  for  killing  rats,  though  what 
connection  there  is  between  these  animals  and 
dry  rot,  we  do  not  at  present  perceive.  Make 
a  hole  for  the  rats  to  come  up,  if  they  do  not 
make  one  for  themselves,  mix  a  nauseous  com- 
pound into  pills  and  place  it  on  the  floor,  with 
a  number  of  saucers  filled  with  water.  The 
•confiding  nature  of  the  rats  will  induce  them 
to  eat  the  compound  before  alluded  to,  which 
will  make  them  so  thirsty  that  they  will  drink 
till,  like  the  sculptor  in  the  conundrum,  they 
"make  faces  and  busts."  "They  can  be 
Juried  in  the  morning,"  adds  thoughtful  Mr. 
Britton.  To  return  to  dry  rot.  Ventilation, 
pitching,  and  charring,  are  the  best  prevent- 
ives fully  pointed  out  by  the  author,  who  then 
quits  his  subject  to  dwell  upon  the  aesthetics 
of  house  painting,  but  returns  to  it  again  finally 
and  briefly  as  follows:  "One  cause  of  the  de- 
cay of  modern  buildings  and  frequent  cases  of 
dry  rot,  is  owing  to  the  employment  of  bad 
builders."  We  are  in  error:  for  in  closing 
this  volume  we  find  one  more  reference  to  the 
subject. 

"In  conclusion,  we  can  only  summarise  our 
remarks  on  the  cause  of  dry  rot  by  saying 
'  season  and  ventilate '  in  every  case.  As  to 
to  the  cure,  that  is  not  so  easy  to  deal  with. 
If  the  reader  has  ever  had  a  decayed  tooth 
aching,  a  friend  has  probably  said,  '  Have  it 
out;'  and  we  say,  whenever  there  is  a  piece  of 
timber  decayed  in  a  building  which  can  be  re- 
moved, '  Have  it  out  and  stop  up  with  new,' 
and  in  so  advising  we  are  merely  following 
the  advice  to  be  tound  in  a  good  old  volume 
which  has  never  yet  been  equaled."'1  Here  follow 
some  verses  from  Leviticus.  The  italics  are 
our  own.  The  above  extract  will  show  that 
Mr.  Britton,  besides  knowing  all  about  dry  rot 
in  timber,  has  quite  a  happy  way  of  communi- 
cating his  knowledge.  The  publishers  have 
done  their  part  well  in  the  preparatian  of  this 
volume.  — Engineering. 


MISCELLANEOUS. 

Deep  Silver  Mine.— In  Pribram,  Bohemi, 
the  Adalbert  Pit,  sunk  in  1779,  has 
reached  in  its  present  adit  in  the  1000-metre 
.shaft  the  depth  of  472.128  metres  below  the 
level  of  the  Adriatic  Sea. 

Steel  Rails  in  Italy. — The  line  from  Rome 
to  Ceprano,  half-way  from  Rome  to 
Naples,  has  been  relaid  with  steel  rails,  the 
first  result  of  which  change  has  been  to  permit 


a  higher  speed  of  travel,  resulting  in  a  total 
saving  of  time  on  the  journey  of  an  hour  and 
a-half. 

ri^HE  New  Russian  Gun.— The  great  Russiam 
1  cannon,  lately  built  at  the  works  at  Obouk- 
owsky,  has  cost  £13,000,  and  weighs  40  tons, 
It  is  a  breech-loader,  entirely  in  crucible  steel, 
20  feet  6  inches  long  ;  its  largest  ring  is  57-j 
inches  in  diameter,  and  the  tube  has  thirty- 
six  grooves. 

LiGnT  Hydraulic  Motor. — An  improved 
hydraulic  motor  for  light  machinery— a 
Swiss  invention — consists  of  an  oscillating  en- 
gine within  a  water-tight  casing,  into  which 
the  water  enters  at  one  side  and  leaves  at  the 
other.  The  oscillating  cylinder,  driven  by  the 
water,  swings  in  bearings,  suitable  entrance 
and  exit  ports  of  the  bearing  permuting  alter- 
nately the  entrance  and  discharge  of  water 
from  the  cylinder.  The  piston  rod  is  pivoted 
to  a  crank  disk  of  the  driving  shaft,  and  the 
power  is  transmitted  by  a  friction  cone  and 
belting,  and  can  be  run  at  different  speeda 
The  regulating  air  chamber  secures  uniformity 
of  motion  under  various  pressures.  The 
casing  is  attached  by  screws  at  any  suitable 
point  near  the  machine  to  be  operated,  and  the 
water  can  be  conveyed  by  rubber  pipes.  N» 
oiling  is  necessary,  as  the  apparatus  works  en- 
tirely in  water.  It  is  said  to  be  capable  of 
from  120  to  500  revolutions  per  minute,  with 
an  average  water  consumption  of  40  gallons. 

Incrustation  op  Boilers. — This  important 
subject  has  occupied  the  attention  of  the 
Paris  Academy  of  Sciences.  M.  Lesueur,  a 
telegraph  inspector,  sent  a  communication  t© 
the  Academy  setting  forth  the  efficacy  of  zine 
in  protecting  boilers  from  incrustation.  M. 
Lesueur  declares  that  in  many  instances  th« 
effect  has  been  found  excellent,  the  deposit 
being  little  and  easily  removed.  It  was  assert- 
ed, in  opposition,  that  in  many  cases,  also, 
the  zinc  had  failed  entirely  to  produce  the 
effect  desired,  and  a  quotation  from  Professor 
Knapp's  "  Chemical  Technology"  was  read,  in 
which  the  author  states  that,  to  the  time  he 
wrote,  the  pretensions  of  the  advocates  of  gal- 
vanic action  seem  to  be  unfounded.  It  was 
recommended  that  the  subject  be  entrusted  to 
a  committee  for  conclusive  trials.  A  long  list 
was  given  of  the  various  substances  which  had 
been  recommended  for  the  preservation  of 
boilers,  such  as  a  mixture  of  tallow,  graphite 
and  charcoal,  of  tar  and  oil,  iron  filings, 
broken  glass,  saw-dust,  clay,  alum,  and  sods 
mixed,  potatoes,  molasses,  coarse  sugar, 
chicory,  trimmings  of  skins,  sal  ammoniac, 
chloride  of  barium,  carbonate  of  barytes,  and 
chloride  of  zinc. 

As  was  stated  before  the  Academy,  the  prob- 
lem in  question  is  a  very  complex  one,  and  it 
is  well  that  all  should  understand  that  it  is  not 
likely  to  be  solved  in  a  general  manner.  There 
can  scarcely  be  any  universal  panacea  Water 
differs  greatly  in  composition,  and  even  the 
same  water  varies  from  time  to  time,  so  that 
the  only  chance  of  success  in  the  adoption  of 
an  anti-incrustation  medium  "w  ould  seem  to 
depend  upon  a  careful  analysis  of  the  water  to 
be  used,  repeated  at  different  seasons. 


VAN     NOSTRAND'S 


ECLECTIC 


ENGINEERING    MAGAZINE. 


NO.  LXXXIV.-DECEMBER,  1875 -VOL.  XIII. 


BRIDGE  AND  TUNNEL  CENTRES. 

Bt  JOHN  B.  McMASTEB,  C.  E. 
Written  for  Van  Nostrand's  Engineering  Magazine. 

II. 


BRACING. 

It  is  to  be  observed  in  connection  with 
the  matter  of  bracing,  that  the  frames 
should  be  arranged  in  such  wise  that  no 
piece  suffers  any  strain  other  than  com- 
pression or  extension  in  the  direction  of 
its  length.  As  it  is,  however,  by  no 
means  an  easy  matter  to  make  the  dis- 
tinction, we  shall  give  the  following  rule 
to  which  there  is  no  exception  : 

Suppose  we  have  two  beams  abutting 
against  each  other  at  their  upper  end, 
and  loaded  at  their  point  of  intersection 
with  a  weight.  Take  notice  of  the  direc- 
tion in  which  this  straining  force  acts, 
and  from,  the  point  at  which  it  acts 
draw  in  this  direction  a  line  representing 
by  its  length  the  intensity  of  the  strain. 
From  the  remote  end  of  this  line  draw 
lines  parallel  to  the  two  pieces  on  which 
the  strain  is  exerted.  The  line  drawn 
parallel  to  one  must  of  necessity  cut  the 
other  or  its  direction  produced.  If  it 
cut  the  beam  itself  the  piece  is  compress- 
ed, and  acts  as  a  strut.  If,  on  the  other 
hand,  it  cuts  the  direction  of  the  beam 
produced,  the  piece  is  stretched  and  acts 
as  a  tie.  We  may  then  lay  it  down  as 
a  general  rule  in  framing,  that  if  the 
piece  from  which  the  strain  comes  lies 
within  the  angle  formed  by  the  pieces 
Vol.  XIII.— No.  6—31 


strained,  the  strains  these  sustain  are  of 
the  opposite  kind  to  that  of  the  straining 
point ;  if  that  is  pulling,  they  are  push- 
ing ;  if  that  is  compressed  they  are 
stretched.  Again,  if  the  piece  from  which 
the  strain  comes  lies  within  the  angle 
formed  by  the  direction  of  the  two  pro- 
duced, all  will  have  the  same  kind  of 
strain  ;  and,  finally,  if  within  the  angle 
formed  by  the  direction  of  one  produced 
and  the  other  piece  itself,  the  strain  will 
be  of  the  same  kind  as  that  of  the  most 
remote  of  the  two  beams  strained,  and  of 
the  opposite  kind  to  that  of  the  nearest. 

The  object  of  all  bracing,  then,  being 
to  convert  all  transversal  strains  into 
others  which  act  in  the  direction  of  the 
length  of  the  beams,  the  frame  must  be 
divided  into  a  number  of  triangles  ;  for 
as  the  triangle,  or  some  modification  of 
it,  is  the  only  geometrical  figure  which 
possesses  the  property  of  preserving  its 
figure  unaltered  so  long  as  the  length  of 
its  sides  remain  constant,  it  is  the  figure 
best  suited  for  structures  in  which  rigid- 
ity is  essential  for  stability.  But,  again, 
some  forms  of  triangles  are  much  to  be 
preferred  to  others  ;  the  strength  of  the 
pieces  forming  the  triangle  depending 
very  much  on  the  angle  they  make  with 
each  other.      Oblique   angles  are  to  be 


482 


van  nostrand's  engineering  magazine. 


avoided.  Acute  angles  when  not  accom- 
panied by  oblique  are  not  so  injurious, 
because  the  strain  can,  in  such  pieces, 
never  exceed  the  straining  force  ;  but  in 
an  oblique  angle  it  can  surpass  it  to  any 
degree. 

In  all  forms  of  bracing,  too  much  at- 
tention cannot  be  given  to  the  joints. 
"Where  the  beams  stand  square  with  each 
other,  and  the  strains  are  also  square 
with  the  beams  and  in  the  plane  of  the 
frame,  the  common  mortise  and  tencn 
is  the  most  perfect  joint,  a  pin  usually 
put  through  both  so  as  to  draw  the  tenon 
tight  into  the  mortise,  and  so  cause  the 
shoulder  to  butt  very  snugly.  Round 
pins  are  much  better  than  square  ones, 
as  they  are  not  liable  to  split  the  bit. 
"Where  the  beams  are  very  oblique,  it  is 
difficult  to  give  the  foot  of  the  abutting 
one  such  a  hold  as  to  bring  many  of  its 
fibres  into  actual  contact  with  the  beam 
butted  on.  It  would,  in  such  case,  seem 
proper  to  give  it  a  deep  bold  with  a  long- 
tenon.  Nothing,  however,  can  te  more 
injurious,  for  experience  has  fully  proved 
that  they  are  very  liable  to  break  up  the 
wood  above  them  and  push  their  way 
along  the  beam.  For  instance,  suppose 
the  head  of  an  inclined  strut  abutting 
on  a  horizontal  beam  to  descend  a  little; 
the  angle  with  this  latter  beam  is  dimin- 
ished, by  the  strut  revolving  round  the 
stress  in  the  tie  beam.  By  this  motion 
the  bed  of  the  strut  becomes  a  powerful 
fulcrum  to  a  very  long  lever  ;  the  tenon 
is  the  other  arm  and  very  short.  It 
therefore  forces  up  the  wood  above  it  and 
slides  along  the  horizontal  beam.  This 
may  be  prevented  by  making  the.tenon 
shorter,and  giving  to  its  toe  a  shape  which 
will  make  it  butt  fiimly  in  the  direction 
of  the  thrust,  on  the  solid  bottom  of  the 
mortise.  When  the  beam  is  a  tie  the 
joint  must  depend  for  its  strength  on  the 
pins  or  bolts,  and  the  iron  straps  placed 
across  it. 

STRIKING   THE    CENTRES. 

Undoubtedly  the  most  dangerous  opera- 
tion connected  with  the  use  of  bridge 
centres  is  the  process  of  striking  them. 
No  matter  with  how  much  care  the  arch 
may  have  been  constructed,  the  drying 
and  squeezing  of  the  mortar  will  cause 
it  to  settle  in  some  degree  when  the  cen- 
tres are  removed,  and  this  degree  of 
settlement  seems  to  be  very  largely  af- 


fected by  the  time  the  centres  are  allow- 
ed to  stand.  By  some  it  has  been  urged 
that  the  centring  should  never  be  remov- 
ed until  the  mortar  in  the  joints  of  the  last 
course  has  had  ample  time  to  harden  ; 
others  going  to  the  other  extreme  have- 
advocated  striking  the  ribs  as  soon  ax  the 
arch  is  keyed,  claiming,  not  without 
some  reason,  that  the  settlement  of  a 
well  built  arch  will  never  be  so  great  as; 
to  become  dangerous  even  though  the 
supporting  frames  be  removed  when  the 
mortar  is  green.  But  possibly  the  best 
practice  lies  not  far  from  either  of  these 
extremes.  It  has,  indeed,  time  and 
again,  been  amply  demonstrated  that  to 
leave  the  centring  standing  till  the  mor- 
tar has  hardened,  and  then  take  away  all 
support,  the  mortar  having  become  un- 
yielding, is  to  cause  the  courses  to  open 
along  their  joints.  To  strike  the  centre,, 
on  the  other  hand,  when  the  arch  is 
green  will,  seven  cases  out  of  ten,  be 
followed  by  the  fall  of  the  bridge  ;  but 
by  easing  the  centring  as  soon  as  the- 
arch  is  keyed  in,  and  continuing  this 
gradual  easing  till  the  framing  is  quite 
free  from  the  arch,  the  latter  has  time 
to  settle  slowly  as  the  mortar  hardens, 
and  the  settlement  will  be  found  to  be 
very  small. 

It  becomes  necessary,  therefore,  to  pro- 
vide some  arrangement  by  which  the 
framing  may  be  slowly  lowered  from  the 
soffit  of  the  arch,  an  operation  accom- 
plished in  a  variety  of  ways  ;  by  folding 
or  double  wedges,  by  striking  plates,  by 
bearing  irons  and  screws,  by  cutting  off 
the  ends  of  the  principal  supports,  and, 
finally,  by  plate  iron  cylinders  filleel  with 
sand.  The  folding  wedges  are,  perhapsr 
most  commonly  met  with  in  practice, 
and  are  finely  suited  for  arches  of  ^mall 
span,  as  a  sill  stretching  from  abutment 
to  abutment  may  then  be  used  to  rest 
them  on.  They  consist  of  two  hard- 
wooel  wedges,  about  15  in.  long,  right 
angled  along  one  edge,  and  placed  one 
upon  the  other  in  such  wise  that  the 
thick  end  of  one  shall  be  over  the  thin 
end  of  the  other,  thus  making  their  sur- 
face of  contact  an  inclined  plane.  These 
wedges  are  placed  under  the  tie  beam  of 
the  rib  and  on  the  sill,  as  is  illustrated 
in  Fig.  2.  It  is  evident  that  by  driving 
the  upper  wedge  up  along  the  inclined 
surface  of  the  lower,  the  rib  which  rests 
upon  the  upper  one  must  rise,  so  that 


BRIDGE   AND   TUNNEL   CENTRES. 


483 


by  placing  a  number  of  these  folding 
wedges  under  each  rib  it  may  easily  be 
keyed  up  to  the  desired  level,  and  by 
driving  the  upper  down  the  inclined  sur- 
face of  the  lower,  the  rib  may  gradually 
be  lowered.  To  keep  the  under  wedge 
in  place,  it  is  usually  made  fast  to  the 
sill  and  the  surface  of  contact  of  each 
wedge  well  greased  with  soft-soap  and 
black  lead.  When  the  wedges  are  in 
place  under  the  rib,  it  is  a  good  practice 
to  mark  each  wedge  at  the  point  where 
contact  ceases,  so  that  when  the  centres 
are  being  lowered  we  may  be  able  to 
know  whether  they  are  lowered  uniform- 
ly or  not.  For  instance,  let  the  lower 
wedges  of  three  pair  of  folding  wedges 
project  two  inches  beyond  the  end  of  the 
upper  ones,  and  mark  with  chalk  on  the 
side  of  each  lower  wedge  the  point 
where  contact  ceases;  namely,  two  inches 
from  its  end.  Now,  if  in  striking  the 
centres  the  upper  wedges  have  all  been 
driven  back  so  that  the  end  of  each  in- 
stead of  being  at  the  line  is  one  inch  be- 
yond it,  then  the  frame  has  been  uni- 
formly lowered  ;  but  if  some  are  one 
inch  and  some  §  inch  from  the  line,  the 
frame  has  not  been  lowered  uniformly, 
and  the  difference  must  be  corrected  by 
driving  all  the  wedges  till  they  are  one 
inch  from  the  chalk  line. 

It  is  evident  that  such  an  arrangement 
of  folding  wedges  can  be  of  but  little 
use  unless  the  horizontal  beam  or  sill  on 
which  they  rest  is  rigidly  supported  from 
beneath,  as  any  yielding  of  the  sill 
would  be  followed  by  a  separation  of 
the  wedges  and  rib.  In  constructing 
bridges  of  wide  span  over  creeks  or  riv- 
ers on  which  there  is  no  navigation  to  be 
inteiTupted,  it  is  usual  to  make  use  of 
the  folding  wedges  and  support  the  sill 
by  a  row  of  piles  driven  into  the  river 
bed,  and  it  then  becomes  especially  ne- 
cessary to  watch  the  wedges  lest  by 
some  settling  of  the  piles  and  sill  they 
have  separated  in  the  smallest  degree 
from  the  tie  beam  of  the  rib. 

In  cocket  centres  the  folding  wedges 
are  replaced  by  a  sriking  plate  placed  at 
each  end  of  the  rib,  and  sustained  by 
strutting  or  raking  pieces  which  abut 
either  on  off-sets  at  the  foot  of  the  pier 
or  on  sills  placed  on  the  ground.  Each 
plate  consists  of  three  parts,  a  lower  and 
upper  plate  and  a  compound  wedge 
driven    between   them.      The   upper  of 


these  plates  is  of  wood  made  fast  to  the 
base  of  the  rib,  and  is  cut  into  a  series 
of  offsets  on  its  under  surface  (see  Fig. 
4).  The  lower  plate  is  likewise  of  wood 
cut  into  offsets,  but  on  its  upper  surface, 
and  is  firmly  attached  to  the  raking 
pieces  which  sustain  it.  The  compound 
wedge  consists  of  a  beam  cut  into  offsets 
both  upon  its  upper  and  lower  sides  so 
as  to  fit  those  of  the  two  plates,  and 
when  driven ,  between  them  is  held  in 
place  by  keys  driven  behind  its  shoul- 
ders. 

Previous  to  the  time  of  Hartley,  the 
rib  was  struck  in  one  piece  by  the  use 
either  of  wedges  or  striking  plates.  To 
him,  however,  we  are  indebted  for  an 
improved  system  of  striking  or  easing 
the  centres  by  supporting  each  lagging 
upon  folding  wedges.  When  this  ar- 
rangement is  used  the  rib  is  firmly  at- 
tached to  its  supports,  and  the  laggings 
rest  upon  wedges  placed  between  them 
and  the  back  pieces  of  the  rib.  A  great 
advantage  gained  by  this,  is  that  the 
laggings  may  be  removed  course  by 
course  from  under  the  arch,  and  replaced 
if  the  settlement  prove  to  be  too  great 
at  any  one  part  of  the  soffit.  Another 
method,  at  one  time  much  in  use  among 
French  engineers,  is  to  cut  off  the  ends  of 
the  chief  supports  of  the  rib  piece  by 
piece,  an  operation  which  cannot  be  ac- 
complished with  much  regularity,  nor 
without  much  danger. 

The  least  objectionable  way  of  strik- 
ing centres,  and  one  accomplished  with 
great  ease  and  regularity  is  by  the  use 
of  sand,  confined  in  cylinders.  A  num- 
ber of  plate  iron  cylinders  one  foot  high 
and  one  foot  in  diameter  are  placed  upon 
a  stout  platform  sustained  by  timber 
framing.  The  lower  end  of  each  cylin- 
der is  stopped  by  a  circular  disc  of  wood 
of  an  inch  thickness  fitting  tightly  into 
the  cylinder,  and  at  about  an  inch  above 
this  wooden  bottom  three  or  four  holes 
an  inch  each  -in  diameter  are  drilled 
through  the  iron  sides  of  the  cylinder 
and  stopped  with  corks  or  plugs  of 
wood. 

Into  the  cylinders  thus  prepared  is 
poured  clean  dry  sand  to  a  height  of  9 
or  10  inches  above  the  bottom,  and  on 
this  sand  in  each  cylinder  rests  a  cylin- 
drical wooden  plunger,  which  fits  so 
loosely  as  to  work  with  ease,  and  forms 
one  of  the  vertical  supports  of  the  rib. 


484 


VAN   NOSTRAND  S   ENGINEERING   MAGAZINE. 


To  prevent  moisture  getting  at  the  sand, 
the  joint  between  the  plunger  and  cylin- 
der is  filled  with  cement.  So  long  as  the 
sand  is  dry  it  remains  incompressible  to 
any  weight  that  may  press  on  it,  and  the 
rib  is  thus  kept  invariably  in  its  place. 
When  the  centre  is  to  be  lowered,  the 
plugs  are  taken  out  of  the  cylinder,  and 
as  the  sand  runs  out  of  each  with  -uniform 
velocity  the  frame  is  uniformly  lowered. 
This  method  is  of  especial  value  for  cen- 
tres of  great  weight. 

The  distance  at  which  the  frames  or 
ribs  of  centres  should  be  placed  apart, 
measuring  from  the  centre  of  one  rib 
to  that  of  the  next,  must  be  regulated 
solely  by  the  weight  of  stone  used  for 
the  arch,  the  distance  varying  inversely 
with  the  increase  of  weight.  That  is 
to  say,  if  we  assume  some  distance  for 
stones  of  a  given  weight,  say  6  feet  for 
stones  weighing  150  lbs.  per  cubic  yard, 
and  wish  to  find  the  proper  distance 
apart  of  the  ribs  when  the  stones  weigh 
but  120  lbs.  per  cubic  yard,  we  have 


150  :  120! !5  :  4 


4  :  5' 


X  4:X- 


Then  making  6  ft.  the 
distance  for  150  lb., 
:30     x=1  ft.  6  in., 


the  proper  distance  for  stones  of  120 
lbs.  per  cubic  yard.  The  following  table 
has  been  calculated  in  this  manner  : 


reight  of  Stone 

per 
Cubic  Yard. 
120  lbs 

Distance  apart 

of  the 
Rib  of  Centring. 
...  7  f t .    6    in. 

125  lbs  

130  lbs 

7  ft. 

6  ft, 

3    in. 
11    in. 

135  lbs 

6  ft. 

8    in. 

140  lbs 

6  ft. 

5    in. 

145  lbs 

6  ft. 

2    in. 

150  lbs 

6  ft. 

0    in. 

155  lbs  

5  ft. 

10    in. 

160  lbs  

5  ft. 

7    in. 

165  lbs 

170  lbs 

5  ft. 

5  ft. 

5    in. 
3    in. 

175  lbs 

5  ft. 

liin; 

0    in 

180  lbs 

5  ft 

185  lbs 

4  ft. 

lOf  in. 

190  lbs 

4  ft. 

8    in. 

195  lbs 

4  ft. 

7    in. 

200  lbs  

4  ft. 

1    in. 

It  now  remains  to  consider  briefly,  the 
subject  of  centring  as  used  in  the  con- 
struction of  the  arched  roofs  of  tunnels. 
In  work  of  this  description,  the  span 
being  always  small,  the  arch  light  and 
the  facilities  for  obtaining  firm  points  of 
support  for  each  rib  as  great  as  can  be 


desired,  all  the  hindrances,  that  so  often 
make  the  framing  of  a  stone  bridge 
centre  a  matter  of  no  small  difficulty 
and  foresight,  are  wanting,  and  the  rib 
admits  of  a  simplicity  of  arrangement 
at  once  favorable  to  economy  of  mate- 
rial and  of  space.  It  must,  however,  be 
remembered  that  although  the  span  is 
small  and  the  ai*ch  light,  the  strength  of 
the  rib  of  a  tunnel  centre  must  be  much 
greater  in  proportion  to  the  burden  it 
has  to  carry  than  that  of  a  bridge  cen- 
tre ;  since  the  former  has  not  only  to  re- 
sist the  weight  of  the  earth  above  it, 
but  must  also  withstand  the  wear  and 
tear  of  many  destructful  causes  to  which 
the  latter  is  never  exposed.  In  tunnel- 
ing through  a  hill  side,  no  matter  how 
short  the  distance,  more  or  less  rock  will 
invariably  be  met  with,  and  more  or  less 
blasting  must  therefore  be  done,  and  the 
shock  and  flying  splinters  of  rock  which 
accompany  each  explosion  do  much  mis- 
chief to  the  ribs  by  disturbing  or  injur- 
ing them.  This  cause  acts  strongly  on 
all  parts  of  the  centre,  but  is  especially 
severe  with  the  leading  ribs,  which,  as 
the  brick  work  must  always  be  kept  well 
up  to  the  heading,  are  directly  exposed 
to  the  violence  of  each  explosion. 

A  second  cause  of  injury  to  the  ribs, 
and  one  quite  as  damaging  and  unavoid- 
able as  the  first,  is  the  repeated  taking 
down,  carrying  forward,  and  putting  up 
of  the  ribs  every  time  a  length  of  arch 
is  completed.  In  bridges,  unless  the 
structure  is  composed  of  a  series  of 
arches,  the  centring  is  never  disturbed 
from  the  time  it  is  first  put  up  until  it 
is  finally  struck  on  the  completion  of  the 
works.  In  tunneling,  however,  to  avoid 
the  foolish  expense  of  building  centres 
from  end  to  end  of  the  tunnel,  it  is  cus- 
tomary to  construct  but  one  length  of 
twelve  or  fifteen  feet  of  centring,  and  to 
move  this  forward  whenever  it  becomes 
necessary  to  turn  a  new  length  of  arch. 
Thus,  for  example,  we  will  suppose  thai; 
we  are  driving  a  tunnel  through  earth  of 
a  moderate  degree  of  heaviness,  and  are, 
therefore,  using  centres  consisting  of  two 
sets  of  laggings  and  five  ribs,  two  made 
without  and  three  with  a  horizontal  tie 
beam.  The  object  in  making  some  of 
these  ribs  without  the  tie  beam  is  that, 
by  so  doing,  the  centring  may  be  brought 
close  up  to  the  heading  without  interfer- 
ing with  the  raking  props,  which  could 


BRIDGE   AND   TUNNEL   CENTRES. 


485 


not  be  done  were  the  beams  to  be  retain- 
ed. These  five  ribs  are  arranged  in 
practice  so  that  one  without  the  tie 
beam  shall  be  placed  at  each  end  of  the 
length  of  centring,  and  between  these 
two  are  the  three  with  beams.  We  will 
suppose  this  to  be  the  arrangement  of 
the  ribs  in  the  present  case,  and  will 
number  them,  beginning  with  that  near- 
est the  heading,  1,  2,  3,  4,  5.  While  the 
arch  is  being  turned  upon  this  length 
the  excavation  for  a  new  one  has  been 
made,  the  invert  built,  the  side  walls 
raised  to  springing  line  and  all  is  ready 
to  carry  forward  the  centring.  This 
•operation,  however,  must  be  done  with 
the  utmost  caution.  If  the  ribs  are 
taken  from  under  the  newly  completed 
arch  before  the  invert  and  side  walls  of 
the  advanced  length  are  built,  the  whole 
piece  of  arch  with  its  side  walls  will  be 
almost  certain  to  separate  from  the 
length  just  behind,  and  move  forward 
several  inches  in  the  direction  the  work 
is  progressing.  If, on  the  other  hand,  after 
the  advanced  side-walls  are  up,  all  the 
ribs  are  taken  from  under  the  arch,  this 
latter  will  be  quite  certain  to  come  down 
in  ruins,  since  it  has  to  uphold  not  only 
the  weight  of  the  earth  resting  imme- 
diately upon  its  bricks,  but,  in  addition, 
half  the  weight  of  the  earth  which  press- 
es upon  the  crown  bars  of  the  newly  exca- 
vated length,  as  one  end  of  all  these 
bars  rests  upon  the  arch  near  its  end. 
Rib  number  1,  then,  which  is  directly 
beneath  the  end  of  the  crown  bars,  can 
not  be  removed  with  any  degree  of  safe- 
ty. It  is  also  desirable  that  number  3 
should  be  left  in  place  to  help  support 
the  laggings.  Numbers  2,  4  and  5  are 
the  only  ribs  left,  and  these  are  to  be 
taken  down  and  set  up  forward,  taking 
care  that  5,  which  has  no  tie  beam,  is 
placed  nearest  the  heading;  the  order  of 
arrangement  then  being  5,  4,  2,  1,  3. 

Over  the  rib  thus  arranged  a  second 
set  of  laggings  is  laid,  and  on  them  the 
arch  is  turned.  When  this  length  is 
completed,  and  all  preparation  made  to 
carry  forward  the  centring,  the  ribs  num- 
bered 4,  1,  3  are  taken  down  and  set  up 
forward  in  the  order  1,  3,  4,  5,  2,  and  so 
on  till  the  centring  reaches  the  end  of 
the  tunnel,  or  meets  that  coming  from 
the  opposite  end  of  the  tunnel,  suppos- 
ing it  to  be  worked  both  ways. 

Now,  it  is  precisely  this  continual  tak- 


ing down  and  setting  up  of  the  ribs, 
that  produces  so  much  injury  to  them, 
since,  in  order  to  pass  them  under  t he- 
forward  ribs  and  props  which  remain 
standing,  it  is  necessary  to  take  them  in 
pieces.  Each  rib,  therefore,  must  be 
framed  in  such  wise  that  it  may  be  re- 
peatedly taken  apart  and  put  together 
again  without  injury  to  its  strength  or 
to  the  joints  of  the  timbers  removed  and 
replaced.  Figs.  5  and  6  afford  an  illus- 
tration of  two  centre  ribs  aiTanged  to 
meet  these  requirements  in  the  simplest 
manner  possible.  Fig.  5  is  a  drawing  of 
a  leading  or  segment  rib,  which  it  will 
be  observed  is  constructed  without  a 
complete  tie  beam  at  the  bottom  so  as  to 
offer  no  obstruction  to  the  raking  props. 
It  consists  of  two  parts  or  segments, 
which,  when  the  rib  is  placed,  join  at 
the  crown  of  the  arch  ancf  along  the  line 
a  b,  and  are  made  fast  to  each  other  by 
two  iron  bars  placed  across  the  joint  at 
the  crown,  one  on  each  side  of  the  back- 
pieces,  and  bolted  through  the  back- 
pieces  as  shown  at  c  c.  An  additional 
band  is  passed  around  the  two  vertical 
beams  as  shown  at  d.  To  prevent  any 
slipping  of  these  beams  along  the  joint 
a  b,  the  surface  of  each  beam  is  notched, 
as  shown  at  e,  and  a  wedge  driven 
through  the  notch.  When  the  rib  is  to 
be  taken  down,  the  band  at  c  c  and  that 
at  d  is  removed,  and  the  wedge  at  e 
driven  out,  and  the  rib  thus  separated 
into  two  segments  may  be  carried 
through  a  comparatively  small  space. 
As  this  leading  rib  is  subjected  to  the 
direct  effects  of  the  blasts,  and  to  flying 
fragments  of  rocks,  its  joints  must  be 
strengthened  by  irons  placed  on  each 
side  of  the  rib,  over  the  joint,  and  bolt- 
ed through  the  timbers  as  shown  in  the 
figure. 

This  form  of  rib  is  finely  adapted  for 
tunnel  centring,  as  it  may  be  taken  apart 
without  removing  a  single  beam,  while 
its  joint  is  so  arranged  that  the  pressure 
of  the  arch  assists  in  no  small  degree  to 
hold  its  parts  in  place.  Indeed,  the  only 
valid  reason  why  this  form  of  rib  should 
not  be  used  in  every  part  of  a  tunnel 
centre  is  the  absence  of  the  tie  beam, 
which  is  certainly  a  great  security  against 
the  spreading  or  contracting  of  the  span. 
Were  this  tie  beam  supplied,  and  it  may 
easily  be  supplied  by  an  iron  screAv  rod, 
this  form  of  frame  would  probably,  in 


486 


VAN   NOSTRAND'S   ENGINEERING   MAGAZINE. 


addition  to  the  convenience  of  taking 
apart  and  resetting,  sustain  any  amount 
of  pressure   ever  likely  to  occur  either 


vertically  or  laterally,  as  also  all  ordi- 
nary wear  and  tear  from  use. 

Fig.   6  represents  one  of  the  interme- 


Fig.  6. 


diate  ribs  called  scarf  or  queen  post  cen- 
tres, which,  as  there  are  no  props  to  be 
interfered  with,  are  provided  with  hori- 
zontal tie  beams.  As  these  ribs  are  also 
to  be  taken  apart  each  time  they  are 
shifted,  the  tie  beam  is  composed  of  two 
beams  joined  by  a  scarf  joint  strenthen- 
ed  by  a  piece  of  timber  placed  above  it, 
and  bound  to  the  tie  by  two  bands  of 
iron  as  shown  in  the  figm*e.  The  hori- 
zontal beam  joining  the  queen  posts  is 
also  movable,  and  is  held  in  place  by 
the  iron  placed  over  its  joints  and  bolt- 
ed through.  In  joints  thus  protected, 
the  holes  through  which  the  bolts  pass 
are  liable  after  a  time  to  become  so  much 
enlarged,  from  the  repeated  driving  in 
and  out  of  the  bolts,  so  as  to  injure  the 
strength  of  the  joint.  This  may  read- 
ily be  overcome  by  using  a  bolt  with 
screw  threads  at  each  end  in  place  of  a 
bolt  with  a  head  and  one  nut,  so  that 
when  once  driven  thi'ough  the  beam  it 
need  not  be  removed. 

By  a  comparison  of  these  two  forms 
of  ribs,  it  is  evident  that  while  the  queen 
post  centre  possesses  an  advantage  over 
the  segment  form  in  that  it  is  not  liable 
to  lateral  spread,  it  is  at  the  same  time 
inferior  to  the  former  in  many  important 
points.     It  cannot  so  well  resist  shocks 


or  side  blows,  and  being  so  taken  to 
pieces  every  time  it  is  moved  is  very  lia- 
ble to  be  injured  especially  at  the  scarf 
joint.  An  additional  recommendation 
for  centres  constructed  on  the  plans  of 
Figs.  5  and  6,  is  the  small  amount  of  ma- 
terial used,  which  is  quite  as  small  as  is 
consistent  with  the  varying  strains  the 
ribs  are  exposed  to,  and  is  so  cut  that 
the  timbers  are  almost  as  valuable  when 
the  tunneling  is  completed  as  they  were 
when  first  purchased  for  the  ribs. 

The  estimation  of  the  dimensions  prop- 
er to  give  each  tie  and  brace  of  the  rib 
is  easily  determined  in  so  simple  an  ar- 
rangement, by  any  of  the  methods  given 
for  bridge  centres.  It  is,  however,  to 
be  remembered  that,  while  the  bridge 
centre  has  to  sustain  but  the  weight  of 
the  arch  stones  and  bonding  mortar,  a 
load  which  can  be  calculated  to  a  pound 
before  one  stone  is  laid,  the  centring  of 
a  tunnel  has  to  resist  the  pressure  not 
only  of  the  brick  roof,  but  also  of  the 
earth  above,  and  that  this  latter  pressure 
is  wonderfully  variable.  The  pressure  of 
the  brick  work  will  of  course  vary  when 
laid  in  cement  and  when  laid  in  mortar. 
From  the  most  careful  experiments  made 
to  determine  the  weight  of  a  cubic  yard 
of  brick  work,  we  find  that   when   the 


BRIDGE   AND   TUNNEL   CENTRES. 


487 


bricks  are  laid  with  cement  the  weight 
per  cubic  yard  is  2,897  pounds,  or  in 
round  numbers  2,900  lbs.;  when  laid  in 
mortar  beds  the  weight  falls  to  2,677,  a 
difference  of  some  220  lbs.  per  cubic  yard. 
It  is  true  that  the  pressure  of  the  earth 
does  not  act  to  any  great  extent  on  the 
centring,  until  the  arch  is  turned  and  the 
crown  bars  drawn  forward  to  form  the 
roofing  of  the  newly  excavated  length, 
but  when  this  is  done,  and  the  three  ribs 
removed  to  be  set  up  in  advance,  the 
pressure  on  the  two  ribs  remaining  under 
the  arch,  is  quite  severe.  This  load  is 
especially  variable  with  the  leading  or 
segment  ribs,  which  it  will  be  remember- 
ed are  placed  at  the  ends  of  the  length 
of  arch,  and  sustain  one  end  of  all 
the  side  and  crown  bars  supporting  the 
earth,  and  the  movement  which  this 
earth  is  at  any  moment  liable  to  take, 
cannot  be  foreseen.  At  times  a  whole 
length  can  be  gotten  out  and  the  arch 
turned  without  any  perceptible  motion 
of  the  earth  either  at  the  sides  or  on  top; 
at  others,  the  earth  will  of  a  sudden  be- 
gin to  move  and  throw  all  its  pressure 
on  the  side  bars  ;  then,  again,  the  action 
will  take  place  at  the  crown  and  become 
so  great  as  to  press  the  bars  down  in  the 
middle  through  a  distance  of  many 
inches,  or  even  to  break  the  stoutest  15- 
inch  oak  beams. 

This  action  of  the  earth,  however, 
seerm  to  be  controlled  by  law,  since  it 
depends  largely  on  the  depth  of  the  tun- 
nel below  the  surface.  The  pressure  on 
the  sides  is  most  severe  in  those  parts  of 
the  tunnel  which  ai*e  deepest,  and  the 
vertical  or  crown  pressure  (and  this  is 
always  the  severer  of  the  two)  where 
the  distance  below  ground  is  less.  At 
first  thought  this  is  precisely  the  reverse 
of  what  we  should  expect  to  be  the  case, 
for  it  seems  but  natural  to  suppose  that  the 
greater  the  depth  of  earth  the  greater  the 
pressure  on  the  arch  beneath.  The  facts 
are,however,quite  the  contrary.  Thus,for 
example,  in  excavating  a  tunnel  through 
a  hill,  as  we  enter  the  hill  side  the  press- 
ure is  almost  exclusively  at  the  crown 
and  very  severe;  as  the  work  progresses 
nearer  and  nearer  the  centre  of  the  hill 
where  the  amount  of  earth  above  the 
arch  is  greatest,  the  vertical  is  changed 
to  lateral  pressure,  and  this  latter  is  in 
turn  changed  to  vertical  as  we  approach 
the  other  end.     This  is  well  accounted 


for,  by  supposing  that  in  the  former  case 
the  depth  of  earth  being  small,  the  whole 
of  it  gets  into  motion  and  acts  vertically 
downwards,  while  in  the  latter  case  the 
amount  of  earth  being  great  only  a 
small  portion  is  put  in  motion. 

The  leading  rib,  then,  must  be  con- 
structed with  no  small  care,  and  its  joints 
well  strengthened.  For  tunnels  of  ordi- 
nary span,  whatever  may  be  the  curve 
of  soffit,  we  may  with  safety  give  the 
parts  the  following  dimensions.  The 
backpieces  two  thicknesses  of  3  in.  plank; 
the  planks  breaking  joints  with  each 
other.  For  the  segment  rib  make  all 
the  braces  6  in.  X  6  m-  5  tne  l°no  strata 
reaching  from  the  half  sills  to  the  crown 
7  in.  X  6  in.,  and  the  vertical  pieces  at 
the  crown  forming  the  joi  nt  a  b  also 
7  in.  X  6  in.  For  the  queen  post  centres, 
make  the  tie  beam  9  in.  X  6  in.,  as  also 
the  short  timber  placed  over  the  scarf 
joint  ;  the  queen  posts  6  in.  X  6  in->  ex~ 
cepting  at  the  upper  and  lower  ends 
where  the  braces  abut  which  should  be 
10  £  in.  X  6  in.  ;  th  e  short  piece  between 
the  queen  posts,  and  just  below  the 
crown  4  in.  X  ^  m->  aiia\  finally,  the 
braces  6  in.  X  5i  in- 

The  m  inner  of  setting  the  ribs  is  il- 
lustrated in  Figs.  5  and  6.  Under  the 
queen  post  ribs  is  placed  a  long  horizon- 
tal beam,  its  two  ends  resting  on  the 
side  walls  and  supported  immediately 
under  the  foot  of  each  queen  post  by 
vertical  posts.  Upon  this  beam  are 
placed  longitudinally  four  thick  planks, 
and  on  these  rest  the  folding  wedges. 
The  segment  ribs  are  supported  in  much 
the  same  way,  each  rib  by  two  short 
timbers,  one  end  of  each  resting  on  the 
side  walls  and  one  on  a  vertical  post 
under  the  heel  of  the  rib  ;  on  these  rest 
the  longitudinal  planks  which  are  placed, 
however,  a  little  oblique  to  the  tunnel 
since  the  heel  of  the  segment  rib  is  not 
so  far  from  the  wall  as  the  foot  of  the 
queen  post. 

It  has  already  been  remarked  that  it 
is  never  wise  to  strike  the  centres  until 
the  side  walls  of  the  newly  excavated 
length  are  up,  as  in  work  of  this  class 
there  is  a  strong  tendency  to  ninve  for- 
ward in  the  direction  of  the  excavation. 
If,  however,  the  ribs  are  struck  in  the 
manner  already  described,  with  the  lag- 
gings of  the  back  length  kept  tight  up 
to  the  arch  by  the  two  frames  left  under 


488 


VAN   NOSTRAND'S   ENGINEERING   MAGAZINE. 


them,  we  shall  always  have  two  lengths 
of  completed  work  remaining  with  their 
supports,  not  only  until  the  next  length 
is  excavated  hut  till  the  side  walls  are 
built  and  ready  for  the  ribs.  Under 
such  circumstances  each  length  is  well 
able  to  uphold  its  burden  till  it  receives 
assistance  from  the  next  advancing  one, 
the  construction  of  which  to  springing 
line  occupies  several  days,  and  the  ce- 
ment or  mortar  has  time  to  harden  be- 
fore the  weight  comes  upon  the  arch 
after  striking  the  centring.  When,  how- 
ever, from  false  motives  of  economy, 
only  three  ribs  and  one  set  of  laggings 
are  used,  the  entire  support  of  one 
stretch  of  arch  must  be  removed  before 
another  can  be  commenced,  and  this, 
again,  before  a  third  is  turned,  leaving 
the  green  arch  unsustained,  in  which 
state  it  is  liable  to  give  way,  the  bricks 
to  crush  and  the  whole  arch  to  come 
down  in  utter  ruin.  Nowhere,  indeed, 
among  all  the  variety  of  engineering 
works  will  a  penny  wise  economy  more 
surely  prove   a  pound  foolish  one  than 


here  ;  nowhere  else  will  an  unwise  sav- 
ing lead  to  so  profuse  an  outlay. 

Tunnel  centres  again  differ  from  those 
of  bridges  in  that  the  laggings  are  very 
differently  adjusted.  In  the  later  case 
it  is  the  custom  in  practice  to  place  all 
the  laggings  on  the  ribs  before  commenc- 
ing to  turn  the  arch,  by  which  means  no 
small  degree  of  stability  is  given  to  the 
ribs.  In  tunneling,  however,  where  only 
a  few  inches  of  space  remains  between 
the  backpieces  of  the  frame  and  the  pol- 
ing which  sustains  the  earth,  it  would  be 
utterly  impossible  to  turn  the  arch  if  all 
the  laggings  were  put  in  place  before 
the  brickwork  is  begun.  To  overcome 
this  difficulty,  only  a  few  laggings,  say 
five  or  six  are  placed  at  a  time.  Thus, 
starting  at  the  springing  line,  we  adjust 
six  laggings  on  each  side  of  the  frame, 
and  carry  the  arch  up  equally  on  both 
sides.  When  it  has  reached  the  upper 
bolster,  we  add  six  more,  and  the  mason- 
ry continued  as  before,  and  proceed  in 
this  way  until  very  near  the  crown  as 
shown  in  Fig.  7,  where  A  A'  is  the  brick 


^W 


Fig.  7. 


work.  At  this  stage  of  the  work  the 
two  laggings  CC  are  placed  on  the  ribs, 
the  top  of  their  inner  edges  being  first 
rabbeted  as  shown  in  the  figure.  In 
these  rabbets  "cross"  or  "  keying -in" 
laggings  B,  consisting  of  stout  planks 
18  or  20  inches  in  width,  are  laid  one  at 
a  time  beginning  at  one  end  of  the  cen- 


tring. The  bricklayer  whose  duty  it  is 
to  key-in  the  arch  stands  with  his  head 
and  shoulders  between  the  brickwork 
A,  A,  and  starting  at  the  end  of  the  last 
piece  of  completed  arch  places  the  first 
cross  lagging,  and  keys  in  the  arch  over 
it ;  then  a  second,  and  in  like  manner 
keys  in  the  arch  over  it,  and  thus  re- 


BRIDGE   AND   TUNNEL    CENTRES. 


489 


treats  along  the  entire  opening  until  the 
whole  length  of  arch  is  keyed  in. 

Among  the  varieties  of  patent  centres 
that  planned  hy  Mr.  Frazer,  affords  a 
most  excellent  specimen,  and  hoth  from 
its   strength,  economy,  ease  of  shifting 


and  the  small  amount  of  space  it  occu- 
pies in  the  tunnel,  has  met  with  much 
approval  from  the  engineering  profession 
in  England.  This  centre  consists  of  but 
three  ribs  each  differing  from  the  other 
two  in  design    as  shown  in  Figs.  9,  10 


Fig.  9. 


Fig.  8. 


and  11,  of  which  9  is  the  leading,  10  the 
middle  and  11  the  hack  rib.  Each  rib  is 
constructed  of  four  pieces  of  timber  four 
and  one  half  in.  thick  by  16  inches  wide, 
scarfed  together  as  shown  in  the  draw- 
ings. In  centres  of  the  ordinary  con- 
struction, the  ribs  when  the  laggings 
are  laid  upon  them  are  all  of  precisely 
the  same  size,  and  of  the  same  span  and 
rise  as  the  soffit  of  the  intended  arch. 
In  Mr.  Frazer's  plan,  however,  all  the 
ribs  differ  in  the  length  of  their  radii  ; 
the  radius  of  the  outer  curve  of  the  lead- 
ing rib  (Fig.  9)  being  greater  ;  that  of 
the  middle  3  inches  less  than,  and  that  of 
the  back  rib  yet  smaller  than  the  radius 
of  the  soffit  ;  so  that  the  middle  centre 
i6  the  only  one  of  the  three  which  acts  in 
the  same  way  as  the  ordinary  centre 
frame,  that  is  to  say  with  the  laggings 
and  arch  resting  immediately  upon  the 
rib,  and  is  consequently   with  the  lag- 


gings on  it  of  the  same  rise  and  span  as 
the  arch. 

The  leading  rib  has  for  its  outlet  edge 
a  radius  12|  inches  larger  than  that  of 
the  arch  soffit,  and  for  its  inner  edge  one 
3^  inches  less  than  the  same  radius  (thus 
making  the  16  in.  thickness)  and  is 
plated  on  both  the  inner  and  outer  sur- 
face with  half  inch  iron  plates  bolted 
quite  through.  The  plate  on  the  inner 
surface  is  six  inches  broad  and  projects 
2  inches  over  that  side  of  the  rib  which 
is  turned  towards  the  middle  rib,  thus 
forming  a  flange  on  which  the  laggings 
rest  (see  Fig.  9).  When  this  rib  then 
is  in  place,  it  must  be  its  whole  thickness 
in  advance  of  the  end  of  the  intended 
arch,  and  as  it  stands  12^  inches  above 
the  soffit  will  cover  12^  inches  of  the 
toothing  ends  of  the  brickwork,  thus 
forming  a  sort  of  mould  to  guide  the 
toothing. 


490 


VAN   NOSTRAND'S   ENGINEERING   MAGAZINE. 


The  middle  rib  (Fig.  10)  is  also  covered 
on  the  under  surf  ace  with  half  inch  plate 
iron  in  one  piece  and  bolted  through  as 
shown  in  figure,  thus  giving  the  rib  the 
strength  it  would  have  if  supported  by 
the  usual  struts  and  braces.  The  lag- 
gings rest  immediately  upon  the  upper 
surface  of  the  rib,  and  therefore  the 
radius  of  this  side  must  be  the  same  as 
that  of  the  arch  soffit,  less  three  inches  to 
allow  for  the  thickness  of  the  laggings. 

Fig.  10. 


Fig.  11. 


The  back  rib  (Fig.  11)  is  covered  on 
the  under  surface  with  a  coating  of  half 
inch  plate  iron  in  one  piece,  which  is 
bolted  through  as  in  the  case  of  the  mid- 
dle rib.  Between  each  bolt  a  hole  is 
made  quite  through  the  rib  and  its 
plating,  and  in  it  is  placed  the  stem  of 
a  bearing  iron.  There  are  as  many  of 
these  irons  as  there  are  laggings,  the  ob- 
ject of  using  them  being  to  support  the 
laggings  which  it  will  be  observed  do 


not  rest  on  the  rib  but  on  the  projecting 
irons.  The  amount  of  projection  is  regu- 
lated by  means  of  adjusting  screws,  by 
screwing  which  the  laggings  may  be 
raised  to  the  required  level,  or  by  un- 
screwing lowered  one  by  one  from  the 
arch  when  completed.  These  last  two 
ribs  are  permanently  attached  to  trestling 
by  brackets,  straps  and  bolts,  and  the 
trestling  in  turn  mounted  on  iron  rollers 
which  run  on  half  timbers  laid  longitud- 
inally as  a  kind  of  tramway.  They  are 
also  steadied  at  the  crown  by  long  iron 
hooks  attached  to  one  rib  and  fitting  into 
eyes  in  the  other. 

The  leading  rib  is  supported  upon 
slack  blocks  placed  on  top  the  brick- 
work of  the  side  walls  and  by  the  prop 
A.  This  prop,  to  allow  for  any  inequali- 
ties of  the  invert  on  which  it  rests,  is 
mounted  at  the  lower  end  on  a  screw  by 
which  it  may  be  raised  or  lowered. 

In  setting  this  patent  centre,  the  lead- 
ing rib  is  first  brought  forward  into  place 
and  wedged  up  on  the  edge  of  the  brick- 
woi-k  to  its  desired  level,  and  the  prop  A 
screwed  up  tight  under  the  heel.  The 
trestles  bearing  the  middle  and  back 
ribs  are  then  rolled  forward  till  the  mid- 
dle rib  is  at  the  proper  distance  from  the 
leading  one.  Three  pairs  of  wedges  are 
then  placed  between  the  bottom  piece  of 
the  trestles  and  the  tramway,  and  the 
trestles  thus  wedged  up  until  the  top  of 
the  middle  rib  is  on  a  level  with  the 
flange  of  the  leading  one,  thus  giving  two 
level  bearings  for  the  laggings.  The 
bearing  irons  of  the  back  rib  are  then 
pushed  out  by  the  adjusting  screws  until 
the  top  of  each  of  them  is  also  on  a  level 
with  the  flange  of  the  leading  rib.  The 
three  bearings  then,  of  each  lagging, 
when  the  ribs  are  thus  arranged  is  first 
upon  the  flange  of  the  leading  rib,  then 
upon  the  middle  rib  itself,  and  finally 
upon  the  bearing  irons  of  the  back  rib. 
When  this  centre  is  to  be  again  moved 
forward  on  the  completion  of  this  length 
of  arch,  a  fourth  rib  called  the  " jack 
rib  "  is  first  fixed  under  the  laggings  in 
the  rear  of  the  back  rib,  this  last  named 
rib  consists  simply  of  a  band  of  iron  1 
inch  thick  by  2 \  wide,  bent  into  the  shape 
of  the  arch.  Opposite  every  alternate 
joint  of  the  laggings  a  screw  passes 
through  the  rib,  and  is  furnished  on  its 
outer  end  with  a  square  head  similar  to 
that  of  the  bearing  plates  of  the  back 


EMBANKMENTS   AND    RESERVOIRS. 


491 


rib,  and  on  its  inner  or  lower  end  is  a 
loop  so  that  it  may  be  easily  turned  with 
a  lever.  The  object  of  placing  these 
screws  opposite  each  alternate  joint  is 
that  by  this  arrangement  only  half  as 
many  screws  are  needed  as  there  are 
laggings.  The  jack  rib  is  itself  support- 
ed at  each  end  by  an  iron  bar  2  feet 
long  driven  temporarily  into  the  wall. 

As  soon  as  this  latter  rib  is  adjusted 
to  take  the  ends  of  the  laggings,  the 
wedges  are  driven  from  under  the  tres- 
tles and  its  rollers  thus  brought  down 
upon  the  tramway  prepared  for  them. 
When  thus  lowered,  it  is  evident  that 
the  two  ribs  (middle  and  back)  will  be 
so  much  below  the  leading  rib  which  is 
left  standing  that  they  will  easily  pass 
under  it.  The  trestle  and  its  ribs  is  then 
moved  forward  until  the  back  rib  is 
within  8  inches  of  the  ends  of  the  lag- 
gings, when  it  is  wedged  up  as  before. 
The  bearing  screws  are  then  screwed  up 
tight  against  the  laggings,  giving  these 
latter  the  same  support  hitherto  obtained 
from  the  leading  rib,  which  now  stands 
between  the  middle  and  back  rib.  The 
wedges  under  the  ends  of  the  leading 
rib  (see  Fig.  9)  are  then  removed  and 
the  rib  carried  forward  over  the  top  of 
the  middle  rib  and  adjusted,  as  previously 


described,  on  the  top  of  the  newly  built 
side  walls.  The  laggings  are  then  drawn 
forward  one  or  two  at  a  time  as  they  are 
needed,  beginning  at  the  springing  line. 

The  great  advantage  which  these 
patent  centres  appear  to  possess  over 
those  of  the  ordinary  construction,-  is  the 
total  absence  of  all  struts,  ties  and  braces, 
thus  leaving  a  fine  open  space  for  the 
scaffolding  and  materials  of  the  masons. 
The  amount  of  repairs  also  is  very  trivial, 
as  they  are  not  so  liable  to  be  injured  by 
flying  rocks.  In  point  of  economy, 
though  the  first  cost  of  patent  centres  is 
much  greater  than  that  of  the  segment 
or  queen  post  centres,  the  amount  expend- 
ed in  repairing  the  latter  soon  makes  up 
the  difference.  In  point  of  strength,  it 
must  be  acknowledged  that,  when  work- 
ing through  heavy  earth,  the  patent  cen- 
tre of  three  ribs  is  by  no  means  so  reli- 
able as  the  all-wood  centre  of  five  ribs 
and  two  sets  of  laggings,  used  as  above 
described.  And  this  is  certainly  a  seri- 
ous objection  in  that,  it  is  impossible  to 
tell  beforehand  at  what  moment,  owing 
to  a  fault  or  to  the  displacement  of  the 
local  beds,  the  character  of  the  earth  may 
change  completely  from  a  light  soil  to 
one  of  great  heaviness. 


EMBANKMENTS   AND    RESERVOIRS— THEIR    FAILURE,  AND 
SUGGESTIONS  FOR  THEIR  CONSTRUCTION. 


From  "The  Building  News." 


We  alluded  sometime  ago  to  the  re- 
cent calamitous  failures  in  the  south- 
western districts  of  England,  occasioned 
by  the  late  floods  ;  and  we  hinted  their 
cause  and  remedies.  The  great  impor- 
tance of  the  subject  urges  us  to  revert 
to  the  question,  to  recall  some  of  the 
weak  points  and  to  discuss  the  modes  of 
construction  usually  adopted.  A  great 
diversity  of  opinion  exists  among  engi- 
neers as  to  the  mode  of  construction  — so 
great  indeed,  that  every  engineer  has 
his  peculiar  views  of  what  should  be  the 
form  and  the  materials  adopted.  A 
variety  of  considerations  should  deter- 
mine in  each  case,  the  plan,  form,  and 
materials  of  embankments.     They  have 


to  sustain  the  depth  or  pressure  of 
water,  to  withstand  the  abrasion  caused 
by  the  normal  condition  of  wind,  waves, 
and  tidal  currents.  The  materials  along 
the  locality  of  the  coast  or  river  have  to 
be  used  to  the  best  advantage,  and  the 
cost  of  land  and  maintenance  must  be 
considered.  Again,  long  slopes  towards 
the  water  offer  least  resistance  to  the 
action  of  the  currents,  and  are  less  liable 
to  injury,  than  more  vertical  ones  ;  on 
the  other  hand,  they  are  more  costly  in 
the  area  of  land  they  occupy,  and  in  the 
amount  of  material  required.  They  also 
do  not  impose  so  effectual  a  barrier  to 
the  waves  of  the  sea,  or  high  tides  and 
floods.     Slopes  of  steeper  inclination,  or 


492 


VAN   NOSTRAND'S   ENGINEERING   MAGAZINE. 


vertical  faces,  expose  less  surface  to  the 
action  of  the  water  :  they  occupy  less 
ground,  and  cost  less  in  material ;  though, 
on  the  other  hand  they  have  more  direct 
pressure  to  sustain,  and  there  is  a  greater 
re-action.  The  hydrostatic  law  that 
the  lateral  pressure  of  a  liquid  is  perpen- 
dicular to  the  side  of  the  enclosing 
walls,  and  is  equal  to  the  weight  of  a 
column  of  the  liquid  whose  base  is  the 
side  and  height  equal  to  the  depth  of  the 
centre  of  gravity  of  the  side — is  one 
that  has  to  be  constantly  kept  in  view 
in  designing  the  embankments  of  reser- 
voirs and  canals.  Under  general  cir- 
cumstances— that  is  to  say,  excluding 
the  effects  of  the  waves — the  depth  of 
water  only,  not  its  expanse  or  area,  has 
to  be  taken  into  account  in  proportion- 
ing the  thickness  of  embankments.  It 
is  as  easy  to  embank  a  foot  or  a  few 
feet  depth  of  the  Atlantic,  as  it  is  to  em- 
bank a  canal  of  the  same  depth,  the 
difference  being  in  the  former  case  there 
would  be  more  wave  force  and  abrasion. 
The  same  lateral  pressure  exists  in  both 
cases.  Let  us  here  speak  first  of  the 
forms  and  materials  of  river  and  coast 
banks,  and  secondly  of  tidal  action  and 
currents.  Engineers  differ  greatly  as  to 
the  best  kind  of  slope.  In  reclaiming 
fore-shores  from  the  sea,  the  banks  are 
made  from  3  to  4  or  5  ft.  above  the  high 
water  of  the  spring  tides,  their  width 
being  4  ft.  to  7  ft.  at  the  crown.  These 
banks  are  best  curved  to  a  convex  form 
to  the  water,  and  no  angular  or  sharp 
projections  should  be  allowed.  In  Hol- 
land, the  sea  slopes  are  generally  inclined 
slightly  to  the  horizon,  or  made  as  flat 
as  possible.  It  is  evident  this  is  a  ques- 
tion that  must  depend  mainly  on  the 
material  and  the  area  of  enclosure.  Col. 
Emy,  an  authority,  has  advocated  a  sec- 
tion of  bank  in  which  the  slope  is  con- 
cave as  the  best  to  resist  the  action  of 
the  waves.  Others  prefer  straight 
slopes,  as  the  angle  of  repose  of  the 
material.  In  flat  slopes,  sand  and  silt 
may  be  made  available,  and,  as  we  have 
seen,  such  slopes  offer  less  resistance  to 
the  tide.  Tidal  action  is  greatest  at  the 
lowest  high  tides  of  the  neaps.  For 
inner  slopes,  the  Dutch,  who  have  great 
experience  in  these  works,  made  the 
batter  about  4  or  5  to  1. 

The  fascine  banks  of  Holland  may  be 
noticed.     Brushwood  twigs  of   about  4 


in.  diameter  are  tied  by  others  at  inter- 
vals. These  fascines  are  from  8  to  13  ft. 
in  length,  of  about  1  ft.  8  in.  girth,  the 
small  and  large  ends  being  placed  to- 
gether alternately.  In  other  cases  the 
fascines  are  placed  horizontally,  the  ends 
of  one  layer  being  successively  within 
the  lower  one  so  as  to  form  a  slope,  the 
whole  being  tied  by  stakes  driven 
through  each,  which  are  hooped  round 
at  the  head.  Sand,  clay,  shingle,  or 
gravel,  is  rammed  between  each  layer. 
A  batter  of  ^  or  1  to  1  in  height  is  given. 
In  many  parts  of  our  country,  as  in 
Wales  and  the  North,  rubble  facing 
should  be  used  as  the  cheapest  and  best 
material.  The  stones  should  be  larger 
and  be  laid  to  a  slope  of  1^  or  2  to  1  ; 
or  the  banks  may  be  pitched  at  that 
part  subject  to  erosion.  Such  partial 
facings  must  have  solid  earth  or  clay 
foundations,  but  we  prefer  loose  rubble 
at  the  lower  angle.  A  double  row  of 
piles  is  a  good  protection  to  the  feet  of 
these  banks,  with  loose  stones  rammed 
between  and  in  front.  Long  slopes  re- 
quire the  least  thickness  of  pitching. 
In  timber  districts,  where  rubble  is 
costly,  the  banks  may  be  protected  by 
timber  or  plank  facings.  The  guide 
piles  are  driven  slightly  inclined,  whaled 
at  the  top,  and  planked  horizontally  in- 
side, the  earth  being  rammed  against 
the  planks.  Occasionally  diagonal  piles 
are  driven  in  the  bank  to  help  the  piling. 
The  Piedmontese  engineers  use  a  tem- 
porary defence  of  sloped  piles  supported 
by  strutting  and  planked  against  the 
water.  But  the  use  of  concrete  as  a 
substitute  for  stone  or  timber  must 
eventually  become  general.  A  concrete 
backing  faced  with  rubble,  or  dressed 
to  a  batter,  makes  a  good  and  imperme- 
able defence.  In  the  Med  way  it  has 
been  adopted  with  success,  and  its  cost 
is  such  that,  wherever  local  materials 
are  wanting,  it  offers  the  best  alterna- 
tive. 

One  fertile  source  of  floods  in  lands 
enclosed  by  these  banks  is  the  difficulty 
in  discharging  the  water  during  variable 
states  of  the  tide,  owing  to  the  sluices 
of  the  outfall  drains  being  closed  by 
the  head  of  water  against  them.  These 
sluices  should  be  of  such  ai-ea  and  fre- 
quency as  required  by  the  propable  con- 
tingencies of  tide,  and  should  be  hung 
so  that  the  pressure  of  the  land  waters 


EMBANKMENTS   AND    RESERVOIRS. 


493 


may  readily  open   them.      We   believe 
half  our  reclaimed  land  is  deluged  on 
account  of  inadequate  provision  in   this 
way.     A  sluice  of  eight  feet  wide  to  60 
or  so  aci*es  is  considered  sufficient,  and 
we  think  a  sluice  working  on  a  vertical 
axis  shutting  against  a  rebate,  and  hav- 
ing the  axis  fixed  so  as  to  make  unequal 
openings   to    prevent    the    tidal    water 
from  entering  under  pressure,  is  one  of 
the  best  kinds.     In  all  tidal  rivers  like  j 
the  Severn,  it  is  of  frequent  occurrence 
that  the  mouths  get  choked  up  by  the : 
rising   of    the   tide    for   a   considerable  j 
period  ;  and,  when  this  takes  place  at 
the  time  of  heavy  storms,  the  danger  of  j 
inundations  is  imminent. 

The  action  of  waves  is  another  great 
cause  of  disturbance  to  embanked  lands. 
On  the  coast  of  Scotland  the  fury  of  the 
Atlantic  produces  an  average  pressure, 
Mr.  Stevenson  found,  of  611  lb.  per 
square  foot  ;  and  on  seacoasts  this  must 
be  added  to  the  depth-pressure.  Con- 
crete blocks  alone  seem  to  withstand  this 
action,  which  is  greatest  at  half-tide. 
Slopes  help  much  to  diminish  the  im- 
petuosity and  power  of  waves,  and  we 
may  take  the  section  of  the  Plymouth 
Breakwater  as  a  good  type  of  construc- 
tion. 

The  Dutch  dykes  may  be  taken  also  as 
good  examples  ;  in  some  of  these,  the 
body  of  the  embankment  is  of  earth, 
with  a  core  of  fascines  and  with  a  fac- 
ing of  rubble. 

Puddle  between  sheet-piles,  or  an  earth 
bank  behind  vertical  sheet-pile  facing,  is 
sometimes  adopted.  A  good  plan  is  to 
form  a  loose  rubble  core  in  the  water 
slope  with  rubble  at  the  base.  When 
sheet  piling  is  used,  inclined  piles  driven 
into  the  embankment  or  shore,  to  resist 
the  pressure,  may  be  desirable.  One 
necessary  pr-ecaution  in  vertical  sea-walls 
which  more  effectually  resist  the  action 
of  waves  is  a  good  impervious  founda- 
tion, as  we  have  before  said.  The  waves 
in  this  case  have  the  effect  of  undermin- 
ing the  defence,  and  therefore  the  foot- 
ing should  be  well-founded  and  consoli- 
dated. The  bursting  of  the  Holmfirth 
reservoir  in  1852,  when  100  lives  were 
suddenly  lost,  arose  from  a  leakage  or 
spring  in  the  seat  of  the  embankment  ; 
and  the  Bradfield  reservoir  failure,  still 
in  the  recollection  of  our  readers,  was 
simlarly  undermined  through  insufficient 


puddling.  The  crowns  of  embankments 
are,  as  a  rule,  not  carried  sufficiently 
high  to  resist  unusual  floods,  and  the 
water,  once  it  gets  the  upper  hand,  soon 
softens  and  disintegrates  the  bank,  dis- 
turbing the  backing  and  causing  settle- 
ment. There  are  some  points,  too,  that 
require  higher  banks  than  others,  as  when 
a  sudden  bend  occui's,  or  a  confluence  or 
eddying  of  currents  exists  ;  and  for  this 
reason  it  is  imperative  that  the  character 
of  the  sea-coast,  or  the  general  curve  of 
the  river,  should  be  preserved  in  the  out- 
line and  section  of  any  artificial  embank- 
ments. Sloped  banks  increased  the 
ascensional  force  of  currents  impinging 
on  them,  and  this  we  know  is  not  taken 
into  account  as  a  rule.  Such  banks 
should,  therefore,  be  made  higher  than 
vertical  or  abrupt  banks.  There  is  a  cer- 
tain angle  of  surface  with  the  horizon  at 
which  this  rise  attains  a  maximum. 

The  law  of  tides,  as  derived  from  as- 
tronomical theory,  is  considerably  modi- 
fied by  local  and  other  disturbances,  as 
the  configuration  of  the  coast,  winds, 
&c.  ;  and  frequently  the  neap  or  quad- 
rature tides  rise  as  high  as  the  spring 
tides,  or  those  happening  at  the  syzigies. 
Thus  we  know,  from  personal  observa- 
tion, that  on  the  coast  of  Hampshire 
the  neaps  occasionally  equal  the  spring 
tides  in  height  by  the  action  of  gales. 
Again,  the  sectional  form  of  coasts  in- 
creases the  height  of  the  tidal  flow  where 
I  it  rises  higher  than  in  the  open  sea. 

At  Chepstow,  the  spring  tide  is  said 
to    rise    60    feet,    and    at     Bristol    40 
|  feet,    while   in   mid-ocean   islands   it   is 
J  not    perceptible.      Pavers    form    capil- 
lary-like  funnels,    which    augment   the 
!  height  and  duration  of  flood-tides  along 
their  flow,  and  thus  we  find  them  dan- 
gerous inlets  when  banks  are  low,  or  the 
natural  level  of  the  river  is  nearly  on  a 
par   with    the    adjacent    country.      At 
Southampton,    Christchurch,    and.   some 
I  other  places,  a  double  tide  is  experienced. 
■  The   double   tide   of   the    Southampton 
J  Water  is  a  remarkable  instance  of  the 
return  or  ebb  tide  being  met  and  driven 
j  back  by  the  larger  tidal  wave  which  flows 
up  the  wider  channel  of  Spithead.    Thus 
;  the  smaller  current,  which  is  a  branch  of 
:  the  great  Atlantic  wave,  loses  its  veloc- 
ity along  the  Western  side  of  the  Isle 
of  Wight,  and  at  its  fall  down  the  estu- 
j  ary  of  Southampton  is  met  by  the  great- 


494 


VAN  nostrand's  engineering  magazine. 


er  weight  which  proceeds  up  the  wider 
or  Spithead  entrance  on  the  eastern  side 
of  the  Isle  of  Wight.  While  affording 
admirable  facilities  for  ocean  steamers 
leaving  Southampton  docks,  by  delaying 
the  fall  of  the  tide,  this  double  tide  acts 
with  fatal  power  in  low-lying  districts 
by  blocking  up  the  outfall  of  the  fresh 
storm  and  land  waters.  Colonel  Emy 
has  noticed  the  "  bore,"  or  the  interfer- 
ence of  the  tidal  wave  by  contractions 
or  bars  in  the  beds  of  rivers.  It  is  really 
a  similar  meeting  of  waters,  causing  a 
Tmdden  rise  at  a  certain  point;  and  in  the 
Severn,  along  which  the  floods  have  done 
so  much  damage,  this  rise  is  considerable. 
But  the  ordinary  cause  of  flooded  dis- 
tricts is  owing  to  the  opposite  flow  of 
the  land  waters  and  the  tide.  They  meet 
somewhere  in  the  river,  and  if  the  volume 
of  outflow  happens  to  be  great,  the  rise 
of  the  water  in  long  rivers  is  considera- 
ble, and  the  effects  disastrous.  Having 
spoken  of  the  action  of  the  tide,  let  us 
briefly  refer  to  the  effects  the  currents 
of  rivers  have  upon  their  banks  and  beds. 
An  erosive  action  is  constantly  going  on 
in  one  part  or  another.  In  steep  parts, 
the  tendency  is  to  deepen  the  bed,  and 
the  excavated  detritus  is  deposited  in 
creeks  and  bays  or  in  sudden  bends, 
tending  to  fill  these  up.  Again,  in  the 
outfall  portions  of  rivers,  the  silt  or  sand 
is  spread  over  the  bottom,  for  the  veloc- 
ity is  diminished,  and  the  power  of  trans- 
porting materials  is  less.  Thus  we  have 
the  delta  of  the  Mississippi  causing  the  j 
mouth  to  be  silted  up.  The  banks  of  a 
river  of  ordinary  flow  corrode  more  than 
the  bottom,  and  heve  we  find  the  great- ' 
est  irregularities  and  deviations  in  most 
of  our  rivers.  We  also  find,  in  observ- 
ing our  river  courses,  that  a  resisting 
bank  on  one  side  produces  a  concavity  ' 
on  the  other  bank.  An  obstruction,  or 
sudden  projection,  similarly,  has  the  I 
same  abrasive  effect,  the  stream  turning 
against  the  opposite  shore.  Again,  we  ! 
find  the  river  deepest  along  the  steepest  | 
bank.  Along  a  concave  bank,  the  stream 
deepens  the  bed,  and  the  silt  is  deposit-  j 
ed  on  the  convex  side. 

By  a  system  of  impervious  banks  we 
increase  the  scour,  and,  therefore,  the  j 
depth  of  a  river.  Planting  willows  or  j 
osiers  along  the  banks  of  wide  rivers,  so  I 
as  to  give  them  an  equal  width  of  water- ; 
way  has  had  a  good  effect ;  banks  are  \ 


formed  by  the  deposition  of  the  sedi- 
J  mentary  matter  and  sand  round  the 
roots.  In  a  like  manner,  a  species  of 
groins  or  spurs  placed  at  right  angles  or 
obliquely  to  the  stream,  is  sometimes 
used,  but  longitudinal  banks  are  least 
expensive  and  most  effective  in  their  ac- 
tion. The  penned-up  lands  should  have 
waste  weirs  to  allow  the  freshets  to  es- 
cape, and,  we  imagine,  in  some  of  our 
inundated  districts  the  outfalls  have  been 
insufficient  for  extraordinary  storm-wat- 
ers. We  may  here  briefly  refer  to  a  very 
important  point  affecting  the  safety  of 
our  water  defences — namely  the  forma- 
tion of  shoals.  At  the  junction  of  streams 
or  rivers  shoals  frequently  occur  owing 
to  the  difference  in  the  specific  gravities 
of  the  fresh  and  salt  water,  to  velocity, 
and  other  disturbances.  The  deltas  of 
our  great  rivers,  arising  from  the  deposit 
of  alluvial  matter  at  their  mouths,  di- 
minished velocity,  and  interference  of 
the  outflow  by  the  tide,  are  instances  of 
obstructions.  Mrs.  Somerville,  in  her 
admirable  work,  notices  the  interference 
of  the  outfall  of  main  streams  by  in- 
creased freshets.  The  Rhine  was  once 
reversed  in  its  flow  by  this  cause,  and 
the  Mississippi  is  much  subject  to  inter- 
ference in  its  flow  by  the  Ohio.  Allu- 
vial deposits  between  the  latter  rivers 
have  formed  an  elongated  island,  and  at- 
tempts have  been  made  to  build  a  city 
upon  it.  In  placing  a  dam  across  a 
stream  to  close  it,  it  is  found  that  the 
best  situation  for  it  is  not  at  the  em- 
bouchure or  point  of  junction,  but  at 
some  distance  above,  so  that  the  deposits 
may  render  it  impervious.  These  depos- 
its occur  by  reason  of  the  stream  becom- 
ing stagnant  before  reaching  the  dam. 
Submersible  dams,  made  by  filling  cais- 
sons with  stones  or  gravel  and  sinking 
them,  may  be  frequently  employed  with 
great  effect,  for  by  contracting  the  water- 
way it  is  deepened  proportionately. 
Sunken  dykes  have  been  employed  in  the 
delta  of  the  Mississippi  with  signal  im- 
provement, and  after  dredging  and  other 
means  have  failed.  We  only  point  to 
these  instrumental  measures  as  useful  in 
their  bearing  upon  the  subjects  of  em- 
bankments ;  for  we  think  that  to  dam  a 
brook  or  a  valley,  or  to  embank  a  stream 
just  where  convenience  dictates,  is  often 
to  open  to  the  insidious  foe  miles  of  as- 
sailable districts  and  undefended  banks. 


PUBLIC    WORKS    IN   EGYPT. 


495 


PUBLIC  WORKS  IN  EGYPT. 

From  "The  Engineer." 


£,  It  is  only  within  the  last  half  century 
that  engineering  works  in  Egypt  have 
been  promoted  and  constructed  in  a 
manner  which  promises  well  for  their 
future  permanency  and  the  real  interests 
of  the  country.  Long  previous  to  the 
time  alluded  to,  engineering  works  of 
enoimous  magnitude  rivalling  those  con- 
structed in  India  during  the  dynasties  of 
the  Abdallahs  and  the  Aurengzbes,  exis- 
ted in  Egypt,  but  with  the  exception  of 
the  Pyramids  but  little  remains  of  either 
their  former  grandeur  or  utility.  With 
the  decadence  of  the  cities,  the  pleasures 
and  wants  of  whose  inhabitants  they 
were  intended  to  minister  to,  they  fell 
into  disuse,  and  shared  in  the  general 
destruction  and  desolation  which  ages 
ago  swept  over  that  portion  of  the  Afri- 
can continent.  But  although  the  nature 
and  extent  of  these  great  works  of  con- 
struction can  now  be  but  guessed  at  by 
the  light  of  some  stray  excavations  here 
and  there,  and  their  successors  bear  but 
little  resemblance  to  them  in  either  de- 
sign or  execution,  yet  the  physical  con- 
dition of  the  country  remains  unaltered. 
Rightly  or  wrongly,  the  origin  of  sur- 
veying— one  of  the  branches  of  our  pro- 
fession— is  attributed  to  the  necessity 
which  compelled  the  Egyptian  land- 
owners to  define  their  properties  by  some 
boundaries  which  were  not  liable  to  be 
obliterated  by  their  annual  natural  floods. 
As  of  old,  so  at  present,  the  ever- 
recurring  periodical  overflowing  of  the 
Nile  constitutes  the  natural  phenomenon 
of  the  country.  From  time  immemorial 
the  efforts  of  the  monarchs  and  the 
people  have  been  directed  towards  the 
one  great  object — viz.,  that  of  regulating 
and  rendering  uniform,  and  turning  to 
the  best  advantage,  the  fertilizing  inun- 
dations of  this  mighty  and  mysterious 
river.  Probably  the  idea  and  attempt 
also  to  unite  the  waters  of  the  Mediter- 
ranean and  the  Red  Sea  may  boast  of 
the  same  degree  of  antiquity.  The  Kile 
being  thus  the  most  important  and,  in  a 
great  measure,  the  sole  source  of  the 
prosperity  and  wealth  of  the  country,  it 
is  evident  that  works  of  irrigation,  and 
others  undertaken  with  the  object  of  im- 


proving the  course  and  condition  of  the 
river,  must  constitute  a  prominent  feat- 
ure in  Egyptian  engineering.  In  Upper 
Egypt  some  extensive  works  of  this 
character  were  carried  out  by  the  father 
of  the  present  ruler.  They  comprised 
canals,  banks,  and  roads,  and  some  idea 
of  the  extent  of  the  undertaking  may  be 
gathered  from  the  fact  that  in  one  year 
the  amount  of  the  earthwork  reached  to 
nearly  seventy  million  cubic  yards.  As- 
may  be  expected  in  a  country  in  which 
skilled  labor  is  both  scarce  and  expen- 
sive, the  use  of  earthwork  instead  of  ma- 
sonry or  brickwork  will,  in  all  cases  to 
which  it  is  applicable,  be  adopted.  It 
forms  not  only  the  cheapest,  but,  when 
of  good  quality  and  sufficiently  plentiful 
to  render  the  maximum  dimensions  of 
no  consequence,  the  best  description  of 
material  for  that  particular  class  of 
work. 

A  glance  at  the  physical  contours  of 
that  portion  of  Egypt  which  lies  between 
the  mountains  of  Libya  on  the  west  and 
those  of  Arabia  on  the  east,  will  demon- 
strate in  what  manner,  and  the  reason 
why,  it  became  affected  by  the  inunda- 
tions of  the  Nile.  If  two  sections  be 
made  of  this  part  of  the  country  nearly 
at  right  angles  with  one  another,  it  will 
be  found  that  one,  which  may  be  termed 
the  longitudinal  section,  has  a  gradient 
or  slope  which  is  practically  identical 
with  that  of  the  river  itself  during  flood 
time.  The  other,  or  cross  section,  has  a 
gentle  fall  from  the  river  banks  towards 
the  desert,  so  that  when  that  point  is 
reached  the  total  difference  of  level 
amounts  to  between  13  ft.  and  14  ft. 
The  nature  of  the  soil  of  Egypt  renders 
these  periodical  inundations  indespensa- 
ble  to  its  permanent  fertility.  A  geo- 
logical section  shows  an  upper  layer  of 
ooze  resting  upon  sand  and  gravel,  which 
in  their  turn  repose  on  a  bed  of  clay. 
The  substratum,  moreover,  is  impreg- 
nated with  various  salts,  to  such  a  degree 
that  if  the  land  be  not  overflowed  for  a 
few  years  it  becomes  so  salted  as  to  be 
perfectly  useless  for  purposes  of  cultiva- 
tion, and  remains  so  until  it  is  thorough- 
ly washed   by   another   inundation.     In 


496 


VAN  nostrand's  engineering  magazine. 


addition  to  the  duty  already  marked  out 
for  the  future  irrigations  works  of  Egypt, 
they  have  other  functions  to  fulfill. 
Among  these  are  the  construction  of 
banks  or  walls  for  the  retaining  and 
storing  of  water,  not  only  to  prevent  the 
salting  of  the  land,  but  also  to  raise  the 
water  so  as  to  enable  it  to  command 
land  situated  at  a  higher  level.  One  of 
the  oldest  works  of  this  kind  was  under- 
taken to  preserve  the  city  of  Memphis. 
It  was  in  the  early  part  of  the  present 
century  that  the  great  work  was  com- 
menced of  forming  throughout  the 
whole  of  Upper  and  Middle  Egypt  a 
series  of  basins  in  which  the  floods 
might  be  successively  and  thoroughly 
utilized.  In  order  to  complete  this  pro- 
ject in  an  effectual  and  certain  manner 
for  the  latter  part  of  the  country,  it  will 
be  necessary  to  construct  a  canal  of  great 
magnitude,  already  proposed,  and  the 
line  of  which  has  been  determined. 

It  has  been  recently  proposed  by  a 
well-known  authority — M.  Linant  Bey— 
to  restore  the  ancient  lake  Maoris,  which 
Herodotus  states  was  an  artificial  lake 
formed  to  store  the  waters  of  the  inun- 
dation, and  distribute  them  as  required 
during  a  season  of  drought,  or  when  the 
floods  were  insufficient  to  irrigate  the 
neighboring  country.  It  is  riot  worth 
while  investigating  the  cause  of  the 
destruction  of  this  lake,  but  we  may 
briefly  notice  the  advantages  which 
would  accrue  from  its  re-establishment. 
It  appears  that  by  the  formation  of  the 
necessary  tanks  forty-two  thousand 
acres  of  fertile  land  would  be  lost  to 
cultivation  ;  but,  on  the  other  hand,  by 
converting  this  land  into  water,  so  to 
speak,  it  would  be  possible  to  irrigate  or 
bring  into  cultivation  during  drought, 
or  seasons  of  insufficient  floods  nearly 
seven  hundred  thousand  acres.  Against 
this  increased  cultivable  area  must  be 
set  the  cost  of  reconstructing  the  neces- 
sary banks,  sluices,  channels,  and  other 
works.  This  cost  is  very  much  enhanced 
by  the  fact  that  the  level  of  the  present 
bed  of  the  ancient  lake  is  nearly  27  ft. 
higher  than  it  originally  was.  M.  Li- 
nant Bey  estimates  that  nearly  thirty 
million  cubic  yards  of  earthwork  would 
be  required  to  construct  the  works. 
Provided  the  result  would  recoup  the 
outlay,    there    would    be   no    difficulty 


either  in  finding  the  necessary  capital  or 
in  carrying  out  the  undertaking. 

Coming  down  to  our  own  times,  the 
public  works  constructed  recently  in 
Egypt  are  of  a  character  which  speaks 
well  for  the  future  prosperity  of  the 
country,  whether  they  be  regarded  as 
intended  to  promote  the  fertility  of  the 
soil,  the  increase  of  intercommunication, 
or  the  interests  of  commerce.  Until  the 
Euphrates  Valley  Railway  is  made, 
Egypt  will  constitute,  as  it  does  now, 
the  shortest  route  to  our  Indian  posses- 
sions and  to  the  East  generally — a  route 
very  considerably  facilitated  by  the 
opening  of  the  Suez  Canal.  Twenty 
years  ago  there  was  no  railway  across 
the  desert,  either  from  Cairo  to  Seuz  or 
from  Alexandria  to  Cairo  At  present 
there  is  comparatively  a  good  port  at 
Suez  on  the  Red  Sea,  while  similar  ac- 
commodation has  been  provided  at  Alex- 
andria, and  recently  very  much  extended 
and  improved.  Both  these  towns  have 
also  been  furnished  with  waterworks. 
Under  the  present  ruler  the  railway  sys- 
tem has  been  greatly  extended,  especially 
in  the  Soudan  district.  Sugar  and  other 
manufactories  have  been  established, 
and  no  efforts  seem  to  be  spared  to  pro- 
mote the  welfare  of  a  country  which  is 
renowned  for  its  antiquity  and  former 
magnificence.  A  point  worth  adverting 
to  in  connection  with  our  subject  is 
whether  it  will  be  found  advisable  in 
future  to  resort  to  other  means  to  irrigate 
the  land  than  that  of  simply  raising  em- 
bankments of  various  heights.  It  is  not 
improbable  that  when  all  the  land  situ- 
ated at  the  lower  and  consequently  more 
favorable  level  be  brought  into  cultiva- 
tion, the  aid  of  machinery  may  be  called 
in  to  raise  the  water  to  a  height  sufficient 
to  command  the  land  placed  at  a  greater 
altitude. 


Railway  to  unite  Greece  and  Tur- 
key.— A  concession  for  the  construction 
of  a  line  to  connect  the  Greek  railway 
lines  with  the  railway  system  of  Turkey 
has  been  granted  to  a  M.  Piat,  an  en- 
gineer, who  has  ceded  it  to  M.  Singros, 
a  banker  of  Constantinople.  The  latter 
is  engaged  in  treating  with  the  Greek 
Government.  The  project  of  construct- 
ing a  line  from  Pi.tras  to  Athens  will 
probably  be  revived. 


REFRACTORY    MATERIA  LS. 


497 


REFRACTORY  MATERIALS— ON  FIRECLAY  AND  OTHER 
REFRACTORY  MATERIALS.* 

By  GEORGE  J.  SNELUS,  F.  C.  S. 
Prom  "Engineering." 


It  will  be  admitted  by  all  concerned 
in  the  manufacture  of  iron  and  steel, 
that  it  is  of  the  utmost  importance  to 
obtain  good  materials  for  building  their 
furnaces,  while  at  the  same  time  it  can 
scarcely  be  said  that  our  knowledge  of 
refractory  materials  is  in  a  satisfactory 
st  ate.  With  these  convictions,  the  writer 
ventures  to  place  the  little  information 
he  has  been  able  to  gather  upon  the  sub- 
ject before  the  Iron  and  Steel  Institute, 
with  a  view  of  eliciting  discussion,  in  the 
hopes  thereby  of  increasing  the  general 
stock  of  knowledge. 

Although  it  is  generally  allowed  that 
the  ultimate  chemical  composition  of  a 
brick  does  not  altogether  decide  its  fire- 
resisting  property,  yet,  it  is  often  possi- 
ble to  judge  from  a  chemical  analysis 
whether  a  clay  will  answer  for  a  given 
purpose  or  not. 

Thus  it  is  found  that  the  presence  of 
alkalies  in  sensible  quantity,  say,  about 
1  per  cent.,  confers  so  much  fusibility 
upon  a  clay  as  to  render  it  unsuitable  for 
very  high  temperatures.  This  is  well 
seen  in  the  analyses  of  clays  from  the 
Dowlais  and  the  Newcastle  district. 
The  Dowlais  clays,  numbered  9  and  10, 
contain  respectively  1.43  per  cent,  and 
1.13  per  cent,  of  potash,  and  though 
bricks  made  from  these  clays  are  used 
for  forge  purposes,  yet  they  will  not 
stand  above  one  month  in  mill  furnaces, 
whilst  bricks  from  'clays  11,  12,  13,  and 
14,  last  for  three  months. 

Mr.  Pattinson  believes  that  it  is  chiefly 
owing  to  the  presence  of  the  rather  large 
proportion  of  alkalies  that  the  New- 
castle bricks  are  less  refractory  than  the 
Stourbridge. 

Lime  and  magnesia  exercise  a  fluxing 
effect  when  present,  but  when  mixed 
with  silica,  as  in  the  Dinas  bricks,  a 
small  quantity  of  lime  is  useful  as  a 
binding  material,  as  it  can  be  more  in- 
timately combined  with  the  particles  of 
quartz  than  any  other  similar  substance. 

Oxyde    of   iron  also  exerts  a   fluxing 

*Paper  read  before  the  Iron  and  Steel  Institute  at  Man- 
chester. 

Vol.  XIII.— No.  6—32 


effect,  though  in  a  less  degree.  It  will 
be  noticed  that  none  of  the  Stourbridge 
clays  contain  over  2  per  cent.,  but  if 
alkalies  are  absent,  iron  oxyde  may  be 
present,  up  to  about  3  per  cent,  without 
affecting  the  fusibility  of  the  bricks  in  a 
very  serious  degree.  This  may  be  seen 
by  a  reference  to  the  analyses  of  the 
well-known  Glenboig  bricks,  and  of  the 
St.  Helens'  bricks.  Blocks  from  St. 
Helens  last  well  in  the.  hematite  furna- 
ces of  West  Cumberland.  The  writer 
has  found  these  bricks  to  bear  the  scour- 
ing action  of  the  highly  basic  slag  of  a 
Bessemer  furnace  better  than  those  from 
the  Leeds  district.  If,  however,  the 
brick  is  required  to  stand  the  intensely 
high  temperature  of  a  steel  melting  fur- 
nace, even  this  small  proportion  of  oxyde 
of  iron  becomes  injurious. 

Alumina  appears  to  be  singular  in  its 
action,  for  while  it  is  well  known  to  be 
one  of  the  most  rnftisible  substances  in 
nature,  and  the  compound  Bauxite,  and 
also  highly  aluminous  clays,  as  for  ex- 
ample the  Glenboig,  and  notably  that 
from  the  large  firebrick  works  in  Mary- 
land, are  highly  refractory,  and  ordinary 
clay,  containing  less  alumina,  is  less  fire- 
resisting,  yet  when  alumina  e.\ist^  in 
small  quantities  in  silica  bricks,  it  ap- 
pears to  increase  their  fusibility.  This 
may  be  seen  by  reference  to  the  tabula- 
ted analysis  and  remarks  attached. 

The  plasticity  of  a  clay  depends  on 
the  presence  of  combined  water,  and  to 
some  extent  upon  the  proportion  of 
alumina.  Thus  the  Glenboig  clay,  which 
contains  a  rather  large  proportion  of 
alumina,  is  frequently  of  such  a  soapy 
character  that  it  is  used  instead  of  soap 
for  washing  the  hands.  The  well- known 
Porcelain  clay  or  Kaolin,  is  highly  alu- 
minous, and  is  prized  chiefly  for  its  very 
plastic  nature. 

These  properties  cause  the  clay  to 
shrink  much  in  drying  and  firing,  but 
after  having  been  highly  tired  the  ma- 
terial then  suffers  much  less  change  of 
volume  by  subsequent  changes  of  tem- 
perature.     Hence   it   is   that  Glenboior 


498 


van  nostrand's  engineering  magazine. 


bricks  expand  and  contract  so  little  upon 
heating  and  cooling,  thus  rendering  them 
valuable  in  situations  where  changes  of 
form  would  cause  serious  inconvenience, 
as  in  the  regenerators  and  roofs  of  Sie- 
mens' furnaces. 

Silica  is  also  a  highly  infusible  sub- 
stance, but  unlike  alumina,  its  particles 
have  no  tendency  to  adhere  or  bind  to- 
gether except  under  the  influence  of  the 
most  intense  heat.  When,  therefore, 
this  material  is  used  for  making  bricks, 
a  building  substance  has  to  be  mixed 
with  it.  This  is  the  case  in  the  manu- 
facture of  the  Dinas,  or  silica  bricks, 
which  were  formerly  made  from  the 
Dinas  rock,  to  which  a  small  portion  of 
milk  of  lime  was  added.  It  is  now  found 
that  these  bricks  can  be  made  from  any 
pure  silicious  stone,  by  grinding  it  up 
and  mixing  about  1  per  cent,  milk  of 
lime  with  it. 

In  the  case  of  the  ganisters,  now  so 
largely  used  for  lining  Bessemer  convert- 
ers, the  cementing  material  is  alumina, 
which  is  found  naturally  combined  with 
the  silica.  But  in  this  case  the  physical 
condition  of  the  substance  is  of  great 
importance,  because  it  is  used  in  the  raw 
state,  or  at  least  without  undergoing  the 
process  of  burning.  It  is,  therefore,  im- 
portant, that  while  it  should  not  shrink 
much  on  heating,  it  should  yet  bind  well 
together. 

The  peculiar  black  ganister  of  Sheffield 
■possesses  these  properties  in  a  high 
degree,  and  the  writer  has  found  none 
beter  than  that  sent  out  by  Mr.  Lowood. 
The  rock  itself  appears  to  have  been 
subject  either  to  extreme  compression  or 
to  heat,  as  it  has  a  peculiarly  close 
texture.  Sheffield  has,  however,  by  no 
means  a  monopoly  of  this  substance,  or 
at  least  of  materials  that  answer  the 
purpose,  as  Dowlais  and  Ebbw  Vale  are 
now  both  making  their  own  from  local 
sources.  Even  pure  quartz  rock  can  be 
made  to  answer,  by  mixing  a  proper 
proportion  of  aluminous  clay  with  it. 
Where,  however,  the  natural  black  gan- 
ister can  be  obtained,  nothing  can 
answer  better  for  all  purposes. 

There  is  another  peculiarity  possessed 
by  silica,  which  is,  that  bricks  made  from 
it  expand  when  burnt,  so  that  in  making 
silica  bricks  the  moulds  must  be  smaller 
than  the  brick. 

Thus,   for  a   9-in.   brick,   the    mould 


would  only  be  about  8f  in.  long. 
Every  mixture,  like  every  clay,  has  its 
own  factor  of  expansion  or  contraction 
for  the  same  amount  of  burning,  and  this 
is  either  increased  or  diminished  by  vari- 
ation in  the  intensity  of  heat  applied. 
The  clay  from  which  the  St.  Helens' 
bricks  are  made  shrinks  considerably 
during  drying  and  burning.  Thus,  for 
a  9  in.  by  4-J  in,  by  2|  in.  brick,  the 
mould  is  9|  in.  by  4j  in.  by  3£  in.  For 
Glenboig  clay,  a  shrinkage  of  one-twelfth 
is  allowed,  that  is,  the  mould  for  a  9-in 
brick  is  made  9|  in.  long. 

Silica  bricks  not  only  expand  during 
burning,  but  do  so  still  more  upon  being 
subject  to  intense  heat,  contracting  again 
on  cooling  ;  and  this  expansion  and  con- 
traction is  one  of  the  most  important  points 
to  take  into  consideration  in  bixilding 
steel-melting  furnaces.  At  Dowlais,  the 
man  in  charge  of  the  furnaces  is  expect- 
ed to  slacken  the  tie-rods  above  the  fur- 
nace while  the  heat  is  getting  up,  and  to 
tighten  them  as  it  goes  down,  so  as  to 
follow  the  expansion  and  contraction  of 
the  roof.  At  Crewe,  it  is  attempted  to 
make  this  self-acting,  by  the  use  of  vo- 
lute springs  between  the  brick  staves 
and  the  nuts  on  the  tie-rods  passing 
through  them  ;  while  at  Creusdt,  they 
try  to  make  the  furnace  casing  so  strong 
(by  the  use  of  wrought-iron  girders  for 
brick  staves,  and  very  strong  tie-rods), 
that  the  centre  of  the  roof  must  rise  and 
fall  to  allow  for  the  expansion  and  con- 
traction. 

Mr.  Riley  states  that,  when  at  Dow- 
lais, he  found  the  quantity  of  iron  made 
in  a  puddling  furnace  was  directly  as 
the  percentage  of  silica  in  the  clay  used 
for  making  the  bricks. 

Titanic  acid  has  been  shown  by  Mr. 
Riley  to  exist  in  nearly  all  clays,  but  it 
does  not  appear  to  influence  their  fusi- 
bility in  any  marked  degree,  and  it  prob- 
ably plays  the  part  of  silica,  to  which  it 
is  closely  allied  in  all  its  properties.  As 
much  as  1  per  cent,  was  found  in  Stour- 
bridge bricks,  but  only  traces  in  silica 
bricks. 

It  need  hardly  be  pointed  out  that  it 
is  not  sufficient  to  have  a  good  material. 
Great  care  must  be  exercised  in  manipu- 
lating it.  If  it  is  to  be  made  into  a 
brick,  every  pains  must  be  taken  to  dry 
it  gradually,  and  to  fire  it  evenly,  and  to 
a  proper  point ;  while,  if  it  is  to  be  used 


BUILDING   STONES. 


499 


in  a  semi-plastic  state,  as  in  the  state  of 
ganister,  it  should  be  equally  moist 
throughout,  so  as  to  dry  evenly,  and  not 
so  wet  as  to  cause  it  to  crack,  or  so  dry 
as  to  prevent  it  binding. 

But  there  is  another  practical  point  in 
the  management  of  firebricks  which  is 
too  often  overlooked.  Bricks  are  very 
porous  bodies,  and  absorb  a  great  deal 
of  moisture,  even  when  under  cover, 
and,  of  course,  much  more  if  allowed  to 
get  wet.  In  fact,  apparently  dry  bricks 
often  contain  a  good  deal  of  water,  and 
if  put  into  a  furnace  in  this  state,  and 
the  heat  is  got  up  rapidly,  the  bricks 
crack  and  crumble,  to  pieces.  This  is 
especially  the  case  with  silica  bricks,  and 


the  writer  has  known  instances  of  bricks 
being  condemned  as  chemically  bad, 
when  the  fault  lay  with  those  who  used 
them  without  properly  drying  them.  It 
is  well  in  the  case  of  silica  bricks  to 
actually  set  them  as  hot  as  they  can  be 
handled.  In  all  cases  when  a  furnace  is 
first  started,  and  especially  with  Siemens 
furnaces,  a  very  small  fire  should  be 
kept  up  for  several  hours  and  then  very 
gradually  increased.  This  plan  will  add 
weeks  to  the  life  of  these  furnaces. 

Most  blast  furnace  managers  know 
and  practise  this  very  slow  and  careful 
drying  of  their  plant,  but  it  is  too  often 
neglected  in  mill  and  other  furnaces. 


BUILDING  STONES.* 

From  "The  Building  News." 


The  working  and  application  of  build- 
ing stones  date  back  to  an  early  time, 
and  the  question  of  their  relative  merits, 
causes  of  decay,  and  means  of  preserva- 
tion have  for  some  time  engaged  the  at- 
tention of  scientific  men.  It  is,  there- 
fore, no  new  subject  I  introduce  to  your 
notice,  but  one  which  I  trust  may,  on  ac- 
count of  its  importance,  prove  of  inter- 
est ;  for,  next  to  the  design  of  an  edifice, 
the  selection  of  the  materials  of  which 
the  building  is  constructed  occupies  a 
prominent  place.  A  proper  knowledge 
of  the  composition  and  durability  of  the 
principal  material  used  in  building  can, 
therefore,  be  hardly  overrated.  Chem- 
istry, geology  and  the  study  of  architec- 
ture and  engineering  have  each  more  or 
less  to-do  with  the  attainment  of  a  true 
understanding  of  the  quarrying  of  stone 
and  its  adaptation  to  building  purposes, 
and  I  therefore  thought  the  Junior 
Philosophical  Society  would  deem  a  dis- 
cussion on  this  subject  one  of  no  mean 
interest.  Without  further  preface  I 
would  classify  stones  employed  in  works 
of  construction  under  two  heads — viz., 
those  suitable  for  foundations  and  those 
adapted  for  face  work.  In  the  former 
case,  if  the  foundations  and  lower  part 
of  a  building  be  under  water,  where  per- 


t  *  A  paper  read  before  the  Junior  Philosophical  Society 
by  A.  T.  Walmisley. 


haps  a  rapid  current  flows,  or  in  the  case 
of  a  sea-wall  subject  to  the  influence  of 
powerful  waves,  a  heavy  quality  of  stone 
must  be  used,  since  the  weight  of  all 
bodies  when  submerged  is  evidently  re- 
duced by  the  volume  of  water  displaced 
— for  instance,  the  lightest  stone  we 
have,  the  Godstone  Gatter  or  litigate, 
belonging  to  the  upper  greensand  forma- 
tion. This  stone,  when  used  on  building 
land,  weighs  103  lbs.  per  foot  cube,  but 
supposing  the  same  stone  used  in  sea 
water  the  effective  weight  would  be  only 
37  lbs.  to  the  cubic  foot,  since  it  would 
then  be  reduced  by  about  66  lbs.,  the 
average  weight  of  a  cubic  foot  of  sea 
water.  The  top  bed  of  this  soft  calcareous 
sandstone  is  used  for  scouring  purposes, 
and  it  is  known  as  hearthstone  ;  the  sec- 
ond bed  of  the  quarry  is  used  for  road- 
making  and  rough-walling,  and  the  third 
bed  is  suitable  for  architectural  works, 
as  it  will  withstand  the  action  of  fire, 
and  is  hence  known  as  Fire  Stone.  "West- 
minster Abbey  was  formerly  built  of  it, 
and  architects  used  it  where  lightness 
was  necessary.  Sandstones  are  composed 
either  of  quartz  or  silicious  grains  in- 
soluble in  water,  cemented  by  argil- 
laceous, silicious,  calcareous,  or  other 
matter,  generally  consisting  of  about  93 
to  98  of  silica,  with  1  to  2  of  carbonate 
of  lime.     When   of    good   quality  they 


500 


VAN    NOSTRAND's    ENGINEERING   MAGAZINE. 


prove  very  serviceable,  and  have  been 
largely  employed  in  the  northern  and 
midland  counties.  The  Cragleith  and 
Stancliffe  or  Darley  Dale  (Derbyshire) 
are  considered  the  best  specimens  of  this 
kind  of  stone.  The  former  has  been 
used  a  good  deal  in  the  neighborhood  of 
Leith.  Many  of  the  public  buildings  at 
Edinburgh  have  been  made  from  it.  It 
is  an  excellent  stone.  When  the  grains 
composing  sandstones  increase  in  dimen- 
sions they  are  designated  conglomerate. 
The  dark  gray  varieties  of  sandstone 
from  the  vicinity  of  Swansea,  the  Forest 
of  Dean  and  Dundee,  are  heavy  enough 
for  water  purposes,  and  weigh  about  170 
lbs.  to  the  foot  cube.  The  granite  of 
Leicestershire  is  one  of  the  heaviest  stones 
we  have.  It  is  really  a  syenite,  not  a 
granite,  as  it  contains  hornblende  and  no 
mica,  which  all  true  granite  possess.  A 
heavy  stone  is  also  found  in  the  western 
islands  of  Scotland,  particularly  in  the 
island  of  Tiree.  This  .  metamorphic 
limestone  is  composed  of  carbonate  of 
lime,  with  a  good  proportion  of  horn- 
blende, or  rather  cocolite,  a  species  of 
augite,  in  small  nodules.  As  a  rule, 
limestones  are  considered  better  than 
sandstones,  but,  in  all  cases  where  stone 
is  continually  acted  on  by  water,  sand- 
stone is  preferable  to  limestone,  since  it 
is  not  so  likely  to  be  acted  upon  by  the 
molluscaea,  which  frequently  bore  cal- 
careous stones,  converting  gradually  the 
smooth  face  of  the  stone  to  a  rough  face, 
and  leaving  interestices  for  the  water  to 
get  into  and'  wear  away  the  stone.  In 
the  case  of  a  sea-wall  entirely  above  the 
water  at  low  tide  limestone  might  be 
employed,  as  at  Tiegnmouth,  or  above 
low  water  mark  in  the  case  where  the 
lower  part  is  always  under  water.  In  the 
construction  of  the  Royal  Border  Bridge 
over  the  River  Tweed,  on  the  Newcastle 
and  Berwick  Railway,  some  experiments 
were  made  on  various  stones  from  quar- 
ries in  the  neighborhood,  in  order  to  test 
the  resistance  they  offered  to  vertical 
pressure.  The  specimens  selected  meas- 
ured 1  in.  square  in  the  cross  section  and 
2  in.  long,  this  being  considered  a  nearer 
approach  to  general  masonwork  than  an 
ordinary  simple  cube  1  in.  in  the  side. 
The  result  gave  an  average  of  195  tons 
per  square  foot.  The  closest  grained 
and  finest  in  texture  bore  as  much  as  362 
tons   per   square  foot,    while   the    more 


coarsely  gritted  specimens,  and  those 
winch  had  a  more  sandy  appearance,  re- 
sisted only  a  pressure  of  6  V  tons  per 
square  foot.  It  is  to  be  observed  that 
no  signs  of  yielding  were  apparent  until 
92  per  cent,  of  the  ultimate  crushing 
weight  was  applied,  when  a  gradual 
crumbling  of  grains  of  sand  proved  that 
they  were  nearly  loaded  to  their  maxi- 
mum power  of  resistance.  In  almost  all 
varieties  of  building,  the  specific  gravity 
or  weight  of  the  stone  employed  enters 
into  the  calculation,  as  it  is  of  the  ut- 
most importance  that  the  amount  of 
pressure  produced  by  an  arch,  wall,  or 
column,  as  the  case  may  be,  should  not 
be  underrated.  As  a  general  rule,  stones 
should  not  be  made  to  carry  a  weight  ex- 
ceeding from  £  to  .i^th  of  the  pressure 
calculated  from  that  which  has  crushed 
them  in  small  experimental  cubes.  In 
the  Royal  Border  Bridge  the  weight 
borne  by  each  square  foot  of  ashlar  in 
the  bridge  was  a  little  above  2  tons, 
whence  it  would  be  seen  that  the  press- 
ure on  the  ashlar  in  that  work  (in  con- 
nection with  the  experiments  made)  was 
about  rVth  of  that  which  would  crush 
the  stone.  In  Gwilt's  "  Encyclopaedia  of 
Architecture,"  the  pressure  on  the  piers 
at  St.  Paul's  and  other  remarkable  struc- 
tures is  given  at  17.7  tons  per  square 
foot  on  the  piers  of  the  cupola  of  St. 
Paul's,  London  ;  13.6  on  the  piers  of  the 
Hospital  of  the  Invalides,  Paris  ;  26.9 
on  the  piers  of  the  cupola  of  the  Pan- 
theon, Paris  ;  27.0  on  the  piers  of  the 
cupola  of  St.  Mery  ;  15.0  on  the  piers  of 
the  cupola  of  St.  Peter's,  Rome  ;  18.1 
on  the  columns  of  San  Paolo  Fuori  le 
Mine,  Rome.  When  the  base  of  solid 
remains  the  same,  height  influences  their 
strength.  A  very  thin  stone  easily  frac- 
tures. The  experiments  which  have 
been  made  with  a  view  to  discover  the 
influence  which  form  has  on  the  resist- 
ance of  stone  have  shown  that  the  dif- 
ferent solids,  the  bases  of  which  have 
an  equal  area,  resisted  best  as  their  sec- 
tion approached  a  circle,  and  that  prac- 
tically the  resistance  is  in  the  inverse 
ratio  of  the  perimeters  of  different  fig- 
ures with  an  equal  area.  It  is  also  found 
that  those  sandstones  which  have  the 
highest  specific  gravity  possess  the  great- 
est cohesive  strength,  about  the  least 
quantity  of  water,  and  disintegrate  the 
least  under  changes  of  the  weather.     It 


BUILDING   STONES. 


501 


is  important  to  bear  in  mind  the  action 
of  the  atmosphere  on  various  specimens 
of  stone,  especially  in  towns,  where,  in 
consequence  of  the  air  and  the  rain  con- 
taining more  or.  less  carbonic  and  sul- 
phurous acids,  derived  from  the  vapor 
of  co;il  in  combustion,  every  kind  of 
building  stone  is  acted  upon  thereby. 
This  is  very  noticeable  in  the  case  of 
sandstones,  which  form  a  sort  of  filter, 
from  their  susceptibility  of  imbibing 
moisture  ;  but  the  power  of  stone  to  ab- 
sorb water  to  a  large  extent  does  not 
prove  that  it  would  not  stand  the  frost. 
A  stone  may  be  durable  as  well  as  porous. 
Good  stock  bricks  absorb  a  large  quan- 
tity of  water,  yet  few  substances  are 
more  durable  and  resist  frost  better. 
When  the  adhesive  strength  of  the  par- 
ticles of  any  stone  is  less  than  the  ex- 
pansile power  of  water  when  converted 
into  ice,  then  common  sense  tells  us  the 
material  would  be  broken  by  the  frost  ; 
but  it  does  not  of  necessity  follow  that 
because  a  stone  takes  up  a  certain 
amount  of  water  it  suffers  from  frost. 
Stone  for  building  purposes  should  pos- 
sess compactness  and  durability,  that  it 
shall  not  be  affected  by  any  natural 
agents  as  the  atmosphere,  water,  heat 
and  frost ;  also  hardness,  or  the  power 
of  attrition,  which  enables  it  to  resist 
blows  and  strength  ;  or  the  power  of  re- 
sistance in  every  direction.  The  under 
beds  in  some  quarries  produce  harder 
and  denser  stones  than  the  upper  beds, 
but  are  more  expensive  on  account  of 
the  time,  labor,  and  cost  of  blasting 
and  removing.  This,  however,  depends 
on  the  position  of  the  quarry.  It  is  al- 
most impossible  to  lay  down  any  fixed 
rule  as  to  what  stone  should,  in  different 
situations,  be  actually  employed.  The 
transport  of  the  material,  expense  of  la- 
bor, &c,  have  to  be  considered  as  well 
as  the  design  and  external  appearance. 
If  possible  and  suitable,  material  near  at 
hand  is  usually  adopted,  it  being  gener- 
ally considered  that  stone  employed  in 
the  vicinity  of  its  native  quarry  with 
stands  the  effects  of  the  atmosphere  bet- 
ter than  when  removed  further  off.  It 
is  to  be  regretted  that  the  large  increas- 
ed demand  for  building  stone  has  been 
attended  with  a  decreased  care  in  its'se- 
lection.  Properly,  stone  should  not  be 
too  hastily  removed  from  the  neighbor- 
hood of  its  quarry.    It  requires  to  season 


quite  as  much  as  timber  does.  There  is, 
as  it  were,  the  sweating  of  the  stone, 
and,  after  quarrying,  it  should  be  allow- 
ed to  remain  for  a  time  in  the  quarry  to 
harden  and  allow  the  quarry  water  to 
run  out. 

Buildings  in  this  climate  are  found  to 
suffer  the  greatest  amount  of  decom- 
position on  the  southern,  western  and 
south-western  fronts,  generally  most  ex- 
posed to  wind  and  rain.  Decomposition 
is  effected  both  by  ehemical  and  me- 
chanical means — the  stone  applied  to 
buildings  being  as  subject  to  its  action 
as  when  attached  to  native  rocks. 

Stones  for  building  are  either  crystal- 
line or  stratified,  and  may  be  classified 
under  three  divisions — Argillaceous, 
Silicious,  and  Calcareous  ;  although  the 
components  of  some  quarries  vary  very 
much,  stone  being  simply-  an  aggrega- 
tion of  particles  composed  of  one,  two, 
or  more  minerals — silica,  alumina,  lime, 
and  magnesia,  combined  with  acids, 
water,  and  other  matter.  The  argillace- 
ous, though  used -largely  in  an  artificial 
state — as  in  the  case  of  bricks — are  not 
suitable  for  building  in  the  natural  state. 
Where  clay  is  plentiful,  brickwork  is 
generally  cheaper  than  stonework  ;  but 
if  much  labor  is  required,  stone  can  be 
used  equally  cheap.  Yorkshire  flag  is 
the  name  generally  given  to  sandstone, 
known  as  Brainley  Fall,  and  is  that  most 
in  use  for  paving  and  coping  where 
strength  and  durability  are  required. 
It  is  a  millstone  grit  from  the  carbonifer- 
ous formation.  The  original  quarry  was 
situated  near  Leeds,  on  the  estate  of  the 
Earl  of  Cardigan,  but  has  been  worked 
out  for  some  years.  There  were  six 
beds,  with  a  total  face  of  34  ft.  The 
top  bed,  about  4  ft.  thick,  was  called  the 
rag;  2nd,  16  ft.  thick,  and  3rd,  4  ft. 
thick,  both  producing  good  stone  ;  the 
4th,  a  red  stone  of  inferior  quality  ;  the 
5th  and  6th,  each  3  ft.  thick,  and  of  good 
quality. 

Granite  is  an  example  of  a  silicious 
stone,  and  one  now  much  used  for  engi- 
neering purposes.  Though  employed  a 
great  deal  by  the  Egyptians,  granite  was 
not  much  used  for  building  purposes  in 
this  country  until  selected  by  Messrs. 
Rennie  for  theirbridges  over  the  Thames. 
Aberdeen  granite,  of  which  London 
bridge  is  constructed,  is  considered 
superior   to    Cornish  granite,    of   which 


502 


VAN  NOSTRAND'S   ENGINEERING   MAGAZINE. 


Waterloo-bridge  is  constructed — the  for- 
mer abounding  more  with  quartz,  the 
latter  more  with  felspar,  possessing  a 
portion  of  potash  in  its  composition, 
which  is  considered  an  agent  of  decay. 
Gray  granite  is  more  generally  employed 
than  red,  the  latter  from  its  excessive 
hardness  being  more  difficult  to  work. 

The  quartz  may  be  considered  as  pure 
sileX' — Si  02,  chief  among  minerals,  spe- 
cific gravity,  2.6  will  scratch  glass. 
The  analyses  of  mica  vary — color  varies 
from  gray  to  black,  specific  gravity  2.0 
to  2.5. 

Felspar,  grayish  white,  or  flesh-red 
tint,  specific  gravity  2.54.  The  felspar 
is  the  first  to  decompose,  next  the  mica, 
but  the  quartz  is  imperishable.  The 
coloring  matter  in  granite  is  felspar. 
Geologists  have  been  much  engaged  in 
settling  the  question  whether  granite 
should  be  classed  as  Metamorphic  and 
not  as  a  Plutonic  rock,  but  opinions 
differ  on  this  point.  Metaruorphic 
rocks  or  stratified  crystalline  rocks  are 
those  produced  I  y  a  species  of  chemical 
action  resulting  in  an  alteration  of  form. 
They  are  the  result  of  long-continued 
chemical,  physical,  and  mechanical 
change,  taking  place  in  rock  masses  by 
which  their  appearance  and  structure 
becomes  quite  different  to  that  which 
they  represented  at  the  time  of  their  for- 
mation. Plutonic  rocks  are  those  igne- 
ous rocks  which  have  not  overflown  sur- 
face, but  cooled  at  great  depths,  and 
differ  from  the  volcanic  rocks,  or  those 
which  have  cooled  at  or  near  surface,  by 
their  more  crystalline  texture  and  by  the 
absence  of  pores  and  cellular  cavities. 
Granite  is  essentially  an  igneous  rock, 
though  it  sometimes  presents  a  bedded 
appearance.  Most  quarry  workers  con- 
sider it  has  a  bed,  but  this  cannot  be  true 
in  a  geological  sense,  the  teim  "Jet?" 
being  peculiar  to  stratified  rocks,  and 
meaning  the  original  plane  of  deposition 
of  sedimentary  or  stratified  rocks.  In 
setting  stones  of  the  latter  description 
care  must  be  taken  to  lay  them  in  their 
natural  or  quarry  bed,  parallel  with  the 
horizon.  All  stone  is  said  to  be  capable 
of  bearing  greater  pressure  when  laid 
in  its  quarry  bed  than  in  any  other  posi- 
tion, but  with  stone  formed  in  strata  and 
laminated  it  becomes  a  necessity,  unless 
a  stone  is  enclosed  on  both  sides  by  other 
stones  laid  in  their  natural  bed,  when  it 


may  be  set  with  its  laminae  perpendicu- 
lar to  the  horizon,  in  the  case  of  a  verti- 
cal pressure,  as  the  side  stones  prevent 
the  side  laminae  buckling  out  or  flaking 
off  through  exposure  to  the  atmosphere 
or  frost  ;  but,  generally  speaking,  in  all 
cases  the  laminae  to  be  properly  set 
should  lie  in  planes  perpendicular  to  the 
pressure  ;  and  in  the  case  of  an  arch 
stone  at  right  angles  to  the  line  of 
thrust.  This  will  appear  evident  if  we 
consider  the  laminae  to  be  represented  by 
the  leaves  of  a  book — a  pressure  on  the 
back  of  a  cover  tending  to  buckle  out 
the  pages  and  a  pressure  on  the  side 
covers  tending  to  bind  the  pages  closer 
together.  "We  find  also  that,  however 
tightly  books  are  packed  in  a  bookcase, 
dust  will  wear  itself  in  at  the  top  or  ex- 
posed edges  of  the  pages,  and  so  will 
air  and  water  wear  itself  into  the  ex- 
posed cavities,  be  they  comparatively 
large  or  minute,  on  the  exposed  face  of 
a  stone.  Stones  of  a  siliciou6  nature  are 
much  less  liable  to  decay  than  lime- 
stones, as  decomposition  generally  com- 
mences with  the  destruction  of  the  base. 
Stones  composed  of  thin  layers  or  plates,. 
as  slates,  and  some  sandstones,  are  not 
so  durable  as  those  in  which  the  texture 
is  unifoim,  or  the  grains  or  concretions 
small,  as  granite  in  which  the  essential 
ingredients,  felspar,  quartz  and  mica,  are 
scattered  irregularly  throughout  the 
mass.  "When,  as  in  the  case  of  sand- 
stone, the  base^  is  highly  impregnated 
with  silica,  it  becomes  hard  and  seems 
to  defy  composition.  As  the  particles 
which  are  held  together  are  not  acted  on 
by  air  or  water  the  quality  of  the  sand- 
stone depends  upon  the  durability  of  its 
cementing  properties.  The  disintegra- 
tion of  rocks  and  the  combination  of 
loose  particles  which  rolled  off  the  sur- 
face from  exposure  to  the  action  of  the 
air  and  water  becoming  indurated  and 
foiming  compact  rocks  lower  down,  sug- 
gested the  aggregation  of  particles  by 
some  common  cement  to  form  an  artifi- 
cial stone.  A  paper  on  building  stones- 
would  be  incomplete  without  alluding  to 
its  use  and  manufacture. 

In  the  artificial  stone,  as  originally 
patented  by  Mr.  Frederick  Ransome, 
broken  flint  suspended  in  wire  baskets 
within  boilers,  is  subjected  to  a  strong 
solution  of  caustic  alkali  (soda  or  potash) 
at  a  high  temperature,  say  300°  Fahr.j, 


BUILDING   STONES. 


503 


under  a  pressure  of  from  50  lbs.  to  80 
lbs.  per  square  inch,  which  in  a  semi-fluid 
state  act  as  a  medium  to  form  a  mass 
uniformly  equal  in  its  composition  and 
texture.  The  alkali  attacking  the  flint 
precipitates  the  earthy  and  foreign  par- 
ticles, which  remain  in  the  bottom  of  the 
vessel  when  the  solution  is  drawn  off  ;  a 
large  proportion  of  the  silica  is  dissolv- 
ed, and  the  solution  can  then  be  evapo- 
rated, as  much  as  may  be  deemed  neces- 
sary, to  any  required  degree  of  consist- 
ency. Taking  soda  as  the  alkali,  with  a 
silica  base,  the  following  proportions — 
20.43  per  cent,  of  silica,  2V.05  per  cent, 
of  soda,  and  52.52  per  cent,  water — 
produce  a  transparent  solution  (average 
specific  gravity  1.6),  which,  on  the  ap- 
plication of  a  strong  acid,  becomes  a 
solid  mass  by  the  precipitation  of  the 
silica.  A  little  powdered  flint  is  gener- 
ally added  for  the  purpose  of  taking  up 
any  excess  of  alkali  which  might  prove 
injurious.  The  whole  being  worked  in  a 
pug-mill  for  about  twenty  minutes  be- 
comes a  sort  of  granulated  tenacious 
substance,  like  putty,  which  can  be 
squeezed  into  moulds  in  any  form  requir- 
ed, and  is  capable  of  sharp  outlines. 
After  leaving  the  mould  the  cast  is  al- 
lowed to  dry  slowly,  and  then  is  sub- 
mitted in  a  potter's  kiln  to  a  gradually 
increasing  temperature,  until  at  the  end 
of  about  forty-eight  hours  it  attains  to 
a  bright  red  heat,  which  is  maintained 
for  some  time,  and  allowed  to  cool  gra- 
dually, occupying  altogether  about  four 
or  five  days.  During  this  process  the 
water  is  entirely  driven  off,  the  silicate 
of  soda  produces  another  silica  insoluble 
in  water  by  part  of  the  soda  combining 
with  an  additional  portion  of  silex  at 
the  high  temperature  to  which  it  is  sub- 
jected, and  the  whole  forms  a  compound 
possessing  the  appearance  and  character 
of  natural  stone,  though  harder  in  tex- 
ture. Its  application  depends  on  the 
materials  employed.  When  worked  up 
with  clean  raw  materials,  such  as  sand, 
clay,  portions  of  granite,  marble,  &c, 
together  with  a  small  portion  of  pow- 
dered flint,  it  is  most  suitable  for  mould- 
ing. When  coarser  descriptions  of  sand, 
grit,  &c,  are  employed,  grindstones  of 
all  kinds  can  be  formed.  By  increasing 
the  quantity  of  silica  and  subjecting  it  to 
a  greater  degree  of  heat,  any  amount  of 
hardness  can   be   attained  ;   indeed  the 


substance  of  the  artificial  stone  appears 
to  be  sand  aggregated  and  held  togeth- 
er mechanically  by  the  tenacious  quality 
of  the  fused  silicate  of  soda,  which,  dur- 
ing the  process  of  manufacture,  becomes 
intimately  combined  with  the  particles. 
Other  varieties  of  artificial  stone  are 
formed  with  lime,  or  its  carbonate  or 
sulphate,  as  the  base,  and  in  a  few  in- 
stances they  consist  partly  of  organic 
matters  combined  with  inorganic  matters 
as  the  base.  The  use  of  silica,  however, 
as  a  base  supplies  a  compound  superior 
in  strength  and  durability  to  these  pro- 
ductions, and  more  capable  of  resisting 
both  impact  and  pressure.  Sir  John 
Hall  some  years  ago  boiled  red  sand 
with  sea  water  for  a  considerable  time, 
subjected  to  pressure,  and  obtained  a 
substance  nearly  as  hard  as  natural  sand- 
stone. Another  experiment,  submitting 
pounded  chalk  to  heat  under  pressure, 
changed  it  into  crystalline  marble,  and 
pounded  basalt  became  converted  under 
the  same  process  into  greenstone. 

In  Ransome's  process  a  well-propor- 
tioned combination  of  silica  and  the 
alkali  forms  a  kind  of  insoluble  glass  in 
the  process  of  baking,  which  firmly  holds 
the  mass  together,  and  affords  protec- 
tion against  air  or  other  fluid  injuring 
the  combined  particles.  Improvements 
have,  since  the  patent  was  taken  out, 
been  made  in  the  manufacture  by  the 
inventor,  and  the  discovery  has  supplied 
a  great  desideratum,  though  it  cannot, 
in  the  author's  opinion,  be  said  to  super- 
sede carved  stone  ;  but,  considering  the 
large  demand  there  is  for  stone  to  be  ap- 
plied for  building  within  a  limited  time 
prescribed  by  contract,  the  manufacture 
of  such  a  material  artificially  is  of  the 
highest  value,  and  capable  of  extensive 
employment  where  good  natural  stone  is 
difficult  to  be  obtained.  It  is  suitable  for 
all  varieties  of  architectural  decorations, 
and,  when  made  in  squares  of  about  l£ 
in.  thick,  for  pavements,  as  in  the  case 
of  the  footpaths  on  the  Albert  Bridge 
over  the  Thames  at  Chelsea. 

Marble  and  other  limestones  belong  to 
the  calcareous.  This  type  forms  the 
principal  ingredient  in  all  cements,  and 
is  very  plentiful.  Numerous  statues  of 
antiquity  bear  testimony  to  the  durabil- 
ity and  value  of  this  class.  Liynest-ones 
sometimes  consist  of  shelly  substances 
cemented  together,  when  the  cement  be- 


604 


van  nostrand's  engineering  magazine. 


comes  affected,  first  causing  unequal  de- 
composition ;  but  they  generally  consist 
of  pure  carbonates  of  lime  and  magnesia 
combined  with  other  matter,  and  are 
more  or  less  durable  in  proportion  as 
the}'  are  more  or  less  crystalline.  Those 
employed  in  building  may  be  divided 
into  three  classes — (l),  the  simple  lime- 
stone ;  (2),  the  oolites,  both  containing 
a  large  proportion  of  carbonate  of  lime; 
and  (3),  the  magnesian  limestones  or 
dolomites.  The  three  principal  oolites 
used  in  this  country  are  the  Portland, 
Bath  and  Caen.  Portland  stone,  a  white 
calcareous  oolite  or  freestone  (so-called 
because  easily  worked  by  chisel),  due  to 
its  being  composed  of  compounds  of 
little  spheres.  Stone  from  the  Portland 
quarries  in  Dorsetshire  was  formerly 
common  in  the  metropolis,  both  for  en- 
gineering and  architectural  works.  Many 
of  the  city  churches  and  public  build- 
ings are  built  of  it.  It  has  also  been 
much  used  for  steps,  window-sills,  cop- 
ings, strings,  and  balusters,  on  account 
of  its  moderate  hardness  ;  but  its  use 
has  of  late  years  been  much  superseded 
in  engineering  by  granite,  and  in  archi- 
tecture by  other  freestones.  It  was  in- 
troduced into  London  at  the  commence- 
ment of  the  seventeenth  century.  Inigo 
Jones  used  it  in  the  construction  of  a 
Corinthian  portico  to  the  west  front  of 
old  St.  Paul's  ;  but  the  stone  Sir  Chris- 
topher Wren  used  in  the  construction  of 
the  present  cathedral  was  of  a  superior 
quality  to  most  of  that  now  brought  into 
the  metropolis,  as  the  quarries  from 
wThich  the  stones  used  in  buildings 
erected  in  the  reign  of  Queen  Anne  was 
"brought  have  been  long  closed,  the  stone 
being  too  hard  to  work.  In  the  com- 
missioners' report  for  1839,  they  stated 
in  reference  to  the  Portland  quarries, 
"The  dirt-bed  is  full  of  fossil  roots, 
trunks,  and  branches  of  trees,  often  in 
the  position  of  their  former  growth. 
The  top  cap  is  a  white,  hard,  and  closely 
compacted  limestone  ;  the  skull  cap  is 
irregular  in  texture  ;  it  is  a  well  com- 
pacted limestone  containing  cherty  nod- 
ules. The  Roach  beds  are  always  in- 
corporated with  the  freestone  bed's  that 
invariably  lie  below  them  ;  they  are  full 
of  cavities  formed  by  the  mould  of  shells, 
and  occasionally  contain  oyster  shells 
and  beds  of  flint  near  the  top.  The  top 
bed  is  the  best  stone.     It  is  a  free  grain- 


ed oolite,  free  from  shells  and  hard 
veins.  The  bottom  bed  is  similar  in 
appearance  to  the  top  bed,  and  of  the 
same  component  parts,  but  the  stone  is 
illcemented  and  will  not  stand  the 
weather.  A  middle  or  curf  bed  occurs 
only  in  the  southern-most  quarries  of 
the  Eastcliff — it  is  soft  to  the  north  and 
hard  to  south.  The  good  workable 
stone  in  the  Eastcliff  quarries  is  generally 
less  in  depth  than  is  met  with  in  the 
same  bed  in  the  Westcliff  quarries,  but 
the  Eastcliff  stone  is  harder,  more  es- 
pecially to  the  south  of  the  island.  The 
bottom  part  of  the  top  bed  in  the  West- 
cliff  quarries  becomes  less  hard  and 
durable  towards  the  south.  The  stone 
in  most  of  the  quarries,  and  sometimes 
in  the  same  quarry,  varies  considerably 
in  quality.  Such  stone  as  contains 
flints,  or  is  met  with  below  layers  of 
flints,  is  inferior  and  will  not  stand  the 
weather.  The  bottom  bed  in  the  West- 
cliff  is  not  a  durable  stone,  but  has  been 
worked  to  a  considerable  extent,  and 
sold  as  a  good  stone  in  the  London  mar- 
ket. In  every  freestone  bed  the  upper 
part  is  the  most  durable  and  hardest 
stone.  The  best  stone  is  in  the  north- 
eastern part  of  the  island,  the  worst  in 
the  south-western.  The  most  durable 
stone  has  its  cementing  matter  in  a  solid 
and  half  crystalline  state  ;  in  the  least 
durable  stone  it  is  in  an  earthy  and  pow- 
dery state."  Much  of  this  stone,  re- 
jected in  the  building  of  St.  Paul's 
Cathedral  as  unsuitable,  has  since  been 
sold  by  contract  for  building.  Concrete 
buildings  have  of  late  been  tried  in  some 
places.  While  all  must  admit  that  a 
good  natural  stone  building  surpasses 
that  of  any  other  material,  it  may  be 
questioned  whether  a  concrete  building, 
or  at  any  rate  one  of  artificial  stone, 
would  not  be  preferable  to  a  bad  natural 
stone  edifice,  Whitbed  is  the  stone 
known  in  London  as  brown  Portland. 
The  so-called  best  bed  or  base  bed  is 
not  the  best,  although  the  name  would 
lead  you  to  think  so.  The  Whitbed  is 
rather  a  darker  color  than  the  base  bed, 
but  not  so  fine  in  texture,  and  liable  to 
have-  unsuitable  cavities  in  it,  which 
have  to  be  stopped  when  the  stonework 
is  cleaned  down.  Among  the  numerous 
works  built  of  this  bed  may  be  mention- 
ed the  new  Foreign  Office,  Holborn  Val- 
ley Viaduct,  and  many  of  the  edifices  on 


BUILDING   STONES. 


505 


the  Duke  of  Westminster's  estate.  If 
carefully  selected  it  stands  the  weather 
very  well,  though  rather  more  costly  to 
work.  The  hase  bed  has  been  more  used 
in  London  for  external  work  than  it 
ought  to  be.  It  costs  less  to  work  and 
makes  a  better  appearance  when  first 
finished,  but  its  use  should  be  confined  in 
London  to  internal  work,  or  such  por- 
tions as  are  not  exposed  to  the  weather. 
The  Roach  bed,  which  is  found  incorpo- 
rated with  the  Whitbed  and  base  bed, 
and  is  called  respectively  Whitbed  and 
base  bed  Roach,  is  hard,  strong,  coarse 
and  durable.  This  latter  was  used  on 
Portland  Breakwater.  Bath  stone,  quar- 
ried in. the  county  of  Wilts,  at  Box  Hill, 
Corsham  Down  and  Farleigh  Down,  also 
in  the  county  of  Somerset  at  Combe 
Down,  belongs  to  the  oolitic  series,  being 
almost  wholly  calcareous,  and  though 
comparatively  soft  when  taken  out  of 
the  quarry  afterwards  becomes  hard  and 
serviceable.  It  is  largely  employed  for 
the  facings  of  buildings.  Combe  Down 
is  quarried  on  the  down  from  which  it 
takes  its  name,  near  Bath.  It  was  used 
for  the  restoration  of  Henry  VII. 's  Chap- 
el at  Westminster,  between  the  years 
1S0S  and  182],  but  needs  to  be  selected 
with  great  care,  the  blocks  being  occa- 
sionally subjected  to  vents  which  will 
not  stand  the  effect  of  the  London  at- 
mosphere. The  major  parts  of  Bath 
and  Bristol  are  built  of  it.  Corsham 
Down  quarries  lie  parallel  with  the  Box 
Tunnel,  and  produce  a  stone  freer  from 
vents,  fine  and  even  in  texture.  A  bed 
of  stone  is  found  below  the  latter  known 
as  Coin  Grit,  a  thoroughly  strong  stone, 
but  too  coarse-grained  to  please  the  eye. 
It  is  largely  used  for  heavy  work.  Box 
Ground  adjoins  the  Corsham,  and  is  used 
for  sills,  plinths,  copings.  It  is  coarse- 
grained and  very  durable.  Farleigh 
Down  resembles  the  Corsham  in  texture, 
but  has  not  been  so  much  used,  as  the 
blocks  average  smaller  dimensions.  Caen 
stone  was  brought  into  London  soon  after 
the  Norman  Conquest,  and  was'  exten- 
sively employed  for  inside  decoration  in 
the  Houses  of  Parliament,  for  which  pur- 
pose on  account  of  its  fine  even  grain 
and  color  it  is  well  suited,  as  it  does  not 
require  half  the  labor  necessary  with 
Portland  stone  ;  but  it  does  not  stand 
well  the  exposure  to  the  atmosphere  of 
towns,  though  during  the  middle  ages  it 


was  much  in  demand  for  buildings  in 
this  country.  The  central  tower  of 
Canterbury  Cathedral,  St. George's  Chap- 
el at  Windsor,  Henry  VII. 's  Chapel  at 
Westminster  were  built  of  it.  Aubigny 
stone,  quarried  near  Falaise,  near  Caen, 
is  very  close-grained,  and  harder  to  work 
than  the  Caen.  Tt  is  of  a  colder  color, 
and  said  to  stand  the  weather  better. 
There  are  only  two  workable  beds  with 
an  intermediate  stratum  of  soft  stone. 
Ancaster  stone,  likewise  oolitic,  found 
near  the  town  of  that  name  in  Lincoln, 
was  used  in  the  construction  of  St.  Pan- 
eras  Station  and  Hotel,  but  more  par  icu- 
larly  in  its  own  district.  Doulting  and 
Ham  Hill  are  both  shelly  limestones  and 
oolitic,  used  largely  near  their  own  dis- 
tricts in  Somersetshire.  Painswiek  stone, 
quarried  near  Stroud,  is  also  a  member 
of  the  oolitic  formation,  close,  white- 
grained,  rather  finer  and  harder  than  the 
Corsham  Down,  and  consequently  more 
expensive  to  work.  The  freestones  of 
Wardour,  ChUmark  and  Tisbury,  in  the 
county  of  Wilts,  belong  to  the  oolitic 
formation.  The  Chilmark  is  a  siliceous 
limestone,  and  was  employed  for  Salis- 
bury Cathedral  in  the  thirteenth  century, 
Sir  Christopher  Wren's  report  upon  this 
edifice  in  1668  speaks  of  the  stone  as  a 
little  inferior  to  Portland.  At  the  pres-  • 
ent  day  the  western  front  is  slightly  de- 
composed, but  the  rest  of  the  building 
is  in  good,  preservation.  Tisbury  stone 
has  been  used  in  the  restoration  of  the 
Chapter  House,  Westminster.  Among 
the  Permian  magnesian  limestones  may 
be  mentioned  the  Mansfield  stone,  quar- 
ried in  the  county  of  Notts.  Three  dis- 
tinct varieties  exist— the  white,  red  and 
yellow — the  latter  from  the  Mansfield 
Woodhouse  quarry.  Owing  to  their  ex- 
pense they  are  not  much  in  request, 
though  very  suitable  for  building  pur- 
poses. The  red  and  white  are  calcifer- 
erous  sandstones,  the  yellow  a  dolomite 
or  magnesian  limestone. 

The  commissioners  appointed  to  in- 
vestigate the  different  stone  quarries  in 
this  country  with  reference  to  the  selec- 
tion of  the  stones  for  building  the  new 
Houses  of  Parliament,  though  they  ad- 
mitted that  many  sandstones  as  well  as 
limestones  possess  many  advantages  in 
buildings,  yet  reccoinmended  the  mag- 
nesian limestone  as  the  most  fit  and 
proper  material,  on  account  of  its  more 


606 


VAN   NOSTEAND'S    ENGINEERING   MAGAZINE. 


general  homogeneous  structure,  and  the 
facility  and  economy  of  its  conversion  to 
building  purposes.  They  selected  the 
magnesian  limestone  in  the  neighborhood 
of  Bolsover  Moor  as  suitable  for  the 
purpose,  being  uniform  in  structure,  and 
containing  51.1  of  carbonate  of  lime, 
40.2  of  carbonate  of  magnesia,  nearly  in 
equivalent  proportions,  with  the  ad- 
vantageous admixture  of  about  3.6  of 
silica. 

A  cube  of  2  in.  square  was  found  to 
require  596.01  cwt.  to  crush  it,  and  the 
facility  and  economy  of  its  conversion 


to  building  purposes  were  ako  in  its 
favor.  Dolomites  vary  very  much.  The 
Museum  of  Geology  in  Jermyn  Street 
and  the  Houses  of  Parliament  were  both 
built  of  dolomite.  The  former  exhibits 
no  signs  of  decay,  while  in  the  latter  it 
is  to  be  regretted  that  much  of  the 
stone  supplied  was  not  taken  from  the 
same  part  of  the  quarry  as  that  approved 
of  by  the  commissioners.  The  former 
shows  that  the  commissioners  could  not 
have  selected  a  better  stone,  while  the 
latter  proves  that  care  is  also  necessary 
in  its  selection  from  the  quarry. 


RAILWAY  SAFETY  APPLIANCES. 

Bt  Me.  F.  J.  BRAMWELL,  C.  E.,  F.  R.  S. 
From  "Iron." 


The  total  number  of  deaths  to  railway 
passengers  from  causes  beyond  their 
own  control  for  the  four  years  1870  to 
1873,  both  inclusive,  amount  to  142,  or 
an  average  of  35j  per  annum,  and  the 
accidents  which  caused  these  deaths 
may  be  divided  into  seven  heads,  and 
more  than  half — viz.,  as  much  as  58.7 
per  cent,  of  those  accidents — are  due  to 
collision,  while  12  per  cent,  are  due  to 
the  trains  being  turned  into  the  wrong 
lines  or  being  "  split,"  and  about  9  per 
cent,  are  due  to  trains  leaving  the  rails, 
another  9  per  cent,  to  defects  in  the 
rolling  stock,  including  boiler  explosions, 
fractures  of  axles  and  tires,  and  matters 
of  that  kind,  and  about  4£  per  cent, 
each  to  accidents  arising  from  trains 
breaking  away  on  inclines  and  to  mis- 
cellaneous causes,  while  not  quite  2  per 
cent,  are  due  to  trains  entering  stations 
at  too  high  a  speed. 

The  first  of  these  relate  to  railway 
wheel  tires.  A  railway  wheel  (in  Europe) 
is  commonly  made  with  a  frame  or  skele- 
ton either  entirely  of  wrought  iron,  or 
occasionally  with  wrought-iron  spokes 
and  rim,  but  with  a  cast  iron  boss,  and 
is  tired  by  a  wrought  iron  or  steel  tire. 
With  respect  to  the  tire,  the  common 
mode  of  manufacture  a  few  years  ago 
was  to  make  a  straight  tire  bar,  then  to 
bend  it  into  a  hoop,  then  to  weld  the 
ends    of   the   bar   together    (and    great 


pains  were  taken  to  devise  a  good  form 
of  weld),  and  then  the  tire  being  heated 
was  shrunk  upon  the  wheel.  But  after 
all  has  been  done  that  can  be  done,  a 
weld  is  still,  it  is  to  be  regretted,  a  mat- 
ter of  uncertainty.  Many  accidents 
arose  from  the  fracture  of  tires  at  the 
welds  and  then  the  engineer  devised  a 
safety  appliance.  But  of  late  years  the 
engineer  has  turned  his  attention  to 
getting  rid  of  the  weld  altogether,  and 
this  he  effects  by  making  the  tire  no 
longer  in  the  form  of  a  straight  bar 
requiring  bending  and  subsequent 
welding,  but  he  makes  it  at  once  in 
the  form  of  a  hoop  in  the  condition 
known  as  a  weldless  tire.  A  weld- 
ed tire  is  now  as  rarely  to  be  met  with 
as  ten  years  ago  it  was  unusual  to 
meet  with  a  weldless  tire  ;  but  although 
this  improvement  in  the  manufacture  of 
the  tire  itself  has  done  away  with  the 
great  source  of  danger  (the  weld),  there 
still  remains  the  risk  of  fracturing  the 
solid  metal,  and  therefore  the  safety- 
ring  is  most  properly  retained  even  with 
weldless  tires. 

Another  source  of  danger  in  the  roll- 
ing-stock is  the  fracture  of  axles,  either 
those  of  the  engines  or  of  the  passenger 
carriages.  These  fractures  most  com- 
monly occur  at  places  where  there  is  a 
change  of  dimensions.  Railway  engi- 
neers were  among  the  first  to  discover 


RAILWAY   SAFETY   APPLIANCES. 


507 


that  the  providing  of  adequate  size  was 
not  sufficient  to  ensure  the  durability  of 
axles  and  of  parts  subjected  to  similar 
strains,  and  that  indeed  harm  might 
actually  be  done  by  increase  of  dimen- 
sions ;  for  that  the  neighborhood  of  a 
large  part  to  a  small  one  not  merely 
made  the  smaller  section  relatively 
weaker  than  the  larger,  but  it  made  it 
actually  weaker  than  if  the  larger  one 
were  not  there  ;  and  the  railway  engi- 
neer found  that  the  only  way  to  ensure 
safety  was  to  prevent  abrupt  change  in 
form,  and  having  so  found  he  applied 
this  safety  precaution. 

Under  the  head  of  accidents  to  rolling- 
stock  comes  the  explosion  of  locomotive 
boilers.  The  explosions  of  locomotive 
boilers  have  a  certain  peculiarity  which 
demand  notice,  but  time  will  not  permit 
me  to  enter  upon  so  wide  a  subject ;  to 
show  you,  however,  the  care  taken  by 
the  engineer  to  prevent  such  accidents, 
I  may  tell  you  what  is  done  at  the  Crewe 
works  of  the  London  and  North-West- 
ern Railway  to  insure  soundness  in  their 
steel  boiler  plates.  In  the  first  place  the 
steel  made  in  large  masses  by  fusion  pro- 
cesses, either  those  of  Dr.  Siemens  or  of 
Mr.  Bessemer,  is  proportioned  so  that  it 
shall  not  have  more  than  two-tenths  of 
1  per  cent,  of  carbon.  Such  a  percent- 
age should,  with  pure  materials  give  a 
perfectly  homogeneous  flexible  ductile 
metal  ;  and  to  ascertain  whether  this 
has  been  obtained  the  plates  are  anneal- 
ed, and  then  they  must  be  capable  of 
being  bent  cold  without  the  slighest  sign 
of  fracture  ;  and  any  piece  of  the  plate 
must  be  competent  to  stand  a  "  punch- 
ing" test — that  is,  a  hole  of  five-eighths 
of  an  inch  diameter  being  drilled  in  the 
plate.  A  succession  of  tapered  punches 
are  driven  in  until  the  hole  is  enlarged 
to  l£  inch,  or  as  much  as  six  times  its 
original  area,  and  this  without  any  frac- 
ture of  the  plate  whatever.  Similarly 
steel  for  axles,  for  tires,  and  for  rails  is 
tested.  To  such  perfection  has  the  manu- 
facture now  attained  that  out  of  500  sets 
of  boiler  plates  of  comparatively  modern 
manufacture  at  Crewe,  which  have  been 
tested,  only  one  plate  has  yielded  under 
the  test. 

In  England,  happily,  we  have  but  few 
single  lines  of  railway,  and  collisions 
arising  from  the  meeting  of  trains 
coming  in  opposite  directions  are  there- 


fore very  rare.  With  respect  to  those 
collisions  which  occur  from  one  train 
overtaking  another,  until  within  the  last 
few  years  the  appliances  employed  by 
engineers  to  prevent  this  class  of  acci- 
dent consisted  of  a  series  of  signals 
placed  at  stations  and  elsewhere  along 
the  line,  which  were  put  "On"  or  to 
"Danger"  as  each  train  passed,  remain- 
ed at  "  Danger  "  for  a  certain  time,  say 
five  minutes,  and  then  were  put  to 
"  Caution,"  remained  at  "  Caution  "  for 
a  further  time — say  five  minutes — and 
then  were  taken  off,  i.  e.,  were  put  to 
"  Safety"  or  "  All  right."  Of  late  years, 
looking  at  the  great  increase  in  traffic 
and  at  the  varying  paces  at  which  trains- 
run,  such  a  time  system  has  been  con- 
sidered no  longer  satisfactory,  and  the 
engineer  therefore  has  resorted  to  the 
block  system,  which  substitutes  the  ele- 
ment of  distance  for  the  element  of 
time  as  a  measure  of  safety,  and  this 
substitution  he  is  enabled  to  effect  by 
the  aid  of  the  electric  telegraph.  Occa- 
sionally, however,  accidents  do  happen 
even  with  the  use  of  the  block  system. 
A  train  has  been  known  to  break  in 
half,  and  the  first  part  of  the  train 
having  gone  past  the  signal  box,  the 
man  there  has  supposed  it  to  be  the 
whole  train,  and  has  telegraphed  back 
"Line  clear,"  while  in  truth  the  helpless 
piece  of  the  train  was  standing  on  the 
line.  Accidents  have  arisen  in  this  way, 
but  very  rarely,  Again,  men  have  made 
mistakes  in  their  signaling.  Sometimes 
a  man  has  signaled  "  Line  clear,"  before 
the  train  has  passed.  Occasionally  a 
man  who  has  not  received  "  Line  clear," 
acts  as  though  he  had. 

Now,  I  do  not  suppose  the  engineer 
with  all  his  pains  will  ever  be  able  to 
entirely  render  himself  independent  of 
the  due  discharge  of  his  duty  by  the 
signalman,  nor  of  the  care  of  others  who 
are  engaged  in  the  conduct  of  the  busi- 
ness of  railways  ;  but  the  engineer  is 
always  trying  to  improve  his  position  in 
this  respect,  and  with  this  object  he  has 
invented  an  apparatus  which  shall  get 
rid  of  the  danger  arising  from  one  of 
the  two  neglects  of  duty  to  which  I 
have  just  alluded,  namely,  that  a  man 
who  has  not  received  the  "line  clear" 
signal  might  act  as  though  he  had. 
This  particular  safety  appliance  is  of  the 
following  construction  : — When  a  signal- 


508 


van  nostrand's  engineering  magazine. 


man  has  put  his  signal  to  "  Danger "  it 
is  locked,  and  that  lock  the  signalman 
cannot  unlock,  although  he  can  apply  it. 
It  must  be  undone  by  apparatus  worked 
electrically  from  the  signal  cabin  beyond 
him,  and  thus,  until  he  has  received 
"  Line  clear,"  he  cannot  again  put  his 
signal  to  "  Safety."  Efforts  are  now 
being  made  to  further  diminish  the 
chance  of  one  train  overtaking  another 
by  enabling  electrical  communication 
to  be  established  between  any  of  the 
signal  houses  and  the  driver  of  a  train. 
This  is  effected  by  having  isolated  sur- 
faces placed  at  regular  intervals  along 
the  line  with  which  electrical  connection 
is  made  by  means  of  a  metallic  brush 
attached  to  the  engine,  and  coming  in 
contact  with  those  surfaces.  By  this 
means,  although  complete  electrical  com- 
munication for  the  purposes  of  conversa- 
tion is  not  kept  up,  the  directions  "  Stop" 
or  "  Go  on"  can  be  given. 

Although  the  question  of  brakes  does 
riot  belong  particularly  to  the  class  of 
collisions  we  are  now  considering,  yet 
brakes  have  to  be  discussed  in  connection 
with  our  subject.  The  improvements 
that  are  in  use  here  all  operate  by  apply- 
ing friction  to  the  wheels,  but  apply 
that  friction  to  a  large  number  of  the 
wheels  instead  of  only  to  a  few,  and 
many  of  the  contrivances  are  made  so  as 
to  put  on  the  pressure  promptly.  Al- 
though it  is  probably  well  to  be  provided 
with  a  maximum  power  of  stopping 
trains,  such  a  power  is  not  an  unmixed 
advantage.  In  the  first  place,  although 
the  theory  is  that  the  brake  shall  be  so 
applied  as  to  let  the  wheels  slowly  re- 
volve, in  practice  the  wheels  are  abso- 
lutely stopped  ;  they  then  rub  along  the 
rails,  flat  places  are  worn  in  the  wheels, 
and  the  comfort  of  traveling  is  destroy- 
ed by  the  disagreeable  jolting  of  the 
carriages,  a  jolting  not  felt  when  the 
brakes  are  applied  to  brake-vans  and 
tenders  only.  Moreover,  the  rails  suffer 
from  the  action  upon  them  of  these 
polygonal  wheels.  Further,  in  certain 
cases  there  can  be  no  doubt  that  the 
rapid  application  of  powerful  brakes  has 
been  the  means  of  destroying  life  in- 
stead of  saving  it.  The  greatest  possi- 
ble brake  power  would  be  an  unalloyed 
advantage  if  it  were  under  the  control  of 
a  man  who  knew  the  exact  nature  of  the 
accident  that  was  happening,  and  who 


had  ample  time  to  reflect  as  to  the  best 
means  of  using  the  power  at  his  com- 
mand ;  but  as,  unhappily,  these  are  not 
the  conditions  which  commonly  attend 
railway  accidents,  it  is  to  be  feared  that 
large  brake  power,  while  most  useful  in 
averting  collisions,  will  be  in  many  cases 
a  cause  of  danger  when  the  accident  is 
one  that  arises  in  the  train  itself. 

I  now  come  to  the  railway  safety  ap- 
pliances which  have  been  devised  for 
preventing  collisions  at  junctions  ;  simi- 
lar appliances  are  also  used  for  the 
avoiding  of  collisions  where  railways 
cross  one  another  on  a  level,  and  indeed 
where  railways  cross  common  roads  on 
a  level,  or  cross  rivers  or  canals  by 
means  of  movable  bridges. 

I  now  wish  to  remind  you  that  the 
railway  locomotive  is  peculiar  in  respect 
of  the  inability  of  the  persons  in  charge 
to  guide  it.  They  may  vary  its  pace, 
they  may  bring  it  to  a  dead  stop,  or 
may  reverse  its  motion,  but  they  cannot, 
guide  it.  In  this  respect  their  powers 
compare  unfavorably  with  those  of  the 
riders  of  horses,  the  drivers  of  horse- 
coaches,  the  drivers  of  common  road 
locomotives,  of  traction  engines,  and  of 
steam  road  rollers,  and  with  the  steers- 
men of  ships  ;  the  only  persons  in  charge 
of  a  moving  machine  who  were  in  a 
similarly  helpless  condition  were  those 
who  navigated  balloons  ;  but,  according 
to  an  able  article  in  the  last  Quarterly 
lievieio,  the  balloon  is  to  become  "  diri- 
gible." But  whether  balloons  ai'e  to  be 
really  made  "  dirigible  "  or  not,  the  loco- 
motive driver  will  still  have  to  depend 
upon  others  for  the  guidance  of  his  loco- 
motive, and  this  guidance  is  commonly 
effected  by  means  of  a  pair  of  moving 
points,  and  these  points,  according  to 
the  position  in  which  they  are  set,  either 
cause  the  train  to  preserve  its  direction 
along  the  main  line,  or  force  it  to  di- 
verge down  the  branch.  The  points 
being  then  the  real  implements  which 
control  the  direction  of  the  train,  one 
sees  of  what  pai'amount  importance  it  is 
that  the  positions  of  these  implements 
should  faithfully  accord  with  the  signals. 
In  truth,  the  principal  function  of  these 
latter  is  to  communicate  to  the  driver 
through  the  eye  the  position  of  the 
points  ;  and  if  this  accord  be  not  assured, 
it  is  obvious  that,  although  the  signals 
exhibited  might  not  be  conflicting  among 


LIME   IN    THE    BLAST   FURNACE. 


509 


themselves,  their  exhibition  might  lead 
to  most  disastrous  results. 

I  come  next  to  safety  appliances  which 
are  used  to  prevent  the  "  splitting "  of 
trains  at  junctions.  Force  of  habit  has 
undoubtedly  on  more  than  one  occasion 
caused  an  unhappy  signalman  to  put  his 
signal  to  danger  to  protect  a  train  as 
soon  as  ever  the  engine  has  passed  his 
box,  and  has  caused  him  to  follow  that 
operation  by  the  pulling  of  the  next 
lever,  whereby  he  has  moved  the  points 
and  split  the  train.  And  to  guard 
against  this  source  of  danger  some  rail- 
way companies  issued  orders  that  a 
signal  was  not  to  be  put  to  danger  until 
the  whole  train  had  gone  by  ;  but  the 
risk  still  remained,  and  again  the  engi- 
neer was  at  hand  with  a  safety  appli- 
ance. 

With  this  it  is  utterly  impossible  for  a 
signalman  even  to  unlock  the  points,  but 
until  unlocked  they  cannot  be  shifted, 
and  in  this  manner  the  danger  of  split- 
ting a  train  is  for  ever  at  an  end.  The 
safety-bar  and  the  locking  of  facing 
points  have  a  far  higher  importance  than 
the  mere  prevention  of  the  splitting  of 
trains  at  junctions,  because  they  have 
done  away  with  the  danger  of  the  points 
not  being  entirely  home,  and  of  their 
being  disturbed  by  vibration  and  causes 
of  that  kind,  and  they  have  therefore 
made  properly  constructed  facing  points 
safe,  to  be  run  through  at  speed  for  the 


main  or  straight  line.  This  being  so,  the 
engineer  no  longer  fears  to  employ  fac- 
ing-points, and  the  ability  to  so  use  them 
at  will  may  be  made  to  greatly  increase 
the  carrying  power  of  a  railway. 

I  may  be,  perhaps,  accused  of  repre- 
senting everything  connected  with  rail- 
way management  as  being  in  an  abso- 
lutely satisfactory  condition,  and  as 
being  incapable  of  beneficial  change. 
Let  me  say  that  this  is  by  no  means  the 
position  I  am  taking  up.  I  am  here, 
as  I  told  you,  to  vindicate  the  engineer, 
not  railway  management,  and  unhappily, 
from  mistaken  policy,  or  from  need,  or 
from  motives  of  false  economy  where 
need  does  not  exist,  the  counsels  of  the 
engineer  are  not  in  all  instances  allowed 
to  prevail,  and  thus  it  is  we  see  certain 
railways  neglecting  their  duties  towards 
the  public  by  not  readily  adopting  safety 
appliances.  With  such  neglect  accidents 
ensue  ;  and  the  public  not  having  the 
means  of  discriminating  between  those 
companies  which  do  take  proper  pre- 
cautions and  those  which  do  not,  blame 
the  whole  railway  system  and  visit  also 
the  engineer  with  censure.  This  should 
not  be  ;  we  should  discriminate  ;  and  if 
we  did  we  should  acknowledge,  I  think 
with  thankfulness,  the '  care  and  pains 
which  are  taken  by  these  who  adopt  all 
known  means  of  safety  to  carry  on  a 
large  traffic  without  injury  to  their  cus- 
tomers. 


LIME  IN  THE  BLAST  FURNACE.* 

By  Mr.  I.  LOWTHIAN  BELL,  M.  P.,  F.  R.  S. 
From  "Engineering." 


In  a  furnace  about  48  ft.  in  height, 
the  carbonic  oxyde  generated  by  the 
combustion  of  the  coke  at  the  tuyeres, 
arrives  at  the  throat  so  speedily  that  it, 
with  the  accompanying  gases,  leaves  the 
orifice  of  the  structure  at  a  comparative- 
ly high  temperature.  The  solid  contents 
filling  the  furnace,  as  a  consequence,  are, 
within  a  few  feet  of  the  charging  plates, 
in  a  state  of  bright  incandescence. 

When  limestone,  in  its  natural  state, 
is  used  as  a  flux,  it  quickly  reaches,  in 


*  Paper  read  before  the  Iron  and  Steel  Institute  at  Man- 
chester. 


such  a  furnace,  a  zone  where  the  heat  is 
sufficient  to  separate  the  carbonic  acid 
from  its  calcareous  base.  The  tempera- 
ture of  this  region,  indeed,  is  so  intense, 
that  not  only  the  carbonic  acid  associat- 
ed with  the  lime,  but  a  portion  of  that 
due  to  the  deoxydation  and  carbon  im- 
pregnation of  the  ore,  is  reduced  to  the 
form  of  carbonic  oxyde. 

I  have  shown,  on  a  former  occasion,  that 
the  smelting  of  a  ton  of  iron  is  probably 
accompanied  by  the  conversion  of  6.58 
cwt.  of  carbon  from  the  state  of  carbonic 
oxyde  to  that    of    carbonic    acid.     The 


510 


VAN   NOSTRAND'S   ENGINEERING  MAGAZINE. 


carbon  in  its  acidified  form  in  the  quan- 
tity of  limestone  consumed,  upon  one 
occasion,  in  a  48  ft.  furnace  was  1.92  cwt. 
Hence,  we  may  infer  that,  were  there  no 
reduction  of  carbonic  acid  to  a  lower 
condition  of  oxydation,  we  ought  to  find, 
for  each  ton  of  iron  produced,  8.50  cwt. 
of  carbon,  combined  with  its  maximum 
dose  of  oxygen. 

Instead  of  this  quantity,  only  5.47 
cwt.  of  carbon  so  oxydized  was  found  in 
the  escaping  gases  of  one  of  the  smaller 
furnaces  referred  to,  per  ton  of  iron  of 
its  make. 

This  change  in  the  composition  of  the 
escaping  gases  of  a  blast  furnace  involves 
more  serious  consequences  than  what,  per- 
haps, at  first  sight  might  appear. 

cwt.  units. 

There  is  the  heat  absorbed  by 
splitting  up  carbonic  acid  con- 
taining (8.50-5.47)  3.03  cwt. 
of  carbon 9,696 

The  decomposition  of  this  car- 
bonic acid  carries  off  the  same 
weight  of  carbon  which  it 
contains,  and  which  escapes 
combustion  at  the  tuyeres,  in- 
volving a  further  loss  of 7,272 

16,968 
To  whieh  has  to  be  added  the 
heat  required  for    expelling 
the  carbonic  acid  from  16  cwt. 
of  limestone, 5,920 


22,888 


The  coke  consumed  upon  the  occasion 
which  furnished  these  data  amounted  to 
28.92  cwt.  per  ton  of  iron,  and  the  heat 
estimated  to  be  afforded  by  its  combus- 
tion, using  air  heated  to  452  deg.  C.  (846 
F.),  was  104,012  units.  The  proportion, 
therefore,  of  the  total  heat  generated, 
which  was  absorbed  by  the  expulsion  of 
carbonic  acid  from  the  limestone,  and 
the  decomposition  of  this  compound  of 
oxygen  and  carbon  amounted  to  22  per 
cent.  Of  this,  16  per  cent,  is  due  to  the 
use  of  limestone,  and  6  to  the  dissocia- 
tion of  the  carbonic  acid,  produced  by 
the  reduction  and  carbon  impregnation 
of  the  ore. 

An  expenditure  of  16  per  cent,  of  the 
heating  power  of  the  fuel,  which  is  ren- 
dered necessary  by  the  presence  of  one 
of  the  constituent  parts  of  our  flux,  af- 
fords prima  facie  a  strong  reason  why 
we  should  seek  to  relieve  the  furnace  of 
&  duty  represented  by  about  4£  cwt.  of 


coke,  particularly  as  half  this  weight  of 
inexpensive  small  coal  sufficed  for  the 
purposes  of  the  lime  kiln. 

I  am  not  aware  that  the  experience  of 
any  iron  smelter  justifies  the  belief  that 
any  approach  to  this  economy  was  ever 
realized  by  the  substitution  of  lime  for 
limestone.  On  referring  to  the  Clarence 
furnace  books,  I  find,  when  using  the 
same  quality  of  coke  in  each  case,  one  of 
the  smaller  furnaces  (48  ft.)  gave  the 
following  results  : 

14  Days' 

make 

per  Mine 

Fur- Aver-  Coke  Yielded, 

nace  age  per  ton   per 

tons.  No.  cwt.     cent.  cwt. 

419    3.34  29.06    41.9  Limestone  per  ton  14.53 

444    2.20  39.64    42.6  Burnt  lime      "      11.14 

Other  examples  from  furnaces  of  simi- 
lar dimensions  gave  the  following  aver- 
ages : 

14  Days' 

make  Yield 

per  per 

Fur-Aver-  Coke  Mine, 

nace  age  per  ton  per 

tons.  No.  cwt.     cent.  cwt. 

404    2.65  29.31    42.0  Limestone  per  ton  15.89 

451    2.10  27.99    42. 6  Burnt  lime      "      11.46 

In  the  first  two  cases  given,  the  con- 
sumption of  fuel  is  practically  the  same, 
but  the  produce  of  the  ironstone  (Cleve- 
land), when  smelted  with  calcined  lime- 
stone, is  somewhat  better.  Discarding 
this  cause  of  difference,  the  sole  advant- 
age from  the  use  of  lime  is  the  increased 
make  and  superior  quality  of  the  iron. 
In  the  next  two  examples,  an  improve- 
ment in  production  and  grade  of  metal 
is  also  observable,  along  with  an  economy 
of  1.32  cwts.  of  coke,  part  of  which  is 
probably  due  to  the  better  yield  from 
the  ironstone  (Cleveland),  as  well  as  to 
a  somewhat  superior  quality  of  coke  re- 
ceived at  the  works,  when  calcined  lime- 
stone was  being  used.  In  none  of  these 
instances,  judging  by  the  relative  quan- 
tities of  burnt  and  raw  limestone  em- 
ployed, has  one  half  of  its  carbonic  acid 
been  expelled. 

The  apparent  want  of  reconciliation 
between  theory  and  practice  in  the  con- 
sumption of  fuel,  when  using  the  flux 
raw  or  calcined,  is,  in  my  judgment,  in 
a  great  measure  independent  of  the  im- 
perfect expulsion  of  carbonic  acid  from 


LIME  IN  THE  BLAST  FURNACE. 


511 


the  latter  ;  and  further,  I  am  of  opinion 
that  a  complete  separation  of  this  ele- 
ment would  fail  to  effect  in  a  larger  fur- 
nace, any  appreciable  good  in  respect  to 
the  coke  required  for  the  process. 

Omitting  the  somewhat  questionable 
economy  of  fuel  exhibited  by  the  figures 
given  above,  it  is  not  surprising  that  a 
furnace  48  ft.  high,  and  containing  6,000 
cubic  feet,  should,  with  a  make  of  200 
tons  to  210  tons  per  week,  be  capable  of 
doing  some  additional  duty  when  reliev- 
ed of  that  portion  of  its  work  represent- 
ed by  calcining  the  limestone.  In  like 
manner,  where  a  furnace  80  ft.  high,  and 
containing  15,000  cubic  feet,  only  runs 
350  tons  a  week,  and  is,  therefore,  com- 
pared with  the  former,  far  above  its 
work,  any  such  relief  as  that  in  question 
may  be  regarded  as  unnecessary. 

The  objects  of  this  communication  are 
to  show  that  this  supposition  is  substan- 
tially correct,  and  to  endeavor  to  recon- 
cile the  apparent  difference  between 
theory  and  practice  just  referred  to. 

For  the  purpose  in  question,  two  of 
the  Clarence  furnaces,  Nos.  9  and  10, 
having  a  height  of  80  ft.,  and  a  capacity 
of  20,500  cubic  feet,  were  chosen.  They 
were  blown  in  about  twelve  months  ago, 
and  were  working  under  precisely  the 
same  conditions.  No.  9  was  supplied 
with  raw,  and  the  other  with  calcined 
limestone,  and  after  a  few  weeks  this 
order  was  reversed — No.  10  was  put  on 
raw,  and  No.  9  on  calcined. 

The  consumption  of  limestone  per  ton 
of  iron,  was  almost  exactly  11  cwt., 
which,  allowing  5  per  cent,  of  foreign 
matter,  would  represent  5.85  cwt.  of  pure 
lime,  or  6.16  cwt.,  including  impurity, 
had  all  the  carbonic  acid  been  expelled. 
By  the  time,  however,  that  the  calcined 
flux  was  reduced  to  8  cwt.,  the  appear- 
ance of  the  cinder  indicated  a  similarity 
of  composition.  This  was  equivalent,  if 
correct,  to  an  admission  that  the  lime 
still  retained  about  one-half  of  its  car- 
bonic acid,  the  truth  of  which  was  prov- 
ed by  an  analysis  of  the  cinder  itself. 

Raw  Calcined 
Lime-    Lime- 
Composition  of  Cinder — using,  stone,  stone. 

Silica 30.84  30.64 

Alumina 25.71  25.45 

Lime 30.85  31.17 

Magnesia 6.92  7.22 

Protoxydeof  iron 23  .06 


Protoxyde  of  manganese...        .26  .28 

Potash 28  .30 

Soda 1.02  1.20 

Phosphoric  acid 34  .44 

Sulphide  of  calcium 4.09  4.52 

100.54    101.28 

Parenthetically  it  may  be  observed, 
that  no  change  was  effected  in  removing 
silicon  or  sulphur  by  the  substitution  of 
calcined  for  raw  limestone,  a  sample  of 
No.  3  iron  from  each  giving  the  follow- 
ing results  : 

Using  Raw     Using 
Limestone.  Calcined. 

Silicon  per  cent 1.91  1.91 

Sulphur  per  cent 038  .033 

With  regard  to  the  main  object  of  the 
experiment,  viz.,  the  consumption  of 
fuel,  there  was  literally  not  the  slightest 
advantage  in  the  use  of  the  flux  from 
which  half  of  its  carbonic  acid  had 
been  expelled.  In  each  case,  the  burden 
of  mine  (Cleveland),  on  a  given  weight 
of  coke,  remained  unaltered,  without 
any  improvement  in  quality  manifesting 
itself,  nor  was  there  any  tendency  to  an 
increased  rate  of  driving.  The  make 
was  in  each  case  61  tons  to  62^  tons  per 
24  hours,  the  quality  averaged  about 
3.75,  and  the  coke  a  trifle  under  22  cwt. 
per  ton  of  iron. 

Applying  the  same  mode  of  computa- 
tion employed  at  the  commencement  of 
this  paper,  the  separation  and  decomposi- 
tion of  half  the  carbonic  acid  in  11  cwts. 
of  limestone,  is  equal  to  about  5,550 
units  per  ton  of  iron,  the  necessity  for 
which  was  avoided  by  the  previous  cal- 
cination of  the  flux.  To  this  must  be 
added  1,950  units,  as  the  heat  which  will 
be  evolved  by  the  lime  reuniting  with 
carbonic  acid  in  the  furnace,  which,  for 
the  present,  we  will  assume  to  happen. 
We  have  thus  7,500  units  of  heat  at  our 
disposal,  which,  at  the  usual  condition 
of  oxydation  of  the  gases  in  an  80  ft. 
furnace  using  limestone  and  driven  with 
air  at  485  deg.  C.  (905  deg.  F.)  represents 
about  1.79,  say  If  cwt.  of  coke. 

I  propose  to  endeavor  to  explain  the 
cause  of  the  disappearance  of  these 
7,500  units,  and  the  consequent  non-ef- 
fect of  their  representative  If  cwt.  of 
fuel. 

In  round  numbers,  calcined  Cleveland 
stone,  in  an  atmosphere  of  carbonic 
oxyde,  may  be  considered  as  commenc- 


512 


VAN  nostrand's  engineering  magazine. 


ing  to  lose  its  oxygen  gas,  or  in  other 
words,  to  suffer  reduction  when  it  is 
heated  to  a  temperature  of  200  deg.  to 
210  deg.  C,  say,  400  deg.  F. 

Metallic  iron  and  carbonic  acid,  with 
some  precipitated  carbon,  are  the  pro- 
ducts of  this  action  ;  but  if  the  tempera- 
ture is  raised  from  400  deg.  to  about  800 
deg.  F.,  then  the  carbonic  acid,  formed 
by  the  reduction  of  the  ore,  commences 
to  reoxydize  the  metallic  iron  formed  at 
the  lower  temperature,  and  this  prone- 
ness  to  oxydation  by  carbonic  acid  in- 
creases rapidly  as  the  temperature  is 
raised.  Thus,  if  a  mixture  of  carbonic 
oxyde  and  carbonic  acid  in  equal  volumes 
is  passed  over  calcined  Cleveland  ore  at 
a  bright  red  heat,  the  latter  cannot  be 
deprived  of  more  than  one-third  of  its 
oxygen  ;  and  in  like  manner,  if  spongy 
metallic  iron  be  similarly  treated,  it  ab- 
sorbs from  the  carbonic  acid  as  much 
oxygen-  as  remains  combined  with  the 
metal  contained  in  the  ore,  i.  e.,  two- 
thirds  of  that  required  to  constitute  per- 
oxyde  of  iron. 

From  the  physical  laws  involved  in 
the  facts  as  just  enumerated  may  be  in- 
ferred : 

1.  That  there  is  a  point  in  which  car- 
bonic acid  will  render  complete  reduction 
of  an  oxyde  of  iron  by  carbonic  oxyde 
impossible. 

2.  That  this  point  varies  with  the  tem- 
perature, i:  e.,  the  reducing  power  of 
carbonic  oxyde  is  lessened  by  the  oxy- 
dizing  power  of  carbonic  acid  rising  as 
the  temperature  increases. 

Now,  my  inquiries  on  this  very  im- 
portant question  connected  with  the  ac- 
tion of  the  blast  furnace  have  led  me  to 
infer  that  the  gases  from  an  80  ft.  fur- 
nace of  say  15,000  cubic  feet,  and  run- 
ning 350  tons  per  week,  are  sattirated 
with  oxygen,  as  far  as  they  can  be,  when 
one-third  of  the  carbon  they  contain  is 
converted  into  carbonic  acid.  The  tem- 
perature of  the  gases  when  cold  iron- 
stone is  used,  will  average  under  the  sup- 
posed conditions  about  300  deg.  C.  (5*72 
deg.  Fahr.). 

By  the  use  of  the  flux,  calcined  as  it 
was  in  the  experiment  we  are  consider- 
ing, 7,500  units  of  heat  per  20  of  iron 
are  practically  added  to  the  contents  of 
the  furnace,  and  the  presence  of  this  heat 
at  once  manifested  itself  by  a  rise  in  the 
temperature  of  the  escaping  gases  which 


corresponds  to  something  like  1,500  of 
the  7,500  units  placed  at  our  disposal. 

I  would  here  observe  that  carbon  as 
well  as  iron,  either  metallic  or  in  its 
lower  stages  of  oxydation,  is  capable  of 
decomposing  carbonic  acid,  and  that  its 
power  in  this  respect  is  also  intensified 
as  the  temperature  is  increased. 

If,  therefore,  where  by  a  change  in  the 
composition  of  the  materials,  an  increase 
of  temperature  in  the  reducing  zone  fol- 
lows as  a  necessary  consequence,  a  larger 
proportion  of  the  carbon  as  carbonic 
oxyde  in  the  gases  may  arise  from  one 
or  two  causes — either  the  oxydizing  in- 
fluence of  the  carbonic  acid  may  be  aug- 
mented by  the  change  of  temperature, 
and  so  require  the  presence  of  a  larger 
quantity  of  carbonic  oxyde  to  effect  re- 
duction, or  the  higher  temperature  may 
enable  the  carbon  to  split  up  more  read- 
ily the  carbonic  acid.  Whichever  of 
these  two"  causes  is  the  correct  one,  the 
result  would  be  the  same,  viz.,  an  un- 
burning,  as  it  were,  of  carbonic  acid, 
which  means  a  large  absorption  of  heat 
and  consequent  waste  of  fuel. 

In  the  case  we  are  considering,  this 
waste  of  fuel  has,  of  course,  been  met 
by  the  additional  heat  generated,  or  not 
required,  as  explained,  by  the  use  of  cal- 
cined limestone,  the  loss  on  the  one  side 
being  balanced  by  the  gain  on  the  other. 

As  a  matter  of  fact,  this  diminution 
of  carbon  existing  as  carbonic  acid  in 
the  gases  is  precisely  what  I  found  took 
place  in  the  furnace  when  calcined  lime- 
stone in  the  experiments  already  describ- 
ed was  employed.  The  analysis  of  the 
gases  will '  require  repeating,  inasmuch 
as  their  ascertained  composition  account- 
ed for  rather  more  loss  than  the  heat 
which  had  been  added  in  the  manner  de- 
scribed. 

There  is,  however,  no  reason  for  delay- 
ing the  communication  of  these  later 
trials  to  the  Institute.  They  extended 
over  a  period  of  six  weeks  at  the  two 
furnaces,  and  the  unmistakable  conclu- 
sion arrived  at  was,  that  the  expense  of 
calcining  the  limestone  was  unaccom- 
panied by  any  advantage  whatever  in  the 
operation. 

I  may  add  that  the  presence  of  caustic 
lime  is  supposed,  by  virtue  of  the  power 
it  possesses  of  absorbing  carbonic  acid, 
to  produce  the  same  effect  as  if  this  acid 
were  introduced  in  the  form  of  carbon- 


LIME   IN   THE   BLAST   FURNACE. 


513 


ate  of  lime.  Now  lime,  in  some  form 
or  other,  exists  in  calcined  Cleveland 
ironstone  to  the  extent  of  from  7  to  8 
per  cent.,  and  magnesia  of  from  4  or  5. 
I  was  therefore  anxious  to  ascertain 
whether  these  earths  were  aide,  in  any- 
high  degree,  to  absorb  carbonic  acid  in 
the  cooler  portions  of  the  furnace,  and, 
in  consequence,  to  cany  it  down  where, 
by  its  reaction  on  carbon,  a  loss  of  coke 
would  ensue.  I  would  remark  that  lime 
and  magnesia  possibly  exist  in  the  native 
Cleveland  ironstone,  chiefly  combined 
with  silica  or  alumina,  or  both  ;  certain 
it  is  that  the  carbonic  acid  in  the  raw 
stone  is  only  about  sufficient  to  form  a 
carbonate  with  the  protoxyde  of  iron 
present. 

Whatever  may  be  the  form  in  which 
lime  exists  in  the  ironstone  in  its  natural 
state,  when  calcined,  a  mere  trace — un- 
der 0.2  percent. — was  washed  out  of  the 
calcined  ore  by  chloride  of  ammonium, 
and  of  this  a  portion  was  probably  soda 
or  potash.  The  ironstone  (calcined),  the 
size  of  mustard  seed,  was  exposed  for 
25  hours,  at  ordinary  temperatures,  to 
cai'bonic  acid.  The  original  ore  contain- 
ed .85  per  cent,  of  this  acid,  and  at  the 
termination  of  the  experiment  it  con- 
tained 1.22  per  cent.  A  second  sample 
was  similarly  treated  in  a  tube  immersed 
in  a  bath  of  melted  zinc,  having  a  tem- 
perature of  probably  800  deg."  to  900 
deg.  Fahr.  The  carbonic  acid  it  con- 
tained at  the  end  of  2^  hours  was  .77 
per  cent.,  after  which  no  change  of 
weight  took  place. 

These  experiments  prove  that  the 
presence  of  lime  and  magnesia,  as  they 
are  found  in  calcined  Cleveland  iron- 
stone, are  inert  so  far  as  any  absorption 
of  carbonic  acid  is  concerned. 

Physically  it  would  be  possible,  by  a 
previous  fusion  of  the  ironstone  with  the 
flux,  to  render  the  lime  of  the  latter  in- 
capable of  absorbing  carbonic  acid  to 
any  extent,  which  acid  would  be  expelled 
by  such  preliminary  treatment.  There 
are,  however,  practical  objections  to 
such  a  course  of  procedure.  Firstly,  in 
a  properly  constructed  blast  furnace,  say 
80  ft.  high,  with  a  capacity  of  15,000  to 
20,000  cubic  feet,  we  have  seen  the  total 
expenditure  of  coke,  entailed  by  the 
presence  of  the  carbonic  acid  of  the 
limestone,  is  only  if  cwts.  There  is, 
therefore,  no  margin  to  meet  any  expense 
Vol.  XIII.— No.  6—33 


which  would  accompany  the  operation 
referred  to.  Besides  this,  the  all 
mechanical  condition  of  the  ironstone 
makes  it  much  less  susceptible  to  the  re- 
ducing influences  of  the  gases  of  the 
blast  furnace. 

I  obtained  the  following  results  from 
specimens  of  Cleveland  ironstone  cal- 
cined to  various  degrees  of  hardness  hut 
broken  from  the  same  lump.  They  were 
exposed  simultaneously  in  the  same  piece 
of  apparatus  during  eight  hours  to  a 
current  of  carbonic  oxyde,  at  a  tempera- 
ture of  nearly  800  deg.  F.  : 

Loss  of  Deposit'd 
original  carbon 
oxygen  per  100 
Specimens  of  Ironstone,  percent,  of  iron. 

Burnt  to  brick  red 56.1        5.6 

Burnt  to  brown,  not  fus- 
ed....'      65.2       21.5 

Burnt    to    dark    purple, 

very  slightly  fused 52.6        x .8 

Partially  fused 30.4        1.5 

Fused 23.9  .51 

Mill  cinder  which,  in  mechanical 
structure,  would  closely  resemble  iron- 
stone fused  with  limestone,  only  lost  1.35 
per  cent,  of  its  oxygen  during  3^-  hours 
exposure  to  a  red  heat.  It  contained  no 
deposited  carbon. 

A  specimen  of  properly  calcined  Cleve- 
land ironstone,  and  a  specimen  of  mill 
cinder  Were  placed  together  during  48 
hours  in  the  escaping  gases  of  a  48  ft. 
furnace.  The  former  lost  52.3  per  cent, 
of  its  oxygen  and  contained  2.42  of  de- 
posited carbon  per  100  of  iron  ;  the  lat- 
ter only  lost  about  16  per  cent,  of  its 
oxygen  and  had  .25  of  deposited  carbon 
per  100  of  iron. 

These  trials  prove  conclusively  that  it  is 
best  to  use  ironstone  burnt  so  as  to  admit 
ready  access  to  the  reducing  gases,  and 
that  if  this  be  not  attended  to,  the  mine 
will  arrive  at  a  point  in  the  furnace 
where  the  carbonic  acid  resulting  from 
its  deoxydation  will  be  split  up  or  un- 
burnt  by  contact  with  highly-heated  car- 
bon, in  the  same  way  as  happens  when 
this  acid  is  supplied  by  the  limestone.    . 


New  Bridge  in  Paris. — The  works 
for  the  new  bridge  joining  the  Boulevard 
St.  Germain,  with  the  He  St.  Louis,  with 
an  extension  to  the  Quai  St.  Paul,  are 
being  pushed  forward  ;  and  it  is  expect- 
ed that  the  bridge  will  be  opened  at  the 
beginning  of  next  winter. 


VAX  nostrand's  engineering  magazine. 


THEORIES  OF  VOUSSOIR  ARCHES. 

By  WM.  CAIN,  A.  M.,  C.  E. 
Written  for  Van  Nostband's  Engineering  Magazine. 


Several  years  ago  the  writer  had  oc- 
casion to  investigate  the  conditions  of 
stability  of  a  segmental  stone  bridge, 
under  every  probable  method  of  loading. 
No  book  in  the  English  language  that 
he  knew  of,  afforded  him  the  means  of 
locating  the  curve  of  pressures  for  an 
unsymmetrical  load  (as  e.  g.  an  engine 
and  train  on  one  side  of  the  bridge),,  or 
of  determining  which  was  the  true  curve 
of  pressures  out  of  the  indefinite  num- 
ber that  could  be  drawn  within  the  arch 
ring. 

Dr.  Hermann  Schemer's  German  treat- 
ise on  the  "Theory  of  Arches "  solved 
the  problem. 

The  writer  presented  this  theory  to 
American  readers  in  the  October  and 
November,  1874,  numbers. of  this  Maga- 
zine, together  with  an  account  of  numer- 
ous experiments  with  wooden  arches,  in 
an  article  entitled  "A  Practical  Theory 
of  Voussoir  Arches."  As  other  theories 
on  this  subject  are  still  being  published 
and  taught,  the  engineering  public  are 
invited  to  consider  what  is  the  true  theory 
of  voussoir  arches  ? 

Some  of  the  points  in  controversy  may 
be  shown,  by  contrasting  Dr.  Schemer's 
theory  with  one  that  has  just  appeared 
in  the  October,  1875,  number  of  this 
Magazine,  by  Prof.  A.  J.  DuBois,  who 
gives  there  an  "Application  of  the 
Graphic  Method  to  the  Arch."  He  states 
that  in  order  that  an  arch  shall  be  stable, 
the  line  of  pressures  must  "lie  within 
the  middle  third  of  the  arch,"  and  "  that 
is  the  true  pressure  curve  which  ap- 
proaches nearest  the  axis,  so  that  the 
pressure  in  the  most  compressed  joint 
edge  is  a  minimum." 

Dr.  Schemer  asserts  that  a  line  of 
pr(  ssures  may  pass,  and  generally  does 
pass,  outside  the  middle  third  of  the 
arch  ring  and  yet  the  arch  be  perfectly 
stable;  also  that  the  actual  line  of  press- 
ures in  any  arch  is  the  one  consistent 
with  the  minimum  horizontal  thrust. 
As  a  theoretical  proof  of  this  last,  where 
vertical  external  forces  alone  are  con- 
sidered, we  say  that  the  sum  of  the  ver- 
tical components  equals  the  weight  of 


the  arch,  but  that  the  horizontal  thrust, 
which  is  constant  throughout  the  arch 
ring,  is  the  minimum  that  can  obtain 
consistent  with  stability,  for  there  is  no 
need  for  a  further  increase  of  the  hori- 
zontal force  after  it  has  caused  stability. 
To  assert  the  contrary,  would  be  equiva- 
lent to  saying,  that  nature  was  extrava- 
gant with  her  forces.  Why  should  she, 
after  calling  forth  sufficient  horizontal 
resistance  to  insure  stability,  prodigally 
increase  these  molecular  stresses  ?  Where 
would  be  the  limit  to  this  increase  ? 
The  Rev.  Canon  Mosely  is  the  author  of 
the  "  Principle  of  least  Resistance"  or 
"Nature's  Economy  of  Force,''''  and  it  in- 
evitably leads  us  to  Dr.  Schemer's  con- 
clusions ;  enabling  us  to  locate  the  only 
true  and  actual  curve  of  pressures  in  a 
very  simple  and' direct  manner.  Num- 
berless illustrations  are  given  in  the 
article  before  mentioned  by  the  writer, 
and  need  not  be  repeated  here.  "  The 
true  pressure  curve "  is  never  by  this 
rule  found  to  be  that  which  approaches 
nearest  the  axis  ;  all  experiments  are 
against  such  an  assumption. 

As  to  the  usual  statement,  that  a  line 
of  pressures  cannot  pass  outside  the 
middle  third  of  the  arch  ring,  without 
the  arch  tumbling  (a  fallacy  of  Raukine 
and  other  authors),  we  have  only  to  re- 
mark that  experiment  undoubtedly  and 
finally  disproves  it.  The  conditions  of 
stability  for  solid  and  voussoir  arches 
are  not  necessarily  identical.  See  every 
experiment  recorded  in  the  former  ar- 
ticle by  the  writer,  in  which  he  says  in 
concluding  his  remarks  upon  the  experi- 
ments :  "  In  every  case  of  stability  of 
the  arches  previously  given,  it  is  impos- 
sible to  draw  a  line  of  pressures  every- 
where contained  within  the  inner  third 
of  the  arch  ring.  In  fact,  if  such  were 
attempted,  it  would  be  found  in  every 
case,  that  such  a  line  of  pressures  would 
pass  outside  the  base  of  the  piers  or  of 
the  arch  if  used  alone."  If  the  reader 
will  construct  the  line  of  pressures  for 
any  of  the  experimental  arches  given  by 
Mr.  Bland  in  his  "Experimental  Essays 
of    the    Princijjles   of    Construction   in 


COUPLED   LOCOMOTIVES. 


515 


Arches,  Piers,  Buttresses,  &c,"  lie  will 
probably  reach  the  same  conclusion. 

A  theory  to  be  of  any  service  to  a 
practical  man  must  agree  with  experi- 
ment. The  chemist  and  physicist  found 
their  theories  on  facts,  and  revise  them 
in  accordance  with  the  latest  experi- 
ments. The  engineer,  strange  to  say,  is 
not  so  fond  of  experimenting,  but  prefers 
to  assume  a  hypothesis  and  compute  the 
deduction. 

This  easily  accounts  for  many  false 
theories  ;  as  e.  g.,  supposing  half  the 
weight  of  two  inclined  rafters  to  be  act- 
ing at  their  junction  ;  assuming,  where 
a  beam  leans  against  a  wall  that  the 
force  there  is  horizontal ;  assuming  that 
the  true  line  of  pressures  in  an  arch  ap- 
proaches nearest  the  axis,  or  is  otherwise 
than  as  determined  by  the  principle  of 
the  least  resistance,  or  finally  in  assum- 
ing that  if  a  line  of  pressures  pass  out- 
side the  middle  third  of  the  arch  ring, 
there  as  in  a  solid  arch  tensile  resistances 
are  needed,  which,  not  being  supplied  by 
the  voussoir  arch,  insures  its  destruction. 
The  experiments  made  by  the  writer  and 
others  go  to  disprove  positively  these 
hypotheses. 

Again,  many  writers  divide  the  arch 
and  spandrel  into  slices  by  vertical  lines 
of  division  to  get  the  partial  weights 
and  thrusts.  As  the  beds  of  the  ring- 
stones  are  inclined,  except  at  the  crown, 
this  is  evidently  an  incorrect  way  of 
procedure.  The  weight  of  any  number 
of  ring  stones  with  their  superincumbent 


load  acting  at  the  centre  of  gravity, 
must  be  combined  with  the  horizontal 
thrust  to  get  the  resultant  on  the  inclin- 
ed bed  joint  of  tin-  lowest  voussoir;  not 
on  any  supposed  vertical  joint.  In  flat 
arches  this  error  may  be  small  ;  in  full 
centre  arches  it  is  appreciable. 

There  are  usually  given  by  writers 
empirical  formulae  lor  the  depth  of  arch 
stones  at  the  crown.  With  a  theory  that 
gives  quick  and  accurate  results  for  uni- 
form or  eccentric  loads,  we  should,  as- 
suming a  depth  at  crown  as  given  by 
practice,  draw  lines  of  pressure  for  every 
variety  of  loading  that  is  usual  and 
whether  the  depth  is  sufficiently  great  ; 
assuming  that  the  lines  of  pressure 
must  not  pass  nearer  the  edges  than  a 
certain  distance,  which  depends  upon 
the  compressibility  of  the  material  used. 
A  series  of  experiments  with  stone  vous- 
soirs  is  probably  the  only  way  in  which 
we  can  hope  to  arrive  at  the  exact  posi- 
tion of  these  limiting  curves  ;  though 
existing  arches  would  lead  us  to  infer 
that  these  curves  are  not  over  one-fifth  the 
depth  of  the  joint  from  the  edge;  still,  as 
bridges  are  subject  to  shocks,  it  would 
seem  that  one-fourth  or  one-third  depth 
of  joint  could  be  assumed  with  safety. 

There  is  scarcely  any  subject  about 
which  so  many  different  theories  havebeen 
from  time  to  time  advanced  as  this  one 
of  arches.  If  experiment  is  to  be  the 
criterion,  which  theory  best  stands  the 
test  ? 


COUPLED  LOCOMOTIVES. 


From  "The  Engineer. 


A  wide  diversity  of  opinion  still  exists 
among  locomotive  superintendents  as  to 
the  relative  merits  of  coupled  and  single 
locomotives.  Keen  discussions  on  the 
subject  were  carried  on  years  ago  in  our 
pages  ;  and  it  would  not  be  difficult  to 
find  a  score  of  combatants  ready  to  enter 
the  lists  again  and  fight  over  this  subject. 
A  very  eminent  locomotive  builder  was 
once  shown  a  very  strange  looking  en- 
gine which  he  was  told  did  very  good 
work.  He  said  he  was  not  surprised  to 
hear  it,   for  "  anything  would  do  for  a 


locomotive."  The  statement  was,  of 
course,  exaggerated  ;  it  was  meant  as  a 
somewhat  bitter  jest,  and  yet  it  was  not 
wholly  untrue.  As  a  matter  of  fact  the 
locomotive  appears  to  possess  an  astound- 
ing power  of  adapting  itself  to  circum- 
stances ;  and  so  long  as  good  material 
and  workmanship  are  present,  the  design 
of  an  engine  appears  to  exert  very  little 
infiuence  on  either  its  economy  or  utility. 
We  hear  it  stated,  of  course,  now  and 
then  that  only  engines  of  a  certain  de- 
sign can  do  a  particular  work,  but  such 


516 


VAX  nostrand's  engineering  magazine. 


assertions  must  always  be  taken  with  a 
grain  of  salt.  Heavy  goods  engines 
with  small  drivers  have  ere  now  been 
beaten  on  their  own  ground  by  express 
passenger  engines  which  have  hauled 
as  great  a  load  at  higher  speed  and 
with  no  excessive  consumption  of  fuel  ; 
and  goods  engines,  on  the  other  hand, 
have  before  now  in  the  hands  of  enter- 
prising drivers  been  on  an  emergency 
made  to  keep  perfect  time  with  express 
trains.  It  is  no  doubt  to  this  wonderful 
power  of  adapting  itself  to  circumstances 
possessed  by  the  locomotive  that  av© 
must  look  for  an  explanation  of  the  fact 
that  so  many  points  of  apparently  vital 
importance  connected  with  its  design 
and  construction  still  remain  entirely 
unsettled,  and  ready  at  any  moment  to 
supply  matter  for  a  warm  dispute  be- 
tween railway  men. 

As  regards  the  question  concerning 
which  this  article  is  written,  it  may  be 
stated  that  little  has  been  done  of  late 
years  to  take  it  out  of  the  region  of  dis- 
cussion based  on  pure  theory.  While  on 
some  lines  the  coupled  engine  grows  in 
favor,  on  others  the  tendency  is  to  re- 
vert to  the  single  engine.  There  is 
scarcely  a  line  in  Great  Britain  in  which 
coupled  passenger  engines  are  not  used 
more  or  less.  But  it  has  been  found  in 
certain  cases  that  single  engines  can  be 
made  to  take  the  place  of  the  coupled 
engines  used  for  years  in  conducting  a 
given  traffic,  and  with  advantage.  There 
is  really  no  inconsistency  in  this  ;  it  is 
well  known  that  single  engines  always 
run  more  freely  and  with  less  internal 
resistance,  if  we  may  use  the  words,  than 
coupled  engines.  On  one  great  line  we 
are  assured  that  the  saving  in  fuel  effect- 
ed by  using  single  instead  of  coupled  en- 
gines amounts  to  approximately  3  lb.  of 
coal  per  mile,  or  to  something  like  10 
per  cent,  of  the  entire  passenger  engine 
coal  bill.  If  this  be  the  case  it  is  not 
wonderful  that  single  engines  have  been 
substituted  with  advantage  for  coupled 
engines.  How  it  is  possible  to  make  the 
substitution  is  easily  explained.  The 
solution  of  the  problem  lies  in  the  fact 
that,  with  steel  rails  and  a  strong  road  it 
is  possible  to  load  a  single  pair  of  wheels 
sufficiently  to  secure  ample  adhesion,  so 
long  as  the  diameter  of  the  wheel  does 
not  get  below  6  ft.  6  in.,  and  the  cylin- 
ders do  not  exceed  17  by  24.     Steel  rails 


have  enabled  us  to  carry  as  much  as  1  6 
tons  with  a  single  pair  of  drivers  ;  ami  a 
very  simple  calculation  will  show  that  in 
the  case  of  such  an  engine  as  we  have 
named  an  averaged  pressure  of  at  least 
60  lb.  on  the  square  inch  throughout  the 
whole  stroke  would  be  required  to  make 
the  wheels  slip  if  the  adhesion  was  but 
one-sixth  of  the  insistant  weight.  It 
may  be  argued  that  one-sixth  is  not 
enough.  The  answer  lies  in  the  fact  that 
it  is  found  to  suffice,  and  a  great  many 
locomotives  are  now  running  most  suc- 
cessf  uly  which  ought  to  slip  their  wheels 
whenever  the  average  effective  cylinder 
pressure  exceeds  60  lb.  on  the  square 
inch,  and  we  are  led  to  the  conclusion 
either  that  the  pressure  does  not  exceed 
this,  or  that  the  coefficient  of  adhesion 
is  much  greater  than  one-sixth,  for  the 
engines  never  slip  enough  to  prevent 
them  from  keeping  time  with  very  heavy 
trains.  It  is  worth  considering  again 
whether  coupling  an  engine  confers  all 
the  benefits  usually  supposed  to  result 
from  the  practice.  When  rails  are  really 
in  bad  condition  four  wheels  seem  to 
possess  no  more  adhesion  than  two,  and 
we  are  disposed  to  regard  the  coupling 
of  passenger  engines,  properly  so  called, 
as  of  very  little  real  advantage.  The 
conditions  under  Avhich  coupling  is  and 
is  not  necessary  may  be  very  easily  de- 
fined. When  the  diameter  of  the  driv- 
ing wheels,  the  load  on  them,  the  capaci- 
ties of  the  cylinders,  and  the  boiler 
power,  are  properly  proportioned  to 
each  other,  a  single  pair  of  drivers  will 
give  all  the  adhesion  requisite  for  even 
heavy  passenger  traffic  in  ordinary 
weather.  The  coupling  of  such  an  en- 
gine would  give  her  a  trifling  advantage 
in  bad  weather — probably  an  advantage 
not  worth  the  extra  consumption  of  coal 
entailed  by  coupling.  This  proposition 
will  not  apply  generally  to  engines  with 
driving  wheels  less  than  6  ft.  6  in.  diam- 
eter. 

When  a  less  diameter  than  this  is 
used,  it  will  be  found  that  with  loads  of 
less  than  16  tons  on  a  single  pair  of 
drivers,  the  engine  will  not  have  ad- 
hesion enough  in  any  weather,  unless 
the  cylinders  are  too  small  and  the  boiler 
pressure  too  low,  and  such  an  engine 
should  be  four-coupled.  When  we  get 
to  driving  wheels  at  and  below  5  ft.  in 
diameter,  with  17  in.  cylinders,  or  there- 


COUPLED    LOCOMOTIVES. 


517 


abouts,  then  the  engine  should  be  coupled 
all  round. 

If  these  propositions  are  accepted  as 
being  approximately  accurate,  then  no 
difficulty  will  be  met  with  in  deciding 
whether  an  engine  ought  or  ought  not 
to  be  coupled.  A  given  diameter  of 
cylinder  may  be  taken  always — within 
reasonable  limits — to  represent  a  given 
weight  of  engine,  available  for  adhesion  ; 
we  may  therefore  dismiss,  in  practice, 
the  size  of  the  cylinder  altogether,  and 
decide  whether  an  engine  should  or 
should  not  be  coupled  by  the  diameter 
of  the  driving  wheels.  Experience  then 
goes  to  show  that  wheels  over  6  ft.  6 
in.  in  diameter  need  never  be  coupled, 
while  wheels  under  5  ft.  6  in.  diameter 
should  always  be  coupled  ;  between  5 
ft.  6  in.  and  6  ft.  6  in.  will  exist  a 
species  of  debatable  land.  It  will  de- 
pend on  various  circumstances  whether 
it  will  be  best  to  couple  or  not  wheels  of 
5  ft.  9  in.,  6  ft.,  or  6  ft.  3  in.  If  the 
road  is  good  and  tolerably  level,  and 
the  climate  dry,  then  coupling  may  bet- 
ter be  dispensed  with  ;  if,  on  the  con- 
trary, the  road  is  bad  and  yielding,  so 
that  the  rail  does  not  stand  well  up  to 
the  driving  wheel,  but  by  deflecting 
tends  to  permit  a  redistribution  of  the 
load,  the  leading  and  trailing  wheels 
taking  more  than  their  due  weight,  and 
*the  climate  wet,  then  coupling  may  be 
resorted  to  with  advantage.  It  must  be 
understood  that  we  have  been  consider- 
ing the  case  only  of  engines  making 
fairly  long  runs,  and  that  we  do  not  re- 
fer -at  all  to  such  exceptional  traffic  as 
that  of  our  metropolitan  railways.  In 
main  line  work  it  is  not  necessary  to  get 
a  train  away  quickly,  and  a  judicious 
driver,  with  the  aid  of  a  little  sand,  will 
easily  get  his  train  into  motion  without 
slipping  whether  his  wheels  are  coupled 
or  not,  always  provided  that  they  are 
not  so  small  that  they  ought  to  be 
coupled. 

We  are  quite  aware  of  the  fact  that 
exception  may  easily  be  taken  to  what 
we  have  advanced,  but  we  believe, 
nevertheless,  that  it  is  in  the  main  con- 
sistent with  the  best  modern  practice. 
An  idea  has  been  floating  about  for  some 
time  that  the  coupling  question  ought  to 
be  settled  by  the  diameters  of  the  driv- 
ing wheels  of  a  locomotive,  and  all  that 
we  have  endeavored  to  do  is  to  put  this 


idea  into  something  like  a  tangible 
shape.  It  may  be  argued  thai  It  is  rash 
to  use  the  diameter  of  a  wheel  as  a 
standard  by  which  to  settle  such  a  ques- 
tion, because  engines  exist  with  wheels 
much  less  than  the  minimum  diameter 
we  have  named  which  do  not  require  to 
be  coupled.  The  answer  is  that  they  do 
not  need  it  because  they  have  small 
cylinder  capacity  in  proportion  to  the 
si'/e  of  the  wheels.  They  are,  in  a  word, 
little  engines  ;  but  such  locomotives  are 
not  used  for  working  main  line  traffic, 
and  it  is  to  such  traffic  and  such  only 
that  we  have  referred.  The  use  of  steel 
rails,  we  may  in  conclusion  point  out, 
has  certainly  reduced  the  necessity  for 
coupling,  by  enabling  locomotive  super- 
intendents to  put  loads  on  their  driving 
wheel,  at  which  an  older  school  of  en- 
gineers would  stand  aghast.  Whether 
in  the  long  run  it  is  better,  for  the  in- 
terests of  share-holders,  to  use  single 
drivers  carrying  these  enormous  loads, 
or  coupled  engines  carrying  much  less, 
we  shall  not  pretend  to  decide,  because 
questions  concerning  the  expense  of 
maintaining  the  road  are  involved,  with 
which  just  at  the  moment  we  have 
nothing  to  do.  We  believe  that  a  single 
engine  properly  proportioned  will  do 
her  work  perfectly,  and  with  less  coal 
and  repairs  than  a  coupled  engine  on  the 
same  job,  so  long  as  the  work  is  not  too 
much  for  a  6  ft.  6  in.  wheel.  Whether 
it  is  or  is  not  judicious  to  attempt  to  run 
fast  passenger  and  express  traffic  with  a 
wheel  much  smaller  than  this  is  a  mat- 
ter on  which  there  is  very  little  differ- 
ence of  opinion.  We  venture  to  think 
that  the  great  majority  of  locomotive 
superintendents  in  Great  Britain  will 
hold  with  us  that  a  much  smaller  wheel 
than  this  is  not  suitable  for  engines 
which  have  to  make  an  average  time 
of  forty-five  miles  an  hour,  or  there- 
abouts. 


The  United  States  Treasury  Depart- 
ment has  just  decided — says  the  Amer- 
ican  Manufacturer — that  the  materials 
of  boiler  bottom,  composed  of  iron,  tin 
and  lead,  similar  to  the  terne  plate  of 
commerce,  loses  its  identity  as  terne 
plate  when  moulded  into  shape  for  use, 
and  is  dutiable  at  thirty-five  per  cent. 
ad  valorem. 


518 


VAN   NOSTRAND'S   ENGINEERING    MAGAZINE. 


THE  CONSTRUCTION  OF  ELLIPSES. 


By  JOHN  H.  GILL,  C.  E. 


Written  for  Van  Nostrand's  Engineering  Magazine. 


In  all  "pocket  books,"  manuals,  and 
instructions  on  Geometrical  Drawing, 
the  Ellipse  fares  badly,  and  its  beautiful 
curve  is  usually  degraded  to  the  oval,  a 
combination  of  circular  arcs,  or  is  made 
to  depend  upon  a  string. 

By  your  leave  I  will  give  some  simple 
directions  for  finding  any  number  of 
points  in  a  given  ellipse,  without  the  use 


of  analytical  formula?,  and  by  which  any 
ellipse  between  its  extremes — aright  line 
and  a  circle — may  be  accurately  drawn, 
or  any  part  thereof,  independently  of  the 
other  parts 

First,  however,  I  will  describe,  by  a 
rough  drawing,  a  simple  machine  I  have 
contrived  for  drawing  ellipses.  It  con- 
sists of  a  frame  A,  A'  (Fig.  1),  and  the 


two  pairs  of  cranks  B  b  and  B'  b\  hav- 
ing grooves  in  them  as  shown,  in  which 


work    sliding  wristpins,   which   may  be 
secured  at  any  point  on  the  cranks  cor- 


THE    CONSTRUCTION    OF   ELLIPSES. 


519 


responding,  in  distance  from  their  cen- 
ters, to  the  semi-major,  and  semi-minor 
axes  of  the  required  ellipse.  Upon  these 
wristpins  work  the  connecting  bars  C 
and  D,  and  these  are  of  such  length 
(EF)  as  to  secure  a  perfect  parallelism 
between  the  two  sets  of  cranks.  C  has 
a  slotted  bar,  H,  at  right  angles  to  C  at 
its  middle  point,  and  L)  is  slotted  in  the 
direction  of  its  length.  A  cross-shaped 
pencil  holder  I,  slides  in  both  these  slots 
simultaneously.  To  use  the  machine, 
the  wristpins  of  C  are  set  on  the  cranks 
B,  B'  (by  a  scale  marked  on  them)  at  a 
distance  from  their  centers  equal  to  the 
semi-major  axis  of  the  proposed  el- 
lipse, and  those  of  D  are  set  on  b,  b'  at 
a  distance  equal  to  its  semi-minor  axis. 
A  pencil  being  placed  in  the  holder,-  and 


gently  pressed  down  by  a  spring  or 
elastic  cord  ;  the  instrument  set  over  a 
sliccl  of  paper,  and  a  revolution  given 
the  cranks,  traces  an  accurate  ellipse. 
The  ratio  of  the  axes  may  be  made  any- 
thingfrona  unityto  infinity.  In  the  first 
case  the  wristpins  of  C  and  D  would  he- 
at equal  distances  from  the  crank  cen- 
ters, and  the  resulting  curve  would  he  a 
circle.  In  the  second  case  one  pair  of 
wristpins  would  he  at  the  crank  centers, 
and  a  right  line  would  he  the  result.  So 
much  for  the  mechanical  method  which 
requires  no  demonstration,  though  the 
following  method  of  geometrical  con- 
struction, of  which  the  mechanical  is  an 
outgrowth,  will  demonstrate  it. 

Draw  through  the  proposed  center.  O, 
(Fig.  2)  of  the  ellipse  two  lines  perpen- 


FlG.    2 


dicular  to  each  other.  Set  off  A  A' 
equal  to  the  major  axis,  and  B  B'  eqmi 
to  the  minor  axis,  and  upon  them  as 
diameters  describe  the  circles  shown. 
Take  any  point  P,  on  the  outer  circle, 
and  draw  the  radius  PO,  cutting  the 
smaller  circle  in  P'.  Through  P  draw 
a  line  parallel  to  BB',  and  through  P' 
draw  a  line  parallel  to  A  A'.  The  point 
of  intersection,  E,  of  these  lines  is  a 
point  of  the  ellipse.  For  PE:P' P"  (or 
EE'):;PO:PO,  which  expresses  the 
relation  between  the  ordinate  of  an  el- 


lipse, and  the  corresponding  ordinate  of 
the  circle  described,  on  its  major  axis. 
Therefore  (Davis  Am.  Geom.  Ellipse, 
Prop.  IV.)  E  is  a  point  in  the  required 
ellipse.  In  the  same  manner  any  num- 
ber of  points  may  be  found. 

Table  for  constructing  any  ellipse  or 
circle,  or  parts  thereof,  whether  the  cen- 
ters or  foci  are  upon  the  paper  or  not  : 

(See  Table  following  page.) 

Example  of  use  of  Table. — Suppose  it 
is  required  to  construct  an  ellipse  whose 


520 


VAN    NOSTRAND  S    ENGINEERING   MAGAZINE. 


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major  axis  is  48,  and  minor  axis  12.    The 
semi-axes  are  24  and  G. 

Under  2  and  a;  are  found  the  abscissas 

1.992,     1.968,     1.930,     1.878,  &c. 

Multiplied  by  10,  we  have  for  20, 

19.92,     19.68,     19.30,     18.78,  &C. 

Under  4  and  £  we  have 

3.984,     3.936,     3.860,     3.756 


Giving  for  24, 

23.904,  23.616,  23,160,  22.536 
which  are  set  off  (Fig.  3)  on  a  line  rep- 


resenting the  major  axis,  from  a  point 
representing  the  center  of  the  ellipse;  or, 
if  this  point  is  not  on  the  paper,  their 
complements  with  respect  to  24  may  be 
taken,  and  these  distances  set  off  in  a 
contrary  direction,  from  the  vertex  of  the 


EXPANSION    OF    SUBSTANCES    ON    SOLIDIFICATION. 


521 


ellipse;  at  the  points  so  found  erect  per- 
pendiculars. Next  under  6  and  under 
y  we  find  .522,  1.038,  1.548,  2.052,  &c, 
as  ordinates,  and  these  are  to  be  set  off 
on  the  corresponding  perpendiculars,  and 
will  give  points  of  the  ellipse. 

For  circles  the  table   is  used  in   the 


same  way,  the  axis  being  equal  the  values 
of  x  and  y  will  be  found  in  adjacent 
columns  under  the  same  bracket. 

The  first  column  on  the  right  gives 
the  angle  which  the  radius  to  the  point, 
represented  by  the  coordinates  on  that 
line,  makes  with  the  major  axis. 


ON   THE   ALLEGED    EXPANSION    IN   VOLUME    OF   VARIOUS 

SUBSTANCES   IN   PASSING   BY  REFRIGERATION  FROM  THE 

STATE  OF  LIQUID  FUSION  TO  THAT  OF  SOLIDIFICATION. 

By  ROBERT  MALLET,  F.  R.  S.,  &c. 
Proceedings  of  the  Royal  Society. 


The  fact  that  water  expands  in  be- 
coming ice,  and  that  the  latter  thus 
floats  upon  the  water,  can  scarcely  have 
escaped  the  observation  or  inference  of 
the  acute  intellects  of  a  remote  antiquity. 
Its  conditions,  when  more  carefully  ex- 
amined in  modern  times,  pointed  out 
the  strange  and,  as  it  has  been  called, 
anomalous  fact  that  water  can  be  cooled 
7°  or  8°  below  its  freezing-point  without 
becoming  solid,  and  that  between  its 
maximum  density  at  about  39°  Fahr. 
and  its  freezing-point  at  32°  Fahr.,  or 
within  the  narrow  range  of  T  Fahr.,  it 
expands  in  the  large  ratio  of  915  :   1000 

Standing  thus  alone  amongst  observed 
phenomena  in  nature,  it  seems  to  have 
suggested  to  many  experimenters  the 
question  whether  other  bodies  when 
liquefied  by  heat  might  not  also  expand 
when  becoming  solid  by  refrigeration. 
I  have  not?  attempted  to  trace  with 
minuteness  the  history  of  past  inquiry 
upon  this  subject,  many  loose  uncertain 
statements  as  to  which  have  for  at  least 
a  century  continued  to  perplex  scientific 
literature.  Reaumur  appears  to  have 
been  the  first  who  gave  currency  to  the 
statement  that  cast  iron,  bismuth,  and 
antimony  all  expand  in  consolidating. 
The  like  fact  has  been  alleged  or  left  to 
b3  inferred  with  respect  to  the  following 
substances  by  the  authorities  named  : 


Silver,  Persoz. 
Copper,  Karsten. 

Mercury    and    Gold,    as   inferred 
Nasmyth  and  Carpenter. 


by 


Iron  and  Furnace- slags,  by  experiment 
of  Heunter  and  Snelus,  as  quoted 
by  Nasmyth  and  Carpenter. 

But  of  this  list  the  only  body,  in  ad- 
dition to  water,  that  really  appears 
proved  to  expand  in  consolidating  is 
bismuth  ;  and  even  this  the  author  can- 
not  affirm  upon  the  basis  of  his  own  ex- 
periments, but  accepts  the  fact,  at  least 
provisionally,  as  true  upon  the  uncon- 
tradicted statements  of  many  chemical 
authors,  and  upon  the  positive  assurance 
which  he  is  permitted  to  mention  by 
Dr.  John  Tyndall  that  he  is  satisfied  of 
its  truth.  With  respect  to  all  the  others. 
it  is  the  object  of  this  communication  to 
show  that  the  evidence  in  support  of  the 
alleged  .fact  of  expansion  by  refrigeration 
is  illusory  and  insufficient,  and  to  offer 
with  respect  to  east  iron,  and  also  with 
respect  to  iron  furnace-slags,  experi- 
mental proof  of  the  untruth  of  the  state- 
ment. 

Certain  connected  but  only  collateral 
facts,  having  regard  to  so-called  anoma- 
lous changes  of  volume  due  to  tempera- 
ture, will  not  be  referred  to  here — such, 
for  example,  as  the  anomalous  expansion 
of  Rose's  fusible  metal,  which  expands 
progressively,  like  other  bodies,  till  it- 
attains  the  temperature  of  111'  :  it  then 
contracts  rapidly  by  added  heat  to  150°, 
when  it  is  densest  (Graham's  "Plenums/ 
vol.  i.,  and  Gmelin's  '  Handbook5),  the 
circumstances  being  here  probably  due 
to  the  successive  segregation  in  the  mass 
of    alloys    differing   from  each  other  in 


522 


van  nostrawd's  engineering  magazine. 


constitution,  dilatability,  and  fusing- 
points.  Or,  again,  the  facts  observed 
with  respect  to  the  expansion  or  contrac- 
tion in  volume  shown  by  certain  salts 
when  crystallizing  from  their  solutions, 
the  whole  of  the  conditions  as  to  which 
have  not  been  as  yet  made  quite  clear. 
The  statement  that  antimony  expands  in 
consolidating,  as  made  by  Reaumur,  has  | 
been  negatived  by  Marx.  The  like 
statement  with  respect  to  silver  and 
copper  appears  to  rest  on  no  better 
foundation  than  the  observation  as 
stated  by  Persoz,  "that  pieces  of  solid 
silver  float,  upon  the  melted  metal, 
showing  that  silver  expands  in  sodidify- 
ing  like  water."  As  to  gold,  there  ap- 
pears no  authority  whatever  for  its  ex- 
pansion on  consolidation.  Air.  Nasmyth 
has  included  it  in  his  catalogue  merely 
on  the  vague  inference  that,  like  silver 
and  copper,  it  "exhibits  surface-con- 
verging currents  in  the  melting-pot  like 
those  depicted  by  him  for  molten  iron," 
which,  as  we  shall  see  further  on,  affords 
no  grounds  for  conclusion  on  the  matter. 
Reaumur's  statement  with  respect  to 
cast  iron  appears  to  have  rested  upon 
nothing. more  than  the  fact  that  he  had 
observed  certain  pieces  of  cold  cast  iron 
to  float  upon  cast  iron  while  in  fusion. 
Until  lately  this  subject  generally  at- 
tracted but  little  attention,  for  it  had 
very  few,  and  these  mere  technical,  ap- 
plications ;  and  to  the  higher  physicist 
they  presented  but  little  interest,  because 
the  loosely  stated  facts,  even  if  accredit- 
ed, did  not  in  the  slightest  degree  tend 
to  elucidate  or  explain  the  remarkable 
and  perhaps  still  isolated  facts  as  to 
water  and  ice.  Accordingly,  with  little 
or  no  examination,  the  statements  given 
for  facts  by  the  older  authorities  have 
been  accepted  and  become  current  from 
book  to  book  of  authors  up  to  the  present 
day,  as  when  Dr.  T.  Thompson  says  of 
cast  iron  that  "it  contracts  considerably 
when  it  comes  into  fusion,"  or  that  of 
Kerl,  that  cast  "  iron  occupies  a  smaller 
space  after  cooling  than  when  in  the 
liquid  state  ;  it  contracts  in  such  a  man- 
ner that,  at  the  commencement  of  its 
solidification,  it  first  expands  so  as  to  be 
able  to  fill  up  the  smallest  depressions 
and  cavities  of  a  mould,  but  after  solidi- 
fying it  contracts" — a  loosely  worded 
statement,  which  in  various  fgrms  may 
be  found  in  a  great  number  of   authors 


upon  metallurgy  and  technology.  So 
likewise  the  statement  often  repeated, 
that  the  value  of  antimony  in  type-metal 
consists  in  its  causing  the  latter  to  ex- 
pand upon  consolidation  and  so  perfectly 
till  the  matrix,  is  presented,  so  far  as  the 
author's  reading  goes,  without  the 
slightest  experimental  proof  of  its  truth, 
and  appears  to  rest  simply  upon  Reau- 
mur's statement  with  respect  to  anti- 
mony itself,  which,  as  already  mentioned, 
has  been  controverted  by  Marx.  This 
subject,  however,  has  now  assumed 
greater  importance,  since  it  has  recently 
been  made  by  Messrs.  Nasmyth  and 
Carpenter  the  foundation  upon  which 
they  rest  their  theory  of  lunar  volcanic 
action,  as  presented  to  us  by  the  surface 
of  our  satellite  ;  and  the  object  of  the 
present  communication  is  to  show  that, 
as  regards  the  two  most  pertinent  of  the 
substances  adduced  by  these  authors, 
viz.  cast  iron  and  iron  furnace-slag,  the 
facts  entirely  fail  in  support  of  their 
theory. 

First,  then,  as  to  cast  iron.  It  is  not 
a  fact  that  all  cast  iron  in  the  solid  state 
will  float  upon  all  cast  iron  in  liquid 
fusion,  though  such  might  be  inferred 
from  the  broad  and  loose  statements  of 
authors.  Even  in  the  limited  form  in 
which  the  statement  is  made  by  Nasmyth 
and  Carpenter— viz.  "that  when  a  mass 
of  solid  cast  iron  is  dropped  into  a  pot 
of  molten  iron  of  identical  quality  the 
solid  is  found  to  float  persistently  upon 
the  molten  metal,  so  persistently  that 
Avhen  it  is  intentionally  thrust  to  the 
bottom  of  the  pot  it  "rises  again  the 
moment  the  submerging  agency  is  with- 
drawn" ('The  Moon^'  p.  21) — is  not  quite 
exact.  * 

It  is  a  fact  that  certain  pieces  of  cast 
iron  in  the  solid  and  cold  state  will  float 
on  certain  descriptions  of  cast  iron  in 
liquid  fusion  ;  but  whether  the  solid 
pieces  shall  float  or  not  float  in  any  given 
case  is  dependent  at  least  upon  the 
following  conditions,  and  probably  upon 
others  not  yet  ascertained  : 

1st.  Upon  the  relative  specific  gravi- 

j  ties  of  the  solid  and   of  the  fused  cast 

iron  both  referred  to  the  temperature  of 

:  the  atmosphere.     Under  the  commercial 

!  name    of   cast   iron   is  comprehended  a 

wide  range  of   compounds  of  iron  with 

1  other,     substances,     which      compounds 

differ  greatly  in  their  physical  as  well  as 


EXPANSION    OF    SUBSTANCES    ON    SOLIDIFICATION. 


523 


their  chemical  qualities,  and  have  a 
range  of  specific  gravity  of  from  nearly 
7.7700  for  the  whitest,  most  rigid,  and 
dense,  down  to  little  more  than  6.300 
for  those  which  are  darkest,  softest,  and 
most  porous.  The  total  dilatation  at 
the  fusing-point  of  the  denser  east  irons 
is  known  to  be  somewhat  greater  than 
that  of  the  less  dense  ;  but  as  the  in- 
crease in  volume  may  not  be  sufficient  to 
equalize  the  specific  gravity  of  a  very 
dense  iron  when  in  fusion  with  that  of 
a  very  light  iron  when  cold,  so  it  is  ob- 
vious that  a  piece,  of  cold  cast  iron 
might  be  so  selected  in  reference  to  its 
specific  gravity,  as  referred  to  that  of 
another  sort  of  cast  iron  in  fusion,  that 
the  former  should  either  sink  or  swim 
upon  the  latter  by  mere  buoyancy,  were 
that  free  to  act  alone. 

2d.  Assuming  the  cold  and  the  molten 
cast  iron  originally  identical  in  quali- 
ties, whether  a  piece  of  the  former  shall 
float  or  not  float  upon  the  latter  depends 
not  only  upon  buoyancy  as  above,  but 
also  upon  the  form  of  the  piece  of  cold 
metal — that  is  to  say,  on  the  relation, 
all  other  things  being  the  same,  that 
subsists  between  its  volume  and  its  sur- 
face. 

3d.  The  force,  whatever  be  its  nature, 
which  keeps  the  piece  of  cold  cast  iron 
floating  is  of  sufficient  energy  to  over- 
come a  considerable  want  of  buoyancy 
in  the  cold  iron  under  certain  conditions, 
so  that  it  may  float  upon  molten  cast 
iron  whose  specific  gravity,  as  such,  is 
much  less  than  that  of  the  colder  iron 
which  floats  upon  it.  Messrs.  Nasmyth 
and  Carpenter  assume,  without  any 
sufficient  proof,  that  solid  cast  iron 
floats  on  liquid  iron  of  the  same  quality 
in  virtue  of  buoyancy  alone,  and  proceed 
to  state  that  "inevitable  inference  from 
this  is  that  in  the  case  of  cast  iron  the 
solid  is  specifically  lighter  than  the  mol- 
ten, and  therefore  that,  in  passing  from 
the  molten  to  the  solid  condition,  this 
substance  undergoes  expansion  in  bulk  " 
('The  Moon,"  pp.  20,  21). 

I  proceed  to  prove  that  this  view  is 
altogether  contrary  to  fact.  The  deter- 
mination of  the  specific  gravity  of  cast 
iron  in  its  molten  condition  is  a  problem 
of  considerable  difficulty,  and  can  only 
be  solved  by  indirect  means  ;  we  cannot 
ascertain  its  specific  gravity  by  any  of 
the    methods    ordinarily  employed,    nor 


can  any  areometric  method  be  used 
any     hydrometer     or    solid    of    known 
specific  gravity  at  common  temperatures, 
when  dipped  into  liquid  cast  iron,  changes 

its   volume    as   well    as    gets    incrusi 
with   adherent  cast   iron  or  it-  oxydes, 
&c.     By   an   indirect    method,    and    by 

operating  upon  a  sufficiently  larg< 
to  eliminate  certain  sources  of  error,  the 
specific  gravity  of  molten  cast  iron  may, 
however,  be  approximately  ascertained 
with  considerable  accuracy.  The  method 
adopted  by  the  author  was  as  folio 
— A  conical  vessel,  was  formed  of 
wrought-iron  plate  by  welding  up  only, 
the  walls  of  the  vessel  being  about  \  in. 
in  thickness.  It  was  perfect!;. 
in  the  inside,  and  the  plane  of  the  lip  of 
the  open  neck  was  carefully  made  paral- 
lel to  the  plane  of  the  base.  Tins  ves- 
sel weighed,  when  empty,  184.75  lbs. 
avoirdupois.  The  orifice  of  the  neck 
being  levelled  as  the  vessel  stood  upon 
the  platform  of  the  weighing-apparatus, 
it  was  filled  up  to  the  exact  level  of  the 
neck  with  water  at  a  temperature  of 
60°.5  Fahr.,  and  again  weighed.  De- 
ducting the  weight  of  the  empty  vessel, 
the  weight  of  its  contents  of  water  was 
found  to  be  94.15  lbs.  avoirdupois. 
From  the  known  volume  and  weight  of 
the  imperial  gallon  of  distilled  water, 
the  capacity  of  the  vessel  was  therefore 
at  60°  Fahr.  =  2605.5  cubic  inches.  As 
a  check  upon  the  results,  both  as  to 
weight  and  capacity,  the  water  was 
measured  into  the  vessel  from  accurate 
glass  standards  of  volume.  The  water 
employed  was  that  from  the  well  at 
Messrs.  Maudslay,  Sons,  and  Field's  En- 
gine Works,  Lambeth,  where  these  ex- 
periments were  conducted,  and  to  whose 
liberality  the  author  owes  the  means 
of  haAdng  performed  them.  The  specific 
gravity  of  this  well-water  did  not  very 
materially  exceed  that  of  distilled  water, 
being  about  1.0004  ;  but  if  we  apply  the 
necessary  correction,  the  weight  of  the 
contents  of  the  iron  vessel  of  distilled 
water  at  60°  Fahr.  is  94.112  lbs.  avoirdu- 
pois. The  vessel  being  emptied,  care- 
fully dried  and  warmed,  and  stood  upon 
a  hard  rammed  bed  of  dry  sand  with 
its  neck  perfectly  level  as  before,  was 
now  filled  perfectly  level  to  the  brim 
with  molten  cast  iron.  As  the  tempera- 
ture of  the  vessel  itself  rapidly  rose  by 
contact  with  the  laro-e  mass  of  molten 


524 


VAN   N08TRAND  S   ENGINEERING    MAGAZINE. 


iron  within  it,  and  by  its  dilatation  bad 
its  capacity  enlarged,  so  tbe  top  surface 
of  the  liquid  cast  iron  within  it  rapidly 
sank,  fresh  additions  of  molten  iron  being 
constantly  made  to  maintain  its  top  sur- 
face level  with  the  brim.     This  was  con- 
tinued until  the  whole  of  the  exterior  of 
the  vessel  was  seen  to  have  arrived  at  a 
clear  yellow  heat,  beyond  which   no  in- 
crease to  its  temperature  took  place.     At 
about  twenty  minutes  after  the  molten 
iron   was   first   poured   into   the  vessel, 
this  point  was  reached,  the  feeding  in  of 
additional  iron  being  discontinued  a  few 
minutes   previously.     The   whole  being 
left  to  cool  for  three  days,  the  vessel  full 
of  the  now  cold  and  solid  cast  iron  was 
again  weighed;  on  deducting,  as  before, 
the   weight   of    the    empty    vessel,    the 
weight  of  the  cast  iron  which  fdled  it 
was  found  to  be  645. 75  lbs.,  which,  with 
certain  corrections  to  be  yet  noticed,  was 
the  weight  of  cast  iron  which,  when  in 
the  molten  state,  was  equal  to  the  capac- 
ity of  the  conical  iron  vessel  in  its  ex- 
panded state  due  to  its  exalted  tempera- 
ture.    We  have  now  to  determine  what 
was  the  capacity  of  the  vessel  in  this  ex- 
panded state.     The  temperature  at  which 
cast  iron  melts  may  be  admitted  as  about 
2400°  Fahr. ;  but    as   iron    tapped  from 
the  cupola  is  always  above  its  melting- 
point,  we  may  admit  that  it  was-  poured 
into  the  vessel  at  2600°  or  2700°  Fahr., 
the  surplus  heat  in  the  cast  iron,  whose 
mass  was  about  four  times  that  of  the 
wrought-iron  vessel  which  contained  it, 
being  given  off   in  the  first  instance  to 
heat   the    latter.     The    temperature    at 
which  wrought  iron  presents  to  the  eye 
a  clear  yellow  visible  in  daylight  may, 
in  accordance  with  the  views    of   most 
physicists,    be    taken    as    between   the 
fusing-points  of  silver  and  of  gold,  or  at 
2000°    Fahr.     The   mean    coefficient    of 
linear  dilatatian  for  1°  Fahr.  of  wrought 
iron  has  been  determined  between   the 
limits    of    zero    and    212c    by    Laplace, 
Smeaton,    Troughton,  and   Dulong,  the 
-average   of   the  four   being   0.00000699 
for  1°  Fahr.;  and  this  is  certainly  below 
the  truth  for  the  whole  range   of  tem- 
perature up  to  fusion,  as  the  rate  of  ex- 
pansion of  all  fusible  bodies  appears  to 
increase  with  the  temperature.    Rinmann 
has  determined  the  linear  dilatation  of  a 
bar  of  wrought  iron,  when  raised  from 
60°  Fahr.  to  a  white  or  welding  heat,  to 


be  zU  of  its  length,  or  .0125  ;  and  taking 
the  total  range  of  temperature  here  at 
2400°,  we  have  a  mean  coefficient  of 
linear  dilatation  =0.0000052  for  1°  Fahr. 
This  is  a  still  smaller  coefficient  than  the 
preceding ;  the  author  has,  however, 
preferred  to  adopt  it  in  order  to  avoid 
any  pretense  to  exaggerate  in  his  own 
favor  the  results  arrived  at.  Applying, 
then,  Rinmann's  coefficient  to  the  dimen- 
sions of  the  cone  at  60°  Fahr.,  and  to 
its  temperature  (2000°  Fahr.)  when  at 
the  maximum,  we  are  enabled  to  deduce 
the  true  capacity  of  the  cone  when  ex- 
panded to  the  utmost  and  filled  with 
molten  iron,  viz.  =2691.77  cubic  inches. 
The  iron  conical  vessel  was  now  cut  off 
by  a  circular  cut  at  the  base  and  another 
up  and  down  the  side  of  the  cone,  and 
separated  from  the  conical  mass  of  iron 
that  had  filled  it  ;  the  interior  surface 
of  the  iron  vessel  was  found  in  several 
places  about  the  lower  part  of  the  cone 
in  perfect  contact  with  that  of  the  cast 
iron  which  had  filled  it  ;  but  in  other 
portions  very  slightly  distant  from  it,  as 
judged  by  the  sound  of  a  hammer  upon 
the  sides  of  the  vessel  before  it  was  cut 
off,  The  cast  iron  was  not  adherent  to 
the  vessel  anywhere.  The  cast  iron  cone 
being  thus  laid  bare,  had  a  V-shaped 
piece  cut  out  of  it  (in  the  "slotting" 
machine),  by  two  planes,  each  passing 
through  the  axis  and  meeting  at  an 
angle  of  about  60°.  The  conical  mass 
proved  perfectly  sound  and  free  from 
cavities  or  blow-holes  anywhere,  except 
very  near  the  summit  or  neck,  where 
there  was  found  to  be  a  hollow  or  cavity 
accidentally  left  during  the  feeding  (as 
above  described).  By  measurement  the 
volume  of  this  cavity  was  found  to  be= 
5.5  cubic  inches  ;  assuming  this  cavity 
filled  with  iron  of  the  same  quality  as 
the  cone,  the  weight  of  the  latter  would . 
be  increased  by  1.43  lb.,  making  thus 
the  corrected  total  weight  of  the  solid 
cone  of  cast  iron  =647.18  lbs.  From 
the  wedge-shaped  piece  cut  out  from  the 
cone  at  half  its  altitude,  and  about  half- 
way between  the  axis  and  circumference 
of  the  sector,  a  piece  was  cut  out,  the 
specific  gravity  of  which,  taken  by  the 
usual  methods,  proved  to  be  7.170, 
which  may  be  taken  as  the  mean  specific 
gravity  at  57°  Fahr.  of  the  whole  of  the 
cast  iron  that  filled  the  cone.  Reverting 
now  to  the  conical   vessel   which    con- 


EXPANSION   OF   SUBSTANCES    ON   SOLIDIFICATION. 


525 


tained  at  60°  Fahr.  94.112  lbs.  of  dis- 
tilled water,  its  capacity  being  2605.5 
cubic  inches  :  this  capacity  was  enlarged 
by  expansion  when  filled  with  molten 
iron  to  2691. 777  cubic  inches,  so  that 
the  conical  vessel  when  cold,  if  it  had 
had  the  same  capacity  as  when  filled 
with  liquid  iron,  would  have  contained 
97.224  lbs.  of  distilled  water.  We  have 
now  all  the  elements  necessary  for  cal- 
culating the  specific  gravity  of  the  cast 
iron  which  filled  the  cone  in  its  molten 
state,  because  we  have  the  actual  weights 
of  equal  volumes  of  distilled  water  and 
of  molten  iron.  The  final  results,  then, 
are,  that  whereas  the  cast  iron  which 
filled  the  cone  had  when  cold  (57°  Fahr. 
a  specific  gravity,  as  above  given,  = 
7.170,  the  same  cast  iron  in  its  molten 
state,  as  poured  into  the  cone,  had  a 
specific  gravity  of  only  6.650 — in  this 
case  thus  proving  that  the  density  of 
cast  iron  in  its  liquid  state  is  not  greater 
but,  on  the  contrary,  very  much  less  than 
that  of  the  same  cast  iron  at  the  tempera- 
ture of  the  atmosphere.  The  quality  of 
cast  iron  employed  in  this  experiment 
was  the  fine,  bright,  close-grained  metal 
usually  employed  by  Messrs.  Maudslay, 
Sons,  and  Field  for  their  engine-castings, 
and  consisted  of 

£  Best  scrap* — all  by  weight. 

x  Gartsherrie,  )  0     ±  i 

iColtness,  '  f  Scotch' 
It  may  be  taken  as  a  typical  or  medium 
example  of  all  good  gray  cast  irons.  I 
have  not  been  enabled  to  repeat  this  ex- 
periment with  the  white,  rigid,  and  crys- 
talline cast  irons,  such  as  are  employed 
for  projectiles  and  other  purposes  ;  but 
as  it  is  a  recognized  fact  amongst  iron- 
founders  that  these  irons  expand  in  the 
range  of  temperature  between  solidity 
and  liquidity  much  more  than  do  gray 
irons,  so  we  may  justifiably  conclude 
that  the  decrease  of  specific  gravity  by 
fusion  of  these  hard  cast  irons  would  be 
in  even  a  greater  ratio  than  that  shown 
by  the  above  experiment  on  gray  iron  ; 
and  generally  the  author  feels  himself 
justified  in  concluding  that  it  is  not  true 
that  any  cast  iron  is  denser  in  the  fused 
than  in  the  solid  state.  Cold  cast  iron, 
therefore,  does  not  float  upon  liquid  cast 
iron  of  the  same  quality  by  reason  of  its 
buoyancy,  but  in  virtue  of  some  force 

"Disused  and  broken-up  castings. 


which  tends  to  keep  it  upon  the  surface 
of  the  molten  metal  in  opposition  to  a 
very  considerable  want  of  buoyancy  or 
tendency  to  sink  by  greater  density  on 
the  part  of  the  solid  iron,  which  is,  by 

the  preceding  results,  — —  of  its  weight, 

whatever  that  may  be,  and  is  probably 
even  greater  than  this  in  the  '-use  of 
hard  white  cast  irons.  The  author's 
chief  object  has  been  thus  far  rather  to 
prove  that  the  cause  assigned  by  the 
writers  already  mentioned  is  not  the 
true  cause  of  the  floating  of  solid  upon 
liquid  cast  iron  of  the  same  quality. 

What  is  the  nature  of  the  force  which 
produces  this  curious  phenomenon  and 
often  in  direct  opposition  to  gravity,  is 
a  different  and  a  much  more  delicate  and 
difficult  inquiry,  which  he  must  leave  to 
physicists  to  fully  investigate.  The 
following  experiments,  however,  may  be 
placed  on  record  as  tending  to  afford 
some  little  dawn  of  light  upon  the  sub- 
ject. 

The  following  experiments  were  made 
with  pieces  of  iron  cast  from  cast  iron  of 
the  same  quality  as  that  which  filled  the 
experimental  cone,  placed  upon  or  im- 
mersed in  molten  cast  iron  of  like  quality 
with  themselves,  so  far  as  such  can  be 
secured  by  "tapping"  at  nearly  the 
same  time  from  the  same  cupola  charged 
with  the  same  materials. 

Before  proceeding  to  describe  these, 
it  will  be  necessary  to  deduce  from  the 
cone  experiment  a  mean  coefficient  of 
total  cubic  dilatation  for  the  whole 
range  between  60°  and  2400°  Fahr.  for 
the  gray  cast  iron  employed  in  these  ex- 
periments. The  total  dilatation  was,  as 
we  have  seen,  such  as  reduced  the  specific 
gravity  of  the  cast  iron  when  cold  (=7.- 
17)  to  6.65  when  in  fusion.  The  cubic 
dilatation  was  therefore  in  the  inverse 
ratio  of  these  numbers,  or  as  1000  :  1078 : 
and  dividing  this  increase  in  volume 
by  2340°  Fahr.,  the  total  range  of  tem- 
perature, we  obtaian  for  the  mean  coeffi- 
cient of  cubic  dilatation  of  this  gray 
cast  iron  for  1°  Fahr.  =  0.0000333.  or 
approximately  for  its  mean  coefficient  of 

0.0000333 
linear  dilatation       — =0.0000111. 

These  coefficients  are  nearly  double 
those  obtained  by  Roy  and  by  Lavoisier 
for  a  range  of  temperature  of  180"  Fahr. 


526 


YAN    NOSTRAND  S    ENGINEERING    MAGAZINE. 


viz.  between  32  and  212°,  which  is  quite 
what  we  should  expect,  as  the  coefficient 
of  dilatation  in  all  bodies  increases  with 
the  temperature. 

We  have  seen  from  what  precedes 
that  two  forces  at  least  are  concerned 
in  the  phenomenon  of  cold  cast  iron 
floating  upon  the  same  when  liquid,  viz  : — 

A.  Buoyancy  or  its  opposite,  depend- 
ent upon  the  relation  between  the  actual 
specific  gravity  of  the  cold  metal  and 
that  of  the  liquid  metal  upon  which  it 
is  placed,  and  whose  absolute  power  for 
any  given  difference  of  specific  gravity 
depends  upon  the  volume  only  of  the 
floating  mass. 

B.  A  repulsive  force  of  some  kind 
tending  to  repel  the  surfaces  in  contact 
of  the  hot  and  cold  metals.  Whatever 
be  the  form  of  the  floating  solid,  this 
repulsive  force  can  only  be  effected  in 
producing  flotation  upon  such  surfaces 
of  the  floating  solid  as  are  parallel  to  the 
surface  of  the  liquid  metal,  or  at  least' so 
circumstanced  that  repulsions  upon  one 
surface,  or  part  of  a  surface,  are  not 
equilibrated  and  nullified  by  repulsions 
upon  others  in.  the  opposite  direction. 
Thus  if  a  parallelopiped  float  with  one 
of  its  surfaces  parallel  to  that  of  the 
liquid  metal,  the  repulsions  Upon  its  im- 
mersed vertical  sides,  taken  two  and 
two  respectively,  are  in  ojDposite  direc- 
tions, and  therefore  nullified,  and  the 
bottom  or  horizontal  surface  is  alone 
effective  m  producing  flotation.  So  also 
if  a  cylinder  float  with  its  axis  horizontal, 
the  ends  are  ineffective,  as  is  also  all  that 
portion  of  the  cylindric  surface  immersed 
which  is  above  the  level  of  the  horizontal 
diameter  of  the  cylinder. 

These  preliminary  explanations  will 
enable  us  better  to  interpret  the  follow- 
ing experiments  : 

Experiment  1.  An  irregular  piece,  be- 
lieved to  be  of  hard  and  dense  cast  iron, 
and  also  a  ball  of  about  1\  in.  diameter, 
believed  to  be  of  close-grained  gray 
iron  :  both  sunk  to  the  bottom  wdien 
thrown  into  the  ladle  of  liquid  iron,  and 
remained  for  some  time  at  the  bottom  ; 
both,'  however,  reappeared  upon  the  sur- 
face when  they  had  acquired  a  tempera- 
ture sufficient  to  have  fused  off  portions 
of  their  respective  masses. 

In  every  fresh-lined  ladle  of  liquid 
cast  iron  there  are  circumferential  ascend- 
ing; and  central  descending  currents  in 


the  metal,  produced  by  the  gases  evolv- 
ed from  the  lining,  as  hereafter  fully  ex- 
plained. It  is  no  doubt  chiefly  to  these 
ascending  currents  that  the  heated  ball 
in  Experiment  1  owed  its  ascent  to  the 
surface  ;  for  if  the  heating  took  place 
in  perfectly  motionless  cast  iron,  there 
seems  no  reason  why  the  place  of  the 
sunken  ball  should  change  up  to  the  mo- 
ment of  complete  fusion. 

Experiment  2.  Two  parallelopipeds, 
each  2"X2"X6",  were  cast  of  close  gray 
iron  ;  one  of  these  was  placed  cold  upon 
the  surface  of  a  large  ladle  of  liquid  iron 
of  like  quality  ;  the  other  was  heated  as 
hot  as  it  would  bear  without  distortion, 
viz.  to  nearly  a  bright  yellow  heat,  in  a 
forge-fire,  and  then  placed  upon  the  sur- 
face of  the  liquid,  metal.  Both  pieces 
floated,  and,  as  nearly  as  could  be  judg- 
ed, both  to  the  same  height  above  the 
liquid,  namely  0.1808  in.  The  volume 
of  the  cold  piece  being  24  cubic  inches, 
the  ratio  of  the  immersed  to  the  emerg- 
ent portions  was  9.6  to  1,  the  effective 
surface  upon  which  the  repulsive  force 
could  act  in  producing  flotation  being 
12  sq.  in.  Assuming  that  the  heated 
piece  has  been  raised  from  60°  Fahr.  (the 
temperature  of  the  cold  piece)  to  2000° 
Fahr.,  and  applying  the  mean  coefficient 
of  cubic  dilatation  as  above  given  to  this 
range  of  temperature,  viz.  2000°  — 60°= 
1940°  Fahr.,  we  find  that  its  volume  was 
enlarged  to  24.75  cubic  inches,  or  =■&  of 
the  volume  when  cold  ;  and  taking  the 
specific  gravity  of  the  cold  piece  to  have 
been  7.17  (see  ante),  that  of  the  hot 
piece  would  be  reduced  to  7.10  ;  the  ef- 
fective repellent  surface  was  slightly  en- 
larged in  the  hot  piece,  and  the  im- 
mersed volume  was  to  the  emergent 
volume  as  9.66  :  1.  The  buoyancy  of  the 
heated  piece  had  been  increased,  or,  more 
correctly,  its  negative  buoyancy  had 
been  decreased,  as  compared  with  that 
of  the  cold  piece,  but  yet  it  has  sunk 
deeper  into  the  liquid  iron  in  proportion 
to  their  respective  volumes.  We  may 
therefore  be  justified  in  concluding  that 
the  repellent  force  which  kept  both 
pieces  afloat  is  diminished  in  energy  in 
some  proportion  as  the  difference  in  tem- 
perature between  the  liquid  metal  and 
the  piece  floating  upon  it  is  diminished, 
and  that  where  the  liquid  and  the  float- 
ing pieces  are  alike  in  quality  of  metal, 
both  the  negative  buoyancy  and  the  re- 


EXPANSION   OF   SUBSTANCES    ON    SOLIDIFICATION. 


527 


pellent  force  must  both  disappear  at  the 
instant  that  the  floating  piece  itself  be- 
comes liquid  by  heat  abstracted  from  the 
molten  metal. 

Experiment  3.  Two  cylindric  pieces 
of  the  same  gray  cast  iron  and  of  the 
same  diameter  (  =  2.375")  were  gently 
placed  with  their  axes  horizontal  upon 
the  surface -of  the  molten  iron,  the  one 
being  at  60°  Fahr.,  the  other  at  about 
300°  Fahr.  ;  they  both  floated  with  a 
segment  of  the  cylinder  whose-  versed 
sine  was  0.31  in.  emergent.  The  volume 
of  either  cylinder  was  22.15  cubic  inches, 
and  the  emergent  was  to  the  immersed 
volume  as  1  :  8.4.  The  effective  repel- 
lent surface  in  each  case  (or  cylindric 
surface  below  the  horizontal  diameter) 
was  18.65  sq.  in.  ;  but  if  we  suppose,  as 
in  fact  we  have  done,  that  the  repellent 
force,  whatever  be  its  nature,  acts  every- 
where perpendicularly  to  surfaces  of  con- 
tact of  the  solid  and  liquid,  then  the 
effective  repellent  surface  here  is  only 
the  difference  between  the  immersed 
surfaces  of  the  cylinder  below  and  above 
the  horizontal  diameter,  or  9.3  sq.  in. 
From  this  we  may  perhaps  conclude  that 
the  repellent  force  is  mainly  dependent 
upon  the  extreme  upper  parts  of  the 
range  of  temperature  between  the  liquid 
and  the  cold  body,  inasmuch  as  an  aug- 
mentation in  temperature  of  the  latter 
of  300°,  or  about  \  of  the  entire  range 
between  solidity  and  fusion  of  the  cast 
iron,  produces  no  very  sensible  altera- 
tion in  the  tendency  to  float  of  the 
pieces. 

Experiment  4.  Three  circular  disks  of 
the  same  gray  cast  iron,  each  of  6"  diam. 
by-  0.375"  in  thickness,  w^XQ  provided 
each  with  a  slender  iron  wire  eye,  cast 
into  the  centre  of  one  surface,  so  that  by 
a  hooked  wire  they  could  be  gently  laid 
upon  the  surface  of  the  liquid  iron  of 
their  own  quality.  The  lower  surface 
and  edge  of  one  disk  were  left  as  it 
came  clean  from  the  sand,  those  of  an- 
other were  rusted  by  wetting  with  solu- 
tion of  sal-ammoniac,  and  those  of  the 
third  were  ground  smooth  and  polished 
by  the  grindstone.  When  the  three 
disks  were  in  succession  laid  upon  the 
.surface  of  the  molten  iron,  they  all  float- 
ed alike  as  nearly  as  could  be  jtulged, 
each  sinking  to  one  half  the  thickness  of 
the  disk,  so  that  the  immersed  was  to 
the    emergent   volume   in   the   ratio   of 


equality:  We  may  conclude  from  this 
that  the  condition  of  the  metallic  surface 
of  the  solid  cast  iron  has  no  material  in- 
fluence upon  its  flotal  ion. 

Experiment  5.  Two  circular  disks,  pro- 
vided with  eye-'  as  in  Experiment  \,  «rere 
prepared,' the " one  being  0  in.  in  diam. 
by  0.375  in  thickness,  ami  the  oth 
in.  in  diam.  by  1.5  in.  in  thickness.  The 
respective  volumes  of  these  two  disks 
are  the  same,  but  the  circular  lint  sur- 
faces respectively  are  as  4  to  1.  The 
surfaces  of  the  two  disks  being  as  they 
came  from  the  sand-mould,  they  were 
placed  gently  upon  the  surface  of  the 
molten  iron  :  both  floated  with  the  same 
portion  in  altitude  emergent.  Tin-  larger 
and  thin  disk  had,  as  stated  in  Experi- 
ment 4,  its  emergent  and  immersed  vol- 
umes in  the  ratio  of  equality  [or  the 
emergent  was  to  the  whole  volume  as 
1  :  2].  In  the  smaller  and  thicker  disk, 
the  emergent  volume  was  to  the  im- 
mersed volume  as  1  to  7.  [Or  the  em- 
ergent volume  was  to  total  volume  as 
1:8;  but  2  :  8|  \1  : 4,  or  the  emergent 
volumes  are  to  the  total  volumes  in  each 
case  respectively  proportionate  to  the 
lower  or  repellent  surfaces  of  the  disk.] 
Now  the  effective  repellent  surfaces 
are  here  those  of  the  lower  circles  of  the 
i  respective  disks,  and  these  surfaces  are 
|  to  each  other  in  the  ratio  of  1  (the  larger) 
to  \  Whatever  be  the  nature,  there- 
fore, of  the  repellent  force,  it  seems  to 
:  be  proportionate  to  some  function  of  the 
effective  surface  as  already  defined,  and 
j  not  to  the  immersed  volume  of  the  solid 
I  cast  iron  which  floats  upon  a  liquid  less 
dense  than  itself. 

In  all  these  experiments  the  mass  of 
I  the  molten  cast  iron  was  large  in  propor- 
!  tion  to  the  pieces  placed  upon  it,  and  the 
surface  was  kept  by  careful  skimming 
almost  perfectly  free  from  scoriae  or 
oxyde.  A  good  deal  of  difficulty  exi-ts 
in  observing  the  phenomena  in  such  ex- 
periments as  these,  owing  to  the  glare 
and  heat  of  the  molteu  metal.  What- 
!  ever  light  these  five  experiments  may 
throw  upon  the  nature  of  the  force  which 
produces  flotation,  the  subject  must  as 
yet  be  viewed  as  very  incomplete.  There 
are  some  facts  of  which  no  complete  ex- 
planation can  be  offered  without  further 
experimental  study  ;  such  as,  for  ex- 
ample, that  a  piece  of  cold  cast  iron 
which  floats  on  liquid  iron  of  its   own 


528 


VAN   NOSTRAND'S   ENGINEERING   MAGAZINE. 


quality  if  forcibly  thrust  to  the  bottom 
and  rapidly  and  at  once  released,  rises 
again  rapidly  to  the  surface  with  all  the 
appearance  of  a  buoyant  body,  which  it 
certainly  cannot  be. 

From  what  precedes,  however,  we  may 
summarize  as  follows  : 

If  F  be  the  force  which  keep  the  solid 
iron  floating,  B  the  buoyancy  ±  of  the 
solid  piece,  and  R  the  repellent  force, 
then,  in  the  case  of  a  piece  floating  upon 
molten  ii*on  of  its  own  quality,  B  is  al- 
ways negative,  and  F=R— B,  the  value 
of  R  for  any  given  case  depending  upon 
the  effective  surface  of  the  solid,  and 
that  of  B  upon  its  volume,  both  being- 
modified  by  the  initial  difference  in  tem- 
perature  between  the  solid  and  liquid 
metals.  In  the  case  of  the  solid  being 
placed  on  liquid  cast  iron  differing  in 
quality  from  it,  B  may  be  either  positive 
or  negative,  and  R  still  dependent  upon 
the  conditions  already  stated.  Hence  in 
any  such  case  we  may  have 

F=R-B  or  =R+  B. 

These  conditions  kept  in  view  may 
clear  up  many  phenomena  at  first  appar- 
ently anomalous. 

[However  feeble  may  be  the  ascending 
currents,  above  referred  to,  upon  the 
floating  disks  in  Experiment  5,  their  ef- 
fect must  be  viewed  as  proportionate  to 
the  lower  surfaces,  and  therefore  propor- 
tionate to  the  repellent  force,  and  as  pos- 
sibly adding,  though  slightly,  to  its  ef- 
fect.] 

The  following  experiments  were  made 
at  the  Royal  Arsenal,  Woolwich,  with  a 
view  to  ascertain  whether  any  sensible 
expansive  force  could  be  recognized  as 
due  to  the  enlargement  in  volume  by 
consolidation  of  a  spherical  mass  of  cast 
iron  : — Two  spherical  bomb-shells,  each 
of  about  10"  in  diameter  and  l".5  in 
thickness,  whose  external  orthogonal  di- 
ameters had  been  carefully  taken  when 
at  atmospheric  temperature  (about  53° 
Fahr.),  were  both  heated  in  an  oven- 
furnace.  One  of  these  having  been  thus 
heated,  but  not  to  a  very  bright  red,  was 
permitted  gradually  to  cool  again,  and 
its  final  dimension  when  cold  noted. 
The  other  shell  was  withdrawn  from  the 
oven  when  at  a  bright  red  heat,  and  im- 
mediately filled  to  a  little  above  the  in- 
ner orifice  of  the  fuse-hole  with  molten 
cast  iron,  the  quality  of  this  being  the 


very  dense  mottled  gray  iron  smelted  at 
Elswick  Works  from  the  Riddesdale 
ores,  and  used  in  the  arsenal  for  casting 
projectiles.  The  fuse-hole  was  closed  by 
a  screw-plug,  which,  however,  did  not 
reach  within  an  inch  of  the  surface  of 
the  molten  metal,  and  the  whole  sur- 
rounded by  a  sheet-iron  screen  to  keep 
off  currents  of  air,  was  allowed  to  cool 
gradually,  the  dimensions  being  taken  of 
the  sphere  as  it  cooled  and  contracted  at 
intervals  of  half  an  hour  until  it  had  be- 
come cold.  The  enveloping  shell  was 
then  cut  through  by  the  lathe  in  a  great 
circle  at  right  angles  to  the  axis  passing 
through  the  fuse-hole.  One  of  the  halves 
of  the  shell  being  detached,  the  interior 
surfaces  of  both  hemispheres  were  found 
in  perfect  contact  with  that  of  the  ball 
of  iron  they  had  contained,  but  no  elastic 
tension  seemed  to  exist  in  the  shell.  The 
ball  of  iron  was  drilled  into  and  split  by 
steel  taper  plugs,  and  sections  of  it  ex- 
posed passing  through  the  diameter  in  a 
line  with  the  axis  of  the  fuse-hole.  There 
was  no  large  cavity  or  "  draw  "  anywhere 
in  the  interior,  but  there  were  two  very 
small  irregular  cavities  very  near  the 
fuse-hole;  and  the  central  portion  of  the 
mass  embraced  by  an  imaginary  sphere 
of  about  3"  in  diameter,  proved  to  be 
"spongy"  and  granular,  as  compared 
with  the  very  dense  and  close-grained 
iron  that  constituted  the  remainder  of 
the  ball. 

The  following  Table  shows  the  course 
of  contraction  in  dimensions  of  the  filled 
shell  and  also  of  the  empty  shell  in  their 
progress  of  cooling  : 

[See  lable  following  ■  pagei\ 

The  object  of  heating  and  cooling  the 
empty  shell  was  to  ascertain  what 
amount,  if  any,  of  permanent  enlarge- 
ment it  might  suffer,  it  being  a  well- 
known  fact  that  all  solids  of  revolution 
of  cast  iron,  and  generally  of  all  metals 
of  sufficient  rigidity,  become  permanent- 
ly enlarged  by  being  heated  red-hot  and 
permitted  to  cool.  This  arises  from  the 
fact  that  the  outer  coaches  of  the  solid 
(a  sphere  for  example)  are  the  first 
heated  and  expanded,  and  have  to-  draw 
off  more  or  less  from  the  less-heated 
mass  within.  Tangential  thrusts  and 
radial  tensions  are  thus  produced  in  the 
material  of  the  outer  couches  which 
disappear,  or  even  become  reversed,  as 
the  progress  of  heating  reaches  the  in- 


EXPANSION   OF   SUBSTANCES   ON    SOLIDIFICATION. 


529 


Time. 


11.30 
12.30 
12.15 
12.55 


12.50 
1.20 
1.50 
2.15 
2.45 
3.15 
3.45 
4.15 
4.45 
5.15 
5.45 
6.15 
6.45 
7.15 
7.45 
8.15 


Cold 

Put  in  oven-furnace  (shell  to  be  filled) 

Put  in  oven- furnace  (empty  shell) 

Withdrawn  from  furnace 

Withdrawn  from  furnace 

After  filling  with  iron,  diameter  was ■] 

After  filling  with  iron,  diameter  was 

After  filling  with  iron,  diameter  was 

After  filling  with  iron,  diameter  was 

After  filling  with  iron,  diameter  was 

After  filling  with  iron,  diameter  was ' 

After  filling  with  iron,  diameter  was 

After  filling  With  iron,  diameter  was 

After  filling  with  iron,  diameter  was. ...   

After  filling  with  iron,  diameter  was 

After  filling  with  iron,  diameter  was 

After  filling  with  iron,  diameter  was 

After  filling  with  iron,  diameter  was 

After  filling  with  iron,  diameter  was 

After  filling  with  iron,  diameter  was 

After  filling  with  iron,  diameter  was 

After  filling  with  iron,  diameter  was 

When  cold 


Diameter, 

Diameter 

filled 

empty 

BhelL 

shell. 

9.850 

10.020 

9.960 

10.030 

10.040 

10.040 

10.020 

9.95S 

10.000 

9.950 

9.995 

9.875 

9.980 

9.978 

9.  SO'! 

9.976 

9.975 

9.854 

9.973 

9.8G2 

9.970 

O.S^ 

9.968 

9.851 

9.965 

9.851 

9.964 

9.851 

9.964 

9.851 

9.963 

9.851 

9.962 

9.851 

9.960 

9.851 

terior  of  the  mass  ;  but  in  the  subsequent 
cooling  the  entire  train  of  forces  is  re- 
versed, the  exterior  couches  lose  heat  by 
dissipation  first,andhave  to  accommodate 
by  tangential  tensions  their  dimensions 
to  the  still  hotter  interior,  the  final  result 
being  that  when  the  whole  has  cooled 
the  dimensions  are  greater  than  before 
the  solid  was  heated.  A  32-lb.  spherical 
shot,  which  is  rather  more  than  6  inches 
in  diameter,  can  be  thus  permanently  in- 
creased mt  of  an  inch  in  diameter,  by  a 
single  heating.  It  is  obvious  that  the 
increase  will  be  much  less  in  a  spherical 
shell  than  in  a  solid  sphere,  and  the  less 
as  the  shell  is  thinner.  On  inspecting 
the  Table  it  will  be  seen  that  the  empty 
shell  had  its  diameter  thus  permanently 
enlarged  by  0.008  of  an  inch  ;  and  had 
it  been  heated  to  as  high  a  temperature 
as  the  filled  shell,  we  may  allowably 
conclude  that  this  enlargement  would 
have  reached  0.01  of  an  inch.  The  filled 
shell  has  had  its  diameter  increased  by 
the  decimal  0".ll  ;  and  if  we  deduct 
from  this  the  amount  of  permanent  en-, 
largement  due  to  heating  only,  equal  to 
that  of  the  empty  shell,  we  have  the 
decimal  0.11 — 0.01  =  0.10  which  has  to 
be  otherwise  accounted  for.  This  shell 
was  at  a  bright  red  heat  visible  in  clear 
Vol.  XIII.—  No.  6—34 


daylight  when  filled  with  the  liquid 
iron,  which  occupied  the  spherical  cavity 
and  about  0.43  in  height  of  that  of  the 
fuse  hole.  The  temperature  of  the  shell 
visibly  rose  by  the  heat  communicated 
from  the  liquid  metal,  and  in  30  minutes 
after  it  was  filled  had  attained  its  maxi- 
mum, the  surface  being  then  at  a  bright 
yellow  heat  in  daylight  when  the  first 
measurement  of  enlarged  diameter  was 
made.  The  successive  measurements 
were  taken  for^  orthogonal  diameters  in 
the  direction  normal  to  the  fuse-hole  by 
means  of  finely  graduated  steel  beam 
calipers  capable  of  being  read  to  0.002 
of  an  inch  or  even  less  ;  the  dimensions 
set  down  in  the  Table  are  the  means  of 
each  pair  of  orthogonal  diameters.  The 
shell  was  thus  heated  at  the  commence- 
ment, and  before  consolidation  of  its 
liquid  contents  had  taken  place  to  any 
considerable  extent,  to  within  probably 
200°  or  300°  Fahr.  of  the  temperature  of 
the  cast  iron  within.  The  shell  ami  it? 
contents  are  therefore  at  the  commence- 
ment very  nearly  in  the  same  condition 
as  though  the  whole  were  a  sphere  of 
molten  iron  without  any  more  or  less 
rigid  envelope,  if  such  could  exist.  Re- 
verting to  what  has  been  said  above  as 
to  the  train  of  forces  called  into  play  in 


530 


VAN   NOSTRAND's   ENGINEERING   MAGAZINE. 


a  cooling  sphere,  let  us  consider  what 
has  taken  place  here.  As  the  heat  is 
dissipated  from  the  exterior  of  the  mol- 
ten mass,  being  transmitted  through  the 
shell,  one  conche  after  another  of  the 
molten  metal  in  contact  with  the  inner 
wall  of  the  shell  consolidates,  the  thick- 
ness constantly  advancing  towards  the 
interior,  where  the  metal  is  still  liquid. 
If  each  of  these  couches  in  consolidating 
expanded  in  volume,  such  expansion 
must  conspire,  with  the  contraction  con- 
stantly going  on  by  the  abasement  of 
temperature,  to  produce  compression  in 
the  central  and  as  yet  unsolidified  por- 
tion of  the  mass.  If,  on  the  contrary, 
each  couche  as  it  solidifies  contracts  in 
volume  (and,  as  is  the  fact,  by  a  larger 
coefficient  of  contraction  for  equal  small 
ranges  of  temperature  before  and  after 
solidification),  then  the  effect  must  be 
that,  after  the  solidified  crust  has  attain- 
ed a  certain  thickness  and  sufficient 
rigidity,  the  further  progress  of  contrac- 
tion of  the  central  portions  as  they  suc- 
cessively solidify  must  be  met  by  their 
tending  to  draw  off  from  the  solidified 
shell,  or  in  other  words,  by  a  dra wing-off 
from  each  other  of  the  particles  of  that 
central  portion  of  the  sphere  which  last 
solidifies.  Now  the  latter  is  exactly 
what  has  happened  :  a  portion  of  the 
exterior  and  first  solidified  crust,  reach- 
ing about  an  inch  and  half  inwards  from 
the  interior  of  the  shell,  was  found  to 
have  a  specific  gravity  of  -7.150  at  57° 
Fahr.,  while  a  portion  taken  close  to  the 
centre  of  the  sphere  had  a  specific  gravity 
of  only  7.037  ;  and  this  specific  gravity 
would  have  been  still  lower  (or,  in  other 
words,  the  central  part  of  the  sphere 
would  have  been  still  more  "  spongy  ") 
had  it  not  been  fed  by  drawing  down- 
wards a  portion  of  the  liquid  iron  which 
partially  filled  the  fuse-hole,  the  portion 
So  drawn  down  being  estimated  by  the 
yolume  of  the  cavities  left  at  0.400  of  a 
cubic  inch  ;  so  that  but  for  this  the 
specific  gravity  of  the  central  spongy 
sphere  taken  at  3"  diameter  would  have 
been  reduced  to  6.776. 

If  we  reduce  this  central  spongy  mass 
of  3"  diameter  and  of  the  last  mentioned 
specific  gravity  to  a  density  as  great  as 
that  found  for  the  exterior  crust,  namely 
7.150,  the  sphere  of  3"  diameter  would 
be  reduced  to  one  of  2".  138  ;  and  it  is 
easy  to  see  that  in  that  case  the  external 


diameter  of  the  whole  sphere  of  metal 
and  of  the  containing  shell  would  have 
been  less  in  a  corresponding  proportion, 
and  that  thus  the  final  dimensions  of 
the  shell  would  have  returned  to  what 
they  were  at  the  commencement,  less  the 
permanent  enlargement,  as  measured  by 
that  of  the  empty  shell.  If  there  existed, 
on  the  other  hand,  any  sensible  expansion 
in  volume  of  the  metal  in  consolidating, 
not  onty  would  a  central  "  spongy  "  por- 
tion be  impossible  and  the  central  be  the 
densest  part  of  the  whole  sphere,  but  an 
enlargement  of  the  entire  mass  and  of 
the  covering  shell  stretched  by  it  must 
have  occurred,  so  large  as  to  be  wholly 
unmistakable. 

[The  importance  of  the  facts  elicited 
from  this  experiment  cannot  be  too  forci- 
bly laid  before  the  reader.  Had  the 
sphere  of  molten  iron,  losing  heat  from 
its  exterior,  expanded  in  volume  as 
couche  after  couche  it  solidified  from  the 
exterior,  the  solidification  constantly  ad- 
vancing inwards,  then  the  central  por- 
tions of  the  sphere  when  ultimately 
solidified  must  be  found  to  be  the  densest 
portions  of  the  whole  mass  ;  the  oppo- 
site of  which  was  found  to  be  the  fact, 
the  central  portions  of  the  experimental 
sphere  being,  as  stated,  the  least  dense 
portions  of  the  whole  mass.  This  alone 
seems  conclusively  to  negative  the  sup- 
position of  any  expansion  in  volume  in 
cast  iron  in  consolidating.  On  examin- 
ing the  Table,  it  will  be  remarked  that 
between  the  hours  1.50  and  2.45  there  is 
an  irregularity  in  the  progress  of  con- 
traction which  might  be  assumed  to  in- 
dicate a  less  rate  of  contraction  within 
this  epoch  ;  and  it  might  be  further  as- 
sumed that  this  apparent  reduction  arose 
from  the  conjoint  action  of  general  con- 
traction and  partial  expansion  operating 
together  within  some  part  of  the  mass  ; 
but-this  view,  which  the  writer  believes 
would  be  entirely  incorrect,  appears 
sufficiently  negatived  by  the  following 
considerations  : 

1.  Between  the  hours  1.50  and  2.45 
but  one  caliper  measurement  was  made, 
namely  at  2.15,  and  upon  this  one  meas- 
urement both  the  existence  and  the 
amount  of  this  anomalous  part  of  the 
curve  depend.  An  error  in  this  single 
caliper  measurement  amounting  to  0.006 
of  an  inch  was  sufficient  to  have  pro- 
duced it  ;  and  as  the  limit  of  reading  of 


EXPANSION   OF   SUBSTANCES    ON   SOLIDIFICATION. 


531 


the  beam  calipers  was  to  a  limit  of 
0.002  or  possibly  0.001  of  an  inch,  a 
mistake  in  the  measurement  at  2.15,  or  a 
misreading  of  only  the  decimal  .004  or 
.005  at  most,  is  sufficient  to  account  for 
the  anomaly. 

2.  It  does  not  necessarily  indicate  ex- 
pansion, and  from  the  early  time  of  its 
occurrence,  viz.  only  1  hour  25  minutes 
from  the  commencement  of  cooling,  it 
seems  highly  improbable  that  it  could 
arise  from  partial  expansion  then  com- 
mencing, while  as  yet  a  very  large  pro- 
portion of  the  entire  mass  must  have 
been  still  liquid. 

3.  If  it  were  really  due  to  expansion, 
It  must  have  shown  itself  later  in  a  form 
that  would  have  unmistakably  declared 
its  origin. 

The  supposition  upon  which  Messrs. 
Nasmyth  and  Carpenter's  theory  rests 
may  be  divided  into  two  distinct  pro- 
positions. 

1st.  That  cast  iron  is  of  greater  den- 
sity in  the  molten  than  in  the  solid  state. 

2nd,  That  cast  iron  in  the  act  of  con- 
solidation expands  in  volume.  These 
propositions  are  not  identical,  although 
the  second  is  involved  in  the  first.  The 
first  proposition  has  been  already  dis- 
posed of,  and  the  last  recorded  experi- 
ments appear  conclusively  to  disprove 
the  second. 

The  phenomena  described  by  Messrs. 
Nasmyth  and  Carpenter,  and  their  ex- 
planation of  the  circulating  currents 
observable  in  large  and  nearly  cylindri- 
cal ladles  of  molten  iron,  appear  at  first 
sight  so  confirmatory  of  their  views  as 
to  the  greater  density  of  cast  iron  in  the 
molten  than  in  the  solid  state,  that  it 
seems  necessary  here  to  present  the  true 
explanation  of  the  facts,  which,  so  far 
as  they  are  here  relevant,  may  be  best 
given  briefly  in  the  words  of  these 
authors  : 

"  When  a  ladle  of  molten  iron  is  drawn 
from  the  furnace  and  allowed  to  stand 
at  rest,  the  thin  coat  of  scoria  or  molten 
oxyde  which  forms  on  the  surface  of  the 
metal  is  seen,  as  fast  as  it  forms  at  the 
circumference  of  the  ladle,  to  be  swept 
by  active  convergent  currents  towards 
the  centre,  where  it  accumulates  in  a 
patch.  As  the  fluid  metal  parts  with 
some  of  its  heat  and  the  ladle  gets  hot 
by  absorbing  it,  this  remarkable  sur- 
face-disturbance becomes  less  energetic." 


This  arises  from  "  the  expansion  of  that 
portion  of  the  molten  mass  which  is  in 
contact  with  the  comparatively  cool 
sides  of  the  ladle,  which  sides  act  as  the 
chief  agent  in  dispersing  the  heat  of  the 
melted  metal  ;  careful  observation  will 
show  that  the  motion  in  question  is  the 
result  of  an  upward  current  of  the  metal 
around  the  circumference  of  the  ladle]. 
"  The  upward  current  of  the  metal  can 
be  seen  at  the  rim  of  the  ladle,  where  it 
is  deflected  into  the  convergent  horizon- 
tal direction,  and  where  it  presents  an 
elevatory  appearance.  It  is  difficult  to 
assign  to  this  any  cause  but.  that  of  ex- 
pansion and  consequent  reduction  of 
specific  gravity  of  the  fluid  metal  in  con- 
tact with  the  sides  of  the  pot,  as,  accord- 
ing to  the  generally  entertained  idea, 
the  surface-currents  above  referred  to 
would  be  in  the  contrary  direction  to 
that  which  they  invariably  take,  i.  e. 
they  would  diverge  from  the  centre  in- 
stead of  converging  to  it." 

The  facts,  so  far  as  they  are  above 
described,  are  generally  correct,  but  the 
explanation  given  is  not  the  true  one. 
The  currents  observable  for  some  time 
after  a  large  ladle  (say,  holding  10  tons) 
is  first  filled  with  molten  iron  are  not 
produced  by  difference  of  temperature 
in  different  parts  of  the  mass,  but  in  the 
following  way  : — Such  a  ladle  is  of 
wrought  iron,  about  half  an  inch  in 
thickness  ;  and  to  preserve  this  tolera- 
bly cool,  even  for  several  hours,  it  is 
lined  with  a  coating  of  earthy  material 
daubed  upon  the  interior  in  a  tough  and 
plastic  state,  from  an  inch  to  an  inch 
and  a  half  in  thickness,  and  dried  within 
it.  The  lining  material  consists  of  plas- 
tic clay,  with  a  proportion  of  siliceous 
sand  beaten  up  together  with  horsedung, 
chaff,  plasterer's  cow-hair,  or  other 
fibrous  material,  conferring  toughness 
upon  the  mass  when  soft  and  porosity 
when  dry.  This  material,  after  drying 
at  a  temperature  averaging  500°  to  TOO3 
Fahr.,  on  being  exposed  to  contact  with 
the  molten  cast  iron,  exhales  torrents  of 
gas  and  vapor,  which  pass  upwards 
through  the  molten  mass  and  determine 
the  direction  of  its  currents  ;  and  it  will 
be  obvious,  on  inspecting  the  figure, 
that  these  currents  will  be  most  power- 
ful round  the  outer  circumference  of  the 
mass,  where  each  unit  of  its  top  surface 
has    a    larger   proportion    of    lining   in 


532 


VAN   NOSTRAND'S   ENGINEERING   MAGAZINE. 


proximity  to  it  than  at  the  central  parts 
of  the  mass,  where  downward  currents 
are  the  necessary  consequence  of  those 
produced  upwards  at  the  circumference. 
The  organic  matters  mixed  with  the 
lining  are  carbonized,  and  give  forth  the 
elements  of  water  as  well  as  nitrogen. 
The  clay,  which  is  a  hydrous  silicate  of 
various  earthy  bases,  gives  forth  its 
water  and  some  of  the  oxygen  of  the 
peroxyde  of  iron  which  most  clays  con- 
tain. More  or  less  carbonate  of  lime  is 
almost  always  interspersed,  and  this 
gives  forth  carbonic  acid  and  water. 
The  gases  thus  streamed  forth  act  me- 
chanically by  their  ascent  and  also 
chemically  upon  molten  iron,  the  water 
being  decomposed,  oxydizing  portions 
of  the  iron  and  forming  scoriae,  which  is 
again  more  or  less  reduced  by  contact  of 
the  hydrogen  and  nitrogen  when  the 
latter  is  present.  These  rapid  combina- 
tions and.  decompositions  are  no  doubt 
the  main  cause  of  those  singular  ver- 
micular startings  referred  to  by  Messrs. 
Nasmyth  and  Carpenter,  which  are 
familiar  to  every  iron-founder,  but  which 
are  entirely  distinct  from  the  ascending 
and  descending  currents  due  to  the  as- 
cent of  the  evolved  gases.  That  this  is 
the  true  explanation  is  supported  by  the 
following  facts  : — 1.  After  a  large  ladle 
has  stood  full  of  molten  metal  for  some 
hours,  and  time  has  been  given  thus  for 
the  whole  of  the  gaseous  contents  of  the 
lining  to  be  driven  off,  the  ascending 
and  descending  currents  cease  to  be  per- 
ceptible, and  if  any  currents  at  all  can 
be  discerned  they  are  in  the  opposite 
directions.  2.  If,  after  this,  such  a  ladle 
be  emptied  of  its  contents,  the  lining  re- 
maining untouched  and  only  coated  with 
a  thin  shell  of  adherent  cast  iron  [and 
oxydes  and  silicates  of  iron],  and  the 
ladle  being  again  filled  with  molten 
iron,  no  such  currents  as  at  first  are  pro- 
duced in  the  molten  mass,  the  lining 
having  been  previously  exhausted  of  its 
gases  and  vapors.  That  the  currents 
described  by  Messrs.  Nasmyth  and 
Carpenter  are  not  due  to  dissipation  of 
heat  from  the  mass  through  the  sides  of 
the  ladle  is  evident  from  the  following 
considerations  : 

A  10-ton  ladle,  which  is  about  4-k  feet 
by  3  feet  in  depth,  loses  heat  so  slowly 
that  after  standing  for  6  hours  the  mol- 


ten metal  is  still  fluid  enough  to  make 
castings.  Let  us  suppose  it  filled  into 
the  ladle  at  a  temperature  of  2800°  to 
2900°  Fahr.,  and  that  after  six  hours  it 
is  still  200°  above  the  temperature  of 
solidification  of  cast  iron,  or  at  2600°. 
The  molten  mass  has  thus  lost  300°  of 
heat  in  360  minutes,  or  .0138  of  a  de- 
gree per  second.  We  may  assume  this 
at  any  instant  as  representing  the  differ- 
ence in  temperature  between  two  verti- 
cal columns,  one  at  the  centre  and  the 
other  at  the  circumference  of  the  molten 
mass.  The  linear  dilatation  of  cast  iron 
for  one  degree  of  Fahrenheit  being 
0.0000111,  as  deduced  from  its  total 
cubic  dilatation  between  60°  Fahr.  and 
the  temperature  of  fusion  at  which  it 
was  poured  into  the  cone,  as  given  in 
this  paper  and  assuming  the  depth  of 
the  colder  of  these  columns,  whether 
that  be  at  the  circumference  or  not,  to 
be,  as  stated,  36",  that  of  the  hotter 
column  will  be  36.0000005514,  and  the 
difference  between  these  two  measures 
the  force  which  alone  can  produce  circu- 
lating currents  in  the  mass  by  difference 
of  temperature  due  only  to  cooling. 
This  is  equally  true  whether  it  be  the 
colder  column  that  is  dilated,  as  suppos- 
ed by  Messrs.  Nasmyth  and  Carpenter, 
or  the  hotter  one,  as  is  the  fact.  And 
if  we  consider  the  viscidity  of  molten 
cast  iron,  it  is  perfectly  obvious  that  the 
circulating  currents  referred  to  by 
Messrs.  !S(asmyth  and  Carpenter  cannot 
be  due  to  so  insignificant  a  cause. 

Want  of  attention,  or  careless  inter- 
pretation of  the  many  and  somewhat 
complicated  conditions  thus  seen  to  be 
involved  in  the  cooling  of  a  solid  by 
dissipation  of  its  heat  from  its  exterior 
has  caused  many  serious  misapprehen- 
sions on  the  part  of  experimenters  as  to 
the  supposed  expansion  of  metals  in 
volume  when  consolidating.  Thus,  even 
in  the  case  of  bismuth,  it  has  been  sup- 
posed a  conclusive  proof  of  its  expansion 
that  a  mass  cooling  in  an  open  crucible 
exudes  from  its  interior  upon  its  top  sur- 
face cauliflower-like  excrescences  ;  but 
although  the  author  does  not  here  deny 
or  affirm  anything  as  to  expansion  being 
a  fact  in  the  case  of  bismuth,  it  is  never- 
theless obvious  that  such  excrescences 
might  arise  merely  from  the  grip  of  the 
crucible  itself,  or  even  of  the  exterior 
portions  of  the  metal  already  solidified 


EXPANSION    OF   SUBSTANCES   ON    SOLIDIFICATION. 


533 


contracting  upon  and  so  squeezing  out 
portions  of  the  still  liquid  interior. 

It  is  stated  on  good  authority  that  a 
distinguished  artillery  officer,  in  former 
years  at  the  head  of  the  Laboratory, 
Woolwich  Arsenal,  satisfied  himself  of 
the  reality  of  the  expansion  of  cast  iron 
in  consolidating  by  the  following  ex- 
periment : — An  elongated  projectile  was 
cast,  with  its  axis  vertical,  in  a  very 
thick  and  massive  mould  of  cast  iron, 
the  mould  being  cold  or  nearly  so  ;  the 
molten  metal  was  introduced  through  a 
narrow  aperture  applied  at  the  base  of 
the  projectile,  the  neck  or  "  gate  "  being 
knocked  off  the  instant  the  mould  was 
filled.  As  the  cooling  rapidly  proceeded, 
portions  of  the  still  fluid  metal  were 
forced  out  at  the  place  where  this  neck 
was  detached  ;  and  the  conclusion  was 
come  to  that  the  exterior  being  already 
solidified  such  excrescence  could  only 
arise  from  expansion  of  the  contained 
liquid  metal  as  it  solidified  in  succession. 
What  really  did  take  place,  and  is  the 
true  explanation  of  the  facts,  is,  that 
when  a  very  thick  iron  mould  of  this 
sort  is  suddenly  heated  by  pouring  molt- 
en iron  into  its  interior,  as  the  heat  ab- 
stracted from  the  latter  can  only  pass 
into  the  material  of  the  mould  at  a  rate 
determined  by  its  conductivity,  so  the 
interior  part  rapidly  becomes  raised  to 
a  temperature  enormously  higher  than 
the  exterior  portions,  which  for  a  time 
remain  almost  cold.  The  expanded  in- 
terior walls  of  the  mould  push  inwards 
as  towards  the  points  of  least  resistance, 
and  so  actually  diminish  the  capacity  of 
the  mould  for  a  time,  the  inner  surfaces 
of  which  press  upon  the  consolidating 
crust  of  metal  within  it,  and  so  squeeze 
out  in  part  its  liquid  contents,  just  as 
water  might  be  squeezed  from  an  india- 
rubber  bottle. 

It  seemed  desirable  to  obtain  some  ex- 
perimental results  in  reference  to  the  ob- 
jects of  this  communication  with  lead. 
It  has  never,  so  far  as  the  author  is 
aware,  been  even  suggested  that  this 
metal  expands  in  consolidating.  Its  co- 
efficient of  dilatation  by  heat  is  enormous- 
ly greater  than  that  of  cast  iron,  being, 
according  to  the  determination  of  La- 
voisier and  Laplace,  between  32°  and 
212°  Fahr.=0.0000474  of  its  volume  for 
one  degree  Fahr.  ;  so  that,  taking  its 
fusing-pojnt  at  617°  (Rudberg),  and  as- 


suming the  coefficient  constant  for  the 
entire  range  from  60°  to  017  (which  Lb 
much  below  the  truth),  its  dilatation 
when  in  fusion  would  be=0.0264  of  its 
volume,  and  the  specific  gravity  of  lead 
at  00"=11.36  ;  that  of  liquid  lead  must 
be  below  11.07.  Indeed  this  enormous 
amount  of  dilatation  is  impressed  upon 
any  Observer  who  sees  the  rate  at  which 
the  lead  in  casting  a  common  bullet  sinks 
into  the  neck  of  the  mould,  and  the 
comparatively  large  cavity  which  al- 
ways exists  in  the  ball  when  cut  in  two. 
From  its  low  temperature  of  fusion  and 
the  suddenness  with  which  lead  passes 
from  the  solid  to  the  liquid  state  with- 
out any  phase  of  intermediate  viscidity, 
and  only  a  brief  one  of  crystalline  brit- 
tleness,  and  the  facility  with  which  its 
surface  can  be  kept  free  from  dross  or 
oxyde,  this  metal  presents  a  "  crucial " 
example  for  experiment  in  reference  to 
our  subject. 

The  following  experiments,  by  the 
kind  permission  of  Messrs.  Pontifex  & 
Wood,  London,  were  made  at  their 
works  : 

1st.  Upon  the  surface  of  a  large  pot 
of  melted  lead,  the  temperature  of  which 
was  estimated  at  from  750°  to  880°  Fahr., 
the  half  of  a  large  pig  of  newly  smelted 
lead,  being  a  semicylindrical  bar  of  about 
5"X2£"  and  about  18"  long,  was  gently 
laid  down  horizontally  ;  it  immediately 
sank  to  the  bottom  and  there  remained. 
When  about  half  its  volume  was  melt- 
ed away,  the  unfused  portion  was  drawn 
up  to  the  surface  and  let  go,  when  it  at 
once  sunk  to  the  bottom  again. 

2d.  A  ball  of  such  lead  -was  cast, 
weighing  17^  lbs.,  diameter  about  4£*  ; 
this  was  put  into  an  empty  hand-ladle, 
which  was  gently  placed  upon  the  sur- 
face of  the  pot  of  melted  lead;  the  ladle 
was  depressed  sufficiently  to  fill  with 
lead,  and  being  left  free  was  carried  to 
the  bottom  of  "the  pot  with  sufficient  im- 
petus to  produce  a  sensible  blow  of  the 
exterior  of  the  ladle  upon  the  bottom  of 
the  pot. 

3d.  A  flat  circular  disk  of  about  1.25 
inch  in  thickness,  being  laid  gently  upon 
the  surface,  after  a  moment's  hesitation 
slowly  went  to  the  bottom.  Another 
disk  of  6"  diameter,  by  rather  less  than 
an  inch  in  thickness,  remained  a  few 
seconds  longer  on  the  surface  and  then 
sunk  to  the  bottom  ;  both  disks,  while 


534 


VAN   NOSTRAND'S   ENGINEERING   MAGAZINE. 


they  floated,  had  their  top  surfaces  but 
very  slightly  elevated  above  that  of  the 
liquid  lead.  One  of  the  disks  being 
gently  lowered  into  the  liquid  lead  ver- 
tically and  edgeways,  at  once  went  to 
the  bottom. 

4th.  Two  disks,  each  6"  diameter,  the 
one  0.57  inch  and  the  other  0.4  inch  in 
thickness,  being  gently  laid  flat  upon 
the  surface  of  the  molten  lead,  floated, 
and  with  an  emergent  portion  sensibly 
greater  than  that  of  the  disks  in  experi- 
ment 2  and  3,  and  remained  floating  un- 
til about  1.25  of  the  radius  had  been 
melted  away  all  round,  when  they  slow- 
ly sunk  in  the  liquid,  as  was  proved  by 
the  slow  disappearance  of  the  slender 
iron  wire  cast  into  the  middle  of  the 
disk  for  the  purpose  of  lowering.  The 
thinner  of  these  two  disks  floated  rather 
longer  than  the  thicker. 

5th.  A  plate  of  sheet  or  laminated 
lead,  clean  from  the  rolling-mill,  of  about 
0".5  in  thickness  and  about  lb"  square, 
being  gently  placed  flat  on  the  surface 
of  the  liquid  lead,  floated,  its  top  sur- 
face being  nearly  level  with  that  of  the 
liquid.  After  about  ten  seconds  a  piece 
was  melted  off  from  one  of  the  edges, 
when  the  plate  canted  in  the  opposite 
direction  and  sunk. 

6th.  Plates  of  about  0".18  thick  float- 
ed much  in  the  same  manner  as  the  pre- 
ceding. The  temperature  of  the  solid 
lead  employed  was  in  all  cases  about 
70°  Fahr. 

It  follows  from  these  experiments  that, 
as  in  the  case  of  cast  iron,  the  solid  does 
not  float  upon  the  liquid  lead  through 
buoyancy,  that,  on  the  contrary,  the 
negative  buoyancy  is  very  marked,  and 
that  the  repellent  force,  whatever  be  its 
nature,  by  which  flotation  is  produced  is 
dependent  upon  the  effective  surface  as 
compared  with  the  volume  of  the  solid. 

They  present  also  a  corroboration  of 
the  view  that  the  repellent  force  upon 
the  unit  of  effective  surface  is  greater 
as  the  difference  of  temperature  between 
the  solid  and  liquid  metal  is  so. 

I  proceed  to  some  remarks  upon  the 
experiments  referred  to  at  the  commence- 
ment of  this  paper,  and  quoted  by 
Messrs.  Nasmyth  and  Carpenter,  as  to 
the  floating  of'  pieces  of  solidified  iron 
furnace- slag  upon  the  same  slag  when  in 
the  liquid  state.  It  is  a  fact  that  blast- 
furnace slags  cooled  below  the  point  at 


which  they  become  rigid  do  very  gener- 
ally float  upon  the  same  slag  in  its  molt- 
en state.  It  is  equally  true  that  the 
basic  silicates  which  constitute  the  chief 
part  of  terrestrial  volcanic  lavas  float 
upon  the  surface  of  these  when  molten. 
But  these  admissions  do  not  suffice  in 
any  degree  to  support  the  conclusion 
deduced  by  Messrs.  Nasmyth  and  Car- 
penter, that  basic  silicates,  whether  as 
furnace  slags  or  lavas,  are  denser  in  the 
molten  than  in  the  solidified  state,  nor 
that  these  bodies  in  the  act  of  solidifica- 
tion expand  in  volume  or  decrease  in 
density  in  any  manner,  irrespective  of 
the  formation  or  enlargement  of  cavities 
or  gas-bubbles  within  them.  The  ex- 
periments of  the  author  upon  the  total 
contraction  of  iron  furnace-slags  for  the 
entire  range  of  temperature  between 
that  of  the  blast-furnace  and  the  atmos- 
phere, made  at  the  Barrow  Iron-Works, 
and  fully  described  in  the  author's 
paper  on  "The  Nature  and  Origin  of 
Volcanic  Heat  and  Energy,"  printed  in 
Phil.  Trans,  for  1873,  leave  no  doubt  as 
to  the  following  facts  : 

1st.  That  the  density  of  such  slags  at 
53°  Fahr.  is  to  their  density  when  molten 
and  at  the  temperature  of  the  blast-fur- 
nace as  1000  :  933,  or,  taken  at  the  melt- 
ing-point of  slag,  as  1000  to  983 — molten 
slag  being  thus  very  much  less  dense 
than  the  same  when  solidified. 

2d.  That  no  expansion  in  volume  what- 
ever occurs  in  such  slags  at  or  near  the 
i  instant  of  solidification. 

The  experiments  of  the  author  above 
referred  to  were  made  by  filling  cast 
iron  slightly  conical  moulds  with  the 
slag  run  direct  from  the  blast-furnace, 
and  permitted  to  consolidate  and  cool 
therein,  by  which  perfectly  solid  slightly 
conical  blocks  were  obtained.  From  the 
method  employed,  and  the  very  large 
scale  upon  which  these  experiments  were 
conducted,  it  is  impossible  that  any  ex- 
pansion in  volume  at  or  near  the  point 
of  consolidation,  if  even  of  a  very  min- 
ute amount,  could  have  occurred  and 
yet  have  escaped  notice.  It  is  only  nec- 
essary for  the  author  here  to  point  out 
that  the  floating  of  crusts  of  slag  or  lava 
is  not  due  to  the  cause  assigned  by 
Messrs.  Nasmyth  and  Carpenter;  nor  is 
it  his  intention  to  enter  at  any  length 
into  what  are  the  causes  of  such  floating 
when  it  occurs. 


EXPANSION   OF   SUBSTANCES    ON   SOLIDIFICATION. 


535 


The  following  remarks,  however,  may 
be  made  : — It  is  impossible  to  obtain  a 
moderate-sized  fragment  of  solidified 
elag  or  lava  free  from  air  bubbles,  and 
from  involved  or  superficial  cavities, 
which  tend  to  float  the  mass  when  thrown 
upon  its  own  material  in  the  melted 
state.  Those  who  have  attentively 
watched  large  volumes  of  slag  issuing 
from  the  blast-furnace  are  aware  that  it 
comes  forth  carrying  with  it  a  large  vol- 
ume of  gaseous,  matter  minutely  diffus- 
ed, which  is  pretty  readily  separated, 
and  is  characterized  by  a  white  vaporous 
cloud  floating  thinly  over  the  issuing 
stream  ;  if  the  slag  be  cooled  rapidly, 
the  gaseous  or  vaporizable  bodies  present 
become  confined  and  render  the  mass 
vesicular,  while  if  cooled  more  slowly, 
and  with  a  free  surface  for  the  escape  of 
these,  the  mass  solidifies  more  solidly, 
often  as  solidly  as  a  block  of  granite. 

Independently  of  the  buoyancy  that  is 
produced  by  the  vesicularity  of  rapidly 
cooled  slags,  it  is  highly  probable  that 
relatively  cold  and  solid  slag,  whose 
buoyancy  is  negative,  may  yet  float  on 
molten  slag,  whose  density  is  less  than 
its  own,  in  virtue  of  that  same  repellent 
force  which,  as  we  have  seen,  acts  under 
like  conditions  in  the  case  of  metals. 

With  respect  to  acid  silicates,  or  slags 
analogous  to  glass  (which,  however,  are 
not  referred  to  by  Messrs.  Nasmyth  and 
Carpenter),  the  author  again  refers  to 
the  results  given  in  his  paper  (Phil. 
Trans.  1873).  These,  and  indeed  the  cir- 
cumstances attending  the  production  and 
destruction  of  the  well-known  "  Rupert's 
drops,"  incontestably  prove  that  these 
silicates  also  are  less  dense  in  the  molten 
than  in  the  solid  state,  and  that  they 
contract  violently  at  or  near  the  instant 
of  consolidation. 

The  author  has  more  than  once  heard 
the  opinion  expressed  by  those  engaged 
about  blast-furnaces,  that  their  slags  do 
expand  in  consolidating,  based  upon  a 
misinterpretation  of  the  following  fre- 
quently occurring  circumstance  :  When 
the  large  parallelopipeds  of  slag  (5  to  6 
feet  square  by  2  to  3  feet  thick)  are 
stripped  from  the  iron  square  frame 
which  formed  their  edges,  and  are  being 
removed  upon  the  iron  wagons  on  which 
they  are  cast,  and  still,  as  often  happens, 
in  a  very  hot  state,  or  even  with  a  still 
liquid  or  viscous  interior,  though  rigid 


externally,  it  occasionally  happens  that 
such  a  block  bursts  asunder,  and  with  a 
suddenness  which  is  sufficient  sometimes 
to  scatter  dangerously  some  of  the  liquid 
interior  ;  or  if  the  fracture  be  not  so 
sudden,  and  the  interior  be  in  a  viscous 
condition,  the  latter  may  continue  for  a 
considerable  time  to  slowly  exude  in 
fantastic  shapes  from  any  aperture  of 
escape  left  free  to  it.  These  facts  have 
been  supposed  to  indicate  that  the  in- 
terior of  the  mass  expands  in  consolidat- 
ing. It  is  scarcely  necessary  here,  how- 
ever, to  enter  into  any  detail  to  prove 
that  the  phenomena  are  due  to  the  con- 
traction of  the  already  solidified  exterior 
upon  the  unyielding  interior  of  the 
mass  ;  the  former  becoming  fractured 
by  its  own  grip,  and  its  material  being 
highly  elastic,  often  yields  with  appar- 
ently explosive  violence  like  a  suddenly 
broken  spring. 

[The  following  remarks  may  be  made, 
in  addition  to  those  preceding,  in  con- 
travention of  the  supposed  expansion  of 
slags  or  lavas  in  consolidating.  It  is 
well  known  that  masses  of  mud  when 
dried  by  the  sun  crack,  the  fissures  pene- 
trating nearly  perpendicular  from  the 
surface  and  separating  into  more  or  less 
symmetrical  prisms.  Blocks  of  starch 
after  desiccation  present  similar  phe- 
nomena, which  are  also  frequently  seen 
exemplified  by  the  uppermost  beds  of 
argillaceous  limestone  (or  calp)  of  Ire- 
land when  first  laid  bare  from  its  detrital 
covering.  In  all  these  cases  there  can 
be  no  doubt  that  the  phenomena  are  due 
to  the  shrinkage  of  the  mass  in  drying. 
But  shrinkage  or  contraction  by  cooling 
and  consolidation  ought  to  present  us 
with  like  results  ;  and  these  we  see 
actually  manifest  in  the  splitting-Tip  of 
basalt  into  columnar  prisms  whose  long 
axis  are  always  found  perpendicular  to 
the  surface  by  which  the  heat  of  the 
mass  was  dissipated.  Such  columnar 
separation  is  not  confined  to  basalt  ;  in- 
stances of  it  are  abundant  in  lavas  of 
every  age,  the  surfaces  of  the  prisms  in 
these  being  sometimes  straight,  some- 
times curved.  Although  much  remains 
yet  to  be  investigated  before  all  the 
circumstances  attending  the  splitting  up 
of  masses  of  basalt  or  lava  can  be  said 
to  be  fully  understood,  yet  enough  is 
already  known  and  clearly  explained  to 
make  it  certain  that  it  is  due  to  contrae- 


536 


VAN   NOSTRAND  S   ENGINEERING   MAGAZINE. 


Hon  of  these  materials  as  they  cool  ; 
and  that  this  form  of  splitting-up  is 
wholly  incompatible  with  that  of  any 
Assuring  that  could  arise  from  the  re- 
frigeration of  a  mass  the  volume  of 
every  part  of  which  exj>anded  in  con- 
solidating.] 

As  in  what  precedes  the  hypothesis 
upon  which  the  lunar  volcanic  theory  of 
which  Messrs.  Nasmyth  and  Carpenter 
rests  is  proved  to  be  without  foundation, 
it   seems  needless  to  enlarge  upon  the 


incongruities  and  contradictious  which 
the  theory  itself  presents  when  fairly 
applied  to  such  knowledge  as  we  have 
of  the  volcanic  features  of  the  moon,  or 
still  more  when  applied,  as  it  must  be 
were  it  true,  to  those  of  our  earth  [as- 
suming the  materials  of  our  earth  and 
satellite  analogous  in  their  physical  and 
chemical  properties  —  an  assumption 
made  by  these  authors  throughout  their 
work,  though  without  any  attempt  to 
support  it  by  truth].    • 


ON  HYPERBOLIC  WHEELS. 

Prof.  L.  G.  FRANCE,  University  of  Pennsylvania,  Philadelphia. 
Written  for  Van  Nostrand's  Magazine. 


The  article  on  spiral  wheels,  published 
by  me  in  the  Franklin  Journal,  Phila- 
delphia, March,  1875,  brought  forward  a 
lively  private  correspondence  from  which 
it  appears  that  several  gentlemen  of 
high  scientific  attainments  took  consid- 
erable interest  in  this  matter.  One  of 
these  gentlemen  makes  the  following  re- 
marks in  his  letter:  "It  is  to  be  re- 
gretted that  in  addition  to  your  article 
on  spiral  wheels  the  hyperbolic  wheel, 
bearing  so  much  resemblance  with  the 
former,  was  not  treated  by  you  in  a  simi- 
lar way.  Most  books*  that  I  have  ex- 
amined and  consulted  on  this  subject 
give  a  number  of  formulas,  the  deriva- 
tion of  which  is,  however,  not  demon- 
strated," &c.  Now,  as  similar  remarks 
had  been  made  to  me  by  students  who 
were  desirous  to  study  this  subject  more 
in  detail,  I  prepared,  therefore,  some  time 
ago,  several  diagrams,  and  derived  some 
formulae  which,  in  my  opinion,  make  the 
subject  clear,  and  which,  in  order  to  ac- 
commodate such  taking  an  interest  in  it,  I 
shall  present  in  the  subsequent  treatise. 

1.    HTPERBOLAID  OF  REVOLUTION. 

f  The  surface  of  this  body,  that  is  used 
for  hyperbolic  wheels,  is  generated  by 
the  revolution  of  a  right  line  about  an 
axis  to  which  it  is  not  parallel  and  which 
it  does  not  meet.  Let  a  b,  ax  bx  be  a 
right  line  (Fig.  1)   revolving  about  cx  dx 

*  Mr.  Willis  in  his  Principles  of  Mechanism  gives  a 
very  thorough  demonstration ;  but  does  not  illustrate  it 
by  numerical  examples. 


as  an  axis  horizontally  projected  at  m. 
The  extremity  o  of  the  perpendicular 
mo  of  the  two  lines  will   describe  the 


circumference  of  a  circle  called  the  gorge 
circle,  and  the  extremities  of  a  b  ax  bx 
describe  circles  called  the  upper  and 
lower  discs.  Any  other  point  like  n'x  nx 
generates  the  circumference  of  a  circle 
belonging  to  the  surface  of  revolution, 
and  when  turned  into  the  meridian  plane 
will  be  projected  at  nlx.  In  this  manner 
any  number  of  points  of  the  curve  B^^B, 
can  be  obtained ;  if  this  curve  is  then  re- 
volved about  cx  dx  the  hyperbolic  surface 
is  produced.  It  is  proved  (Church's  Dis. 
Geom.   pp.  58  and   59)    that   the  curve 


ON   HYPERBOLIC   WHEELS. 


537 


Bx  on  B,  is  a  hyperbola  and  the  lines  6,  o, 
and  ol  q  when  projected  on  the  meridian 
plane  are  the  respective  asymtates. 

If  the  same  line  a  b,  a1b1  revolves 
about  another  fixed  line  not  in  the  same 
plane  with  it,*  a  second  surface  of  revo- 
lutions will  be  generated  tangent  to  the 
first  along  the  generating  line,  and  if  the 
two  solids  of  revolution  in  contact  are 
placed  in  frames  and  motion  is  given  to 
one  of  these  it  will  be  imparted  to  the 
other  by  partly  rolling  and  sliding  con: 
tact. 


*  The  position  of  this  second  axis  can,  however,  not  be 
taken  arbitrarily  as  shown  in  the  following  figures  2  and 


Suppose  PD  and  P  C  to  betwohyper- 
boloids  along  the  line  P  B,  the  axis  P  D 
and  PC  to  be  parallel  to  the  vertical 
projection  plane.  We  have  then  for  the 
axial  distance  at  P  (Fig.  1),  a=r+rt, 
equal  to  the  sum  of  the  radii  of  the  two 
gorge  circles  containing  the  point  of  con- 
tact at  P.  If  a  plane  P,  B  is  passed 
through  P,  perpendicular  to  the  axial 
line  it  will  contain  the  element  of  con- 
tact, as  this  plane  is  parallel  to  both  axes 
PC  and  PD  (Fig.  3).  Now  to  fix  the 
position  of  P  B  we  must  know  either  the 
numbers  of  revolution  or  the  number* 
of  teeth  of  both  bodies.  Suppose  n  and 
n.  to  be  the  numbers  of  revolution,  and 


r 
r 


ft 


N  and  N,  the  numbers  of  teeth  of  the 
bodies  of  revolution  of  which  P  C  and 
PD  are  the  respective  axes.  It  is  then 
n  :  nx\  ;Nt  :  N,  and  if  we  assume  B  to 
be  the  point  of  contact  of  the  upper 
discs,  we  have  also  : 

BC=PB.  Sin/?  and  BD=PB.  Sin/?, 
which  gives 

BCSin  /?  __  w,_N 
BD~Sin  /3~n  ~N,' 


(1) 


It  appears  then  from  (Fig.  3)  that  th© 
angle  d  is  divided  in  such  a  maimer  that 
the  lines  B  D  and  B  C,  which  represent 
the  sines  of  /?,  and  (3  respectively  are 
in  an  inverse  ratio  to  the  numbers  of 
revolution  and  in  a  direct  ratio  to  the 
numbers  of  teeth. 

If  we  put  for  /3=d —  /Sl5  we  obtain  : 

Sin  {(1-/3,)      n  s 
Sin  #      ~n   ' 


538 


VAN   NOSTRAND'6   ENGINEERING   MAGAZINE. 


Developing  the  first  number  we  have, 

Sin  d,    Cos  /?,  -  Sin  /?,.  Cos  rf     n, 

Sin  //,  "~  w  ' 

^         ^j      — '  +  Cos  d      m, 
Cotg  fi  =  n  .     That  is: 


Sin  d 
Sin  (? 


Tang/*^ 


(2) 


Since  the  axial  distance  a=r  +  rJ  is  per- 
pendicular to  the  line  of  tangency,  we 
obtain  graphically  the  lengths  of  r  and 
r,  when  we  erect  PM  =  «  perpendicular 
to  PB  (Fig.  3),  and  move  PM  parallel 
to  itself  till  it  lies  between  P  C  and  P  D. 
It  appears  then  that  r=PQ  tangent  JSX 
and  r,=P  Q  tangent  JBi;  which  gives  : 


Sintf 


r  _  Tang  /?  _  w, 

r 


(3) 


+  Cosd     — !  +  Costf 


Tang  jff,  Sin^ 


3  +  Cos  tf 


+  Cos  d 


n 


but  r^  —  a—r  introduced  into  (3)  we  find: 


H .     Cose? 


1  +  2—.  Cosd+ 


(I)' 


(*> 


These  equations  then  determine  the 
respective  radii  of  the  gorge  circles  and 
point  of  tangency  when  the  axial  dis- 
tance=ffl,  and  the  respective  numbers  of 
teeth  or  numbers  of  revolution  1ST,  N  and 
ii.  n  are  known. 


Fie.  2. 


Finally,  it  is  required  on  the  other 
hand  to  find  the  two  radii  of  the  upper 
discs  as  C  Vand  DS  (Fig.  2),  which  may 
be  obtained  in  the  subsequent  manner. 
Since  the  plane  P,  Ba  contains  the  line 
of  contact — P  B  passing  through  the  line 
of  tangency  which  latter  contains  the 
points  of  contact  P  and  B.  Therefore 
DB=D1B]  and  TQ=PQ=rJ  (Fig,  2). 


Hence  if  the  line  PB=/  is  assumed,  we 
find: 

Since  DB=P  B.      Sin  /3t=^l  X  Sin  /?,= 

(5) 

PVi=DS=TB1  =  vV1s  +  ?I2     and  ) 

R^CVvrM^f;    where [q=l.'  Sin/?.) 


ON   HYPERBOLIC    WHEELS. 


53& 


Introducing  into  the  above  derived 
general  formulas,  particular  angles  we 
obtain,  for  example,  d=90°  from  (4). 


b4^  Mf  >' 


a     n  +n' 
and  on  the  other  hand 


(6)  and 


\      (?) 


Li- 
es-" 


'n*  +  n 


For  c?=0  the  hyperbolic  wheels  pass 
into  common  spur  wheels. 

The  subsequent  numerical  example 
will  explain  the  use  of  the  preceding  for- 
mulae, and  how  they  are  applied  in  con- 
structing these  wheels. 

1.  Example.  —  Given  the  axial  distance 

7% 

#=10  inches  and— 2=4:  further  the  axial 

n     2' 

angle  of  projection  <r?=60°.  It  is  re- 
quired to  find  the  radii  of  the  gorge 
circles  and  upper  discs,  also  the  position 
of  the  line  of  contact. 

To  find  r  and  r  we  have  from  formu- 
lae (4) 

_r_       l  +  2.Cos60  l  +  i     2 

id- 14-2.  2  Cos  60  +  4^' 


3  +  4      7 


hence 


20     •     i.  j  *A     20     50 

?*=-rr=inches,  and  r  =10  — 


7  '"'  l     "      7  — 7 

To  find  J3  and  /3l  we  have  from  (2) 
Sin  60 


inches 


Tan; 
Hence 


A= 


"i  +  Cos60       £  + 


0,866 

-=0,866. 


/?=40.°  53'   and  y3=60  — 40°  53=19."  7'. 

Assuming  the  distance  from  the  points 
of  tangency  of  the  gorge  circles  and  the 
upper  discs  £=18  inches,  we  find  from 
(6).  

R,=f/(18.  Sin40.53)s  +  (y)L]3,8  in. 

R=V  (18.  Sin  19.7)2+(y)l=6,52  in. 

2.  Example. — Given  N=15  and  N  = 
27  (number  of  teeth),  further  the  axial 
distance  «=5  inches,  and  the  axial  angle 
<?=90°,  also  the  length  of  line  of  con- 
tact £=12  inches.  It  is  required  to  find 
the  radii  of  the  gorge  circles  and  those 


of  the  upper  discs  and  the  pitch.  To 
perform  the  division  of  the  angle  c£=9G= 
into  fi  and  /?,,  we  have  from  (6)  : 


Tang  /?  =  $  =  0,555  .  .  .  Hence 


nee 


£=29.°  3'  while  fic=d— /3=60° 

=40°  57'. 


29.°  3' 


To  obtain  r  and  jrf  we  have  from  (7), 
and  since  n,=>%  n. 


(*«)' 


(a) 


25 


tta  +  (f?i)'J— l  +  (f)5 
125 


106 


Hence  r= —  =1,1 8,  while  r,=5  —  1,1 8= 
106       '     ' 

3,82  inches. 

To  find  the  two  radii  of  the  upper 
discs  in  contact,  we  have  the  perpendicu- 
lar distances  from  the  point  of  contact 
to  the  respective  axis  : 

q=l.  Sin/?=12.  Sin  29°  3.     Hence 

R=V(12.  Sin  29  3)2  +  (l,18)s 

and  R1=A/(12.  Sin40°57T  +  (3,82)3 

which  gives 

R=6,08  inches,  and  R1=ll,8  inches. 

If  instead  of  lx  the  radius  of  one  of 
the  discs  is  assumed,  for  example,  Rx,  we 
find  : 

q=l  Sin  /?=VR,3-r3  and  since  ^=3 


*=?■* 


To  find  the  pitch  of  each  wheel  : 
2  it.  11,  8 


IV 


P== 


27 
2  7T.  6,  08 


15 


=2,  74  inches,  and 
2,  54  inches. 


While  two  spiral  wheels  in  contact 
have  only  one  point  common,  it  appears 
that  two  hyperbolic  wheels  touch  along 
the  whole  element,  and  while  the  sum 
of  the  tangential  angles  and  axial 
angle  of  two  spiral  wheels  in  contact 
amounts  to  180°  ;  the  axial  angle  of  the 
hyperbolic  wheel  limits  the  tangential 
angle,  which  indicates  that  a  less  num- 
ber of  varieties  of  hyperbolic  wheels  is 


540 


VAN   NOSTRAND'S   ENGINEERING    MAGAZINE. 


possible  than  of  spiral  wheels,  a  fact 
that  has  often  been  overlooked  in  apply- 
ing these  two  kinds  of  wheels. 

In  practice,  as  in  the  case  of  conic 
wheels,  a  narrow  f  rustrum  only  is  requir- 
ed of  each  hyperboloid  (Fig.  4),  and  these 
parts  include  so  small  a  portion  of  the 
curve  that  straight  lines  may  be  substi- 
tuted without  sensible  error.  Several 
wooden  models,  which  were  made  in  ac- 
cordance with  the  above  calculation, 
work  very  well;  some  of  them  work  by 
friction  only  produced  by  the  pressure 
upon  the  surface  of  contact,  others  were 
furnished  with  teeth  of  a  similar  form 
to  those  of  conic  wheels. 

As  to  the  axial  positions,  the  hyper- 
bolic Avheels  bear  much  analogy  with 
spiral  wheels.  The  above  (Fig.  4)  repre- 
sents the  above  mentioned  thin  frusta 
where  the  positions  of  the  teeth  are  in- 
dicated by  right  lines  obtained  from  the 
common  line  of  contact. 


Spanish  Mining. — In  the  mining 
district  of  Mansilla,  Logrono,  Old  Cas- 
tile, two  Ferroux  rock-drills,  to  be  work- 
ed by  steam  power,  are  being  put  up  by 
the  Swiss  firm  of  B.  Roy  &  Co.,  of  Vevey. 
The  scarcity  of  labor  is  much  felt  in  the 
mining  districts  of  Spain.  The  Revista 
Miner  a  states  that  these  two  rock-drills 
are  the  first  drills  that  have  been  yet 
used  in  the  country.  Great  animation 
is  reported  from  the  mining  district  of 
Teruel.  By  a  decree  of  the  Governor  of 
Biscay  the  exportation  from  Bilbao  is 
prohibited  of  gunpowder,  sulphur,  salt- 
petre, dynamite,  petroleum,  lead,  raw  or 
worked,  brass,  tin,  tin-plate,  copper  and 
iron,  whether  ore  or  metal,  and  every 
class  of  coal.  By  royal  ordinance  of 
June  12th,  steel  rails  pay  the  same  im- 
port dues  with  iron  ores.  The  directors 
of  the  mining  undertaking  of  the  basin 
of  Belmez  and  Espiel  are  endeavoring 
to  obtain  a  railway  direct  between  Mad- 
rid and  Ciudad-Real. 


THE  CHANNEL  TUNNEL. 


541 


THE  CHANNEL  TUNNEL— POS  [TION  OF  THE  ENTERPRISE. 


From  "  The  Builder." 


At  length  this  vast  enterprise,  which, 
if  completed,  will  certainly  confer  upon 
the  engineering  genius  of  the  nineteenth 
century  a  conspicuous  fame,  has  a  chance 
of  triumph  over  all  the  obstacles  that 
have  been  predicted.  The  latest  meas- 
ures in  connection  with  the  project  have 
been  of  the  utmost  importance.  A  bill 
has  passed  the  two  Houses  of  Parlia- 
ment, authorizing  the  acquisition  of  cer- 
tain lands  in  the  parish  of  St.  Margaret 
at  Cliffe,  in  the  county  of  Kent ;  and, 
at  the  same  time,  the  French  Assembly, 
before  its  dispersion,  gave  at  least  nomi- 
nal effect  to  a  scheme  for  opening  simi- 
lar works  on  the  opposite  shore  of  the 
British  Channel  at  Sangatte.  Neither 
in  the  English  nor  in  the  French  Re- 
ports or  Bills  is  there  found  a  full  ex- 
planation of  the  plans,  as  they  lie  now, 
in  manuscript,  at  the  Board  of  Trade  ; 
but  an  examination  of  the  documents,  or 
the  raw  official  materials  of  which  they 
are  composed,  suffices  to  inform  us  as  to 
the  actual  state  of  the  question.  It  is 
simply  this  : — In  the  year  1862  a  com- 
pany was  incorporated  to  construct  an 
underground,  and  also  submarine,  tunnel 
between  England  and  France,  with  all 
necessary  approaches,  accessories,  and 
conveniences,  so  as  to  afford  the  means 
of  perfect  land  communication  between 
the  two  countries,  and  the  powers  it 
proposed  to  claim  were  legally  justified. 
It  would  be  superfluous  to  enter  upon 
the  legislative  wranglings  over  plans, 
acts  to  be  abolished  or  construed,  pur- 
chases, and  costs,  since  the  principal  im- 
portance of  the  subject  to  the  public 
consists  in  the  mighty  mechanical  work 
to  be  undertaken.  This  will  not  be,  at 
the  outset,  it  may  be  as  well  to  explain, 
an  attempt  directly  to  tunnel  beneath 
the  Channel  for  a  railway  line.  It  is 
only  contemplated,  according  to  the  last 
statements  deposited  at  the  Board  of 
Trade,  to  examine  into  the  probabilities, 
or  possibilities,  of  opening  a  way  for  the 
locomotive  and  the  train  at  a  safe  depth 
below  the  sea.  The  present  idea,  then, 
is  to  sink,  on  both  sides  of  the  Channel, 
at  particular  points  which  are  indicated, 
shafts  through   the  gray  chalk,  or  that 


which  is  almost  nonporous  and  imperme- 
able by  water,  and  thence  to  conduct  an 
excavation  tending  to  meet  from  oppo- 
site ends,  which  should  equal, — as  it 
would,  if  triumphant,  more  than  equal, 
— the  perforation  of  Mont  Cenis.  How- 
ever, the  lawyer's  aspects  of  the  question 
are,  at  this  stage,  of  little  importance  ; 
the  two  Governments  are  agreed,  and 
the  thing  has  now  only  to  be  done.  But 
what  millions  have  been  sunk  in  an 
effort  to  cross  the  British  Channel,  and 
conquer  that  "  thin  streak  of  sea-sick- 
ness" which,  as  popular  tradition  still 
asserts,  frightened  the  famous  Boulogne 
flotilla  !  Leaving  out  of  consideration 
four  of  the  Channel  ports, — Hamburg, 
Rotterdam,  Antwerp,  and  Ostend,  as- 
well  as  Havre  and  Dieppe,  upon  which 
this  achievement,  by  the  way,  would 
not  inflict  any  great  injury,  because  they 
are  commercial,  rather  than  passenger, 
ports, — it  is  the  narrowest  sea  which  is 
the  most  formidable,  which  is,  indeed, 
the  "  moat "  of  the  Continent.  The 
sufferers  who,  in  default  of  a  subway  or 
drawbridge,  endured  the  tortures  of  this 
brief  passage,  amounted  last  year  to 
nearly  half  a  million,  and  no  number  of 
Castalias  or  Bessemers,  no  matter  how 
scientifically  built,  can  meet  the  demand 
for  those  who  feel  an  ineradicable  hatred 
of  salt  and  swelling  water.  There  are 
excellent  steamers,  no  doubt,  employed 
upon  the  Channel  service  already,  but 
where  and  what  are  the  harbors  ?  It  is 
not  the  mere  Channel  passenger  who 
finds  himself  inconvenienced.  The  in- 
valid from  Australia,  or  India,  often  de- 
clares that  this  bit  of  chopping  sea-cur- 
rent is  the  most  trying  part  of  his  voy- 
age. He  hates  it  worse  than  the  rollers 
of  the  Atlantic,  or  the  sultry  nights  of 
the  Red  Sea.  Thus  affirms,  at  any  rate, 
Captain  Tyler,  whose  report  is  in  course 
of  preparation  for  the  next  session  of 
Parliament.  His  estimates  concerning 
this  little  water  journey  between  France 
and  England  are  of  peculiar  interest. 
There  is  an  average,  he  says,  in  the 
course  of  the  year,  of  thirty  storms  ;  of 
100  days  bringing  with  them  heavy  seas 
and  troublesome  breezes  :  of  108  moder- 


■542 


VAN  NOSTRAND's  ENGINEERING   MAGAZINE. 


ate  days  happening  in  succession  ;  and 
90  of  cold  weather.  The  two  opposite 
coasts,  so  to  speak,  are  hostile  in  charac- 
ter,— what  with  their  cliffs,  bars,  sands, 
necessity  for  breakwaters,  masonry, 
piers,  curves,  capes,  and  shallows  ;  and 
the  problem  has  been,  for  many  years, 
how  to  avoid  the  dilemma  so  long  felt. 
Calais  is,  undoubtedly,  so  to  speak,  the 
English  harbor  of  France.  It  may  be, 
geographically,  a  little  less  direct  on  the 
road  to  Paris  than  Boulogne  ;  but  it  has 
been  selected,  whether  for  one  reason  or 
another,  as  the  great  centre  of  communi- 
cation, by  way  of  Brussels  and  Cologne, 
for  Strasburg,  the  Rhine,  the  North  of 
Europe,  and  North  and  South  Germany. 
There  is  nothing,  therefore,  to  be  won- 
dered at  in  the  circumstance  that  so 
constant  desire  should  have  existed,  or 
«o  continuous  an  endeavor  been  made, 
to  abridge  and  facilitate  this  traffic, 
which,  it  may  be  said  without  exaggera- 
tion, is  vital  to  the  common  life  of 
Europe. 

.  In  the  first  place,  however,  it  was 
deemed  necessary  to  ascertain  the  proba- 
bility of  successful  excavation.  Geolog- 
ically, the  bed,  and,  nautically,  the 
depths,  of  the  Channel,  are  well  known; 
yet  sufficient  has  been  ascertained,  in 
other  respects,  to  induce  an  opinion  that 
the  experiments  should  be  undertaken, 
not  precisely  at  Calais,  but  at  a  point 
near  Ambleteuse,  near  the  familiar  vil- 
lage of  Andresselles,  where  the  deepest 
water,  near  that  coast,  is  to  be  found. 
Originally,  as  every  one  is  aware,  the 
project  was  regarded  as  an  impossibility, 
and  enormous  steamers,  or  ferry-boats, 
were  suggested,  which  would  have  in- 
volved a  world  of  new  piers,  basins  and 
sluice-gates  ;  indeed,  the  fluctuations  of 
ideas  upon  the  subject  has  been  the  chief 
cause  of  its  being  left  so  long  to  wither 
in  the  pigeon-holes  of  speculation.  After 
the  great  ferry  scheme  had  broken  down, 
the  designs  of  Mathieu,  the  French  en- 
gineer, for  a  Channel  tunnel  were  delib- 
erately brought  upon  the  carpet,  but  as 
deliberately  brushed  away  ;  for  they 
were  lost,  and  have  never  been  recover- 
ed; Gamond  came  next,  with  a  series 
of  geological  demonstrations,  which  have 
sustained  the  criticisms  of  time  and  sci- 
ence, and,  at  his  instance,  a  Commission 
was  granted  by  the  late  Emperor  of  the 
French,  "  which,"  in  the  language  of  the 


report,  "  appears  to  have  come  to  the 
conclusion  that  it  was  desirable  to  test 
his  investigations  by  sinking  shafts  and 
driving  short  headings  under  the  sea,  at 
the  joint  expense  of  the  two  Govern- 
ments." But  this  is  a  French  rather 
than  an  English  view  of  the  matter. 
Another  countryman  of  our  own,  Mr. 
Low,  also  laid  a  plan  before  the  Emperor, 
in  1867,  as  Sir  John  Hawkshaw  had 
done,  with  even  more  elaboration,  in  the 
previous  year,  and  Mr.  Remington  in 
1865, — and  their  rivals,  whose  names  de- 
serve to  be  noted,  although  their  ideas 
cannot  be  here  described  at  length,  were, 
— MM.  Franchot,  Tessier,  Favre,  Mayer, 
Dunn,  Austin,  Sankey,  Boutet,  Hawkins 
Simpson,  Boydon  and  Brunlees.  It  is 
worth  while  to  observe  the  list,  because, 
if  the  work  has  not  yet  been  accom- 
plished, it  has  evidently  not  been  for 
want  of  ingenuity  and  will.  It  has  mis- 
carried, however,  to  a  certain  extent, 
through  the  variety  and  contradiction 
of  the  schemes  projected.  Apparently, 
this  difficulty  has  been  overcome,  and 
the  resolve  has  been  arrived  at  definitely 
to  pierce  the  stiff  gray  chalk.  Mr.  Rem- 
ington, as  appears  from  the  printed  re- 
marks forwarded  by  him  to  the  Board 
of  Trade,  would  have  selected  the  line 
from  Dungeness  to  Cape  Grisnez,  in  order 
to  avoid  the  chalk  and  fissures  which  he 
dreads  encountering  in  the  bed  of  the 
Channel,  and  to  work  in  the  Wealden 
formation,  which  he  believes  would  af- 
ford a  greater  chance  of  success.  Such 
is  the  latest  aspect  of  the  matter,  as  pre- 
sented to  the  Department  at  Whitehall. 
But  the  report  does  not  stop  short  here. 
It  recapitulates  the  dreams,  as  some  of 
them  may  indeed  be  termed,  of  other 
adv'enturous  engineers.  There  were  two 
or  three  who  proposed  bridging  the 
Channel,  and  one  actually  professed 
himself  prepared  to  build  a  "marine 
viaduct"  from  Dover  to  Cape  Grisnez, 
with  iron  girders  propped  on  190  tow- 
ers, 500  ft.  apart,  and  500  ft.  above  the 
water,  and  he  estimates  the  cost  of  such 
an  edifice  at  simply  £30,000,000  !  Again, 
there  was,  as  already  mentioned,  Mr, 
Hawkins  Simpson,  with  his  submarine 
tunnel  on  a  pneumatic  system,  called  by 
him,  however,  the  "Eolian"  principle, 
for  which  he  claims  the  merits  of  cheap- 
ness, expedition,  superior  ventilation, 
and  easier  utility.     It  is  interesting  to 


THE   CHANNEL   TUNNEL. 


543 


note  the  inexhaustibility  of  inventors  in 
these  respects.  There  is  Mr.  Alexander 
Vacherot,  who  has  submitted  to  the 
Board  of  Trade  a  scheme  which,  we 
ought  to  say,  he  laid  before  the  Emperor 
of  the  French  in  1856,  for  "  laying  on 
the  bed  of  the  sea  a  tunnel  made,  or 
formed,  so  as  to  constitute,  so  to  speak, 
a  monolith."  He  would  "  construct  it 
on  the  shore,"  and  "  complete  it  in  sec- 
tions, to  be  drawn  down  into  their  places 
when  finished." 

The  representative  officer  of  the  de- 
partment dismisses  most  of  these  projects 
with  a  critical,  yet  downright,  denial  of 
their  practicability,  and  his  language 
may  be  worth  quoting  : — "  Although  it 
was  desirable  to  advert  to  these  various 
expedients,  it  is  not  necessary,  in  this 
place,  to  say  more  in  regard  to  them, 
than  that,  while  I  am  unable  to  convince 
myself  of  the  feasibility  of  any  bridge 
scheme,  I  conceive  that  it  might  be  wise 
to  test  the  practicability  of  a  tunnel  by 
means  of  preliminary  driftways."  This 
is  precisely  what  it  has  been  agreed,  by 
both  Governments,  both  Legislatures, 
and  the  united  companies,  shall  be  done. 
It  is  true  that  not  far  from  forty  years 
have  elapsed  since  M.  Thome  de  Gamond 
first  attempted  to  prove  that  a  subma- 
rine thoroughfare,  between  the  two 
countries,  was  possible  ;  but  gigantic 
advances  have  been  made,  during  the 
interval,  no  less  in  opinion  than  in 
science  and  mechanics.  No  international 
fears  are  now  created  by  the  Mont  Cenis 
excavation,  or  the  Suez  Canal.  They 
are  regarded,  indeed,  as  treaties  and 
pledges  among  the  Powers  of  civilization. 
The  shores  of  the  Atlantic  have  been 
united  by  a  cable  ;  the  barrier  of  the 
Alps  has  been  virtually  destroyed  ;  and, 
with  reference  to  the  latest  and,  perhaps, 
grandest  project,  a  careful  geological 
survey  has  shown,  at  any  rate,  the  possi- 
bility of  cutting  a  tunnel  through  the 
narrowest,  or  almost  the  narrowest,  part 
of  what  are  sometimes  designated  as  the 
Straits  of  Dover,  a  distance  of  twenty- 
two  miles,  or  slightly  more.  Trial  bor- 
ings and  soundings  taken  at  different 
points  by  Sir  John  Hawkshaw  and  the 
late  Mr.  Brassey  indicate  a  bed  of  chalk 
as  the  stratum  through  which,  after 
leaving  the  coasts  on  either  side,  the 
perforation  is  to  be  made.  Of  course, 
on  the  freedom  of  this  bed   from  acci- 


dental fissures,  dislocations,  and  "faults," 
the  success  or  failure  of  the  vast  experi- 
ment depends  ;  but  there  is  every  reason 
for  believing  that  it  lies  in  a  mass,  con- 
tinuous and  compact,  between,  as  it 
were,  two  impenetrable  ramparts  of 
clay.  From  the  boring  on  the  English 
coast,  in  St.  Margaret's  Bay,  a  great  un- 
broken depth  exists, — 175  ft.  of  "  upper" 
chalk,  and  295  ft.  of  "lower"  or  gray, 
chalk  which  is  occasionally  confounded 
with  the  clay  itself  ;  while  the  workings 
on  the  French  side,  near  Sangatte,  show 
270  ft.  of  the  upper,  and  480  ft.  of  the 
lower.  Experimental  shafts,  on  a  nafrow 
scale,  resembling  somewhat  the  borings 
for  an  artesian  well  have  been  carried 
to  a  depth  of  600  ft.;  but  these  supple- 
mental demonstrations,  in  point  of  fact, 
were  superfluous,  the  main  object  being 
to  ascertain  the  depth  and  nature  of  the 
Channel  bottom,  which,  at  its  deepest, 
is  180  ft.,  and  its  average  rather  more 
than  100  ft.  below  the  surface  of  the 
water.  No  sudden  changes  of  profund- 
ity, and  no  reefs  or  banks,  are  discerni- 
ble, to  the  knowledge  of  the  most  ex- 
perienced men,  and  the  bed  of  the  "  thin 
streak  "  is  shown  to  be  a  gradual  and  al- 
most equally  rising  and  falling  concavity 
between  the  two  coasts.  Under  these 
conditions,  as  the  reports  inform  us,  and 
taking  into  account  the  deep  homogene- 
ous strata  to  be  bored — about  509  ft. 
thick — not  less  anywhere  than  200  ft. 
between  the  crown  of  the  arch  and  the. 
bed  of  the  Channel  (allowing  for  the 
precipitous  cliffs  on  either  side)  — every 
hope  may  be  entertained  that  the  enter- 
prise, though  so  incomparably  superior 
in  its  magnitude  to  that  of  Isambard 
Brunei  for  constructing  a  Thames  sub- 
way, will  be  successful.  The  Thames 
Tunnel  was,  indeed,  in  some  respects,  a 
more  hazardous  enterprise.  Little  was 
then  known  about  sub-aqueous  boring  ; 
the  materials  were  more  shifting  than 
those  which  the  Channel  excavators  will 
have  to  encounter, —  irregular  strata  of 
loose  earth,  masses  of  sand,  gravel,  mud, 
and  clay,  liable  to  constant  disturbance  ; 
and  a  formidable  tidal  action.  In  re- 
memberance  of  these  obstacles,  it  was 
thought  that  a  tunnel  beneath  the  sea 
must  present  insuperable  difficulties. 
But  we  have  gone  through  the  groat 
submarine  galleries  of  the  Cornish,  Cum- 
berland, and  other  mines,  and  observed 


544 


van  nostrand's  engineering  magazine. 


no  more  drip  than  would  be  evident  in 
any  cavern  of  the  Derbyshire  Peak. 
For  instance,  the  mine  of  Shiel  Lode 
runs  to  a  length  of  80  fathoms  below  the 
level  of  the  sea,  at  a  depth  of  less  than 
18  ft.  from  the  water.  It  has  never 
been  inundated,  nor  have  the  workmen 
(workwomen  also,  we  are  sorry  to  add) 
suffered  through  deficiency  of  ventila- 
tion, space,  and  provisions  for  their  com- 
fort. To  conclude,  practically,  however, 
the  first  boring  is  to  be  about  9  ft.  each 
way,  which  dimensions  are  asserted  are 
the  least  that  can  be  depended  upon  as 
a  test,  or  even  as  an  experiment.  Then 
will  follow  the  work  of  enlargement, 
along  the  walls  and  roof,  through  the 
agency  of  a  machine  which,  it  is  affirm- 
ed, can  bore  chalk  at  the  rate  of  a  yard, 
or  more,  an  hour.  A  difficulty,  however, 
may  still   have   to   be  met.     The  most 


costly  labor  of  any  will  be  the  removal 
of  the  excavated  stone,  clay,  and  soil. 
Tunnels  driven  underground  have  usual- 
ly shafts,  at  intervals,  through  which  the 
disturbed  earth  is  raised,  and  their  fre- 
quency, by  enabling  the  excavation  to 
be  broken  up  into  short  lengths,  reduces 
considerably  the  arduousness  of  the 
work.  Such  advantages,  however,  will 
not  exist  in  the  case  of  the  projected 
Channel  Tunnel.  All  the  earth,  or  rock, 
or  clay,  or  chalk  will  have  to  be  removed 
to  the  terminal  shafts  at  either  end,  and 
this  toil  and  expenditure  must  increase 
as,  by  progression  of  industry,  the  head- 
ings are  removed  to  greater  distances 
from  the  ends.  Nevertheless,  the  task 
is  now  fairly  in  hand,  and  we  may  rely 
upon  the  spirit  and  the  genius  of  the  age 
in  which  we  live  to  carry  it  through 
effectually. 


RELATIONS  OF  TITANIUM  TO  IRON. 

By  RICHARD  AKERMAN,  of  the  Stockholm  School  of  Mines. 


From  "Iron. 


Titanium  occurs  in  many  iron  ores, 
and  sometimes  in  very  large  quantity. 
Thus  a  magnetic  iron  ore  from  Ulfo,  in 
the  Archipelago  of  Angermanland,  con- 
tains, according  to  an  analysis  by  Dr.  A. 
Tamm,  9.51  per  cent,  titanic  acid.  Fur- 
ther, Herr  Fernquist  has  found  in  a  mag- 
netic iron  ore  from  Taberg,  near  Jonkop- 
ing,  6.30  per  cent.  ;  and  in  a  magnetic 
iron  ore  from  Longhult  Mine,  in  Smoland, 
8.5  per  cent,  titanic  acid.  Finally,  in 
similar  ore  from  Inglamola,  in  the  same 
province,  5  per  cent,  titanic  acid  has 
been  found. 

Titanium  is  very  difficult  to  reduce, 
and  the  incomparably  greatest  part  of 
an  iron  ore's  content  of  this  substance 
passes  in  the  furnace  process  into  the 
slag,  the  color  of  which,  in  consequence, 
becomes  dark  to  completely  black,  while 
in  the  pig-iron  produced  it  is  commonly 
difficult  to  detect  the  least  trace  of  it. 
Thus  Herr  J.  E.  Eklund,  in  an  examina- 
tion made  at  the  Stockholm  School  of 
Mines,  found  scarcely  a  trace  of  titanium 
in  the  pig-iron  produced  from  the  ore 
from  Taberg,  mentioned  above  ;  but  the 


slag  belonging  to  it,  on  the  contrary, 
contained  8.55  per  cent,  titanic  acid,  and 
another  furnace-slag  from  Taberg  ore  has 
been  found  to  contain  10  per  cent,  titanic 
acid. 

Professor  Eggertz,  too,  while  assaying 
very  titaniferous  iron  ores,  has  never 
succeeded  in  obtaining  any  titanium  in 
the  pig-iron  produced.  Nor  did  any 
success  attend  an  experiment  made  in 
Percy's  laboratory  to  produce  titanifer- 
ous iron  by  fusing  together  oxyde  of 
iron  and  finely  pulverized  titanic  acid  in  a 
graphite  crucible,  inasmuch  as  no  titan- 
ium was  found  in  the  metallic  buttons 
produced;  but  Sefstrom  on  the  contrary 
— probably  in  consequence  of  stronger 
blowing,  and  the  higher  temperature 
thereby  occasioned — obtained  a  very 
titaniferous  iron  by  heating,  in  a  graph- 
ite crucible,  a  mixture  of  oxyde  of  iron 
and  titanic  acid,  and  a  similar  mixture 
along  with  the  bisilicate  of  lime.  In  the 
former  case  he  obtained  a  very  hard  but 
malleable  iron,  with  4.78  per  cent,  titan- 
ium ;  and  in  the  latter  a  velvet  black 
soft  iron,  with  2.2    per  cent,  titanium. 


RELATIONS   OF   TITANIUM   TO   IRON. 


545 


In  a  third  experiment,  similar  to  the  sec- 
ond, there  was  obtained  an  unmalleable 
white  and  hard  pig-iron,  with  0.5  per 
cent,  titanium.  That  this  substance  is 
sometimes  also  found  in  pig-iron  pro- 
duced in  the  common  way  appears  from 
the  fact  that  Mr.  Riley,  after  several  un- 
successful trials  with  different  varieties 
of  pig-iron,  finally  found,  in  several 
which  were  produced  partly  from  titan- 
iferous  bog  ore  from  Ireland,  very  con- 
siderable contents  of  titanium,  or  from 
0.5  to  1.6  per  cent.  Further,  Rammels- 
berg  has  found  a  small  content  of  tita- 
nium in  a  spiegeleisen  from  Lohhiitte, 
in  Miisen,  and  finally  Karsten  says  that 
a  trace  of  titanium  may  be  found  in 
many  varieties  of  pig-iron. 

Besides  occurring  in  the  furnace-slag, 
titanium  is  also  found  in  copper-colored 
compounds  which  are  found  most  fre- 
quently in  the  form* of  small  cubical 
crystals,  but  also  in  an  uncrystallized 
state,  partly  on  the  bottom  and  walls  of 
the  furnace,  partly  in  the  so-called  pig- 
iron  clots,  and  partly  also  in  the  slag  it- 
self. These  were  at  first  believed  to 
consist  of  metallic  titanium,  but,  accord- 
ing to  Wohler,  their  composition  is  rep- 
resented by  the  formula  TiC2N2,  +  3Ti3N2. 
This  compound  of  titanium  may,  accord- 
ing to  Herr  Zincken,  be  volatilized  at  a 
high  temperature,  and  its  occurrence  is 
by  Wohler  considered  to  be  connected 
with  the  formation  of  the  cyanide  of 
potassium  in  the  furnace. 

In  the  dry  assay  of  titaniferous  iron 
ores  there  is  commonly  observed  between 
the  pig-iron  and  the  slag,  and  also 
around  both,  a  copper  red  film,  which, 
in  all  probability,  also  consists  of  the 
compound  of  titanium  just  mentioned. 
Karsten  further  states  that  he  also  found 
in  pig-iron  small  red  grains,  and  that  it 
is  only  in  the  pig-iron  in  which  they  oc- 
cur, that  any  noticeable  content  of  tita- 
nium is  found,  in  consequence  of  which 
he  doubts  whether  iron  and  titanium  can 
enter  into  any  true  chemical  combina- 
tion with  each  other. 

Ores,  rich  in  titanium  are,  as  has  al- 
ready been  mentioned,  specially  difficult 
of  reduction,  so  that  the  quantity  of 
fuel  required  for  their  dry  assay  is  much 
greater  than  when  other  ores  are  em- 
ployed, and  this  circumstance  may  per- 
haps be  explained  in  this  way,  that  the 
titanic  oxyde  or  acid  indirectly  increases 
Vol.  XIII.— No.  6—35 


the  difficulty  of  reduction,  inasmuch  as 
it  tends  to  retain  a  part  of  the  oxyde  of 
iron  in  combination  with  itself.  When 
the  black  slag  obtained  in  the  dry  assay 
from  titaniferous  iron  ores,  has  boon 
fused  several  times  in  succession,  in  a 
graphite  crucible,  small  buttons  of  pig- 
iron  have,  according  to  J.  Akerman, 
been  obtained  every  time  ;  but  the  re- 
maining slag  has  been  still  of  the  same 
degree  of  blackness.  It  is  also  remark- 
able that  titaniferous  iron  ores  are  often 
smelted  in  a  graphite  crucible  with  the 
same  result,  whether  they  are  fluxed 
with  lime  or  quartz. 

The  salts  of  titanium  are  fusible  with 
difficulty,  on  which  account  titanium 
makes  a  charge  difficult  to  smelt;  but, not- 
withstanding all  this,it  may  yet  be  a  ques- 
tion if  titanium  is  not  favorable  to  the 
formation  of  spiegeleisen.  It  cannot  be 
considered  as  absolutely  established,  but 
it  is  a  fact,  that  spiegeleisen  can  very 
readily  be  produced  from  Taberg  ore, 
notwithstanding  the  small  quantity  of 
manganese  (0.4  per  cent,  protoxyde  of 
manganese);  and  this  ore,  notwithstand- 
ing" its  richness  in  magnesia  (18.3  per 
cent.)  and  poverty  in  iron  (31.5  per 
cent.),  differs  from  the  Swedish  ores  only 
in  this  that  it  contains  a  litttle  vanadium 
and  a  great  deal  of  titanium.  Some- 
what larger  percentages  of  manganese 
have  indeed  sometimes  been  found  in 
Taberg  ore  than  that  mentioned  above  ; 
but  that  the  fitness  of  this  ore  for  the 
production  of  spiegeleisen  must  be  de- 
rived from  some  other  cause  than  the 
common  one — that  is  to  say,  the  presence 
of  manganese — is  believed  to  be  shown 
by  the  fact  that  two  pieces  of  spiegel- 
eisen from  different  works  in  Taberg 
district,  analyzed  at  the  Stockholm 
School  of  Mines,  contained  0.15  to  0.2 
per  cent,  manganese  ;  and  it  appears 
probable,  therefore,  that  either  vanadium 
or  titanium  is  the  cause  wherefore 
spiegeleisen  is  so  easily  formed  from  this 
ore. 

Ulfo  ore  has,  in  consequence  of  the 
difficulty  of  reducing  it,  been  used  only 
to  inconsiderable  extent,  and,  as  far  as  I 
know,  no  spiegeleisen  has  been  produced 
from  it  ;  but  that  it  tends  to  give  a 
white  pig-iron  appears  from  Clason's  ex- 
perience that  when  not  more  than  19.4 
per  cent,  of  a  basic  charge,  which  pre- 
viously gave  dark  gray  pig-iron,  was  at 


546 


VAN   NOSTRAND's  ENGINEERING    MAGAZINE. 


Bollsta  furnace  exchanged  for  Ulfo  ore, 
the  iron  became  white,  with  only  here 
and  there  a  gray  speck  interspersed. 
Titanium  may  possibly  therefore  favor 
the  tendency  in  iron  to  combine  with  the 
carbon  occurring  in  it  ;  but  if  this  is  in 
truth  the  cause  of  the  phenomena  just 
mentioned,  the  action  of  titanium  must 
be  very  powerful,  for  the  pig-irons  thus 
produced  have  been  found  to  contain,  as 
has  been  already  mentioned,  scarcely  a 
trace  of  the  substance  in  question.  How- 
ever this  may  be,  it  is  worthy  of  notice 
that  the  specimen  of  spiegeleisen  from 
Taberg  has  not  been  found  to  contain 
more  carbon  than  common  charcoal-pig, 
and  that  it  is  not  brittle  like  other 
spiegeleisen,  but,  on  the  contrary,  very 
difficult  to  break  in  pieces. 

With  reference  to  the  difficulity  of  re- 
ducing titanium,  and  its  tendency  to 
combine  with  oxygen,  it  is  probable 
that  the  titanium  sometimes  occurring  in 
pig-iron  is  oxydized  during  the  refining 
process,  and  in  malleable  iron,  so  far  as 
I  know,  titanium  has  never  been  found. 

By  fusing  together  99  parts  of  steel 
and  one  part  of  metallic  titanium  Kars- 
ten  obtained  a  good  steel  throughout, 
but  its  content  of  titanium  was  very 
variable,-  and  Karsten  finds  in  this  cir- 
cumstance an  additional  support  to  his 
views  that  titanium  and  iron  in  the 
metallic  state  do  not  enter  into  any  true 
chemical  combination,  but '  are  merely 
mechanically  mixed  with  each  other. 
This  steel,  after  polishing  and  etching, 
took  on  a  very  fine  damascening. 

Faraday  and  Stodart  have  attempted, 
by  fusing  together  steel  filings  and  a 
mixture  of  charcoal  in  one  case  with 
titanic  acid,  and  in  another  with  titanif- 
erous  iron  sand,  to  produce  titanic  steel. 
In  this  way,  too,  a  good  steel  was  ob- 
tained which  took  on  damascening,  but 
no  trace  of  titanium  could  be  discovered 
in  it,  and  this  notwithstanding  that  a 
specially  high  temperature  was  employ- 
ed for  its  production. 

From  what  has  been  stated  it  is 
thought  to  follow  that  it  is  only  excep- 
tionally 'that  any  reduction  of  titanium 
has  taken  place  in  the  case  of  mixtures 
of  titanic  acid  or  compounds  of  oxydes 
of  titanium  with  iron  and  charcoal. 
Attempts  have  been  made  to  produce 
titanic  steel  by  fusing  together  com- 
pounds of  titanic  acid  with  charcoal  and 


iron,  but  Percy  states  that  many  well- 
known  analysts  have  sought  for  titanium 
in  such  steel  without  success  ;  and,  with- 
out setting  up  for  a  judge  in  this  ques- 
tion, I  may  add  that  I  have  not  found 
any  titanium  in  such  steel.  This  is  also 
the  case  with  Mr.  Riley,  who  has  taken 
so  much  trouble  with  determinations  of 
titanium,  and  who  found  so  considerable 
quantities  in  some  varieties  of  pig-iron. 

To  how  great  an  extent  the  titanium 
crotchet  has  been  carried  is  best  seen 
from  the  circumstance  that  the  superior- 
ity of  Daunemora  iron,  and  other  first- 
rate  brands  of  steel-iron,  has  been  attri- 
buted to  the  richness  in  titanium  of  the 
ores  used  in  their  production  the  fact 
being  that,  so  far  as  I  know,  no  titanium 
has  been  found  either  in  Daunemora 
ores  or  in  any  of  the  other  Swedish  ores, 
from  which  the  most  renowned  varieties 
of  steel-iron  are  produced. 

From  the  facts  above  stated  it  appears 
to  follow  that  if  titanium  is  of  any 
observable  use  in  the  manufacture  of 
steel,  its  influence  on  the  qualities  of  the 
ii'on  must  be  so  exceedingly  strong  that 
so  small  a  quantity  as  can  with  difficulty 
be  discovered  by  analysis  acts  upon  it  ; 
and  this  is  confirmed,  to  some  extent,  by 
the  fitness  of  Taberg  ore  for  the  pro- 
duction of  spiegeleisen  ;  or  the  influence 
of  titanium  must  be  indirect,  by  con- 
ducing to  the  removal  of  substances 
hurtful  to  the  steel.  This  perhaps  may 
be  the  case,  at  least  so  far  as  sulphur  is 
concerned,  for  at  the  furnaces  where 
Ulfo  ore  is  used  it  is  believed  that  the 
danger  of  red-shortness  is  considerably 
diminished  by  a  mixture  of  less  than  10 
per  cent.  Ulfo  ore  in  a  charge  con- 
taining sulphur.  There  are  those  also 
who  affirm  that  titanium  purifies  from 
phosphorus,  but  I  know  of  no  facts  to 
prove  this.  On  the  other  hand,  it  is 
contradicted  by  the  fact  that  Dr.  A. 
Tanim  has,  in  the  pig-iron  produced  in 
the  dry  assay  of  Ulfo  ore  at  the  School 
of  Mines,  recovered  the  whole  of  its 
content  of  phosphorus,  which,  however, 
was  so  small  (the  ore  containing  only 
0.07  phosphoric  acid)  that  a  final  con- 
clusion can  scarcely  be  deduced  from 
this  experiment. 

i^i 

The  dismissal  of  European  employes 
on  the  East  Indian  Railway  has  been 
stopped  by  the  Supreme  Government. 


1'HE  MAIN   DRAINAGE   01-    PARIS. 


54? 


THE  MAIN  DRAINAGE  OF  PARIS. 

From  "The  Building  Xews." 


Almost  coincidently  with  the  formal 
completion  of  the  main  drainage  system 
in  London  has  been  issued  a  statement 
from  those  who  may,  in  English  phrase, 
be  termed  the  Commissioners  of  the 
Seine,  on  a  precisely  kindred  subject  in 
Paris.  It  begins  by  contradicting  the 
popular,  and  especially  the  foreign,  idea 
that  the  capital  of  France  is  a  dry  city 
— asserting,  on  the  contrary,  that  the 
average  daily  rainfall  equals  half  the 
amount  artificially  supplied  for  the  con- 
sumption of  all  the  inhabitants.  Tide 
floods,  which,  mingle  together,  contami- 
nated by  the  pollutions  of  streets,  of 
dirty  roofs,  and  all  else  constituting  an 
infectious  flow  wherever  any  popula- 
tion, great  or  small,  is  gathered  to- 
gether, must  be  got  rid  of  systematically, 
somehow.  The  gutters,  sinks,  vertical 
pipes  down  the  fronts  of  houses,  the 
gratings  and  runnels  in  the  streets,  were 
useless  without  the  immense  number  of 
subterranean  canals  carrying  off  all  this 
excess,  at  a  point  far  from  Paris,  into 
the  river,  though  necessarily  not  so  near 
to  the  sea,  as  are  our  own  sewage  out- 
falls. There  is  a  curious,  though  not  an 
exact,  parallelism  between  the  history 
of  the  two  systems.  That  of  the  Eng- 
lish metropolis  was  ordered  by  Act  of 
Parliament  to  be  carried  out  in  the  year 
1858  ;  in  the  same  year  that  of  the 
French  metropolis  was  completed.  It 
is  needless  to  dwell  upon  the  crying- 
necessities  which  existed  for  both  ;  but 
Paris  was,  perhaps,  in  the  worse  condi- 
tion of  the  two.  In  distant  times  the 
state  of  her  streets  was  an  abomination 
patent  to  the  eyes  even  of  those  who 
looked  out  from  palace  windows  :  in 
more  modern  days  the  evil  became  so 
intolerable  that  wealthy  private  indi- 
viduals protected  their  lives  by  draining, 
at  their  own  expense,  the  thoroughfares 
in  which  they  resided.  Later  still,  after 
a  storm,  the  streets  of  the  lower  town 
had  to  be  crossed  on  temporary  wheeled 
bridges,  always  kept  in  readiness  ;  and, 
so  late  as  1839,  a  petition  of  the  inhabi- 
tants represented  to  the  Government 
that  whole  quarters  would  be  depopula- 
ted if  some  abatement  of  the  evil  did 
not    take     place.       Even     then    nearly 


twenty  years  elapsed  before  the  grand 
reform  was  effected  ;  but  it  was  a  real 
one,  and  upon  a  magnificent  scale.  The 
French,  who  are  fond  of  splendid 
phraseology,  declared  that  a  new  or 
underground  Paris  had  been  created  ; 
but,  apart  from  the  national  habit  of 
verbal  exaggeration,  it  was  perfectly 
true  that  an  immense  work  had  been 
accomplished  in  the  face  of  stupendous 
difficulties.  For,  at  that  time,  and 
since,  the  city  was  being  converted 
above,  as  well  as  below,  by  means  of 
new  streets,  squares,  public  edifices,  and 
railway  termini  ;  and  it  was,  moreover, 
found  that  there  were  three  miles  of 
habitations  for  every  mile  of  sewer. 
The  task  at  that  time  taken  in  hand 
occupied  about  nine  years  in  its  fulfill- 
ment, and  the  results  have  been  now 
about  eighteen  years  in  operation.  That 
their  success  has  been  great,  as  the  Ad- 
ministration asserts,  is  not  to  be  denied. 
It  has  had  the  happiest  effects  upon  the 
health,  the  pleasantness,  and  even  the 
external  aspects  of  Paris ;  but  that 
nothing  remains  to  be  done,  more  par- 
ticularly in  the  outer  circle  of  the  city, 
not  even  the  Board,  as  we  should  term 
it,  of  "Bridges  and  Roads"  attempts  to 
show.  Indeed,  its  primary  object  in 
drawing  the  attention  of  the  Minister  to 
the  subject  is  that  he  may  be  induced  to 
support  a  supplemental  plan  for  bring- 
ing within  the  cope  of  the  Parisian 
main  drainage  system  the  outlying  vet 
contiguous  districts,  which  can  scarcely 
any  longer  be  regarded  as  suburbs.  The 
undertaking,  it  is  urged,  would  be  neither 
formidable  in  the  obstacles  presented  by 
it,  nor  costly  in  the  execution,  because — 
the  argument  is  an  official  one,  be  it  re- 
membered, and  not  altogether  supported 
by  experience — the  existing  chief  arter- 
ies, constructed,  not  to  answer  the  pur- 
poses of  a  generation  or  two,  but  de- 
signed upon  a  scale  of  more  than  Roman 
grandeur — literally — are  capable  of  re- 
ceiving any  number  of  affluents  that 
could  possibly  be  directed  into  them. 
In  magnitude,  of  course,  they  do  not  ap- 
proach those  of  London,  but,  in  every 
other  respect,  they  are  not  less  remark- 
able.     The  entire  arrangements   is  dis- 


548 


VAN"   NOSTRAND  S   ENGINEERING   MAGAZINE. 


tinguished  under  two  heads — principal 
arteries  and  feeders.  Little  value  is  as- 
signed to  pumping  stations  or  reservoirs. 
The  French  comparison,  in  fact,  is  that 
of  a  fish's  skeleton  running  beneath  the 
roadway  :  the  dorsal  hone  is  the  "  col- 
lector," the  lateral  hones  are  the  drains, 
whether  from  the  houses  or  the  gutters. 
The  former,  or  the  largest  of  them,  fol- 
lows the  Hues  of  the  valleys  which  so 
characteristically  mark  the  configuration 
of  the  French  capital,  so  that  they  may 
receive  the  tribute  of  the  more  elevated 
quarters,  and  they  are  three  in  number  : 
— One,  on  the  right  bank  of  the  river, 
known  as  the  "  departmental,'"  on  ac- 
count of  its  vast  extent,  the  wide  basin 
it  drains,  and  its  'eing  regarded  as  tak- 
ing precedence  of  the  other  two  ;  and 
this  divides  into  three  large  branches, 
gorged  by  the  sewage  of  the  worst 
quarters — the  cattle  markets,  the  public 
slaughter-houses,  the  gasworks,  the  im- 
mense industrial  establishments  of  La 
Villette,  Montmartre,  Belleville,  St. 
Denis,  and  even  the  crowded  hamlet  of 
Bondy.  Eighteen  months  ago  it  was 
considered  more  than  siifficient  for  any 
conceivable  accumulation  ;  but  it  is  now 
affirmed  that  the  outlet  into  the  river 
not  far  from  Saint  Ouen  is  occasionally 
so  choked  that  its  arch  threatens  to 
burst.  This,  however,  it  is  explained, 
may  be  accounted  for  by  the  fact  that, 
at  a  particular  point,  one  embouchure 
carries  off  the  load  brought  down  by 
two  of  the  vast  vaulted  subways  that 
intersect  subterranean  Paris.  The  sec- 
ond great  collector,  on  the  same  side  of 
the  stream,  starts  from  the  Arsenal 
Basin,  and  continues  its  course  through, 
a  purer  neighborhood,  until  it  reaches 
the  village  of  Asnieres,  where  it  vomits 
— to  employ  the  word  in  its  Roman 
sense — its  contents  into  the  Seine,  to  the 
infinite  detriment  of  waters  that  would 
otherwise  be  delightful.  The  Govern- 
ment is  urged  to  take  this  fact  into  con- 
sideration, in  conjunction  with  the  muni- 
cipality, and  to  relieve,  if  possible,  so 
favorite  a  pleasure  resort  of*  the  Pari- 
sians from  so  noxious  a  neighbor.  For,  it 
is  pointed  out,  besides  the  crowded 
tract  of  town  between  the  Arsenal  and 
the  railway,  it  bears  a  pestiferous  load 
from  the  Sebastopol  district,  the  Rue  de 
Rivoli,  with  all  its  mansions,  hotels,  side 
thoroughfares,  and  royal  dwellings;  and 


elsewhere,  including  the  Place  de  la  Bas- 
tille, the  Boulevard  Malesherbes,  &c.  ;  it 
receives,  in  fact,  the  discharge  from  the 
great  sewer  of  the  Petits-Champs,  and 
the  dangerous  drain  named  after  Riche- 
lieu, which,  at  the  first  drop  of  rain,  is 
choked,  and  much  dreaded  by  the  work- 
men on  account  of  its  steep  falls  from 
the  higher  to  the  lower  level.  On  the 
other  or  left  bank  of  the  Seine  there  is 
only  one  "  collector,"  which  includes, 
however,  that  which  was  once  a  pretty 
running  water — the  Biviere,  which,  for 
many  years  was  the  Fleet  Ditch  of  Paris, 
famous  for  the  abominations  it  poured 
(many-colored  and  foetid)  into  the  stream 
which  is  the  pride  of  Paris,  near  the 
bridge  of  Austerlitz,  This  also  makes 
an  exchange  with  its  parallels  beneath 
the  opposite  bank,  and,  after  traversing 
many  populous  neighborhoods,  adds  its 
unclean  flood  to  the  Seine. 

Thus,  in  a  space  of  nine  or  ten  years, 
Paris  is  reminded  it  acquired,  at  a  rough 
estimate,  400  miles  of  new  or  renovated 
drainage,  constructed  upon  improved 
principles.  Formerly  its  sewers  were 
built  of  common  ragstone,  soft,  pervi- 
ous, and  perishable  ;  then,  of  what  is 
called,  in  the  vicinity  of  Paris,  where  it 
abounds,  "millstone  rock."  In  1844 
Roman  cement  was  employed  for  the 
arching  only;  but,  after  1855,  the  en- 
tire surface  of  the  "  gallery  "  was  coated 
with  hydraulic  cement,  ensuring  a  solid- 
ity and  a  capacity  for  cleanliness  unpre- 
cedented. Few  cases  of  asphyxia,  Ave 
are  told,  now  occur.  The  strange  phe- 
nomena which,  in  the  reign  of  Louis 
XIII.,  were  known  by  the  equally  strange 
designation  of  "basilisks,"  have  been 
driven  away  ;  overgorgings,  whether  of 
water  or  rubbish,  are,  in  the  main  chan- 
nels, so  rare  as  hardly  to  be  taken  into 
account.  The  slopes  were,  in  the  first 
instance,  carefully  settled,  though,  here 
and  there,  they  are  in  actual  course  of 
improvement  ;  and  a  visit  to  the  sewers 
of  Paris  is,  in  our  days,  equivalent  to  a 
pleasure  trip — that  is  to  say,  there  are 
certain  show  sections  ;  but  they  must 
not  be  taken  as  more  than  an  exemplifi- 
cation of  drainage,  de  luxe,  beginning 
with  the  Place  du  Chatelet  and  ending 
at  the  Madeleine.  They  are  not,  how- 
ever, to  be  despised  on  that  account. 
The  gigantic  hall,  whence  branch  the 
grand   "  canals,"  leads  to   underground 


THE   MAIN   DRAINAGE   OF    PABIS. 


549 


roads,  whence,  looking  up,  the  eye  is  at- 
tracted by  a  series  of  metal  conduits, 
black  and  polished  as  ebony,  which 
carry  across  this  twilight  highway  the 
waters  of  the  Ourcq  and  of  the  Seine 
itself  ;  and,  farther  oir,  of  the  Vanne — 
engineering  works  of  which  the  French 
are  not  unjustly  proud.  Along  the  sides 
of  these  Titan  tunnels  run  the  tubes  of 
the  pneumatic  dispatch  ;  in  the  thick- 
ness of  the  wall  are  offices  for  clerks  and 
lamplighters  ;  lights  enclosed  within 
porcelain  globes  hang  from  the  iron 
columns  ;  there  are  rails  and  trains 
through  the  long  perspective  of  semi- 
darkness.  But  this,  as  already  suggest- 
ed, is  little  in  connection  with  the  prac- 
tical drainage  works.  A  little  further 
on,  and  sewage  barges  float  upon  a 
stream  which  calls  up  an  idea  of  the 
classic  Acheron.  They  are  manned  by 
the  pilots  of  a  singular  navigation,  which 
shuts  and  taps  as  it  passes  the  several 
districts,  and  so  in  a  manner  regulates 
the  general  outpouring.  A  distinction 
will  here  be  seen,  broad  and  unmistake- 
able,  between  the  London  and  the  Paris 
systems,  even  if  only  mechanically  con- 
sidered. But,  we  may  repeat,  the  sub- 
terranean Paris  exhibited  to  visitors 
does  not  comprise  all  that  might  be 
shown — at  least  to  observers  of  a  more 
practical  class.  The  attention  of  the 
Minister  is  drawn  by  the  original  engi- 
neer of  the  works  that,  since  they  were 
nominally  completed,  twelve  different 
types  of  drains  have  been  experimented 
upon  ;  the  grand  "  collector,"  with  its 
broad  sideways,  the  hollow  within  a 
hollow,  leaving  room  for  cleansing  and 
the  search  after  lost  valuables ;  the 
drains  from  private  houses,  generally 
very  steep  in  their  descent  towards  the 
central  "  collector  ;"  and  seven  or  eight 
other  varieties  in  form  and  size.  As  to 
size,  it  is  scarcely  possible  to  exaggerate 
the  precautions  that  are  necessary  when 
a  tempest  of  rain  occurs.  In  July,  1872, 
a  storm  broke  over  Paris,  accompanied 
by  a  startling  fall  of  rain  ;  the  great 
running  vault  beneath  the  Rue  Riyoli 
was,  within  a  quarter  of  an  hour,  full  ; 
the  water  burst  through  the  street  grat- 
ings ;  many  workmen  were  swept  away  ; 
and,  even  now,  notwithstanding  the 
superb  proportions  of  "  subterranean 
Paris,"  five  minutes'  flood  will  imperil 
the  city.     It  is  by  no  means  asserted  by 


the  memorialists  that  the  principle  of 
the  Paris  system  is  defective.  On  the 
contrary,  they  insist  upon  its  architec- 
tural spaciousness  and  massiveness,  its 
capacities  of  on) -throw,  and  it>  power 
of  "collecting"  the  superfluous  waters 
of  a  storm.  But  the  "statement" — it 
might  be  wrong  to  speak  of  it  as  a  re- 
port— although  we  hare  used  the  term 
"sewage,"  really  says  very  little  con- 
cerning sewage  at  all.  It  is  nearly  all 
confined,  us  were  the  plans  of  M.  Bel- 
grand's  engineers,  to  the  carrying  off  of 
superfluous  water.  There  is  nothing, 
or  scarcely  anything,  said  to  the  Govern- 
ment about  the  exuvia  of  the  city  ;  yet 
suggestions  are  made  vaguely  in  respect 
of  this  vital  question,  since,  as  the  report 
(if  so  it  may  be  termed)  puts  the  point 
plainly,  a  system  of  main  drainage, 
which  is  made  also  a  plan  of  promenades, 
cannot  be  very  practical  except  before 
being  employed."  But,  it  adds,  a  great 
advantage  is  gained  through  the  power 
of,  at  any  time  within  a  few  hours, 
shutting  off  and  drying  up  a  part  of  the 
extraordinary  labyrinth  for  purposes  of 
examination  or  repairs  ;  and  a  special 
characteristic  is  the  machinery  employed 
— invented,  indeed,  since  the  ostenta- 
tious opening  of  the  works — -for  the  lift- 
ing up  and  disposal  of  such  extraneous 
offal  as  masses  of  stable  straw,  hanged 
cats,  drowned  dogs,  and  unfeathered 
mattresses,  the  amount  of  which,  the 
commissioners  say,  "  stupefied  us."  An- 
other and  more  tragic  aspect  of  these 
vaulted  highways  might  be  alluded  to, 
but  it  is  unnecessary.  In  the  parts,  it  is 
officially  affirmed,  which  are  not  liable 
to  inspection  by  strangers,  every  possi- 
ble experiment  is,  even  now,  being 
tried,  so  far  as  regards  arches  of  a  mar- 
ble unity,  walls  exuding  and  absorbing 
little  damp,  floors  impermeable  to  any 
moisture  except  that  which  they  carry 
away,  and  the  fluted  earthenware  pipes, 
which,  according  to  the  same  authority, 
act  as  final  adjuncts  to  the  rest.  An- 
other, and  even  a  grotesque,  aspect 
might  be  given  to  the  subject  by  the 
grave  reflections  bestowed  upon  that 
which  has  generally  been  regarded  as  a 
ludicrous  aspect  of  the  Parisian  main 
drainage — the  rats.  The  sewers  of 
Paris  engender  these  vermin  in  their 
worst  aud  most  ferocious  form,  and. 
incredible  though  it  may  seem,  they  were 


550 


VAN    NOSTRAND  S    ENGINEERING   MAGAZINE. 


long  under  a  kind  of  official  protection 
for  the  sake  of  their  skins,  which  afford- 
ed a  great  supply  to  the  kid-glove-mak- 
ing trade  of  the  capital,  and  to  various 
other  industries  of  that  versatile  metrop- 
olis, which  are  not  yet,  perhaps,  suffi- 
ciently understood.  This,  however,  at 
the  best  is  only  a  parenthesis.  It  is  im- 
portant to  know  that,  according  to  the 
appeal  addressed  to  the  Minister  of 
State,  the  example  of  London  is  at  last 


quoted,  and  that  the  produce  of  the 
Parisian  sewers  will,  before  long,  be 
spread  around  in  endeavors  to  further 
irrigate  and  fertilize  the  long-exhausted 
districts  around. 

But  for  the  moment  it  suffices  to  ap- 
preciate the  enormous  and  complicated 
works  which,  upon  a  scientific  and 
practical  representation  to  the  French 
Government,  it  is  at  length  proposed  to 
complete. 


THE  USE  OF  STEEL.- 


Bt  J.  BABBA,  Naval  Constructor  at  Orient. 


So  much  remains  unknown  regarding 
the  nature  of  steel,  so  much  that  is  de- 
sirable to  know  and  is  presumably  dis- 
coverable, that  every  new  claim  to  fresh 
information  on  the  subject  of  steel  is  re- 
garded with  interest  provided  the  source 
is  trustworthy. 

The  little  work  of  M.  Barba,  just 
translated  by  Mr.  Holley,  bears  in  the 
names  of  the  author  and  translator,  suf- 
ficient guaranty  of  its  superior  value. 
Although  the  author  dwells  mostly  upon 
the  uses  of  steel  in  large  structures,  his 
remarks  upon  the  nature' of  the  metal 
and  the  classification  of  the  grades  and 
kind  are  so  appropriate,  and  altogether 
interesting,  that  copious  extracts  from 
this  part  of  the  work  will,  we  trust,  find 
favor  with  the  reader. 

Mr.  Holley's  preface,  setting  forth  the 
present  condition  of  the  steel  problem, 
we  first  give  almost  entire. 

"There  are  two  groups  of  facts  re- 
garding the  modern  steel  business,  which 
especially  concern  the  American  manu- 
facturers and  users  of  this  material. 

1st.  Three  French  men-of-war,  built 
out  of  Bessemer  and  Martin  steels,  were 
so  successfully  constructed  in  1873  that 
three  more  large  ships  were  ordered  in 
1874  to  be  built  from  the  same  materials. 
Several  Bessemer  works  in  England  are 
running  exclusively  on  a  general  mer- 
chant product  having  a  large  range  of 

*  "The  Use  of  Steel  for  Constructive  Purposes;  Meth- 
od of  Working,  Applying  and  Testing  Plates  and'Bars." 
By  J.  Barba,  Chief  Naval  Constructor  at  l'Orient.  Trans- 
lated from  the  French,  by  Ales.  J.  Holley,  C.  E.  New 
■V  ork  :  D.  Van  Nostrand, 


grades  and  uses,  and  taking  the  place  of 
both  crucible  steel  and  wrought  iron. 
The  Continental  works  are  turning  prob- 
ably a  third  of  their  Bessemer  product 
and  nearly  all  their  Martin  product  into 
other  forms  than  rails.  All  the  late  lo- 
comotives— many  hundreds — on  the  Lon- 
don and  Xorth  Western  Railway  are 
built  of  Bessemer  steel,  excepting  only 
the  wheels  and  necessary  castings.  Every- 
where, abroad,  Bessemer  and  Martin 
steels  are  more  and  more  extensively  and 
satisfactorily  employed  for  ship  and 
boiler  plates,  beams,  channels  and  angles 
for  ships,  bridges  and  other  structures, 
railway  tires  and  axles,  general  shafting, 
agricultural  implements  and  the  multi- 
tudinous forms  of  machinery  bars,  and 
forgings.  In  the  railway  and  machine 
shops,  the  bridge  works  and  ship  yards 
of  Europe  and  of  France  especially,  the 
method  of  treating  steel — of  heating 
and  shaping  it  and  building  it  success- 
fully into  machinery  and  engineering 
structures,  has  become,  what  it  must 
everywhere  become,  before  this  material 
can  be  employed  to  the  best  advantage, 
a  distinct  and  highly  developed  art. 

2d.  In  the  United  States,  out  of  a  Bes- 
semer product  of  350,000  tons  per  year, 
probably  less  than  6,000  tons  are  used 
for  other  purposes  than  rails.  Very  few 
Bessemer  works  have  any  machinery  for 
producing  the  various  constructive  shapes 
required,  or  any  experience  in  making 
steel  of  high  or  low  trades.  Bessemer 
manufacturers  are  talking  about  reduc- 
ing products,  in  the  fear  that  rail  orders 


Til  K    USE    OF    S'lKI  [.. 


.1.) 


will  fall  below  the  capacity  of  their 
works.  Martin  steel  is  now  made  in 
American  works,  regularly  and  success- 
fully, of  all  grades,  from  springs  down 
to  boiler  plates,  thus  furnishing  every 
constructive  grade  required.  Engineers 
and  machinists  are  generally  asking  for 
just  such  material  as  steel  has  proved  to 
be  abroad,  but  are  yet  hesitating  about 
the  use  of  steel,  because  our  Bessemer 
manufacturers  have  not  got  much  into 
the  way  of  making  other  grades  than 
rail  steel,  and  Martin  manufacturers  have 
not  until  quite  recently  begun  to  adopt 
those  improvements  in  plant  and  prac- 
tice which  will  make  steel  cheaply  ;  and 
also  because  our  artisans  have  not  in 
most  cases  made  any  study  of  the  art  of 
working  steel,  and  are  therefore  afraid 
of  it.  Experts  say  that  the  use  of  wood, 
not  only  in  ocean  vessels,  but  in  river 
and  lake  boats  and  barges,  must  soon 
give  way  to  the  use  of  metal,  as  it  has 
done  abroad  and  is  beginning  to  do  here ; 
and  there  are  thousands  of  wooden 
bridges  on  our  railways  and  highways 
which  must  soon  be  replaced  by  metal  ; 
so  that  for  these  two  large  uses,  not  to 
speak  of  general  machine  construction, 
there  is  growing  up  a  vast  market  for  a 
better  material  than  iron.  Excellent  pig 
for  the  production  of  cheap  steel  is  ob- 
tainable in  all  parts  of  the  country,  and 
ferro-manganese,  upon  which  important 
qualities  of  constructive  steel  depend, 
is  now  cheap  enough  to  warrant  its  gen- 
eral use. 

In  short,  with  every  facility  for  mak- 
ing the  products  so  largely  needed  here, 
and  so  largely  used  abroad — with  the 
best  steel  works  in  the  world,  and  work- 
ing organizations  in  them  which  have 
increased  product  and  decreased  cost  in 
a  remarkable  degree,  we  are  devoting 
more  concentrated  action  to  schemes  for 
preventing  over  production  than  we  are 
to  adapting  grades  and  shapes  of  pro- 
duct to  the  various  constructive  uses, 
and  to  teaching  artisans  how  to  heat, 
shape  and  apply  them. 

In  view  of  this  state  of  affairs,  it  seems 
to  me  that  the  dissemination  among  our 
steel  makers  and  users,  of  the  facts  con- 
tained in  M.  Barba's  little  book,  should 
be  of  great  advantage,  1st,  to  our  en- 
gineers and  machinists,  by  making  more 
conspicuous  the  nature  of  steel  and  of 
the  new  and  important  art  of  working 


steel  ;  2d,  to  the  managers  and  owners 
of  large  enterprises  in  construction  and 
transportation,  by  revealing  to  them  the 
fact  that  steel  is  such  a  tractable  and 
valuable  material  ;  and  -u\,  to  our  steel 
makers,  by  showing  them  thai  a  vast 
want  exists  for  products  which  they  can 
make,  and  what  kind  of  steel  and  treat- 
ment of  steel  will  enable  them  to  take 
advantage  of  this  existing  want. 

it  is  to  be  regretted  that  M.  Barbadid 
not  give  us  the  analyses  of  the  steels 
employed — not  even  their  percentages 
of  carbon.  This  addition  would  have 
made  his  work  complete.  But  by  com- 
paring the  tensile  resistance  and  elonga- 
tions of  the  steels  he  mentions,  with 
those  of  other  steels  from  the  same  works 
and  with  Belgian  steels,  of  which  I  have 
analyses  and  mechanical  tests,  1  judge 
the  materials  put  into  these  French  ships 
to  have  had  between  0.25  and  0.33  per 
cent,  of  carbon.  These  or  even  lower 
steels  can  be  readily  and  uniformly  pro- 
duced in  our  Bessemer  works,  while 
Martin  steel  can  be  made  as  low  as  0.10 
carbon  without  difficulty. 

It  is  very  interesting  and  important  to 
note  that  steels  which  harden  and  tem- 
per as  readily  as  these  do,  and  which 
hence  so  readily  acquire  dangerous  in- 
ternal strains,  can  be  made  so  completely 
tractable  and  can  be  so  insured  against 
fracture  in  manufacture  and  use,  by 
proper  manipulation  and  by  heating  at 
the  right  times — additions  to  the  ordi- 
nary iron -working  processes,  which  arc 
not  so  very  costly  when  works  are  once 
fitted  out  with  suitable  apparatus. 

Another  important  fact  demonstrated 
at  the  Barrow  works  in  England  (set 
forth  by  Mr.  Josiah  T.  Smith,  in  a  late 
paper  before  the  Inst,  of  Civil  Engin- 
eers), and  most  completely  proved  by 
these  French  experiments,  is  that  the  in- 
jury done  to  steels  of  rail  grade  and  be- 
low, by  cold  punching,  is  confined  to  the 
skin  of  the  hole  (-nhr  inch  thick  in  this 
case)  ;  and  that  this  injury  is  only  hard- 
ening by  pressure  which  may  be  com- 
pletely removed  by  tempering  or  anneal- 
ing, or  by  reaming  out  this  thin  ring  of 
hardened  metal.  The  manner  in  which 
this  was  proved,  is  a  commentary  on  the 
nicety  of  French  experimenting. 

It  has  not  probably  occurred  to  many 
boiler-makers  who  could  do  nothing  with 
these  grades  of  steel,  and  so  have  eon- 


552 


VAN    NOSTRAND'S    ENGINEERING   MAGAZINE. 


demued  steel  altogether,  that  shearing 
and  locally  hammering  plates  put  them 
in  a  condition  similar  to  that  produced 
by  cold  punching,  which  reduces  the 
strength  of  the  parts  most  affected,  above 
20  per  cent.  Nor  has  it  perhaps  occur- 
red to  engineers  who  believe  in  steel  and 
are  anxious  to  give  it  a  fair  chance,  to 
dispense  with  that  class  of  smiths  and 
boiler  makers  who  cannot  be  told  any- 
thing about  the  treatment  of  steel,  and 
will  not  yield  to  any  new  requirements 
— just  as  these  French  engineers  turned 
out  the  skilled  workmen  who  could  not 
treat  plates  and  bars  without  cracking 
them,  and  substituted  carpenters,  who 
being  willing  to  follow  instructions,  made 
a  success  from  the  start. 

The  adaptability  of  steel  to  construc- 
tive purposes  is  specially  shown  in 
stamped  work,  such  as  pieces  shaped 
like  a  low-crowned  hat,  of  which  700 
were  produced  without  losing  one,  while 
not  one  good  piece  could  be  stamped 
out  of  iron.  The  facts  that  steel  crys- 
tallizes less  than  iron  by  heating  without 
working,  and  that  steel  plates  have  prac- 
tically the  same  strength  with,  and  across 
the  "  grain,"  are  greatly  in  its  favor. 

The  hardening  of  beams  and  angles  of 
comparatively  uniform  section,  in  the 
last  passes  of  the  rolls,  is  demonstrated, 
and  this  should  be  a  rebuke  to  those  en- 
gineers who  insist  that  a  rail  is  as  unlike- 
ly to  break  when  it  has  a  very  thin 
flange  which  must  come  out  of  the  rolls 
at  a  dark  red  heat,  as  if  it  had  a  thicker 
flange  which  would  finish  hotter. 

The  manner  in  which  carbon  exists  in 
steel — in  solution  and  in  mechanical  mix- 
ture— also  the  hardening  effects  of  sud- 
denly cooling  steel  and  of  cold  hammer- 
ing, shearing  and  punching,  viz.,  harden- 
ing due  to  pressure  ;  also  the  solution 
and  dissemination  of  carbon  by  heat,  are 
fully  treated  in  this  work,  and  will 
doubtless  make  clear  a  subject  which  in 
many  practical  minds  has  been  more  or 
less  indefinite  if  not  mysterious. 

The  more  important  conclusions  as  to 
treatment,  to  which  the  author  comes, 
and  to  which  the  artisan  in  steel  will 
have  to  come,  and  which  are  also  set 
forth  by  Mr.  Krupp  and  other  steel  mak- 
ers who  have  pushed  their  wonderful 
products  against  the  tide  of  "  practical " 
conservatism  into  vast  constructive  uses, 
are  ; 


1st.  Avoid  local  pressures  in  working 
cold  steel. 

2d.  If  local  pi-essures  must  occur,  re- 
move their  effects  by  annealing — not 
once,  but  as  often  as  dangerous  pressures 
are  produced. 

The  rationale  of  this  treatment  is  ob- 
vious ;  steel  is  more  dense  than  iron, 
hence  it  must  be  more  humored  in  its 
cold  treatment.  But  when  it  once  gets 
into  working  shapes  without  internal 
strains,  it  is  much  stronger  and  safer 
than  iron. 

It  should  seem  that  such  careful,  thor- 
ough and  obviously  trustworthy  experi- 
ments as  those  detailed  in  this  book,  and 
the  conclusions  to  which  they  inevitably 
give  rise,  should  prove  a  stimulus  to  our 
steel  makers,  to  enlarge  the  range  of 
manufacture  rather  than  to  curtail  pro- 
duction because  their  one  specialty  may 
possibly  exceed  the  present  demand — 
and  to  engineers  and  to  constructors  of 
government  works,  to  take  a  leading 
part  in  all  efforts  to  adapt  the  new  ma- 
terial and  its  treatment,  rather  than  to 
wish  them  well  from  afar  off." 

Thus  far  Mr.  Holley  presents  the  ques- 
tion. 

The  French  author  discourses  at  length 
upon  the  "  Composition  of  Steel,"  and 
upon  the  "  Classification  of  Steels,"  in 
separate  chapters,  from  both  of  which  we 
herewith  present  liberal  extracts  : 

COMPOSITION  OF    STEEL ITS    CHIEF  PROP- 
ERTIES  TEMPERING  AND  ANNEALING. 

The  metals  designated  in  the  trade  as 
cast  iron  and  steel  owe  their  character- 
istic properties  to  the  presence  of  a  cer- 
tain quantity  of  carbon  either  mechani- 
cally mixed  or  in  solution  with  the  iron. 
These  metals  may  contain  other  sub- 
stances more  or  less  affecting  these  prop- 
erties ;  chiefly  phosphorus,  silicon,  sul- 
phur and  manganese.  But  neither  of 
these  substances  is  necessary  to  the  con- 
stitution of  cast  iron  or  steel.  It  is  suf- 
ficient to  mention  that  they  are  present 
in  most  of  the  irons  of  commerce,  with- 
out studying  the  considerable  influence 
they  may  exert. 

Putting  aside,  then,  all  considerations 
relating  to  the  presence  of  foreign  mat- 
ters, cast  irons  and  steels  are  carburized 
irons.  Carbon  exists  in  them  either  in 
a  state  of  solution  or  of  mixture,  with- 
out forming  any  clearly  defined  carburet, 


THE    USE   OF    8TEEL. 


oo3 


"  Steel  is  a  solidified  solution  of  carbon 
in  chemically  pure  iron.  This  solution 
in  a  liquid  state  is  not  saturated  except 
in  case  of  the  steel  which  contains  the 
maximum  of  carbon  which  iron  can  hold 
in  solution.  Cast  iron  is  a  saturated 
solution  of  carbon  in  iron,  with  an  excess 
of  carbon  in  a  state  of  mehanical  mix- 
ture. It  might  be  defined  as  steel  con- 
taining carbon  in  mechanical  mixture. 
In  this  state  (mixture)  the  amount  of  car- 
bon is  larger,  in  proportion  as  that  held 
in  solution  is  smaller,  or  as  the  total 
quantity  of  carbon  contained  is  greater. 
So  gray  cast  iron  is  a  slightly  carburized 
steel  with  much  carbon  mixed,  and 
white  cast  iron  is  a  more  carburized 
steel  with  less  mixed  carbon." 

The  phenomena  of  the  solution  of 
carbon  in  iron  to  form  steel,  group  them- 
selves around  the  four  following  princi- 
pal laws  : 

1.  The  quantity  of  carbon  iron  can 
contain  in  solution  is  greater  as  the  tem- 
perature increases. 

2.  By  slow  cooling,  part  of  the  car- 
bon is  separated  from  the  solution  and 
remains  in  a  state  of  mixture. 

3.  By  rapid  cooling  or  by  a  sufficient 
external  pressure,  the  greater  part  of 
the  carbon  is  maintained  in  solution. 
Rapid  cooling  acts  in  this  case  by  the 
pressure  resulting  from  it.  If  the  car- 
bon is  mixed,  an  external  pressure  pro- 
duces a  solution  in  greater  or  less  pro- 
portion according  to  its  intensity. 

4.  The  temperature  at  which  melted 
steel  is  solidified  decreases  in  proportion 
to  its  richness  in  carbon. 

These  laws  of  the  solution  of  carbon 
in  iron  conform  to  those  which  regulate 
the  solubility  of  solids  and  gases  in 
liquids. 

1st.  The  solubility  of  solids  generally 
increases  with  the  temperature. 

2d.  When  a  solution  made  at  a  high 
temperature  is  cooled,  part  of  the  solid 
is  separated. 

3d.  The  solution  would  probably 
maintain  itself  under  a  sufficient  press- 
ure ;  but  no  experiment  has  been  made 
on  this  subject,  to  my  knowledge  ;  a 
trial,  to  verify  this  point,  would  proba- 
bly be  very  difficult  of  execution,  on  ac- 
count of  the  enormous  pressure  required. 
The  solubility  of  gases  increases  with 
the  pressure. 

4th.  Finally,    solutions   are  generally 


solidified  at  temperatures  decreasing  as 
the  solutions  become  more  intense. 

The  rapid  and  slow  cooling  of  heated 
steel  constitute  tempering  and  annealing, 
two  operations  whirl)  play  an  important 
part  in  the  use  of  the  material. 

When  any  metal  is  tempered,  that  is 
to  say,  rapidly  cooled,  the  external  layer 
cools  first,  and  it  does  this  all  the  quick- 
er as  the  difference  in  temperature  be- 
tween the  body  and  the  liquid  in  which 
it  is  immersed  is  greater.  The  conduct- 
ing power  of  the  liquid  used  has  also  a 
great  influence  on  the  rapidity  of  cool- 
ing :  tempering  in  mercury,  for  instance, 
will  be  more  intense  than  tempering  in 
water. 

This  cooled  external  layer  contracts 
and  presses  strongly  on  the  inside,  which 
is  yet  at  a  high  temperature  ;  recipro- 
cally, it  receives  from  the  inside  the 
same  pressure.  Another  phenomenon  is 
a  consequence  of  this  contraction ;  in 
order  to  contain  the  internal  volume,  the 
external  layers  must  stretch  at  the  ex- 
pense of  their  elasticity  ;  if  the  temper- 
ing has  been  intense  enough  they  may 
exceed  their  limit  of  elasticity  and  stretch 
permanently.  If  tempering  has  been 
incomplete  or  slight,  this  limit  not  being 
reached,  the  extension  will  be  but  mo- 
mentary, and  will  disappear  when  cool- 
ing is  complete. 

It  is  known  that  these  phenomena  are 
practically  taken  advantage  of,  to  break 
cast  iron  blocks,  which  could  not  be  eas- 
ily effected  by  blows  ;  they  are  heated 
red  and  cooled  in  a  stream  of  water. 
The  external  surface  contracts  and  passes 
its  elastic  limit ;  as  it  is  capable  of  only 
slight  stretching  before  breaking;  cracks 
show  themselves  on  the  surface,  and  a 
comparatively  light  blow  is  sufficient  to 
break  the  block  into  several  pieces. 

During  the  second  period  of  temper- 
ing, the  cooling  spreads  to  the  centre. 
In  their  turn,  the  central  fibres  contract 
on  account  of  the  lower  temperature  ; 
but  they  are  bound  to  the  external  fibres 
which  have  exceeded  their  limit  of  elas- 
ticity; they  must  then  stretch  at  the  ex- 
pense of  their  elasticity  as  they  contract : 
they,  at  the  same  time,  cause  a  contrac- 
tion of  the  external  fibres. 

A  tempered  body  is  therefore  sub- 
jected to  direct  forces  which  are  bal- 
anced by  molecular  tensions.  The  forces 
which  exist  after  tempering  can  be  ex- 


554 


VAN   NOSTRAND  S   ENGINEERING    MAGAZINE. 


hibited  by  suppressing  a  part  of  them. 
If  a  bar  of  tempered  iron,  squared  on  all 
sides,  is  cut  in  two  longitudinally  in  a 
planer,  care  being  taken  to  bold  it  in  an 
invariable  position,  each  of  the  pieces 
assumes,  when  left  to  itself,  a  curved 
form,  the  concavity  of  which  is  on  the 
planed  side.  This  form  demonstrates  a 
tension  in  this  pai't,  resulting  from  the 
second  period  of  tempering.  The  forces 
brought  into  play  in  the  first  period 
would  have  produced  the  opposite  effect 
if  they  alone  had  acted. 

Bodies  increase  in  volume  when  they 
are  tempered.  M.  Caron  has  observed 
the  following  variations  of  steel  bars  : 

Table  No.  I. 


Natural 
state. 


At  Red 
Heat. 


Length '  20.00  20.82 

Width l  l.OO  1.03 

Thickness. . .  1.00  1.03 

Volume I  20.00  20.00 


In  these  bars  the  length  decreased  and 
the  width  and  thickness  increased  ;  un- 
der the  influence  of  an  internal  pressure 
the  bar  behaves  like  any  homogeneous 
body  subjected  to  deformation  by  an  in- 
ternal force  ;  it  tends  to  assume  the 
spherical  form. 

M.  Caron  mentions  another  instance 
of  a  bar  of  rolled  steel  : 


Table  No.  II. 


Natural 

state. 


After 
Tempering. 


Length 20.00 

Width 1.51 

Thickness 3.70 

Volume 111.74 


20.45 

1  51 

3.70 

114  25 


Ln  this  example  tempering  has  again 
produced  an  increase  of  volume  ;  but 
unlike  the  preceding  case,  the  greatest 
dimension  has  increased  and  the  others 
have  not  changed.  This  contradiction 
is  apj>arent  only.  It  is  explained  by  the 
lack  of  homogeneity  in  a  rolled  bar 
which  is  capable  of  stretching  more 
readily  in  the  direction   of  the  rolling. 


After  tem- 
!    pering. 


19.95 
1.01 
1.01 

20.351 


than  perpendicularly  to  it.  The  longi- 
tudinal fibres  exceed  their  elastic  limit 
before  this  limit  is  attained  transversely  ; 
the  addition  to  the  volume  consists  in 
increased  length. 

Tempering  should  produce  these  effects 
in  homogeneoiis  bodies  only,  the  compo- 
sition of  which  does  not  vary  with  tem- 
perature and  pressure.  In  steels  and 
other  carburized  irons  tempering  is  com- 
plicated by  the  presence  of  carbon,  the 
solution  of  which  it  partly  brings  about. 
It  is  difficult  to  know  whether  the  in- 
crease in  volume  observed  in  tempered 
steel  is  to  a  certain  extent  modified  by 
this  solution  ;  by  continuing  the  com- 
parison between  the  laws  of  solubility 
of  solids  in  liquids,  we  may  suppose  that 
the  increase  in  volume  does  not  result 
from  this  cause  ;  for  a  solution  never 
has  a  larger  volume  than  the  total  vol- 
ume of  the  bodies  it  contains. 

The  solution  brought  about  by  tem- 
pering steel  produces  a  body  endowed 
with  properties  different  from  those  it 
possessed  before  tempering  ;  but  this 
body,  at  the  time  of  sudden  cooling,  is 
always  under  the  influence  of  the  phe- 
nomena we  have  just  explained.  The 
pressure  resulting  from  the  two  phases 
of  tempering  maintains  in  solution  a 
part  of  the  carbon  that  would  have  be- 
come separated  by  slow  cooling ;  this 
portion  will  be  greater  as  the  pressure 
is  stronger,  and  the  tempering  more 
rapid. 

If  a  non-homogeneous  body  is  temper- 
ed, composed  for  instance  of  steels  at 
different  degrees  of  carburization,  the 
action  will  be  complex  ;  it  seems  proba- 
ble that,  when  the  body  is  hot,  the  car- 
bon will  be  distributed  a  little  less  ir- 
regularly, and  that  this  dissemination 
can  increase  only  under  the  pressure  of 
the  cooled  external  fibres.  If  we  sup- 
pose this  body  represented  by  different 
tints  according  to  its  amounts  of  carbon 
in  different  parts,  the  lines  of  demarca- 
tion, instead  of  being  decided  as  in  the 
original  state,  will  be  blended  after 
tempering. 

This  phenomenon  of  transfusion  of 
carbon  through  iron  or  steel  heated  to  a 
sufficient  temperature  is  well  known.  A 
bar  heated  with  charcoal  is  cemented,  or 
dissolves  carbon  first  on  the  surface, 
then  more  deeply,  and  finally  to  the  cen- 
tre, if  cementation  lasts  long  enough, 


THE    USE    OF    STEEL. 


555 


When  steel  is  subjected  to  different 
degrees  of  tempering,  the  carbon  is  kept 
in  solution  in  a  much  larger  proportion, 
as  tempering  is  more  energetic.  With 
each  class  of  steel,  there  should  corres- 
pond a  degree  of  temper  at  which  the 
maximum  effect  is  produced,  that  is  to 
say,  when  tempering  would  cause  the 
solution  of  all  the  carbon  contained  in 
the  steel.  If  the  effort  of  contraction 
were  the  same  for  all  steels,  the  inten- 
■  sity  of  temper  producing  this  effect 
should  increase  with  the  degree  of  car- 
burization.  But  the  contraction  or  press- 
ure due  to  rapid  cooling  is  generally  in- 
sufficient to  produce  this  result.  The 
more  the  rapidity  of  cooling  is  increased, 
the  more  the  steel  changes  its  proper- 
ties. The  least  carburized  steels  only 
could  be  excepted  ;  beyond  a  certain 
point  the  solving  effect  produced  by  an 
increase  of  intensity  in  tempering  ought 
to  be  nothing  ;  alternations  in  elasticity 
only  could  be  observed.  But,  in  these 
bodies,  the  limit  of  elasticity  is  reached 
under  relatively  slight  effects,  and  tem- 
pering, by  a  variation  of  temperature 
such  as  we  can  effect,  does  not  produce 
a  sufficient  pressure  to  dissolve  all  the 
carbon 

Tempered  bodies  generally  regain  their 
properties  when  they  are  annealed,  that 
is  to  say,  when  they  are  made  to  cool  slow- 
ly after  having  been  heated  sufficient- 
ly. When  a  homogeneous  body,  the 
composition  of  which  does  not  vary  by 
heating,  is  annealed,  the  effect  is  merely 
to  restore  its  original  elasticity.  To  in- 
sure thorough  annealing,  the  operation 
must  be  performed  at  a  sufficiently  high 
temperature,  and  the  cooling  must  be 
slower  as  the  size  of  the  body  is  greater, 
so  that  there  may  be  between  the  inte- 
rior and  exterior,  but  a  slight  difference 
in  temperature.  The  first  condition  is 
necessary  to  allow  the  metal  to  recover 
the  elasticity  it  lost  in  tempering  ;  the 
second  condition  should  prevent  in  the 
successive  phases  of  cooling,  the  produc- 
tion of  undue  strains. 

In  complex  bodies  like  steel,  the  effect 
of  annealing  is  complex  ;  besides  this 
restitution  of  elasticity  to  the  fibres  al- 
tered by  tempering,  it  produces  the 
separation  of  a  part  of  the  mixed  car- 
bon. This  separation  must  take  place 
equally  throughout  the  mass  to  render 
the  bodies  homogeneous  after  annealing  ; 


and  it  is  easily  understood  that  a  very 
slow  cooling  is  necessary  to  insure  this 
result.  For  large  pieces  of  steel,  tliis 
cooling  must  occupy  several  'lays,  sonic- 
times  several  weeks. 

When  steel  is  properly  annealed,  the 
different  molecular  tensions  previously 
produced  are  suppressed  ;  the  fibres  re- 
lax under  the  influence  of  heat,  and 
return  to  their  first  elasticity. 

If  annealing  is  applied  to  a  piece 
having  undergone  local  tempering,  tin- 
effect  will  be  the  same.  In  a  bar  made 
up  of  steels  of  different  degrees  of  car- 
burization,  annealing  will  establish  a 
little  more  homogeneity.  Owing  to  the 
high  temperature  the  bar  will  have  to 
bear,  the  lines  of  demarcation  will  no 
longer  be  as  clearly  defined,  and  the 
difference  between  the  several  parts  will 
be  less,  as  the  piece  is  exposed  longer  to 
the  fire.  In  annealing,  this  more  regu- 
lar dissemination  of  carbon  is  due  only 
to  the  high  temperature  to  which  the 
piece  is  raised,  while  in  tempering,  the 
effect  is  increased  by  the  pressure  result- 
ing from  rapid  cooling. 

Annealing  must  not  be  performed  at 
too  high  a  temperature^ — near  the  melt- 
ing point, — less  the  fibrous  texture  of 
the  metal  acquired  by  forging,  should 
be  changed  ;  slow  cooling  would  crys- 
tallize it,  and  it  would  then  have  no 
elasticity, — it  would  be  burned. 

In  the  same  steel  there  may  exist  a 
series  of  intermediate  states  between  the 
natural  state  and  the  state  correspond- 
ing to  the  maximum  temper  it  can  take. 
The  several  properties  of  the  same  steel 
follow  a  continuous  law  of  variation  be- 
tween these  two  extreme  points.  In  the 
natural  state,  steel  possesses  a  hardness 
increasing  as  it  contains  more  carbon 
and  as  it  approaches  more  and  more  the 
maximum  of  saturation.  Tenacity,  or 
resistance  to  breaking  follows  the  same 
law,  increasing  in  a  continuous  manner 
from  soft  iron  to  the  hardest  steel. 

The  stresses  steel  can  bear  before 
reaching  its  limit  of  elasticity  follow  the 
same  law.  On  the  contrary,  the  attain- 
able stretching  increases  when  the  quan- 
tity of  carbon  and  consequently  the 
hardness  and  tenacity  increase.  The 
welding  properties  vary  like  the  stretch- 
ing qualities  ;  they  are  very  high  in 
slm-htlv  carburized  irons,  and  are  reduc- 


556 


VAN   NOSTKANDS    ENGINEERING    MAGAZINE. 


ed  to  almost  nothing  in  steels  rich  in 
carbon. 

When  steels  are  tempered  under  the 
same  conditions,  hardness,  tenacity  and 
stretching  follow  the  same  law  that  ob- 
tains in  the  natural  state  ;  hardness  and 
tenacity  increase  with  temper,  and  duc- 
tility decreases.  In  short,  the  difference 
between  a  steel  in  the  natural  state  and 
the  same  steel  tempered  is  less  as  carbon 
decreases  and  as  the  metal  approaches 
pure  iron. 

We  will  consider  here,  only  temper 
obtained  by  rapidly  cooling  steel  heated 
to  a  high  heat  in  a  cold  liquid.  Under 
these  conditions  the  changes  of  consti- 
tution induced  by  tempering  should  de- 
crease as  the  operation  is  performed  on 
less  carburized  steels.  With  very  high 
steels,  the  elastic  limit  is  reached  under 
a  very  heavy  load  only  ;  with  soft  steels 
the  elastic  limit  is  much  more  quickly 
attained ;  the  same  degree  of  cooling 
will  then  produce  a  contraction  and 
pressure  much  smaller  in  the  second  case 
than  in  the  first. 

From  this  statement  we  may  conclude 
that,  whenever  hardness  and  tenacity 
are  required,  and  a  material  liable  to  de- 
formation before  breaking  is  not  desir- 
able, the  highest  or  most  carburized  steel 
must  be  used  ;  from  this  class  is  chosen 
the  steel  for  tools  that  are  not  worked 
under  blows.  For  constructive  purposes 
where  a  more  elastic  material  is  needed, 
less  carburized  iron,  in  other  words,  soft 
steel  must  be  used. 

We  can  conceive  that  tempering  fol- 
lowed by  annealing  might  be  used  to 
improve  certain  more  or  less  carburized 
iron,  especially  to  restore  homogeneity 
lost  in  the  different  stages  of  manufact- 
ure. All  merchant  irons  contain  slight 
quantities  of  carbon,  and  consequently 
yield,  but  in  a  less  degree,  to  the  in- 
fluences of  tempering  and  annealing. 
Heat  produces  in  iron,  a  more  complete 
solution  of  the  carbon  and  a  dissemina- 
tion of  that  mixed  in  the  metal  ;  proba- 
bly also  of  other  foreign  ingredients. 
The  pressure  which  follows  tempering 
increases  this  dissemination.  Finally, 
while  anne'aling,  the  heat  continues  the 
effect  produced,  and  slow  cooling  allows 
the  molecules  to  group  themselves  so  as 
to  nearly  remove  the  sevei*al  internal 
strains. 

In  a  great  many  cases  tempering  is 


followed  by  such  an  incomplete  anneal- 
ing as  tends  to  lessen  the  molecular  ten- 
sions, while  preserving  in  the  metal  the 
greater  part  of  the  properties  due  to 
tempering,  viz.,  hardness,  tenacity,  and 
also  a  more  homogeneous  composition. 
Afterwards  more  or  less  annealing  is 
given  according  to  the  degree  of  elastic- 
ity which  is  to  be  restored. 

Partial  annealing  after  tempering  is 
used  in  armor  plates.  The  tempering 
they  undergo  after  rolling  renders  them 
more  homogeneous  throughout  their 
mass,  by  the  compression  it  produces  in 
every  direction.  Hardness,  or  resistance 
to  the  penetration  of  projectiles  is  in- 
creased, but  the  metal  becomes  brittle, 
as  the  tempering  is  more  complete,  or, 
with  the  same  range  of  temperature, 
as  the  plates  are  thicker. 

Complete  annealing  Avould  destroy  all 
brittleness ;  but  in  order  to  preserve 
some  hardness  and  prevent  any  internal 
crystallization,  annealing  is  carried  only 
to  dark  red  ;  this  temperature  is  insuffi- 
cient to  restore  to  the  different  fibres,  all 
their  elastic  properties,  but  it  allows  a 
preservation  of  the  greater  part  of  the 
hardness  proceeding  from  tempering. 

In  plates  measuring  less  than  20  centi- 
metres (.78V  in.)  in  thickness,  this  an- 
nealing is  sufficient  for  the  purpose  men- 
tioned ;  the  result  is  a  metal  able  to 
withstand  the  penetration  of  projectiles 
and  rarely  breaking  under  their  impact. 
In  thicker  plates  submitted  to  temper- 
ing and  annealing  under  the  same  condi- 
tions, the  molecular  tensions  after  tem- 
pering preserve  more  value  after  anneal- 
ing; the  places  satisfactorily  resist  pene- 
tration; they,  however,  have  considerable 
brittleness.  To  avoid  this  defect,  it 
would  be  necessary  to  give  more  inten- 
sity to  annealing;  the  plates  would  then 
offer  less  resistance  to  penetration,  but 
they  would  no  longer  break  under  blows. 

The  same  result  ought  to  be  attained 
by  reducing  the  intensity  of  temper;  the 
heat  to  which  the  plates  have  to  be  rais- 
ed cannot  be  lessened,  since,  in  order  to 
obtain  homogeneity,  a  solution  of  all 
foreign  matters  in  the  iron  must  be  pro- . 
duced  ;  but  the  rapidity  of  cooling  can 
be  diminished  by  using  a  liquid  which  is 
a  less  good  conductor  than  water,  or  by 
raising  the  temperature  of  this  water. 
By  this  latter  means  the  heated  piece 
will  be  sixbjected  at  first  to  a  rapid  cool- 


THE  USE  OF   STEEL. 


m 


ing  to  prevent  separation  of  the  carbon 
from  its  solution,  then  a  much  slower 
one,  to  prevent  extreme  molecular  ten- 
sions. 

These  considerations  are  verified  by 
M.  Caron's  recent  researches.  In  labora- 
tory experiments  he  has  succeeded  in 
bringing  to  the  same  degree  of  hardness, 
tenacity  and  elasticity,  some  steel  springs 
tempered  and  annealed  by  the  ordinary 
process,  and  others  simply  tendered  in 
hot  water.  He  expresses  himself  as  fol- 
lows, upon  his  experiments  : 

"  Tempering  in  hot,  or  rather  boiling 
water  singularly  modifies  soft  steel  con- 
taining from  rdoo  to  roW  of  carbon  ;  it 
increases  its  tenacity  and  its  elasticity 
without  sensibly  altering  its  mildness." 

M.  Caron,  in  experiments  reported  in 
the  same  article,  succeeded  in  regenerat- 
ing burned  iron  by  tempering  it  in  a  hot 
licpiid  ;  he  used  a  solution  of  sea  salt 
heated  to  110  degrees  centigrade.  The 
primitive  texture  is  then  restored  to  the 
metal  by  the  strong  pressure  due  to 
tempering  and  the  drawing  out  of  the 
fibres  which  results  from  it.  The  slow 
cooling  following  this  first  effect,  allows 
the  fibres  to  recover  the  greater  part  of 
their  elastic  properties,  notwithstanding 
the  previous  rapid  cooling.  It  is  well 
known  that  burned  iron  is  restored  by 
raising  it  to  a  white  heat  and  submitting 
it  to  an  energetic  hammering.  It  will 
be  seen  that  tempering  acts  the  same  as 
hammering;  it  constitutes  a  real  forging 
action,  producing  a  drawing  out  of  the 
metal.  It  follows  from  this  that  the 
quality  of  cast  ingots  might  be  improved 
by  a  series  of  temperings  which  would 
bring  them  to  the  same  state  as  if  they 
had  undergone  a  preliminary  forging  or 
rolling.  We  have  not  been  able  to  veri- 
fy this  deduction,  not  having  steel  in- 
gots at  our  disposal. 

CLASSIFICATION    OF    STEELS — ^SOFT    STEELS 
USED  AT  L'ORIENT  AND    BREST TESTS. 

The  various  properties  of  steels — their 
resistance,  their  stretching,  the  manner 
in  which  they  are  affected  by  tempering 
— furnish  a  convenient  way  of  com- 
paring and  classifying  these  metals  ;  it 
would  be  difficult  to  do  so,  practically, 
by  taking  their  composition  as  a  Tlasis. 

Until  a  few  years  ago,  steels  more 
carburized,  and  much  more  liable  to  the 
defects  pointed  out  above,  than  the  very 


soft  metal  now  manufactured,  were  gen- 
erally used.  The  substitution  of  ferro- 
manganese  for  Spiegel,  to  y>roduce  car- 
burization  at  the  end  of  the  Bessemer 
process,  or  in  the  Siemens-Martin  fur- 
nace, has  contributed  to  the  production 
of  materials  containing  very  small  quan- 
tities of  carbon,  though  free  from  the 
oxydes  of  iron  that  the  manganese  was 
designed  to  reduce  or  remove.  To  dis- 
tinguish this  steel  from  the  one  they  had 
previously  put  in  the  market,  the  manu- 
facturers have  given  it  the  name  of 
m'etal  fondu,  or  cast  metal. 

The  steel  used  in  France  and  England 
in  building  large  ships  may  always  be 
classified  among  soft  steels  ;  but  France 
alone  has  so  far,  we  believe,  worked 
cast-metal  on  a  large  scale. 

The  constructors  of  the  English  navy 
demanded  for  their  steel  plates  a  ten- 
sile resistance  of  32.9  tons  per  square 
inch  in  the  direction  of  the  fibre,  and 
29.8  tons  perpendicularly  to  the  fibre. 

The  resistance  should  in  no  case  ex- 
ceed 39.9  tons  per  square  inch. 

For  the  ships  built  at  L'Orient  and 
Brest,  where  cast  metal  alone  has  been 
used,  the  minimum  tensile  resistance 
required  was  28.5  tons  per  square  inch, 
with  a  corresponding  stretching  of 
20  per  cent,  at  least.  For  deck  beams 
made  up  of  I  bars,  lift  in.  deep,  the 
lowest  limit  of  stretching  was  put  down 
to  18  per  cent,  in  consideration  of  the 
difficulties  of  manufacture.  The  plates 
were  furnished  in  nearly  equal  quantities 
by  the  works  at  Creusot  and  at  Terre- 
Noire.  The  I  beams  were  manufactured 
by  MM.  Marrel  Bros,  of  River  de  Gier 
from  Terre-Xoire  steel ;  the  other  rolled 
bars  and  beams  were  furnished  by  the 
Creusot  works. 

The  steels  were  manufactured  at  Terre- 
Noire  by  the  Bessemer  process,  and  at 
Creusot  by  the  Siemens-Martin  process. 
Both  these  great  works  have  succeeded 
by  means  of  numerous  tests,  and  the  cer- 
tainty of  their  manufacture,  in  furnish- 
ing soft  steels  of  obviously  even  quality. 
They  can,  however,  vary,  at  the  wish  of 
the  buyer,  the  properties  of  their  pro- 
ducts. The  bars  subjected  to  test  were 
all  turned  to  3.93  in.  in  length,  the  sec- 
tion being  0.31  square  in.  Tempering 
was  done  in  oil,  the  bars  being  heated  as 
unformly  as  possible  to  a  temperature 
corresponding  to  bright  red. 


558 


VAN   NOSTRAND  S   ENGINEERING  MAGAZINE. 


The  steel  furnished  to  the  Govern- 
ment works  at  L'Orient  and  Brest,  offer- 
ing a  minimum  tensile  resistance  of  2 8.. 5 
tons  per  square  inch  was  to  reach  its 
limit  of  elasticity  only  under  a  heavier 
load  than  13.94  tons.'  Estimating  that 
iron  plates  reach  this  limit  of  elasticity 
under  a  load  of  10.4  tons  per  square 
inch.,  which  is  rather  above  the  average, 
it  will  be  found  that,  in  construction,  an 
iron  plate  of  thickness  e'  can  be  replaced 


by  a  plate  of  thickness  e'  determined  by 
the  relation  : 

22  e   —  3  6.5  e,  or  e'  =  %  e. 

This  is  the  case  only  when  the  plates 
suffer  a  direct  tensile  strain.  An  iron 
plate  0.47  inch  thick  can  then  be  re- 
placed by  a  steel  plate  0.35  inch  thick. 

At  L'Orient,  all  the  tensile  tests  on 
Creusot  or  Terre-JSToire  steel  were  made 
with  a  scale  built  by  M.  Frey,  having  a 


Fig.  1. 
'Scale  for  Measurement  of  Tensile  Strains. 


range  of    0  to    25    tons  (Fig.    1).     The 
test  bars,  a  sketch  of  which  is  given  in 


i 


0 


Fig.  2.— Test  Bar. 

Fig.  2,  were  brought  to  a  uniform  sec- 
tion for  a  length  of  more  than   7§  inch. 


Each  end  was  wider  than  the  body,  and 
these  different  widths  were  connected  by 
easy  curves.  In  the  outline,  great  care 
was  taken  to  avoid  any  angle  in  which  a 
rupture  might  originate.  At  each  end 
holes  were  drilled  allowing  the  bars  to 
be  connected  to  the  jaws  of  the  testing- 
machine  by  heavy  pins.  The  beam  of 
the  scale  was  always  kept  horizontal  for 
this  purpose,  the  lower  fixed  point  of 
the  bar  was  moved  down  while  the 
stretching  was  taking  place.  The  ten- 
sile strains  were  obtained  by  loading 
successively  one  or  the  other  scale  beam  ; 
they  were  gradually  increased,  44  lbs.  at 
a  time,  leaving  a  certain  interval  of  time 
between  each  increment  of  load  to  give 
to  the  successive  elongations  time  to 
develop  themselves. 

To  ascertain  the  limit  of  elongation  a 
length  of  7  in.  was  defined  by  two  cen- 
tre punch-holes  ;  on  these  marks  were 
fixed  the  extremities  of  a  small  appa- 
ratus (Fig.  3)  ;  this  apparatus  was  fre- 
quently applied,  and  indicated  by  its 
graduation  the  successive  elongations. 
An  observer  followed  the  travel  of  the 
index,  and  noted  after  each  rupture,  the 
figure  given  by  the  instrument,  also  the 
load  put  on  the  scales.  These  tests  were 
always  made  by  the  same  men. 


THE  USE  OF  STEEt. 


m 


3. — Measurement  of  Elongation. 


Besides  these  tests  of  tension,  the 
toughness  of  the  metal  was  frequently 
ascertained  by  bending  strips  out  from 
plates  or  bars  ;  this  was  done  by  ham- 
mering only  on  the  extremities  of  the 
specimens  and  never  where  flexion  was 
taking  place  ;  the  bending  was  stopped 
when  the  first  crack  appeared  and  the 
results  obtained  were  noted  and  kept  as 
a  basis  of  comparison.  Sometimes  the 
bending  was  done  under  a  hydraulic 
press,  thus  allowing  work  without  blows; 
the  specimens  so  tried  gave  the  same 
curves  as  those  bent  by  the  hammer 
under  the  conditions  just  described. 

The  Steels  from  Creusot  and  Terre- 
Noire  subjected  to  these  different  tests 
did  not  give  the  same  results  ;  it  was 
therefore  important  to  repeat  them,  in 
order  to  determine  the  relative  value  of 
the  products. 

The  grain  of  the  metal  (as  shown  by 
fracture)  indicated  at  first  sight,  a  slight 


difference  ;  in  order  to  examine  it,  nicks 
were  made  in  plates  and  beams  with  a 
chisel ;  the  use  of  a  sledge  was  avoided, 
as  it  might  have  altered  the  grain  ;  the 
specimens  were  then  broken  as  usual  by 
bending.  The  Bessemer  metal  showed 
a  very  fine  grained  break,  slightly  slate 
colored,  and  approaching  the  fracture  of 
steel  proper  ;  by  tempering,  the  grain 
became  still  finer,  the  color  or  brightness 
not  varying  sensibly.  In  I  beams,  the 
grain  was  a  little  more  steely  than  in 
the  plates.  The  Martin  metal  from 
Creusot  gave  a  finer  grained  fracture, 
whiter  and  brighter ;  it  approached 
more  by  its  brightness  and  color  the 
fracture  of  fibrous  iron  ;  tempering  did 
not  modify  it  in  a  very  appreciable 
manner.  In  every  case  the  grain  evinced 
the  greatest  homogeneity,  at  every  part 
of  its  surface. 

Some  strips  were  cut  on  a  planer  from 
plates  from  both  makers  ;  the  mean  de- 


4. — Bessemer. 
Natural  State. 


5. —Martin. 

Natural  State. 


6. — Bessemer. 
Tempered. 


formations  (Fig.  4)  were  obtained  on  a  i  Figs.  6  and  7  give  the  mean  defornia- 
series  of  Bessemer  plates,  and  (Fig.  5)  tions  obtained  after  tempering,  and  Figs, 
on  a  series  of  Martin  plates.  I  8  and  9  after  tempering  and  annealing. 


VAN  NOSTRAND  S   ENGINEERING  MAGAZINE. 


7. — Martin.  8. — Bessemer.  9. — Martin. 

Tempered.  Tempered  and  annealed.  Tempered  and  annealed. 


Tempering  was  done  by  heating  the 
plates  to  cherry-red  and  dipping  them 
into  water  at  50°  Fahr.  Annealing  was 
obtained  by  heating  to  cherry-red. 
These  experiments  were  made  on  speci- 
mens 0.31  inch  thick  for  Bessemer  metal 
and  0.35  inch  thick  for  Martin  metal ; 
the  trial  was  consequently  a  little  harder 
for  the  latter. 

Martin  steel  bore  the  bending  test  in 
the  natural    state,  a   little   better   than 


Bessemer  steel ;  the  difference  was 
slight,  but  very  decided  after  tempering, 
and  we  notice  from  this  stand-point  a 
marked  inferiority  in  the  products  from 
Terre-Noire.  Finally,  after  annealing, 
elasticity  was  obviously  restored  to 
what  it  was  before  tempering. 

Strips  cut  out  of  I  beams  gave  in  the 
natural  state,  the  average  deformations, 
Fig.  10,  when  cut  from  the  flange,  0.53 
inch  thick  on  the  average,  and  Fig.   11 


10.— Fers  en  H.  11.— Fers  en  H. 

(Flanges,  Natural  State.)  (Web,  Natural  State.) 


12.— Fers  en  H. 
(Flanges,  Tempered.) 


when  cut  from  the  web,  0.42  inch  thick. 
After  tempering,  cracks  were  observed 
when  the  specimens  were  of  the  form 
Fig.  12  for  the  first,  and  Fig.  13  for  the 


13. — I  beam,  Web  Tempered. 

others.  The  I  beam  metal,  chiefly  in 
the  region  of  the  web,  seems  to  experi- 
ence by  tempering  an  alteration  in  elas- 
ticity much  more  prominent  than  that 
observable  in  Bessemer  plates  under 
similar  circumstances. 

Two  series  of  tensile  tests  made  on 
plates,  angles,  and  I  beams  gave  the 
following  average  results  : 


Table  IV. 
Untempered  Steel. 


Resistance  to 

Rupture  per 

sq.  inch  of 

the  original 

section . 

Per  cent,  of 
Stretching. 

Bessemer  Plates. . . . 
Bessemer  I  Beams. . 

31.60 
32.81 
28.69 
29.00 

20.2 
19.5 
24.1 
21.7 

A  few  more  tensile  tests  after  temper- 
ing were  made  at  L'Orient.  Tempering 
was  done  in  the  manner  described  above 
for  the  trial  strips. 

The  result  was  as  follows  : 


ON    RIVER   GAUGING-   AND   THE   DOUBLE   FLOAT. 


561 


Table  V. 


Resistance  to  Rupture  in 

tons  per  square  inch  of 

the  original  section. 

Per  cent,  of 

Stretching. 

Lengthwise. 

Crosswise. 

Lengthwi.se.    Crosswise. 

Bessemer  Plates 

30.95 

30.83 

22.9                21.9 

Martin  Plates 

29.88                  30.07 
33.39 

24.2                23.5 

Bessemer  I  Beams 

21.1 

Martin  Angles 

30.45 

24.5 

Table  VI. 


Resistance  to 

Rupture  in 

tons  per  sq. 

Per  cent,  of 

inch  of  the 

Stretching. 

original 

section. 

Bessemer  Plates  . . . 

44.22 

Bessemer  I  Beams. 

47.69 

6.4 

34.58 

A  few  more  tensile  tests  were  made 
after  tempering  and  annealing.  It  was 
observed  that  annealing,  well  done,  re- 
stored to  the  metal  in  every  case  its 
previous  tenacity  and  elasticity,  as  modi- 
fied by  tempering. 

Finally,  by  trying  these  different 
products  with  a  file,  it  was  noticed  that 
the  I  beams  were  the  hardest  to  cut  ; 
then  came  the  Terre-Noire  plates  ;  the 
Creusot  plates  and  angles  were  obviously 
softer  than  the  preceding.  After  tem- 
pering hardness  could  be  classified  in  the 
same  order. 

We   may   then    conclude   from  these 


1  different   experiments  that  Terre-Xoin* 

steels  have  more  resistance  to  rupture, 

more  hardness  and  less  elasticity  than 

the    Creusot   products  ;    they  are  much 

more  modified  by  tempering  ;  in   short 

they  evince  the  characteristics  of  more 

I  carburized    iron.     Moreover,   the  rolled 

i  beams  seem  a  little  more  steely  than  the 

1  plates  from  the  same  origin.     It  is  hard 

:  to  explain  this  fact,  without  knowing  all 

the  circumstances  attending  manufacture. 

It  may  be  that  the  plates  undergo  in  the 

heating  furnace  a  more  decided  decar- 

burization   than   the    beams  ;    the   thin 

plates  present  in  the  last  heatings,  with 

the  same  volume,  a  larger  surface  to  the 

action    of   flames  that  may  be  slightly 

oxydizing. 

The  remaining  chapters  of  this  valua- 
[  ble  treatise  relates  chiefly  to  the  more 
technical  matters  of  treatment  of  plates, 
beams  and  angle  bars,  both  in  manufac- 
turing and  in  the  processes  of  punching, 
|  drilling,  riveting,  &c,  during  the  pro- 
gress of  their  employment  in  building. 
We  must  leave  these  chapters  for  another 
occasion. 


ON  RIVER  GAUGING  AND  THE  DOUBLE  FLOAT. 

By  S.  W.  ROBINSON,  Professor  of  Mechanical  Engineering  in  the  Illinois  Industrial  University. 
Written  for  Van  Nostkanb's  Magazine. 


In  the  October  number  of  the  Maga- 
zine will  be  noticed  an  article  by  Gen. 
H.  L.  Abbot  on  the  "  Hydraulic  Double 
Float,"  in  which  numerous  references  are 
made  to  my  paper  on  "  River  Gauging 
and  the  Double  Float,"  which  appeared 
in  the  August  number.  I  feel  called 
Vol.  XIII.— No.  6—36 


upon  to  make  mention  of  the  General's 
article  for  two  reasons  :  1st.  because  I 
feel  highly  complimented  by  its  receiv- 
ing attention  from  one  so  distinguished 
as  he,  and  hence  should  return  my  will- 
ing tribute  of  thanks;  and  2d.  to  correct 
the  impressions  which   his  remarks  may 


562 


VAN    NOSTRAND'S    ENGINEERING    MAGAZINE. 


have  induced,  in  regard  to  a  few  points 
in  my  article. 

The  facts  brought  out  by  my  investi- 
gations, given  in  the  article  referred  to, 
I  think  I  stated  in  as  mild  terms  as  con- 
sistent with  the  facts  themselves  ;  and 
without  aiming  to  detract,  in  the  least, 
from  the  real  value  of  the  very  import- 
ant work  reported  upon  in  the  "  Physics 
and  Hydraulics  of  the  Mississippi  River," 
because  I  consider  the  work  and  the  re- 
port as  exceedingly  complimentary  to 
its  authors,  as  well  as  a  most  valuable 
treatise  on  River  Hydraulics.  The  dis- 
covery that  the  mid-depth  velocity  is 
unaffected  by  wind  currents,  I  regard  as 
of  great  importance  and  value  ;  and 
which,  alone,  is  worthy  of  the  issue  of 
a  book.  But  having  found,  by  my  in- 
vestigations, that  a  correction  should  be 
applied  to  double  float  observations 
whenever,  and  wherever  made  with  a 
large  connecting  cord  in  use,  in  order 
that  the  observations  be  reduced  thor- 
oughly in  keeping  with'  science,  I  felt 
prevailed  upon,  on  account  of  the  great 
labor  involved,  to  make  it  public,  with  a 
view  to  aiding  such  as  may  desire  to  use 
the  double  float,  or  to  study  observations 
made  with  it. 

The  General  sets  out  by  saying  that  he 
will  correct  a  few  misapprehensions  into 
which  I  have  fallen;  the  most  important 
one,  as  appears  from  his  remarks,  being 
the  "  entire  inapplicability  to  the  Mis- 
sissippi River,  of  the  equations."  In  re- 
ply to  this  I  must  say,  with  all  due  re- 
gard, however,  for  the  General's  honesty 
in  defending  his  supposed  faultless  re- 
duction of  the  Mississippi  observations, 
that  I  did  not  in  the  least  misapprehend 
the  matter  ;  that  it  was  in  studying  the 
results  of  the  float  observations  of  the 
Mississippi  itself  that  I  became  convinc- 
ed that  when  a  large  connecting  filament 
is  used  between  the  floats,  the  resulting 
observed  velocity  should  be  corrected  ; 
that  on  completing  my  formulas  I  found, 
by  applying  them  to  the  Mississippi  ob- 
servations, they  gave  a  correction;  that, 
at  the  time  of  publishing  my  article,  I 
had  not  applied  them  to  any  other  ob- 
servations ;  and  as  there  appears  to  be 
no  good  reason  why  the  formulas  should 
not  apply  with  equal  force  to  the  double 
float  when  used  in  Mississippi  River 
water,  as  well  as  in  the  water  of  any 
other  river,  "  we  are  not  left  in  doubt  as 


to  their  entire"  applicability  to  the  Mis- 
sissippi observations. 

I  must  contend  that  I  have  proved^  not 
merely  stated,  to  any  one  who  has  care- 
fully looked  over  my  article,  that  the 
best  and  most  truthful  results,  obtain- 
able from  double  float  observations,  can 
only  be  realized  by  including,  among 
others,  the  needed  correction  for  the 
connecting  cord,  and  this  proof  I  cannot 
give  up  for  a  statement  only.  When,  for 
instance,  as  pointed  out  in  the  article, 
four-sevenths  of  the  actual  float  area, 
presented  to  river  current,  is  made  up  of 
the  cord  itself,  every  part  of  which,  for 
great  proportional  depths,  is  in  swifter 
water  than  the  lower  float.  How  can 
there  remain  a  trace  of  a  doubt  of  at 
least  some  slight  resulting  influence  act- 
ing to  hurry  along  the  float  combination  ? 
That  the  float  velocity  should  be  mate- 
rially modified  by  the  presence  of  a  large 
connecting  cord,  in  an  instance  like  the 
above,  is  so  self-evident,  even  were  it 
unsupported  by  vigorous  analytical 
proof,  that  the  description  of  the  bob- 
bing flag  is  insufficient  to  effect  the 
burden  of  proof  without  accompanying 
figures  showing  the  unmistakable  and 
exact  position  of  float,  the  precipe  depth 
of  river  at  the  very  point,  and  the  length 
of  float  to  its  extreme  bottom  /  and  even 
then,  if  one  or  the  other  must  be  doubt- 
ed, can  it  be  otherwise  than  the  figures 
defining  the'condltions  of  the  float  as  to 
proximity  to  bottom,  rather  than  the  en- 
tire absence  of  action  of  the  current 
upon  more  than  half  of  the  float  area  ? 

Again,  if  a  cord  nearly  a  quarter  of 
an  inch  in  diameter  is  ever  necessary, 
as  represented  by  the  General  to  ha\  e 
been  on  the  Mississippi,  it  maybe  safely 
employed  by  simply  providing  for  its 
errors.  This  maybe  done  by  an  empiri- 
cal method  as  well  as  by  analysis.  But 
the  fact  that  it  is  necessary  can,  it  is 
plainly  evident,  be  no  guaranty  that  the 
current  will  not  act  upon  it,  nor  that  it 
will  be  exempt  from  correction. 

The  criticism  in  regard  to  neglecting 
the  masses  of  the  floats,  if  it  applies, 
must  be  with  respect  to  a  correction 
which  I  made  no  attempt  to  elucidate  ; 
and,  hence,  another  error  which  the 
Mississippi  observations  are  subject  to. 
|  The  observations  which  I  treated  were 
supposed  corrected  for  all  errors  except 
i  that  due  to  the  large  cord  and  upper  float. 


REPORTS    OF   ENGINEERING    SOCIETIES. 


563 


Also,  if  the  pulsations  and  whorls  exist, 
their  action  npon  the  cord  would  crook 
it  into  unaccountable  curves,  every  one 
of  which  would  shorten  the  distance  be- 
tween the  floats,  and  prevent  contact 
with  river  bottom  ;  and,  hence,  an  argu- 
ment by  the  General  himself  against  his 
own  theory  of  touching  of  bottom  by 
lower  float,  and  consequent  oscillation 
of  upper  float  and  flag.  If,  therefore, 
my  formulas  err  at  all,  they  err  on  the 
side  of  giving  too  few  corrections,  in- 
stead of  erring  on  the  side  of  "  entire 
inapplicability  to  the  Mississippi  River." 

The  modern  watch  or  clock  needs 
regulating  that  it  indicate  correctly,  so 
the  meter  needs  its  coefficient  of  velocity. 
But  who,  at  the  present  day,  would 
throw  away  his  watch  or  clock  in  prefer- 
ence for  the  sundial,  because  the  latter 
needs  no  coefficient  of  velocity  ? 

Also,  the  General  makes  the  statement 
with  considerable  force  that  Gen.  Ellis 
finds  the  float  and  meter  to  "  give  sen- 
sibly the  same  result,"  an  argument  of 
his  own  in  favor  of  the  meter.  Again, 
just  before  that,  he  says  that  the  efforts 
to  determine  the  curve  of  velocities  "  ut- 
terly failed "  till  the  double  float  was 
used.  But  why  should  the  meter  have 
failed  if  it  gives  sensibly  the  same  re- 
sult as  the  float  ? 

In  my  article,  my  formulas  were  only 
applied  to  observations  taken  in  the 
Mississippi  River,  where  a  large  con- 
necting cord  was  used.  To  show  how 
the  errors  disappear  when  a  fine  wire  is 
used,  agreeably  to  the  requirements  in- 
dicated in  the  discussion  of  my  formulas, 
I  have  computed  some  of  the  corrections 
for  the  float  observations,  made  by  Gen. 
Abbot  himself  in  a  feeder  of  the  Chesa- 
peake and  Ohio  Canal,  and  given  on  page 
253  of  the  Mississippi  Report,  where  the 
upper  float  presented  an  area  of  a  quar- 
ter of  a  square  inch,  and  the  lower  float 
17  square  inches,  the  floats  being  con- 
nected with  a  "  very  fine  wire."  Depth 
of  canal,  seven  and  a  tenth  feet;  W  esti- 
mated at  0.005  lb.,  Cx=0.75,  (X  =  1.75. 
Using  data  as  given,  I  find 

Fory=5ft,     #=.08  ft.     va—-vx=. 043 
"      6  "     .39   "  "         .061 

which  show  no  appreciable  rising  of  the 
lower  float  on  account  of  its  falling  be- 
hind the  upper,  and  corrections  only 
about  a  tenth  of  those  found  where  the 


large  cord  was  used,  which  indicate  a 
decided  advantage  in  use  of  wire  if  the 
observations  are  to  go  uneorrecR-d. 

Permit  me  to  remark,  finally,  that  I  see 
no  cause  for  altering  either  my  analy.-.i- 
or  results  of  the  same,  on  account  of  the 
interesting  additional  particular-  regard- 
ing the  Delta  Survey,  which  Gen.  Abbot 
has  so  kindly  given  in  his  article. 

REPORTS  OF  ENGINEERING  SOCIETIES. 

American  Society  op  Civil  Engineers. — 
The  twenty  third  annual  meeting  of  this 
Association  was  held  on  Wednesday  last. 

The  annual  report  of  the  Board  of  Direc- 
tion upon  the  affairs  of  the  Society  was  read, 
from  which  it  appears  that  the  increase  in 
membership  during  the  year  was  48,  and  the 
present  number  is  492.  By  donation  and  pur- 
chase, there  were  added  to  the  Library  about 
850  books  and  pamphlets,  many  photographs 
and  other  illustrations  of  engineering  struc- 
tures. The  treasurer's  report  shows  the  fi- 
nances of  the  Society  to  be  in  satisfactory  con- 
dition ;  the  increase  in  receipts  keeping  pace 
with  increased  expenditures  during  the  year 
incident  to  change  in  location  of  the  Society 
rooms. 

Officers  were  elected  as  follows  : 

George  S.  Greene,  President. 

Theodore  G.  Ellis,    )  Vice-Presidents 
•  W.  Milnor  Roberts,  f  Vice  ^resiQents- 

Gabriel  Leverich,  Secretary. 

John  Bogart,  Treasurer. 

Octave  Chaunte,  Alexander  L.  Holley,  Fran- 
cis Collingwood,  Quincy  A.  Gillmore,  and 
Julius  W.  Adams,  Directors. 

Subsequently  the  Standing  Committees  were 
appointed  as  follows  : 

On  Finance — Messrs.  Roberts,  Gillmore  and 
Collingwood. 

On  Library — Messrs.  Holley,  Boffart  and 
Ellis. 

The  Norman  Medal  was  awarded  for  a  paper 
"Description  and  Results  of   Hydraulic  Ex- 
periments with  large  Apertures  at  Holvoke 
Mass.,  in  1874,"  by  Gen.  Theodore  G.  Ellis. 

Reports  of  Committees  on  "  Tests  of  Amer- 
ican Iron  and  Steel ;"  "Time  and  Place  of  the 
Eighth  Annual  Convention  ;"  "  Mutual  Benefit 
Society  ;"  and  on  "  Policy  of  the  Societv," 
were  adopted.  It  was  determined  to  hold  the 
next  Annual  Convention  at  Philadelphia,  June 
13th — 15th,  1876.  The  matter  of  presenting 
American  Engineering  at  the  Centennial  was 
referred  to  a  Committee.  A  proposition  that 
action  be  taken  towards  adopting  the  metric 
system  of  weights  and  measures  was  discussed; 
and  amendments  to  the  By-Laws  relating  to 
the  appointment  of  Committees  to  report  on 
professional  topics  or  perform  expert  service  ; 
Annual  Conventions  being  declared  business 
meetings  ;  making  Past  Presidents  of  the  So- 
ciety members  of  the  Board  of  Direction  ; 
holding  social  meetings  at  the  Society's  rooms 
during  the  winter  ;  and  other  matters  were 
considered  and  duly  referred. 

The  Animal  Dinner  was  held  at  Delmonico's 


564 


VAN    NOSTRAND  S    ENGINEERING   MAGAZINE. 


— Gen.  Theodore  G.  Ellis  presided  and  in- 
formal speeches  were  made  by  Messrs.  Roberts, 
Briggs,  Holley,  Bloor,  "Western,  Thurston  and 
others. 

The  American  Association  for  the  Ad- 
vancement op  Science,  on  "Weic-ihts 
and  Measures. — The  special  committee  of 
this  association,  to  which  this  subject  was  re- 
ferred, report  upon  the  steps  taken  the  past 
year  for  the  establishment  an  t  perpetuation  of 
the  basic  units  of  the  metric  system,  and  the 
results  of  the  conference  of  delegates  from 
twenty-one  nations.  The  United  States  was 
represented  by  Prof.  Joseph  Henry,  of  the 
Smithsonian  Institute,  and  Julius  G.  Hilyard, 
of  the  Coast  Survey  (now  President  of  the  as- 
sociation). The  original  standard  meter  and 
kilogram  were  adopted,  and  steprs  taken  for 
authentic  reproduction  of  them  for  distribu- 
tion, and  for  comparison  with  other  standards 
of  dimension  or  quantity.  The  report  com- 
ments upon  and  lauds  the  co-operation  of  our 
executive  government  in  this  great  effort  for 
universal  civilization,  and  asks  from  all  scien- 
tific bodies  an  expression  of  opinion  to  urge 
upon  Congress  the  monetary  aid  desirable  to 
meet  the  national  share  of  the  expenses  ;  esti- 
mating  the  same  at  $12,000  original  appropria- 
tion, with  about  $1,000  per  anhnm  subsequent- 
ly. The  committee  say:  "It  is  to  be  con-! 
sidered,  that  this  is  not  designed  merely  to 
advance  the  interests  of  the  metric  system  of 
weights  and  measures,  or  to  serve  as  a  means  | 
of  promoting  the  extension  of  that  system. 
The  design  is  higher  than  that.  To  secure  the 
universal  adoption  of  the  metric  system,  would 
be  undoubtedly  to  confer  an  immense  and  in- 
calculable benefit  upon  the  human  race  ;  but 
it  would  be  a  benefit  felt  mainly  in  the  in- 
creased facilities  which  it  would  afford  to 
commerce,  and  to  exactness  in  matters  that 
concern  the  practical  life  of  humanity.  On 
the  other  hand,  to  secure  that  severe  accuracy 
in  standards  of  measurement  which  transcends 
all  the  wants  of  ordinary  business  affairs,  yet 
which,  in  the  present  advanced  state  of  science, 
is  the  absolutely  indispensable  condition  of 
higher  progress,  is  an  object  of  interest  to  the 
investigators  of  nature  immensely  superior  to 
anything  which  contemplates  only  the  increase 
of  the  wealth  of  nations.  .  .  .  . " 
A  series  of  resolutions  were  offered  by  the 
committee,  and  were  unanimously  adopted  by 
the  association.  Those  of  our  readers  who  are 
interested  especially  in  the  metric  system,  will 
find  this  report  in  full  in  the  proceedings  of 
the  association,  which  will  shortly  be  publish- 
ed.— Franklin  Institute  Journal. 


IRON  AND  STEEL  NOTES. 

Mr.  David  Mtjshet  states  in  his  paper  on 
"  Iron  and  Steel,"  that  4  tons  of  coke  was 
the  quantity  of  fuel  employed  about  the  year 
1810  for  each  ton  of  pig  iron  made  in  Great 
Britain.  In  Shropshire  it  was  ascertained, 
about  the  year  1840,  by  Mr.  William  Jessop 
that  the  quantity  of  pig  iron  made  amounted 
to  82,750  tons,  consuming  in  its  manufacture 
409,000  tons  of  coal,  or  nearly  5  tons  of  coal  to 


each  ton  of  pig  iron.  In  Great  Britairj,  in  the 
same  year,  Mr.  Jessop  further  ascertained  that 
the  quantity  of  pig  iron  made  amounted  to 
1,396,400  tons,  consuming  4,877,000  tons  of 
coal,  or  an  average  of  3^  tons  of  coal  to  each 
ton  of  pig  iron  manufactured.  In  July,  1867, 
the  commissioners  appointed  by  a  Royal  Com- 
mission in  the  previous  year  to  inquire  into 
the  question  of  the  probable  duration  of  our 
coal-fields  and  their  resources,  began  the  im- 
portant inquiry  entrusted  to  them,  and  periodi- 
cally for  five  years  pursued  their  investigation. 
This  investigation  of  the  Coal  Commission,  as 
regards  the  statistical  inquiry,  was  entrusted 
to  the  late  Sir  Roderick  I.  Murchison  and  Mr. 
Robert  Hunt,  Keeper  of  Mining  Records,  and 
forms  vol.  iii.  of  the  Coal  Commission  Report, 
consisting  of  nearly  500  pages.  The  deduc- 
tions drawn  from  this  report  show  that  in  the 
year  1869  the  quantity  of  coal  employed  in  the 
manufacture  of  a  ton  of  pig  iron  amounted  to 
3  tons  in  Great  Britain,  and  the  inquiries  sub- 
sequently instituted  by  the  Mining '  Record 
Office  show  that  in  Shropshire  in  the  years 
1872  and  1873,  it  amounted  to  the  like  quantity, 
while  taking  the  average  of  Great  Britain  in 
the  same  years,  1872  and  1873,  we  find  that 
51  cwt.  of  coal  was  the  quantity  used  in  the 
making  of  each  ton  of  pig  iron.  — Engineer 

The  Iron  Trade.— The  iron  trade  is  at 
present  passing  through  one  of  those 
crises  which  appear  to  arise  once  every  six  or 
seven  years  in  its  history.  Naturally  the 
danger  is  most  threatening  where  there  has 
been  the  most  rapid  growth  and  expansion — 
namely,  in  the  North  of  England.  The  con- 
dition of  the  trade  was,  perhaps,  never  more 
perilous,  nor  required  greater  prudence  and 
judgment  on  the  part  of  those  responsible  for 
its  welfare.  Several  heavy  failures  have  oc- 
curred, and  more  will  undoubtedly  follow  if 
the  tide  of  doubt  and  suspicion  which  has  set 
in  be  not  quickly  stemmed.  When  bankers 
suddenly  withdraw  the  facilities  which  have 
for  years  been  ungrudgingly  granted  to  a  hith- 
erto thriving  and  prosperous  district,  the  effect 
may  be  in  some  respects  beneficial,  but  it  may 
be  purchased  at  a  cost  which  those  who  pro- 
duce it  may  find  somewhat  expensive. 

The  question  is,  Is  the  iron  trade  really  un- 
sound ?  Has  it  ceased  to  be  a  profitable 
staple,  and  is  the  present  depression  likely  to 
be  lasting  '? 

It  is  undoubtedly  a  trade  liable  to  severe  al- 
terations of  adversity  and  prosperity,  but,  on 
the  whole,  it  has  been  signally  prosperous, 
and  has  advanced  truly  by  "  leaps  and  bounds." 

In  1852  the  capital  embarked  in  the  iron 
trade  in  the  North  of  England  did  not  exceed 
£300,000  and  the  whole  manufacture  of  iron 
did  not  exceed  a  value  of  £500,000.  In  1874 
the  capital  employed  in  the  trade  was  various- 
ly estimated  at  from  £5,000,000  to  £6,000,000 
while  the  value  of  pig-iron  and  manufactured 
iron  produced  amounted  to  £15,000,000.  The 
growth  of  the  Middlesborough,  Stockton,  and 
Hartlepool  has  been  one  of  the  most  remarka- 
ble features  of  the  past  quarter  of  a  century. 

Of  the  £6,000,000  of  capital  now  sunk  in 
machinery,  plant,  buildings,  &c,  fully  £5,000,- 


KAILWAY   NOTES. 


565 


000  has  been  the  result  of  untiring  industry 
and  thrift.  Scarcely  a  moneyed  man  has  ever 
come  into  the  district,  and  it  is  a  curious  fact 
that,  except  two,  there  is  not  yet  a  gray-haired 
man  in  the  iron  trade  in  Middlesborough, 
Stockton,  or  Hartlepool. 

This  great  growth  has  been  several  times 
arrested,  and  despairing  croakers  have  been  as 
prophetic  of  evil  things  to  come  in  years  past 
as  they  are  at  the  present  moment.  But  after 
a  year  or  two  of  dulness  there  has  been  the 
invariable  rebound,  enduring  for  several  years, 
when  manufacturei's  have  flourished,  and  the 
producing  power  of  the  district  has  been  large- 
ly developed. 

Profits  have  been  invariably  spent  on  addi- 
tional works,  and  when,  as  happened  in  a  re- 
cent case,  bankers  shut  up  their  pockets,  the 
struggling  manufacturer  has  to  go  to  the  wall, 
although  it  is  confessed,  if  his  works  and 
plant  could  be  turned  in  a  month's  time  into 
cash — which  is  impossible — he  would  have  suffi- 
cient to  pay  his  creditors  40s.  in  the  pound. 

In  1852  there  was  a  general  impression  that 
pig  iron,  which  in  the  early  part  of  the  year 
was  36s.  per  ton,  would  never  see  40s.  again. 
By  the  end  of  the  year  the  price  was  65s.  per 
ton,  all  other  descriptions  of  iron  advancing  in 
similar  proportions. 

In  the  panic  of  1857  a  similar  state  of  affairs 
supervened. 

In  1866,  when  all  English  railways  fell  into 
discredit,  it  was  generally  believed  that  the 
iron  trade  had  passed  its  highest  powers  of 
demand  and  production,  and  that  no  good 
could  be  expected  from  it  again.  Pig-iron  fell 
to  51s.  per  ton,  and  remained  there  for  a  long 
time  ;  but  in  1871  we  saw  it  at  140s.  and  such 
a  demand  accompanied  this  price  that  a  large 
stock  of  nearly  700,000  tons  was  cleared  off, 
while  production  itself  had  made  unprecedent- 
ed strides. 

For  a  year  and  a  half  the  trade  has  been  in  a 
languishing  and  unprofitable  state.  Manu- 
facturers have  lost  money,  but  not  a  fleabite 
of  their  earnings.  The  bad  debts  of  mer- 
chants have,  on  the  whole,  not  been  serious. 

When  the  worst  has  come  the  tide  turns, 
and  there  are  symptoms  that  the  dullness  which 
has  pervaded  the  whole  commercial  world  is 
beginning  to  lessen.  Wherever  civilization 
spreads  iron  will  be  in  request,  and  there  is  no 
reason  to  fear  either  that  as  a  great  staple  of 
this  country  it  will  be  in  less  request  or  that 
any  other  country  can  beat  us  in  the  race  of 
competition. 

If  the  timidity  of  some  and  the  shortsighted- 
ness of  others  should  cause  the  present  depres- 
sion to  be  the  cause  of  widespread  ruin  and 
disaster  in  a  district  which  has  been  remarka- 
ble for  its  industry  and  integrity,  it  will  indeed 
be  a  matter  of  very  great  regret. — London 
Times. 

RAILWAY  NOTES, 

Paris  Tramways  and  Railways. — On  their 
next  assembly,  the  Paris  municipality  are 
expected  to  apply  for  powers  to  construct  a 
new  line  of  tramway  from  Porte-Maillot  to  the 
Bridge  of  Suresnes,  passing  through  the  whole 


j  length  of  the  Bois  de  Boulogne.  Tramway 
extension  in  Paris  has  proceeded  at  a  rate 
j  which  seems  to  indicate  a  high  appreciation  of 
I  the  value  of  the  old  Roman  motto,  Ft 
lente.  The  Vincennes  tramway  was  author- 
ized on  February  10th,  1854,  and  opened 
to  the  public  August  25th,  1875,  after  a  delay 
of  twenty-one  years,  six  months  and  seven 
days.  Proceedings  at  the  present  moment, 
however,  are  active  enough.  Since  January, 
besides  the  line  from  the  Louvre  to  Vincenne 
the  Compagnie  des  Omnibus  have  began  that 
from  the  Point  de  Boulogne  to  Saint-Cloud, 
and  from  la  Villette  to  the  Place  de  I'Etoile  : 
while  the  Compagnie  des  tramways-nord  began 
the  lines  from  Courbevoie  to  Suresnes,  from 
Saint-Augustin  to  Levallois-Perret,  and  from 
the  Place  Pereire  to  Neuilly.  Three  other 
lines  are  being  made  from  la  Villette  to  the 
Place  du  Trone,  from  the  Place  Clichy  to 
Saint-Denis,  and  from  the  Place  Saint-Ger- 
main-des-Pres  to  Clamart,  while  plans  are 
being  drawn  for  two  others,  one  from  the 
Place  de  I'Etoile  to  Saint-Augustin,  and  an- 
othei  from  Courbevoie  to  Reuil.  Railway 
communications  between  Paris  and  the  suburbs 
are  becoming  little  by  little  easier  and  more 
abundant,  the  last  section,  14  kilometres  long, 
of  the  short  railway  from  Paris  to  Vincennes 
and  Brie  Comte-Robert,  with  a  total  length  of 
36  kilometres,  was  opened  on  August  5th  last, 
the  first  concession  for  the  railway  bearing 
date  August  17th,  1853.  On  August  7th  last 
another  suburban  railway,  that  from  Bondy  to 
Annay,  connecting  the  line  of  Soissons  with 
that  of  Avricourt,  was  inaugurated.  This  con- 
nection, 8  kilometres  long,  will  be  thrown  open 
with  the  least  possible  delay. — Engineer. 

Brake  Experiments. — In  consequence  of  a 
statement  made  by  one  of  the  principal 
officers  of  the  Midland  Railway  Company, 
with  reference  to  the  collision  at  Kildwick,  to 
the  effect  that  the  engine-driver  of  the  mail 
train  would  have  been  able,  with  the  means  at 
his  disposal,  if  traveling  at  the  rate  of  fifty 
miles  per  hour,  to  stop  his  train  in  400  yards, 
certain  brake  experiments  were  made,  in  the 
presence  of  Captain  Tyler,  on  the  Derby, 
Castle  Donnington  and  Trent  line,  on  the  21st 
ult.  There  were  four  trials.  In  the  first  of 
these  experiments  all  available  means  were 
used  to  stop  the  train,  viz.,  tender-brake  and 
one  guard's  van-brake  at  rear  of  train  applied, 
sand  used,  and  engine  reversed  and  steam 
against  it,  with  the  Le  Chatelier  tap  open. 
The  gradient  was  level ;  the  train,  the  total 
weight  of  which  was  102  tons  7  cwt.  2  qr. .  was 
running  at  the  rate  of  49.9  miles  per  hour 
when  the  brake  was  applied.  The  result  was 
that  54  seconds  were  occupied  in  stopping  the 
train,  which,  after  the  application  of  the 
brake,  ran  a  distance  of  SOT  yards.  In  the 
second  experiment  all  available  means  were 
used  except  reversing  the  engine  ;  gradient,  1 
in  330,  up  and  level  ;  speed.  40.9  miles  ;  time 
occupied,  60  sees.;  distance  run.  S43  yards. 
In  the  third  experiment  all  available  means 
were  used,  and  when  the  engine  i>Yas  reversed, 
the  regulator  was  allowed  to  remain  wide  opeu 
all  the  time  ;  gradient,  1  in  220  down  ;  speed. 


566 


VAN  nostrand's  engineering  magazine. 


52.5  miles;  time  occupied,  55  sees.;  distance 
run,  867  yards.  In  the  final  experiment  all 
available  means  were  used.  When  reversing 
the  engine  the  steam  was  first  shut  off,  then 
the  lever  pulled  into  hack  gear,  and  then  steam 
was  turned  on  again  as  in  first  experiment  ; 
gradient,  level  ;  speed,  52.5  miles  ;  time,  50 
sees. ;  distance,  787  yards.  The  weather  was 
fair,  and  the  rails  slightly  greased.  Captain 
Tyler,  in  his  report  to  the  Board  of  Trade, 
states  that  the  engine-driver  of  the  mail  train, 
who  at  present  awaits  trial  on  a  charge  of  man- 
slaughter, could  not  have  acted  so  promptly 
as  these  who  on  the  experimental  train  listened 
for  the  word  of  command.  He  adds  that  in- 
stead of  400  yards  800  yards  should  have  been 
stated  as  the  distance  in  which,  with  the  as- 
sistance of  the  guard,  he  would  have  stopped 
his  train. — Iron. 

ENGINEERING  STRUCTURES. 

TThe  Tunnel  under  the  London  Docks. — 
1  The  works  on  the  East  London  Railway, 
by  which  the  line  will  be  extended  from  the 
present  terminus  at  Wapping  to  the  Liverpool 
Street  Station  of  the  Great  Eastern  Company, 
are  now  rapidly  approaching  completion,  and 
it  is  expected  that  the  extension  line  will 
shortly  be  opened  for  traffic,  when  there  will 
be  through  communication  between  Liverpool 
Street  and  New  Cross,  where  the  line  forms  a 
junction  with  the  London  and  Brighton  and 
the  South-Eastern  lines.  The  most  formidable 
engineering  portion  of  the  works  is  the  tunnel 
under  the  eastern  basin  of  the  London  Docks, 
which  has  just  been  completed.  The  water 
communication  between  one  side  of  the  basin 
is  restored,  and  vessels  of  large  tonnage  may 
now  be  seen  berthed  in  the  basin  immediately 
over  the  submarine  railway  which  has  been 
formed.  Operations  were  carried  on  by 
means  of  coffer-dams  and  dredging  trenches  in 
the  bottom  of  the  dock  until  the  London  clay 
was  reached.  The  driving  of  the  piles  and 
the  construction  of  the  walls  of  the  coffer- 
dams was  one  of  the  most  formidable  portions 
of  the  work.  The  arches  of  the  tunnel  are  of 
the  ordinary  horseshoe  shape,  built  with  seven 
rings  of  brick,  and  are  surrounded  with  three 
feet  of  puddled  clay.  About  two-thirds  of  the 
Shadwell  Station  are  already  completed,  and 
the  covered  way  northwards,  in  continuation, 
is  also  nearly  all  finished  to  about  50  feet  north 
of  Commercial  Road.  The  retaining  walls  for 
the  Whitechapel  Station  are  also  nearly  finish- 
ed, and  the  station  itself  will  soon  be  com- 
pleted. The  line  continues  from  Whitechapel 
Station  to  its  junction  with  the  Great  Eastern 
line  at  Brick  Lane,  and  the  works  at  this 
point,  which  are  comparatively  light,  are 
actively  proceeding.  The  whole  of  the  works 
have  been  designed  by  Sir  John  Hawkshaw, 
and  are  being  caried  out  by  Mr.  Hunt,  the 
resident  engineer.  The  estimated  cost  of  the 
works  is  set  down  at  £500,000  per  mile. 

The  Eighty-one  Ton  Gun. — The  trial  of 
the  81-ton  gun  took  place  the  other 
week,  at  the  butts  within  Woolwich  Arsenal. 
The  weight  of  the  shot  first  fired  was  1250  lb. 


!  and  the  charge  of  powder  was  170  lb.     It  took 
twelve  men  to  ram  the  charge  home,  and  the 
shot  was  elevated  to  the  mouth  of  the  gun  by 
hydraulic  apparatus.     The  gun  was  fired  by 
means  of  electricity.     It  was  found  that  the 
shot  had  penetrated  45  feet  of  sand,  and  that 
the  gun  had  a  recoil  of  234-  feet.     A  second 
shot  was  fired  with  a  charge  of  190  lb.     The 
distance  of  penetration  was  over  50  feet,  and 
the  recoil  32  feet.     The  experiments  were  at- 
|  tended  with  great  success,  and  no  flaw  was  de- 
tected.    So   satisfied  were  the  authorities   of 
i  the  Royal  Gun  Factories  that  the  gun  would 
prove  a  success  that  application  has  been  made 
to  the  War  Office  for  permission  to  construct 
four  other  guns  of  the  same  weight,  and  on 
!  precisely  the  same  plans,  and  the  preliminary 
forging  and  other  preparations  for  these  are 
i  already  considerably    advanced.      This    gun, 
i  which  may  be  considered  as  an  experimental 
piece  of  ordnance,  is  bored  to  a  calibre  of  14J- 
inches,  and  the  walls  are  consequently  much 
[  thicker  than  they  will  be  when  the  tube  is 
|  bored  out  to  a  diameter  of  16  inches,  while  the 
strain  upon  the  gun  will  of  necessity  be  in- 
!  creased    by    every    addition    to    the    powder 
:  charge,  which  it  is  intended  to  augment  gradu- 
ally up  to  300  lb.     This  is  60  lb.  more  than  has 
yet  been  fired  ;  but  the  strain  has  been  care- 
fully calculated  and  provided  for  with  a  mar- 
gin of  endurance  to  spare.     So  well,  has  ex- 
j  perience  qualified  the  authorities  to  calculate 
j  results  that  the  velocity  attained  by  the  gun  in 
j  its  its  first  round  was  foretold  as  1390  feet  per 
seeond,  and  it  proved  to  be  1393  feet,  within 
3  feet  of  the  velocity  worked  out.     The  length 
|  of  the  gun  is  33  feet,  and  its  diameter  varies 
:  from  about  2  feet  at  the  muzzle  to  about  6  feet 
;  at  the  breech.     Internally  the  bore  measures 
|  27  feet.     The  gun  is  not  to  be  fired  in  its  pres- 
ent state  any  more,   but  it  has   many  more 
trials  in  store  ;  its  whole  lifetime  will,  it  is  ex- 
!  pected,    be  a  series   of  trials,   for,  while  its 
\  sister  guns  are  being  manufactured  to  go  on 
1  service  in  the  ironclad  fleet,  the  four  next  for 
the  turrets  of  the  Inflexible,  this,  the  original 
gun,  will  be  devoted  to  experiments  for  the 
benefit  of  science. 

Water  Contrivances  in  India. — The  con- 
trivances used  in  India  for  raising  water, 
and  for  other  purposes,  are  of  a  rather  primi- 
tive kind,  and  our  engineers  have  something 
|  to  do  to  instruct  natives  in  some  of  the  sim- 
plest of  our  appliances.-    A  pump,  as  we  have 
I  it,  is  comparatively  unknown,  a  kind  of  chain 
pump  being  used,  with  pots  or  leather  bags 
attached.     These  primitive  appliances  some- 
times frustrate  the  calculations  of  our  engi- 
neers unaccustomed  to  them,  and  a  few  facts 
1  may  be  interesting,  which  Mr.  Lowis  D.  A. 
Jackson,  in  his  "  Hydraulic  Manual  "  furnishes 
us  with.     Our  English  mode  of  bucket  baling 
is  unknown  in  India.     Instead  of  this,  the  na- 
tives use  a  flat  kind  of  dish,  made  of  leather, 
or  wood  bark,  rendered  water-tight,  and  stiff- 
ened by  a  frame.     At    each  side  cords  are 
i  fastened,  the  ends  of  which  are  held  by  two 
1  men,  who,  by  a  quick  mode   of  dipping  and 
!  swinging,   raise  the  water  to  the  receptacle 
above.     For  clearing  foundations  where  there 


ORDNANCE   AND    NAVAL. 


567 


is  swinging  room  it  answers  very  well,  the  lift 
being  generally  about  5  ft.  About  400  cubic 
feet  of  water  per  hour,  or  20,000  gallons  per 
day  of  eight  hours,  may  be  raised.  The 
"beam  and  bucket"  contrivance  is  a  rather 
more  scientific  appliance  for  raising  water  by 
hand  labor.  It  consists  of  a  large  earthenware 
vessel  suspended  at  one  end  of  a  beam,  which 
is  rather  thick,  and  so  poised  on  a  fulcrum  by 
a  counterweight  at  the  other  end,  that  the 
force  of  one  man  may  easily  raise  the  vessel 
when  full. 

The  "  picotah  "  of  Southern  India  is  a  de- 
velopment of  the  principle  ;  a  long  tree  be- 
comes in  this  case  the  balance-pole,  which  is 
worked  by  the  weight  of  a  man,  who  walks 
or  runs  up  and  down  along  the  heavier  arm  of 
the  lever.  Another  man  manages  the  vessel, 
and  the  height  of  the  lift  is  sometimes  as  much 
as  20  feet.  The  smaller  appliance  previously 
described  we  find  can  raise  82  cubic  feet  per 
hour,  or  about  4,100  gallons  per  day.  Another 
similar  contrivance  is  called  the  "dal,"  or  "  jan- 
tu."  This  consists  of  a  wooden  trough  or  gut- 
ter working  on  a  pivot.  It  is  worked  usually 
by  cords.  As  much  as  21,000  gallons  can  be 
raised  by  this  simple  means  in  a  day,  and  a  lift 
of  5  feet,  with  two  men,  can  be  performed. 
Another  very  primitive  method  of  raising 
water  is  by  the  "  mot,"  which  is  a  vessel  made 
of  ox-hide,  bound  to  a  wooden  hoop,  raised 
and  lowered  by  a  cord  over  a  pulley  by  oxen, 
the  animals  performing  the  work  by  descend- 
ing an  inclined  plane,  and  the  bucket  some- 
times emptying  itself  by  a  catch  cord.  A 
more  advanced  mechanical  appliance,  like  the 
ancient  chain  of  pots  used  in  Egypt,  Syria, 
and  by  the  Romans,  is  called  the  "Persian 
Wheel. "  It  is  composed  of  two  endless  ropes, 
united  and  passing  over  a  wheel,  the  endless 
ropes  hanging  a  little  below  the  water  in  the 
well ;  earthen  or  leathern  vessels  are  attached 
to  the  loop,  which,  after  being  filled,  discharge 
into  a  trough  through  the  vertical  wheel,  which 
is  double.  Motion  is  given  by  a  vertical  shaft, 
turned  by  bullocks.  Our  modern  chain  pumps 
are  constructed  on  this  plan.  This  last  appli- 
ance is  undoubtedly  more  economical  as  a 
labor-saving  machine,  and  is  used  largely  in 
Northern  India.  This  appliance,  lifting  40 
feet,  will  raise  16,500  gallons  per  day,  if  it  has 
a  double  chain  of  pots.  All  these  methods, 
however,  require  a  good  coefficient  of  reduc- 
tion to  be  applied,  us  an  amount  of  work  is 
lost  by  leakage,  imperfect  construction,  &c. 


ORDNANCE  AND  NAVAL. 

The  "Castalia." — England's  insular  secur- 
ity is  gone.  Against  an  invading  force 
we  thought  we  had  the  iron-clads.  "What  that 
amounted  to  the  Iron  Duke  has  shown.  Still 
there  was  the  mal  de  mer.  But  in  the  Times 
recently  we  find  a  jubilant  epistle  from  a 
Frenchman,  who  came  over  from  Calais  in  the 
Castalia  in  a  heavy  sea  on  the  previous  day, 
and  whose  only  abnormal  sensation  during  the 
voyage  was  a  tendency  to  drowsiness.  Capt. 
Dicey  really  appears  to  have  achieved  a  great 
success,  and  left  the  Bessemer  nowhere.  All 
classes  of  Her  Majesty's  subjects,  chief  con- 


structors at  shipbuilding  yards,  artists,  medi- 
cal men,  clergymen,  lawyers,  ladies,  crowd  the 
columns  of  the  Times,  and  all  with  the  same 
story,  the  absence  of  sea  sickness  on  hoard  the 
twin  ship,  owing  to  the  absence  of  pitching, 
and  the  very  slight  rolling  or  tremulous  motion 
experienced.  Other  minor  causes  of  nausea, 
such  as  the  smell  of  the  engines  and  the  close- 
ness of  the  cabin,  are  reduced  to  a  minimum. 
The  only  drawback  is  want  of  speed,  which 
would  probably  be  helped  by  the  use  of  more 
powerful  engines. 

Submarine    Operations  and    the   "  Van- 
guard."— The   attempts    to.  recover    the 
Vanguard  and  the  material  sunk  with  her  are 
likely  to  test  to  the  utmost  not  only  the  skill 
and  endurance  of  the  divers,  but  also  the  num- 
erous and  ingenious  appliances  for  submarine 
work  that  have  been  invented  of  late  years. 
So  far  as  these  have  been  tried  upon  the  sunk- 
en ironclad,  they  have   apparently  fallen  far 
short  of  the  necessities  of  the  case.     In   the 
first  place,  although  she  only  lies  about  seventy 
feet  below  low-tide  level,  the  pressure  of  the 
superincumbent  fluid  appears  to  be  too  much 
for  the  strength  of  the  most  competent  and 
well-accustomed  divers.     The  two  dockyard 
men  who  have  been  employed  in  this  capacity, 
and  who  in  powers  of  endurance  and  experi- 
ence are  said  to  be  equal  to  any  two  members 
of  their  amphibious  profession  in  the  kingdom, 
can  only  remain  under  water   at  the  depth, 
named,  for  fifteen  minutes  at  a  time,  and  then 
come  to  the  surface   completely  prostrated. 
The  immense  dead  weight  of  the  hull  forbids 
any  hope  of  raising  it  by  the  means  which 
have  often  proved  efficient  in  the  case  of  light- 
er ships,  and  those  engaged  have  spent  weeks 
in  a  futile  attempt  to  dislodge  the  vessel's  iron 
masts.    It  is  now  proposed   to    place  round 
these  bands  of  dynamite,   and  blow  them  out 
of  the  hull,  the  effect  of  which  will  be  farther 
to  strain  if  not  break  it,  and  thus  to  render  the 
!  success  of  future  attempts  to  raise  the  ship 
I  still  more  problematical.     She  must  also  from 
her  great  weight  sink  to  some  extent  in  the 
j  sand  on  which  she  rests,  however  hard  that 
|  may  be,  and  there  must  be  more  or  less  of  a 
i  silting  process  going  on  from  currents  even  at 
the  depth  of  eleven  or  twelve  fathoms.     In 
;  connection  with  these  salvage  operations  there 
have  been  some  very  interesting  experiments 
made  in  Cork  Harbor  with  the  Denayrouze 
'  submarine  lamp.     When  at  the  bottom  of  the 
harbor,  the  diver  who  had  charge  of  the  lamp 
i  read  aloud  from  a  newspaper  an  account  of 
the  examination  of  the  prow  of  the  Iron  Duke, 
which  was  distinctly  heard  through  the  Denay- 
:  rouze  speaking-tube,  an  adaptation  of  a  species 
|  of  popular  entertainment  at  once  novel  and  re- 
markable.    This  lamp,  which  can  be  lighted 
J  under  water,  is  likely  to  prove  one  of  the  most 
|  useful  aids  to  submarine  operations  that  has 
yet  been  invented,  and  from  the  way  in  which 
fishes  and  other  marine  creatures  are  attracted 
to  light,  it  is  probable  that  had  the  diver  in 
the  instance  noted  been  in  a  less  confined  loc- 
ality, he  would,  like  St.  Anthony,  have  had  a 
much  larger  audience  under  than  above  the 
surface  of  the  water. 


568 


VAN"   NOSTRAND1  S    ENGINEERING    MAGAZINE. 


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Discourses  on  Architecture.  By  Eugene 
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strongly  tinged  with  national  jealousy. 

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signs of  English  writers  and  architects. 

In  this  new  treatise,  we  have  at  least  the 
ideas  of  a  writer  who  occupies  a  different 
stand  point,  and  so  far  as  prejudice  is  concern- 
ed, it  is  at  least  not  of  the  kind  which  is  pos- 
sible in  our  standard  works.  That  the  author 
is  a  competent  man  for  the  task  of  presenting 
the  principles  of  design,  may  be  judged  from 
his  record  both  as  architect  and  author. 

The  translator  says  of  him  :  "  And  here  al 
last  is  a  man  who  lias  studied,  measured,  an- 
alyzed, and  drawn  Greek  and  Roman  monu- 
ments in  Italy  and  the  Greek  colonies,  certain- 
ly with  singular  fidelity  and  intelligence  ;  who 
has  rebuilt  and  completed  the  great  Gothic 
Chateau  of  Pierrefonds,  built  the  town  halls 


BOOK    NOTICES. 


569 


of  Narbonne  and  St.  Anton  in,  restored  numer- 
ous churches  ;  constructed  the  fleche  and  sac- 
risty of  the  Cathedral  of  Paris ;  repaired  the 
fortifications  of  Carcassone  ;  architect  of  the 
works  on  the  Cathedrals  of  Laon,  Sens  and 
Amiens,  and  the  Abbeys  of  St.  Denis  and 
Vezelay  ;  author  of  the  exhaustive  '  Diction- 
aire  Raisonnie  de  l'Arohitecture  Francaise,  du 
Xe  au  XVIe  Sciecles,'  and  other  works  of 
large  research.  Thus  equipped,  M.  Viollet-le- 
Duc  appears  upon  the  scene  and  endeavors  to 
set  forth  the  true  principles  of  design.  *  * 
We  do  not  mean  to  assert  that  the  author  has 
succeeded  in  all  things,  but  we  think  it  im- 
portant to  give  a  new  publicity  to  this  honest 
and  earnest  effort,  and  to  place  it  side  by  side 
with  similar  essays  of  literary  men  and  ama- 
teurs, that  it  may  do  its  work  with  theirs." 

The  book  is  in  elegant  style,  and  is  finely 
illustrated. 

The  New  Method  of  Graphical  Statics. 
By  A.  J.  DuBois,  Ph.  D.,  Prof,  of  Civil 
Engineering,  Lehigh  University.  New  York : 
D.  Van  Nostrand.     Price  $2.00. 

The  method  of.  Graphical  Statics  is  less 
widely  known  in  this  country  than  in  either 
France,  Germany  or  Great  Britain.  In  each 
of  these  countries  text-books  expounding  the 
principles  of  the  method  are  easily  obtained. 
Here  the  demand  for  such  treatises  is  just  be- 
ginning to  be  heard;  and  already  the  value  of 
this  branch  of  science  is  recognized  by  the  use 
made  by  instructors  of  such  published  articles 
as  have  appeared  in  this  and  one  or  two  other 
periodicals. 

Prof.  Du  Bois  is  first  in  the  field  to  present 
to  American  Students  a  systematic  exposition 
of  theelements  of  this  important  subject. 

Beginning  with  the  rudimentary  steps,  the 
system  is  quite  completely  set  forth,  so  that  the 
learner  can  easily  master  the  subject  without 
aid  from  an  instructor,  providing  always  that 
he  is  familiar  with  elementary  plane  geometry 
and  the  elements  of  mechanics.  The  funda- 
mental principles  once  learned,  the  applica- 
tions to  the  important  problems  of  engineering 
are  exceedingly  easy  and  rapid. 

In  the  opening  chapters  of  the  present  treat- 
ise, the  author  thus  discourses  upon  the  cha- 
racteristics of  the  method  : 

"The  object  of  the  following  pages  is  to 
call  more  general  attention  to  a  new  method 
for  the  graphical  solution  of  statical  problems, 
which  has  during  the  last  ten  years,  mainly  in 
Germany,  been  gradually  developed  and  per- 
fected, and  which  offers  to  the  architect,  civil 
engineer,  and  constructor,  a  simple,  swift,  and 
accurate  means  for  the  investigation  of  a  great 
number  of  practical  questions.  When  once 
thoroughly  understood  and  familiarized,  it  \ 
will  be  found  greatly  superior  to  the  graphic 
methods  at  present  in  general  use.  Thus,  for 
instance,  in  the  determination  of  the  centre  of 
gravity  and  moment  of  inertia  of  areas  and  \ 
solids  ;  of  the  resultant  of  forces  either  in 
space  or  in  the  same  plane,  and  having  the 
same  or  different  points  of  application,  as  also 
in  the  resolution  of  forces  generally,  the  meth- 
od alluded  to  will  be  found  of  easy  and  uni- 
versal application.  When  applied  to  determine 


the  strains  in  the  various  members  of  a  roof 
truss,  bridge  girder,  or  similar  framed  struc- 
ture, it  furnishes  a  system  of  '  diagraming ' 
which  can  be  applied  independently  of  any 
special  assumptions  as  td  load  distribution, 
which  gives  the  strain  in  each  member  by  a 
single  line,  which  is  simple  and  rapid  of  exe- 
cution, and  which  checks  its  own  accuracy. 
In  its  application  to  '  continuous  girder*'  it  fur- 
nishes the  only  method  of  complete  solution 
for  variable  loading,  without  calling  in  the  aid 
of  the  higher  analysis,  or  having  recourse  to 
intricate  formulae  and  wearisome  calculations. 
Thus,  a  girder  continuous  over  three  or  more 
supports,  at  different  elevations,  and  sustain- 
ing a  '  concentrated  load'  at  any  point,  can  be 
investigated  with  nearly  the  same  ease  and  ac- 
curacy as  one  resting  upon  only  two  supports. 
Here  especially  those  already  familiar  with  the 
analytical  method  can,  by  a  union  of  the  two, 
greatly  shorten  the  time  and  labor  usually  con- 
sumed in  such  cases. 

"  "To  Prof.  Mohr,  of  the  Stuttgart  Polytech- 
nicum,  the  new  method  owes  its  origin,  as  well 
as  many  of  its  most  important  improvements 
and  extensions.  But  it  was  not  till  1866  that 
the  complete  and  systematic  presentation  of 
the  subject  by  Culmann  directed  general  atten- 
tion to  the  subject,  and  excited  general  inter- 
est. 

' '  During  the  eight  years  which  have  since 
elapsed,  the  method  has  been  considerably  ex- 
tended, notably  in  the  treatment  of  continuous 
girders  above  referred  to,  and  the  new  edition 
of  Culmann's  original  work,  which  is  soon  to 
appear,  and  which  has  been  so  long  promised, 
is  looked  forward  to  in  Germany  with  consid- 
erable interest. 

"Admirable  as  Culmann's  treatment  of  the 
subject  undoubtedly  is,  still  for  a  long  time 
this  interesting  and  useful  method  failed  to 
meet  with  that  appreciation  and  recognition 
from  professional  men  to  which  it  had  just 
claims  ;  partly,  perhaps,  because  of  a  natural 
disinclination  in  old  practitioners  to  relinquish 
well  known  and  familiar  methods,  and  partly 
because  the  treatment  of  Culmann  required 
for  its  comprehension  a  knowledge  of  the  so- 
called  '  Modern  Geometry,'  or  Theory  of  Trans- 
versals. 

"  This  method  of  treatment  is,  however,  by 
no  means  necessary.  The  system  admits  of  a 
clear  and  logical  development,  which  can  be 
followed  and  apprehended  by  any  one  familiar 
with  the  elements  of  geometry  as  generally 
taught ;  and  to  give  in  just  such  a  manner  the 
outlines  of  the  subject,  indicating  its  most  im- 
portant applications,  and  thus  to  bring  it  with- 
in the  reach  of  those  in  this  country  for  whose 
benefit  it  seems  so  especially  designed,  is  the 
purpose  of  these  pages." 

The  book  is  neatly  printed,  with  the  plates 
so  folded  in  as  to  open  out  in  the  best  manner 
for  the  references  which  are  certainly  neces- 
sary. 

It  is  already  in  demand  for  class  use. 

Examples  ox  Heat.      By  R.  E.  Day.  M.  A. 
Longmans  &  Co.     London,  1875. 
There  is  no  doubt  that,  in  order  to  give  a 
real,   practical  character  to  the  teaching-  of 


570 


VAN  nostrand's  engineering  magazine. 


physical  science  in  our  schools  and  colleges, 
the  working  by  the  students  themselves  of  such 
problems  as  the}7  would  actually  encounter  in 
the  every-day  life  of  engineering  or  other  pur- 
suits is  of  great  importance,  and  in  this  respect, 
we  are  sorry  to  say,  our  scientific  class-books 
have  hitherto  been  vary  deficient.  It  is  in 
consequence  almost  impossible  for  a  lecturer, 
when  discussing  the  expression  of  any  physi- 
cal law  in  a  mathematical  formula,  to  go  into 
it  except  in  general  terms  ;  and  between  this 
and  the  actual  use  of  it  for  practical  purposes 
there  is  a  very  wide  gap.  A  thorough  ac- 
quaintance with  such  formula?  can  scarcely  be 
acquired  by  the  student  from  merely  reading 
about  them,  or  seeing  them  written  on  a  black 
board,  whereas,  if  he  has  once  worked  out 
numerically  a  few  examples  of  them,  he  ac- 
quires confidence  in  their  use,  and  a  real  grasp 
of  their  actual  signification.  This  small  vol- 
ume, which  has  just  been  published  by  Messrs. 
Longmans,  deserves  a  welcome  for  these  rea- 
sons, its  object  being  to  familiarize  the  student 
with  the  laws  of  heat  by  affording  him  suffi- 
cient exercise,  not  so  much  in  the  manipula- 
tion of  algebraical  expressions,  as  in  the  nu- 
merical solution  of  practical  problems.  We 
notice,  as  of  special  interest  to  engineers,  that 
it  contains  examples  of  the  conduction  of  heat 
in  boiler-plates  and  the  expansion  of  railway 
metals,  while  there  are  a  large  number  of 
problems  which  involve  the  idea  of  the  con- 
nection between  thermal  energy  and  mechan- 
ical force.  As  the  answers  are  given  to  all  the 
questions,  the  working  of  the  problems  is  put 
within  the  reach  of  private  students. 

The  value  of  the  book,  however,  would  have 
been  materially  increased  if  the  several  sec- 
tions of  examples  into  which  it  is  divided  had 
been  headed  with  the  formula?  applying  to 
them,  and  we  advise  the  author  to  add  them  to 
the  next  edition.  The  little  work  gives  evi- 
dence of  having  been  most  carefully  prepared, 
and  we  can,  on  the  whole,  recommend  it  con- 
fidently to  all  who,  whether  as  teachers  or 
learners,  are  desirous  of  gaining  a  real,  work- 
ing knowledge  of  the  laws  of  heat.  We  trust 
that  what  the  author  has  thus  succeeded  in 
doing  to  facilitate  the  study  of  heat,  he  will 
repeat  for  the  other  branches  of  physical  sci- 
ence. — Engineer. 


MISCELLANEOUS. 

Talc  has  been  recommended  by  MM.  Vigier 
and  Aragon  for  the  prevention  of  incrus- 
tation in  boilers.  It  is  used  on  the  Paris  and 
Lyons  Railway,  and  it  is  stated  that  the  quan- 
tity of  talc  introduced  into  the  boiler  is  about 
one-tenth  of  the  weight  of  deposit  accumu- 
lated between  two  consecutive  blow-offs.  It 
is  stated  not  only  to  prevent  but  to  loosen  and 
remove  old  incrustation. 

Belgian  Ikon  Trade. — The  manufactured 
iron  trade  of  Belgium  is  reviving,  in  con- 
sequence of  the  low  rates  of  pig-iron,  and  the 
rolling  mills  are  getting  again  into  work.  At 
Acoz  a  new  rolling  and  flatting  mill — a  third 
one — has  been  opened,  for  the  manufacture  of 


merchant  iron  of  every  variety,  in  view  of  the 
demand  likely  to  arise  from  the  exhaustion  of 
the  present  stocks  of  rails.  The  new  mill  can 
turn  out  40  tons  of  finished  iron  per  day  of 
twenty-four  hours.  The  Societc  de  Sclessen 
is  said  to  be  getting  100  kilos,  of  pig-iron  with 
97  kilos,  of  coke,  being  the  first  furnace  in  Bel- 
gium which  has  obtained  such  a  result. 

A  New  Metal. — Gallium  is  the  name  given, 
"  in  honor  of  France,''  to  a  new  element 
which  has  been  discovered  by  M.  Lecoq,  an 
amateur  savant,  of  Bois-Baudran,  Cognac. 
The  celebrated  chemist,  "Wurtz,  presented  to 
the  Academie  des  Sciences,  in  its  sitting  of 
September  20th,  a  note  on  the  part  of  M.  Lecoq, 
announcing  the  discovery,  particulars  of  which 
had  been  communicated  under  seal  as  far  back 
as  August  27th.  This  new  element  has  not 
yet  been  isolated,  and  has  not  therefore  been 
seen  by  any  one  ;  its  physical  characteristics 
remain  so  far  unknown.  It  is  an  analogue  of 
zinc  and  cadmium,  of  which  metals  it  is  an 
alloy,  and  was  found  in  a  blende  from  Pietraf- 
ita,  Spain.  The  forms  under  which  it  is 
known,  so  far,  are  those  of  the  chloride  and 
sulphate.  The  discoverer  is  a  student  of  the 
phenomena  of  the  spectroscope,  and  it  was  in 
the  course  of  his  observations  that  the  new 
metal  presented  itself,  its  character  being  re- 
vealed by  a  spectrum  which  no  simple  body 
had  ever  given.  Two  lines,  one  much  bright- 
er than  the  other,  both  situated  in  the  violet— 
the  region  occupied  by  the  brightest  lines  of 
the  zinc — were  noticed,  the  place  of  the  for- 
|  mer  line  being  at  the  417th  degree  of  the  scale 
I  of  lines,  and  the  other  at  the  404th. 

The  affinities  which  gallium  has  with  zinc 
|  are  declared  by  chemical  analysis  as  well  as 
1  by  its  spectrum.  Like  zinc  it  is  not  thrown 
down  from  solution  in  hydrochloric  acid  by 
sulphuretted  hydrogen  ;  and  preserves  its  an- 
alogy with  zinc  by  being  precipitated  by  the 
same  gas  from  an  acetic  acid  solution.  Under 
these  conditions  it  is  obtained  before  the  zinc, 
.  and  on  fractionation,  the  two  are  got  sepa- 
rately. Like  zinc,  the  new  metal  gives  a 
white  precipitate  with  the  sulphide  of  ammo- 
nium. On  immersing  a  piece  of  zinc  in  a  solu- 
tion of  the  new  metal  it  separates  and  comes 
out,  not  in  a  metallic  form,  but  under  that  of 
an  oxyde,  precisely  as  aluminum  does  under 
similar  circumstances.  The  analogy  with 
aluminum,  however,  is  not  long  sustained, 
for  if  a  small  dose  of  ammonia  precipitates  the 
gallium  an  excess  redissolves  it.  Up  to  the 
present  time,  only  a  very  small  quantity  of 
gallium  has  been  obtained,  but  M.  Wurtz, 
who  presented  the  paper,  has  given  the 
;  Academy  tubes  of  solution  for  experiment ; 
and  on  asking  for  a  commission  to  examine  in- 
to the  question  and  to  place  gallium  on  the 
list  of  simple  bodies,  the  Academy  named  M. 
Wurtz  himself,  joining  with  him  M.  Fremy. 
The  actual  number  of  known  elements  is  63,  47 
of  which  are  metals  and  16  metalloids.  If  the 
•  new  element  takes  the  place  claimed  for  it, 
France  will  have  obtained  an  honor  equal  to 
that  of  England  which  discovered  thallium, 
and  approximative  to  that  of  Germany,  the 
;  discoverer  of  casium  and  rubidium. 


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